The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
The determination of the erodity and sedimenting area and evolutionary situation of the basins from the comparative view of point by using dimensionless hypsometric curves (Case study: Vzneh and Baneh Bsins)
Mamand salari1, Phd student,
physical geography,Geomorphology,Tehran university
Dr saeid kamyabi,
Assistant of professor,Islamic Azad university, Semnan Branch
Omid moradi,
Master of science, Geomorphology, Tehran university
Abstract The physical attributes of Basins have great effects on the process of erosion. Among the most important parameters of basins that directly or indirectly have great effects on the erosion. for example the elevation of basin indicates its climatic condition and it is effective in raining and considering the face that each rainfall has its own hydrology it has special role in erosion. therefore in order to analyze the condition of erosion and sedimentation with a comparative view in the basins of Vazne and Bane, undimensional hepsometric tables and curves have been designed.It becomes clear that in the Vazne basin the development of plain and elevation is to some extent balanced. The low space between two curves is indicative of the approach of the basin to equilibrium .in contrast in Bane basin considering the condition of the curves it becomes clear that tis Basin is more away from that equilibrium and is younger and less development.
Key word: Bane basin,Vazne basin, Erosion, dimensionless hypsometric curves
Introduction Erosion has a Latin stem meaning attrition of ground surface. This term was first used by Pank in 1894 (Refahi, 2004). In fact accelerated ground erosion is considered as a global issue due to its effects on economy and environment (Lim et al, 2005). Dimensionless hypsometric curves are very important tools among others by which some important physical indices of basins can be obtained which are used for basins comparison (Alizadeh, 2003). On the other hand, there is obvious relationship between hypsometry curves and river basins evolution (Huang, 2006). Thus in order to examine sedimentation and erosion in two basins and their related areas and identify evolution condition and determine basins equilibrium, real and theoretical dimensionless hypsometric curves and tables are drawn and then are compared.
Material and Method Research method is based on field and library study as well as using environmental and geographical science tools and techniques such as maps and software. Hypsometric curves
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 can be drawn both classically and in dimensionless form. Its classic form which is indicative of surface per altitude distribution can be interpreted in terms of erosion or sedimentation stages, but can not be interpreted like mathematical equations qualitatively. Thus, Long Bin developed hypsometric curves analysis in dimensionless form (Farifte, 1370). Therefore real and theoretical dimensionless hypsometric curves are calculated and drawn for both basins, which are qualitatively interpretable like mathematical equations and by which status of erosion and sedimentation in basins can be studied. In real dimensionless hypsometric curves, X value is obtained by partial accumulative area (a) division to total basin area (A) (X=A/a) and Y value is obtained by accumulative partial altitude difference (h) division to total basin altitude difference (H) (Y=h/H) which are placed in two diagram’s axes. It is clear that Y and X difference range always varies in 0 and 1 (Movaheddanesh, 1995). It should be mentioned that obtained diagrams can be interpreted both qualitatively and quantitatively. However, theoretical dimensionless hypsometric curves are also drawn for both basins in order to better understanding and comparison of erosion and sedimentation in basin surfaces. For drawing these curves, X and YC values are used that X=a/A and YC can be calculated by following equations (eq.1,Movaheddanesh, 1995).
∑ log y d − (x + a) Z Z = u = × a yc = u ∑ log u ()x + a
Where Yc is theoretical calculated altitude, a is selected distance to source and d= 1 + a. in other word, a = 0.2, d = 1.2, and z = 0.42. This equation shpae indicates three stages of erosion: youth (erosion), maturity (equilibrium) and senility (sedimentation) which can be observed in figure 1 (Farifte, 1991).
Situation of Areas Under Study Vazneh drainage basin is located in northwest of country, in south of West Azarbayejan Province and northwest of SardaSht town. Its geographical situation is in altitude 45´-16´ and 45´-26´ in east and latitude 36´-12´ and 36´-24´ in north (Fig.2). basin area was estimated 185.4 km2 by GIS software in ILWIS environment and its altitude average of sea level is 1713.3 m (Salari, 2006). Baneh drainage basin is also located in northwest of country, in southwest of Kordestan Province and northeast of Baneh town. Its geographical situation is in altitude 45´-56´ and 46´-02´ in east and latitude 36´ and 36´-04´ in north (Fig.3). basin area was estimated 96.28 km2 by GIS software in ILWIS environment (Moradi, 2007).
Vazneh Basin Desired values are calculated based on mentioned mathematical relations in order to evaluate and analyze errosion. Then, real and theorethical dimentsionless hypsometric curves and tables are drawn (Table 1, Fig.5). real and thoretical curves of these basins are obtained based on Eq.2 by r = 0.99 (correlation coefficient). This coefficient is relaible with relaiblity level of 0.99. Eq.2 is as following: In above figure, the diffrence of real gradients (what should be) with theoretical curve and actual gradients (what it is now) with real curves can be observed (Nakhei & Ghanavati, 2006). Regarding dimensionless hypsometric curve of Vazneh basin,
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 theoretical curve is set upper than real one in upstream indicating errosin in this part of basin. With regard to dominant erosion trend, it can be said that this part is composed mainly of high and slope areas in which erosive processes are strong (Salari, 2006). On the other hand, the role of climatic processes is considerable in area under investigation (Jafarpur, 1978). In other words, this trend is extending toward about altitude of 1700m that in this altitude there would be equilibrium. Equilibrium in basin is matched to high areas of Vazneh plain. Beyond that, theoretical curve is set below the real curve indicating sedimentation in bed. By observing real and theoretical curves, it can be found that there is low difference between two curves which indicates erosion decrease and approximating basin to equilibrium state. Then theoretical and real curve are coincided completely in 1500m altitude and after that to basin exit, they have low difference. Generally about 40% of basin is subject to erosion and about 60% is subject to sedimentation(Fig4).
Baneh Basin By observing real and theoretical curves drawn for this basin it can be found that theoretical curve is clearly upper than real one in upstream indicating considerable erosion for this part of basin. Curves are set with large distance to each other in this part suggesting strong erosion. This trend begins from basin altitude peak (2700m) extending to about 1600 altitude where two curves approximate to each other clearly and there is equilibrium. Then theoretical curve is set below the real curve indicating sedimentation in bed. This condition there is from 1600m altitude downward, in other words, to about basin exit in 1100m altitude. Generally almost 64% of Baneh basin is subject to erosion and about 36% is subject to sedimentation(Fig5).
Conclusion In upstream of Vazneh basin, about 40 percent of area is subject to erosion. In remaining 60 percent, the position of two curves is vice versa and in these areas there is possibility of sedimentation in bed. It should be stated that the low distance between two curves indicates erosion decrease and tendency toward equilibrium. On the other hand, regarding real dimensionless curve it is noted that plain and altitude expansion is somehow balanced and overall shape of curve shows a basin in equilibrium state. By comparison, in Baneh basin, about 64 percent of theoretical curve of basin is set upper than real one, and therefore it is subject to erosion. It should be mentioned that most erosive areas are matched to mountain areas that upward slope as well as reduction of vegetative cover and fluidity power increase are its main reasons. In remaining 36 percent the position of is two curves is vice versa and sedimentation in bed is probable in these areas. By observing real and theoretical curves with regard to two basins comparison, it is noted that in Vazneh basin, the distance between two indicator measuring curves is small suggesting equilibrium state. But in Baneh basin, the curves’ distance is larger in upstream and therefore, there is more strong erosion condition. Also in lower parts there is more severe sedimentary condition. Curve shapes indicate more evolutionary basin for Vazneh and younger basin for Baneh.
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
Fig1- Stag of erosion in basin Fig2:The situation of vazneh basin
Fig3:The sitution of Baneh basin Fig4:Actual and Theoric Dimensionless hypsometric curves(Vazneh)
Fig5: Actual and Theoric Dimensionless hypsometric curves(Baneh basin)
Referenace 1-Refahi,H., 2004, water erosion and conservation:Tehran,university Tehran press,4 th Edition. 2- Salari,M,2006, Analysis of hydrogeomorphological charactistics and the estimation of erosion and sediment inVazneh basin, A thesis of the Master of arts, Tehran, university of Tehran. 3-Moradi,O,2007, Survey of hydrogeomorphology of Baneh basin and the estimation of erosion and sediment, A thesis of the Master of arts, Tehran, university of Tehran. 4- Movaheddanesh,A,.1995, The Hydrology of the water surface of iran,Tehran,samt press, 1th edition.
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5- Huang.X.Jiang.(2006), Impacts of watershed hydrology on long-term landscape evolution. 163 pages; ProQuest, AAT 3229409. 6- .Lim,J,et al.(2005),GIS-based sediment assessment tool.Catena,64,pp 61-80. 7- Alizadeh,A,.2003,Principles of applied hydrology, Mashhad, astan qods press,14th Edition. 8- Jafarpoor,E, 1978, Climatological reaserch in west iran, Tehran, issue 15, institute of geography press.
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 Biofacaies and lithofacies study of Tirgan Formation in central kopet dagh basin( Shorak area)
M. Vahabzadeh, M.; Allameh, M.; Torshizian H. A.
Department of Geology, Islamic Azad University-Mashhad Branch
Absract The Kopet- Dagh sedimentary basin is eastern north of Iran has fult contact with Tooran platform from the north and is bounded to the south by Bindalood mountains. According to Berberian and King (1981), this zone becomes sedimentary basin after early Kimmerian organic event (It happened when the concurrence of Iran and Tooran finished) and thick sediments were gathered with various facies from Jurassic to Miocene without important stratigraphic gap. These sediments were deformed under late Alpine organic events and formed various anticlines and synclines with northwest- southwest strike. The main aim of this research is to view sedimentary environment of Tirgan formation in central part of Kopet- Deagh basin. Type section of Tirgan formation in the 40th kilometer of Dargaz is 780 meters thick with the age of Neocomian- Aption. The thickness of this formation is very different in different regions so that it is equal to 40 meters in the east of Kopet- Deagh basin in Mozdooran. The contact of these two formations (Shoorigeh and Sarcheshmeh) is sharp. In some part Kopet- Deagh sedimentary basin, Tirgan formation is as reservoir rock of gas resources in the north of Iran. Mozdooran and Tirgan formations are also counted ad kartsic formation in Kopet-Deagh basin and are valuable regarding to water resources. (From the point of water resources). In this research, Tirgan formation was studied in Shorak in detailed. 95 hard samples and 10 soft samples were taken with average distance of 3.5- 4 meters and thin sections were taken from hard samples. Detailed pictographic studies resulted in distinction of 13 microfacies. They are as follows: 1- Calimudstone. 2- Biocalstic wackstone 3- Bioclastic packstone 4- Oncolithic packstone 5- Oolitihc< biocalstic> garinstone 6- Oolithic
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Geberally, sedimentation of Tirgan formation sere formed in Tidal flat (supradital, intertidal) and subtidal environments. This basin was deepended with the passage of time so that shaley and Marly sediments of sarcheshmeh formation were placed over Tirgan formation conformably and with variation of facies change into open marine environment. According to these results, horizontal model of depositions of Tirgan formation was drown. Features, processes and important diageneric environments is Tirgan formation are as follow: Micritization, Bioturbation, Geopetal fabric, Isopaques fibrous rim cements and early dolomitization were distinguished in marine pheriatic. Early compaction Aragonitic shells winnowing werer formed is under saturated fresh, water pheratic zone. Filling cavity and fractures by Spry cement, forming syntaxial overgrowth drusy cement, poikilolopic cement and Neomorphism happened in active saturated fresh water phriatic zone. Meniccus, pendent cement and vadose sitl were formed in fresh wated vadose zone. Late compaction, Stylolitization, late dolomitztion (Saddle dolomite) Formation of Authigenic minerals and late fracture filing happened in burial environment. Cathodolominecence analyses, Electron Microprob analyses were done in some thin sections. Cathodlominecance analyses demonstrated than cementation was occurred in different phases. Fibrous cement deposited in environment. For more detailed studies of diagenes marine and investigation of environment of dolomite formation. Isotopic investigation, Electromaicroprob analysis, SEM and cathololminecance studies and needed. But according to petrographic documents and staining by Alizarine red s and potacium ferrocianore we can conclude that dolomitization in this formation in interidal region lagoon reqion and also bar region which probably was the result of mechanism of reflux and seepage and dolomtization in burial diagenesis.
Ref Al-Husseini, M., 1997, Jurassic sequence stratigraphy of the western and southern Arabian Gulf”, GeoArabia, v.2, 361-382. Bachman, M., Hirsch, F., 2006, Lower cretaceous carbonate platform of estern Levant (Galilee and the Golan Heights): stratigraphy and second-order sea level change., Cretaceous Research, v. 27, 487-512. Bernecker, M., 2007, Facies architecture of an isolated carbonate platform in the Hawasina Basin: The Late Triassic Jebel Kawr of Oman, Palaeogeography, Palaeoclimatology, Palaeoecology, v. 252, Issues 1-2, 270-280. Betzler, C., Pawellek, T., Abdullah, M. and Kossler, A., 2007, Facies and stratigraphic architecture of the Korallenoolith Formation in North Germany (Lauensteiner Pass, Ith Mountains), Sedimentary Geology 194, 61–75. Brett, C.E., 1998, Sequence stratigraphy, paleoecology and evolution clues and responses to sea level flactuations, Palios, v.13, 240-262. Brookfield, M.E., Hashmat, A., 2001, The geology and petroleum potential of the North Afghan platform and adjacent areas (northern Afghanistan, with parts of southern Turkmenistan, Uzbekistan and Tajikistan), Earth science Reviews, v.55, 41-71.
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
The comparison of the petrography and petrogenesis mass granitoid of Dehgheybi in Mashhad and Seyed Morteza in Kashmar
M. E. Fazel Valipour, R. Sharifiyan Attar, S. Khosravan
Department of Geology, Faculty of Sciences, Islamic Azad University, Mashhad Branch
Abstract The study areas are located in the North East of Iran, 10 Km. from South West of Mashhad and 6 Km. from North of Kashmar. Granitoids of Dehgheybi of Mashhad is located in eastern Alborz, Binalood zone. Plutonic body of Seyed Morteza of Kashmar introduce as Loot block, Sabzevar zone and Taknar zone in divisions of structure geology unites of Iran. The volcanic rocks of granitoid and monzogranite outcrop in Dehgheybi of Mashhad. Plutons of Seyed Morteza of Kashmar have variety of composition include of monzogranite, granodiorite and quartz diorite. Field observations, petrography and especially geochemistry data shows all of them are calc alkaline and per aluminous essence. Further observations show that this granite created from melting of sedimentary rocks and has S type. Different diagrams of tectonical difference show that tectonically environment of this granitoid plutons depended on continental contact tectonically environment (CCG).
Key words: S type, Dehgheybi, Seyed Morteza, Calc alkaline, Granitoid.
1. Introduction Mass granitoid of dehgheybi is located on east southern at a distance of 10 Km from Mashhad between geographical longitudes 59° 28′ - 59° 36′ East and latitudes 36° 9′ - 36° 15′ North (fig. 1) [Army geographical organization 1982] which based on Iran structural – geology units divide is located on East Alborz zone in Binalood area [Alavi, 1991]. Penetration mass of Seyed Morteza in Kashmar between is located on North at a distance of 6Km from Kashmar between geographical longitudes 57° 30′ – 58° 30′ East and latitudes 35° – 36° North (fig. 1) [Army geographical organization, 1963], which in Iran structural units dividing introduce under the name of Loot block, Sabzevar zone and Taknar zone. Penetration mass of
Dehgheybi area is a kind of granitoid stones which are calling G1 and G2 [Majidie 1978] in North of it, there are transformation stone units with direction of West North – East South that its kind is phyilite, schist, slate and meta volcanic belongs to upper Paleozoic (Permian- Carbonifer) (fig. 2) [Aalaminia 2007 ]. From stone units which are existed in Kashmar, Seyed Morteza area, we can refer to penetration mass of granodiorite, granite, quartz diorite. Penetration mass of dacite and andesite quartz also could be seen in Penetration mass of Seyed Morteza, Kashmar. In West of study area of seyed Morteza, sedimentary units belongs to Paleogene are seen (fig. 2) [fazel Valipour 1992].
2. Method Geology researches almost are done in a similar and general pattern including laboratory and desert studies. At first, with using of air pictures and desert walking, geology map of regions under study were provided with 1:20000 scale. After field studies, thin sections were prepared from stone samples. These sections were studied by petrography. From collected samples,
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 intact samples were analyzed and according to XRF style, tectono magma studies of regions were done by this analysis.
3. Discussion 3.1. Petrography Petrography, field studies of penetration masses of Dehgheybi shows that this mass is composed of monzogranite, granodiorite and granite. Granular text often could be seen in these stones. Their major minerals including formed plagioclases which transformed to phyllo silicate minerals (clay and mica minerals) as a result of considerable decomposition, that this has done mostly from feldspar's central parts which shows zone mode (Fig. 3-L ). Further more, there are feldspar alkali of microcline, quartz, brown biotite and muscovite kind. In some regions, alkali feldspar shows poekilitik text by having fored crystals. Brown biotite is like wide blades and they often have zircon seeds and its surrounding hols. In some samples, biotite transformed to chlorite. Apatite and opaque minerals are minor minerals in these masses. These masses also cut by aplite and even orthoclase veins which some times have quartz in some parts. Some times, aplite veins are wrinkle and cut by other veins (Aalaminia, 2007) .This case shows different aplite production in region which are different in their combination, as basically secondary veins have less feldspar and more tourmaline (Fig. 3-M & 3-N) and it matches with rules of penetration mass in Seyed Morteza Kashmar, have a combination of granite, porphyry granite, granodiorite and quartz diorite which granite stones almost are more than others. Very little restricted area is full of porphyry granite. These stones are extremely altered and grinding are extreme in them. Porphyry granites are usually exclusive for penetration masses with little bulk or margin stones of large masses; in Seyed Morteza region, the first made occurs. Granodiorites are expanded in the region like granites and in some parts of region; they are in the form of dyke. Diorite quartz masses are less expanded than granites and granodiorites (Fig. 2) (Fazel Valipour 1992). These stones are mostly hipidiomorph granular, poikilitic, microgranular and graphical texture (Figure 3-a, 3-b, 3-c, 3-d). Their maker minerals are quartz, plagioclase of albite till oligoclase kind, Orthoclase, biotite and Hornblende. Metamorphic production minerals are of serisite, chlorite, clay minerals, Epidot, zoizite kind (Fig. 3-R) and minor minerals i.e. Apatite and Zircon also can be seen in them (Fig. 3-z).
3.2. Geochemistry Collected samples analyzed by XRF style in order to geochemistry analysis of penetration stones of under study regions, then result were processed by minpet 2.02 software and they were used in different charts to examine characteristics of intrusive rocks of region. Regarding to shtrakizen (1976) categorization, collected samples of Dehgheybi region were monzogranite, granodiorite and collected samples of Seyed Morteza, Kashmar region were granite, granodirite and quartz diorite. 1-Magma series 1-1- Limet-Alkalin index
SiO2-NaO+K2O chart (Pakook, 1931) was used in order to determine of this index in penetration stories of both regions and according to this chart penetration stories of under study areas called sub Alkaline.
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2-1- AFM chart: Regarding AFM chart, penetration stories of Dehgheybi region has no iron enrichment and they trend to A pole and their limitation is Calc Alkaline (Figure 6). However, in Seyed Morteza Kashmar, collected samples observed in two forms of iron enrichment and non- enrichment. Anyway, all samples placed on Calc Alkaline limitation. 3-3- Saturation coefficient of Albumin or Shand index: A/NK – A/CNK chart used to determine saturation coefficient of Albumin for penetration stories of both areas which regarding that both of them placed in Per Aluminous limitation (Fig. 7).
3.3. Tectonic environment Variety of data like geochemistry of major and rare elements, field geology and petrography were used to analyze magmatism tectonic environment of both regions and in order to present a proper tectnomagma sample and model. For this purpose, it was tried to use geochemistry evident as assisted and supplementary with field geology and Petrography evident. 2-1- presenting tectono magma model of study regions according to geochemistry of major elements: Maniar and Picoolie chart (1984) was used to analyze tectono magma sample of under study region according to main element’s chemistry (figure 8) above mentioned chart shows ration Mw% - Fw%, and has three limits: a- IAG+CAG+CCG limit which involves clashing environments. b- RRG+CEUG limit which involves internal plate environments. c- POC limit Recording this chart, samples of Dehgheybi placed on a (IAG+CAG+CCG) which present clashing environment. collected samples from Seyed Morteza also placed in a limitation (Fig. 8). Since this chart doesn’t determine clashing environment type, other evidence like geochemistry of rare elements were used to analyze more and to determine type of clashing environment. 2-2- presenting model of limitation tectono magma based on rare elements geochemistry: Different charts were used to determine sample of granitoid masses tectono magma based on rare elements geochemistry, in following section, we present charts which are used for presenting model of granitoid rocks of under study limitation. Bachelor and Boden (1985) state some measures and metrics for granites that based on current chart, intrusive rocks of both regions placed on syn-collision limitation (Fig. 9). Regarding to chart of Pierce and colleagues (1984) which state first new categorization of samples according to Log Nb with regard to Log y of granitoid rocks of under study region placed on VAG+Syn-COLG zone (Fig. 10). In order to exact separation, Log Rb ration to Y+Nb chart was used (Pierce and Colleagues, 1984) that according to this, granitoid rocks of region are placed on Syn-COLG domain (figure 11).
3.4. Granitoids type According to granite categorization by Chapel and White (1974) that they categorize them to I and S type, any petrologist who study granites, tried to check granites of his under study region with Chappel and White findings and possibly expanel them. Geochemist try, field and
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 petrography studies show that granites of both regions are S type and they produced by upper crust melting of sedimentary materials which must have pert alumine magma.
4. Conclusions Granitoids mass of Dehgheybi are monzogranite and granodiorite that they crossed by veins of Aplite and Pegmatite in the most part of granitoids mass of Seyed Morteza, Kashmar rocks are granite and granodiorite and there is a little quartz diorite. Based on petrography, field studies and geochemistry data, granitoids rocks of both study regions are calc alkaline type. according to mentioned data, garanite collection of both study regions show characteristics of S type granites. Also, diagrams of tectonic environment differential show that these granites belongs to continent collision granites (CCG).
References Aalaminia, Z., 2007, Petrology study of Khalaj’s transformation rocks (South West of Mashhad) whit considering application of geographical information system (GIS) in its mineral potential analysis, MA thesis, Tarbiyat Moalem university,Tehran. Alavi, M. 1991, Sedimentary and structural characteristics of the Paleo-Tethys remnants in northeastern Iran. Geol. Soc. Am. Bull., 103, 983-92. Chappel, B.W. & White, A.J.R., 1992, I-and S-type granites in the Lachlan fold belt, Tansaction of the royal society of Edinburgh: Earth Sci, 83, 1-26. Darvishzadeh, A., 1991, geology of iran, Amir kabir university. Filipov, M., Janasi, V.D.A., 2001, The Maua granitic massif, central Riberia belt, Saupaulo, Petrography geochemistry and U-Pb dating. Revista Brasileira de Geocie, 31, 341-348.
Holtz, F., Pichavant, M., Barbey, T., & Johannes, W., 1992c. Effects of H2O on liquidus phase relations in haplogranite system at 2 and 5Kb Am. Mineral. 77, 1223-1241. Majidi, B. 1978, Etude petrostructural de la region de Mashhad (Iran). Les problems des metamorphites, serpentinites et granitoides hercyniens. France, These universite Scientifique et Medicale de Granoble. Maniar, P.O., Piccoli, P.M. 1989, Tectonic discrimination of granitoids, Geol. Soc. Am. Bull., 11, 635- 643. Pearce, J.A, Harris, N.B.W. & tindie, A.G., 1984, trace element discrimination diagrams for the tectonic interpretation of granitic rock, Geol. Soc. Spec. Pubel., 7, 14-24. Rollinson, H.R., 1993, Using geochemical data, Longman, 325p.
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Fig. 1- Geographical situation and communication routes of regions which are under study [Army geographical organization 1963, 1982], Right: study limitation situation of Seyed Morteza, Kashmar, Left: Study limitation situation of Dehgheybi, Mashhad.
Fig. 2- Geology map of stone unites in regions which are under study [Fazel Valipour 1992, Aalaminia, 2007]. Right: Geology map of Seyed Morteza Kashmar. Left: Geology map of Dehgheybi Mashhad.
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Fig. 3-a and 3-b: Poikilitic texture in granites. Biotite-zirconia minerals, plagioclase and feldspare in context of quartz . A: in PPL, (Seyed Morteza region, Kashmar). B: in XPL, (Seyed Morteza region, Kashmar). C: Granular hepidomorph texture ( Seyed Morteza region, Kashmar) D: Graphic texture (XPL light, Seyed Morteza region, Kashmar). E: A picture of plagioclase transformation to Epidot and Carbonate (XPL light, S yed Morteza region, Kashmar). F: Quartz Diorite aggregation of minor crystals of Zirconia in Sersitic Plagioclase (XPL light, Seyed Morteza region, Kashmar). G: Granite Plagioclase decomposition started from internal parts (XPL light, Dehgheybi region, Mashhad). H: Granite that has tourmaline. Tourmaline can be seen in picture (XPL light, Dehgheybi region, Mashhad). I: Aplite vein that has Tourmaline and penetrate in Granites (Dehgheybi region, Mashhad).
20 quartzolite 18 16 Qtz-rich 14 12 10 Granite 8 Alkaline af tonalite Na2O+K2O grano 6 syeno monzo 4 2 Subalkaline qafs Quartz Quartz Quartz Qtz 0 afsy syenite monzonit monzondiorit diorit 35 40 45 50 55 60 65 70 75 80 85 SiO2
Fig. 4. (Right). Categorization for penetration stones of under study regions (using Shtrakizen, 1976). Fig. 5. (Left). Ratio of Alkaline to Silica chart for determining Magma serie of Granitoide stones in region (using Pakock, 1931).
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FeOt
Tholeiitic
Calc-Alkaline
Na2O+K2O MgO
Fig 6. (Right). AFM chart, for separation Calc Alkaline series from to litie for Granitoide stones of region (Arvin & Baragara, 1971) Fig 7. (Left). Ratio of ANK/CANK for Granitoid stones in region (Manir and Picoolie, 1989).
2500 60 1 - Mantle Fractionates RRG+CEUG 2 - Pre-Plate Collis ion 2000 3 - Pos t-Collis ion Uplift 50 4 - Late-Orogenic 5 - Anorogenic 6 - Syn-Collis ion 1 40 POG 1500 7 - Pos t-Oroge nic
2 30 R2
Fw% 1000 3 20 4 500 6 10 5 7 IAG+CAG+CCG 0 0 0 500 1000 1500 2000 2500 3000 0 10 20 30 R1 Mw%
Fig 8. Tectno magma environment of granitoide mass in under studied region (Maniar and Picoolie, 1984). Fig 9. Tectno magma environment of granitoid mass under studied region (Bachelor and Booden, 1985).
2000 1000 1000 Syn-COL G WPG WPG 100 100
Nb Rb VAG+ Syn-COL G 10 10
VAG ORG ORG
1 1 1 10 100 10002000 1 10 100 10002000 Y+Nb Y
Fig. 10. Tectno magma environment of granitoid mass in under studied region (Pierce and Colleagues, 1984). Fig. 11. Tectno magma situation of granitoid mass in under studied region (Pierce and Colleagues, 1984).
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Geodynamics Evolution of the Oil Traps in Southern Regions of Zagros Due to Closing of Neotethy
1 2 Naser Ebadati , Ahmad Adib
1- Islamic Azad University Islamshar branch, drebadati @yahoo.com
2-Islamic Azad University Tehran Jonub branch
Abstract: In the northern part of the Persian Golf & the Southern region of Zagros, the signs of Oil hydro carbore from the Silurian period can be chased .Also it has determined the beginning of Oil producing in some formation of Middle Jurassic .This shows the great accumulation of Oil & gas before the Orogenic of Zagros in several regional heights. After the Complete closing of Neotethys & formation of the anticlines in the end of Miocene & Pliocene, great amount of Oil & gas has been piled up. The thickness for various formations from Jurassic till Miocene have revealed that these heights with lightly steep limbs have been stretched from Qatar to southeastern part of Hormoz island & the center part of the fars Zone. High amount of the produced Oil in Silurian Basin is gathered in the heights of Qatar arc & the rest is amassed in northern parts of Bandar Abbas. At the end of cenomanian, the fault system of N-S Paleozoic has been activated & since the end of cretaceous the produced gas has made the Oil move to the sides & formed the oil sources in both sides of the heights. During the upper Miocene & Pliocene a portion of this gas gathered in new structure of Zagros & even some of the oil reached to the earth's surface. Generally the oil traps of this region are divided into these parts: 1) Large anticlines with slightly steep limbs which are not due to the pressure or folding of Zagros .In Persian Gulf area & the southern parts mostly these kinds can be found. 2) The NW- SE anticlines in folded parts of Zagros that are grown up by the function of the final stages of closing Neotethys .These deformations have kept on till now like in Asmari regions. 3) The functions of the faults & the rising pieces of the basements caused the formation of N-S anticlines. 4) The oil traps that are the result of infracambrian salt diapers in Persian Gulf.
Keywords: oil Trap, Tectonic, Zagros.
Introduction According to status of oil fields reserves of Persian Gulf, only 12-15% of oil reserves of this region are in anticline that are formed after Alp orogenic at mountainside of South Zagros and more than remained 85% are accumulated at Platform and anticlines with different processes due to continent and salt movement before Alp orogenic. During infra-camberian the Arabian plate was gone under tension phase performance and as a result of creation of mountains and opening sediment basin and Arabian evaporate sediment some breaking were created inside of shells. In continuation for orogenic katangaei the Strike Slip and in next stages shallow sediments and evaporite sediments at broad Graben and Rift basin of Oman, Persian Gulf, Zagros, Pakistan were created (Husseini 1988). There are several movements of Transform Fault and Sinestral at Graben basin of South Oman, Persian Gulf and Zagros. Tension in
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 continent shell at the end of infra-camberian has created initial linear indentations and normal faults alongside of rift. Creation of indentation is accompany with parallel faulting at border of indentations and because of different sagging, large volume of shallow marine sediments and evaporate sediments of source rock are developed during initial period and simultaneously hydrocarbon source rock with salt reserves and non-metal elements and magnates are created at rift basin, consequently cap rock will be created(Fig 1). Lower Paleozoic sediments contain great organic materials and rock that are suitable for source rock. During priming period the changes of thickness is very low because of shallow sediments and platforms. During Triassic period at regions of Qeshm and north of Bandar Abbas the sinking was continued and maximum Triassic thickness is seen at north of Bandar Abbas. At Qatar region toward north and Shiraz there is lower thickness of Triassic and it seems that salt movements from start of Triassic create ascending and in Jurassic the continent and salt movements has ascended Persian Gulf region. In cretaceous because of continent and salt movements the region of hall, Boushehr, Kangan, Bahrain, Qatar and Ghavar are ascended and lower thickness is seen at this region during Cretaceous period and on the contrary at regions of Sarvestan, Shiraz, Dezfoul, Lorestan, north of Hormoz and Oman some descending and increasing thickness of Cretaceous sediments can be seen. During Tertiary period the condition was vice versa and thickness of sediments at north of Persian Gulf and Shiraz, Dezfoul and Lorestan is decreased.
Fig 1: Uplift and diapiric structure at Permian to Jurassic in the south of Zagros belt
Hydrocarbon Source Rock: Generally we can say that source rock for oil gas of Permian are among greatest organic fields and Silurian Shale, limestones and Permian dolomite because of high heat and pressure of organic materials are changed into gas in sediments and have lateral immigrate to anticlines at upper part of Persian Platform i.e. Qatar, Pars, Kangan and Bahrain oil field. Source rock for Jurassic limestone reserves at North of Persian Gulf and some parts of shale are started from Masjed Soleiman region and continue to west north. Type of source rock for cretaceous reserve is formation; Borgan and Zobeir toward east and north east are respectively changed into Kazhdomi & Gadvan shale. Oligocene source rock has Marl, Shale, Pabdeh and Gorpi formation. That are located beneath Asmari limestone reservoir; then after Alp orogenic and formation of anticline of South Zagros the hydrocarbons with Pabdeh and Gorpi formation at indentation of Dezfoul and anticlines of Asmari reservoir will be immigrated (Fig 2).
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Fig 2: Structural trends over the major oil and gas fields in the Persian Gulf region (cited from Beydom et al., 1992).
Effect of Diapirism on Reservoir: There are 3 factors that have fundamental role in changes of reservoir and source rock that include: a) Speed for ascending salt dome b) Speed of sediment and c) Speed of subsidence. These factors have very important role on creation of reservoir. In case that speed of ascending will be higher than speed of sediment and speed of subsidence will be steady, growth structure will be achieved and thickness of reservoir at top section of anticline will be lower than limb. Under such condition the volume of reservoir will be steady up to some level that decrease in top of reservoir will be compensated by increasing thickness at limbs. In case that speed of ascending will be more than speed of sediments and speed of subsidence, the environment of sediment will be changed and deep environment will be changed into shallow environment and in continuation it will change into shore region, consequently conditions of reservoir will be improved. Increase in ascending will cause formation of erosion and conglomerate, that its result is low angle slopes (Motiei 1988). Some researchers believe that movement of salts at south of Iran and Persian gulf goes back to Permian period and proportion of changes in speed during sediment may result in creation of growth structures, eliminating floors, changes in sediment and disrupting the structure. Oil structure zone at south of Zagros: The most south fold section of Zagros that is asymmetric with anticline structure is specified alongside of west north and east south and as
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 it was mentioned, it is separated into several sections with different hydrocarbon characteristics (Fig 3).
Fig 3: Main structural subdivisions of the Zagros fold (MacQuillan.1993 & Sherkati. 2004)
Dezful depression: Dezful depression is limited to Kazeroun fault at east and high bending weight at north. Generally Dezful depression is called to a zone in which there is Outcrop Asmari. Dezful depression contains 15km Paleozoic sediments and most of oil fields of Iran are located at this zone. This zone has oil system that is different with other hydrocarbon zones of Iran. At this zone the puberty of source rock and existence of oil and formation of oil traps are important incidents that specify nearly young oil systems which has occurred at 15 million years ago. Prompt accumulation of 1500 to 2000m salt and formation of Gachsaran has occurred during Miocene period and Kazhdomi source rock at Dezful zone has reached to stage of oil bearing. Simultaneous with formation of great folding of Zagros and formation of oil traps, oil is accumulated at descending sections of Dezful. At Gachsaran, Aghajari and Bakhtiyari zone of formation on the contrary of descending at Dezful it has lower thickness and broadness and mountain bearing movements at Miocene and ascending cause to create conditions that oil will be produced and accumulated. After production of oil, it will be in Bangestan group and Pabdeh and Gorpi caprock are cut because of fault and oil is immigrated to Asmari formation. Formation including Sargelo will be possibly created and discharged at Dezful depression before formation of oil traps. Fars Zone: Bounds of this structural zone is west bound of Kazeroun fault, assumed east bound that separates Bandar Abbas from Fars, north bound to trust and south bound is shore line of Persian Gulf. Continuation of Basement and Arabian Platform via Qatar subduct to this zone may create platform conditions from Mesozoic period until now at Fars zone. Existence of salt domes at anticlines of Fars zone is among important characteristics of this zone. Anticlines of this zone have different directions, so that besides direction of Zagros toward east-west, north east the direction of west south can be seen. At Fars zone there are some source rocks that do not have oil bearing ability and the recognized source rock at this zone is Silurian Shale that are introduced as Sarchahan formation. Triassic Kangan formation is lower than carbonates and shale with thin oil layer are formed from organic materials that
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 have potential for bearing hydrocarbon. Reservoirs are gas source that have been dominating since start of Mesozoic period under platform conditions at Fars zone that sedimention the sediments that are poor from organic materials. Characteristics of source rocks are so that large sources of hydrocarbon including Dezful depression are not seen at this zone but this zone is important because of its gas sources. Bandar Abbas Zone: This zone is bounded to Zendan-Minab fault at east, its north is toward some lines are regarded and south bound is toward folding front of Zagros. Most anticlines of this zone are alongside of eastern-western, eastern-north and west-south. Lorestan Zone: This zone from south is toward upper bending, its north and west north border is border of Iran and Iraq and has gas and oil reserves. Abadan Plain: Abadan plin is located at west south of Iran, its north and north west bound is toward folded belt of Zagros and from south it is toward Sosangerd, Abteimour and Mansour anticlines and after passing from Rage-Sefid fields it will enter into Gulf. North section of this line enters into Iraq. Anticlines of this zone lack superficial effect and even some structural continuity is not seen at Asmari. Anticlines trend of Abadan plain ends to north south that are in contradiction with usual direction of Zagros. These anticlines are formed based on movement of basement faults (Motiei 1996). During Alp orogonic the pressure tension may create concentric folding and slip bending. Several studies have shown that base rock and Zagros basin are not same. Magnetie maps of this zone indicate that bound of Karoun fault is from separating place of Fars base rock to Dezful depression base rock (Morris 1977) and Hormoz formation at depreesion zone of Dezful and Lorestan lack development. Exploratory excavations for buildings with infra-camberian salt under surface are only concentrated at Fars zone. Anyway folds at Fars zone because of growth before folding are not similar to concentric Zagros and the thickness of limes will be increased and top anticlines will be thin. We can conclude that uplift movement at Fars zone has two parallel components. First general and regional platform movement of Fars is not seen at maximum amount in Gavbandi and other issue is direction of movement for uplift of salt domes (Motiei 1988). General uplift movement may decrease general sediment layers and finally decrease thickness of source formations that its ability of birth is limited and movement of salt domes will aggravate the phenomena of decreasing thickness. Thus by uplift movement the depth of source rock will be decreased, for example if Kazhdomi formation at Dezful depression will be 3500m it will be located at 2000m of Fars platform. In short it can be said that during different periods of plastic formation and Hormoz salts have movement and anticline buildings are created on the contrary of general process of Zagros. In mountain bearing Alp phase the old anticline buildings are located at bound of Zagros folding and repeatedly folded(like Kangan and Boustaneh). Those anticlines that are more farther will be remained without any change and old rupture with process of north-south and old folding are influenced at Persian Gulf and some process that are different with Zagros process are shown (Fig 4).
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Fig 4: Growth gradual of Zagros belt at Eocene to present.
Conclusion 1- Oil accumulation at south of Zagros do not follow from integrated structural pattern, rather during tectonic evolutions the Paleozoic and Mesozoic because of tension phases of first stage, uplift of salts during Mesozoic and faulting of ancient orogenic and folding because of Alp orogenic and different oil trap will be formed. 2- During Paleozoic with formation of oil source rock in Silurian, first oil is accumulated as zones including Qatar, Gavbandi, north of Bander Abbas and South East of Lorestan and then after Zagros folding it will immigrate to anticlines. 3- Fault oil traps at direction of Dezful, Fars and north depression are mainly related to north section of folding of Zagros and south depression and west and east direction are under influence of tectonic at first period. 4- Generally structures that are created during first, second and third periods at oil traps in south of Iran including anticlines with direction of north west and south east are related to rock faults, north and south processes and oil traps of infra-camberian salt bearing dome and has created compound structures. At the end open and broad anticlines at Zagros trust that has same process with folding of North West and south east and Persian Gulf will be deepen.
References 1- Bahroudi. A, koyi. H.A ;( 2004): Tectono – Sedimentary framework of the Gachsaran Formation in the Zagros Foreland basin, pub. Marin and Petrolem Geology V01.21, P.1295-1310.
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2- Canerot, J, (1990); Diapirism and Geodynamic evolution of The Wrench Fault Margins of the Western pyrenees (France), the Eastern Iberides (Spin) and The Western Atlas (Morocco). Comparison with the Iranian models, Sym. Diapirism, Ministry of Mines and metals. Iran V0l, 2, 81-94. 3-Emami, M, H, (1990); Diapirism and volconicdom occurrence, Sym, Diapirism, Ministry of Mines and Metals, Iran, P.50-160. 4- Ghazban, F, (2007); Petroleum Geology of the Persian Gulf, Tehran University and National Iranian Oil Company, 707 P. 5- Mobosher. K,Babaie .H.A;(2008); Kinematic significance of fold – and fault – related fracture systems In the Zagros mountains , Southern Iran , Pub. Elsevier, Tectonphysics, 451.P, 156-169. 6- Motiei, H (1994); Geology of Iran: Stratigraphy of Zagros, Geological Surrey of Iran, P.497. 7- Murris, R.J, (1981); Middle East Staratigraphic evolution and oil habital geol En mijabouw. V.60, P. 467-486. 8- Safaei,H,(2009) ; The continuation of the Kazerun fault system across the Sanandaj – Sirjan zone(Iran) , pub . Elsevier, Journal of Asian Earth Sciences, rol.35 P 391-400. 9- Shrkati ,S,Letouzey .J (2004) : Variation of structural style and basin evolution in the Central Zagros (Izeh zone and Dezful Embayment) Iran , Elsevier, Marine and petroleum Geology, 21,335- 554.
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Mafic Dykes Of Moyar Shear Zone, North Kerala, India: Emplacement History And Petrogenetic Interpretation Based On Structure, Geochemistry And Magnetic Fabric
P.Pratheesh, V.Prasannakumar and K.R.Praveen
Department of Geology, University of Kerala, Kariavattom Campus, Thriruvananthapuram, Kerala, India - 695 581, Ph: 919847148224, 0471-2308403 E-mail address: [email protected] Received: Wed, Feb 17, 2010:
Abstract Cretaceous mafic dykes in Moyar Shear Zone (MSZ) area, north Kerala, India, provide signatures to probe into the nature of their source and thereby the evolution of the Mesozoic lithospheric mantle beneath the South Indian Granulite Terrain (SIGT). Bulk of the dykes in northern parts of Kerala is broadly in spatial association with the shear system. Mafic dykes striking NE-SW, NW-SE, NNW-SSE and ENE-WSW are widespread in the MSZ and surrounding areas. Width of these dykes varies from 30cm to 5m in general, while dykes wider than 10m also occur. These mafic dykes are olivine/quartz normative tholeiites showing strong correlation to N-Type MORB and within plate basalt affinity. Anisotropy of Magnetic Susceptibility (AMS) data imply normal magnetic fabrics nearly parallel to dyke trends, but with highly variable plunge of magnetic lineation. The compositions of the least altered and least metamorphosed dykes help to define the properties of their mantle source region, as well as the nature of the crust through which the magma traveled. The present contribution on the mafic dyke swarms in Moyar Shear Zone (MSZ) provides new interpretations on the temporal relations of magmatism and tectono-metamorphic evolution of the south Indian high grade terrain.
Keywords: Mafic Dykes, Moyar Shear Zone, Tholeiite, Anisotropy of Magnetic Susceptibility
Introduction Mafic dyke swarms which are widespread in the earth’s crust occurring in a variety of tectonic environments, provide a record of the orientation, kinematics and timing of crustal extension. Emplacement of mafic dykes is strongly associated with the lithospheric and mantle processes like plume events, rifting or coalescence of lithospheric blocks and they are therefore important sources for unraveling internal processes of the Earth and their expression in geodynamics. Dykes of various composition and age have been studied in detail to bring out the crustal evolution history (Delaney 1986; Ernst and Baragar 1992; Ernst et al., 1996). The continental flood basalts and major dyke swarms have their origin also related to the up- rise of hot mantle plumes that may lead to rifting and ultimately to continental break-up (Morgan 1971; Fahrig 1987; LeCheminant and Heaman 1989; Oliveira et al., 1990; Srivastava and Sinha 2004 Mallikharjuna Rao et al., 2005). Mafic nature of dykes is very common and the study of mafic dyke swarms is an important tool in understanding the evolution of the sub-continental lithosphere (Tarney 1992). The Indian shield also hosts mafic dyke swarms having diverse orientations and emplaced in contrasting tectono-metamorphic settings (Murthy 1987; Chandrasekharam 2008; Devaraju 2009).
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Geochemical and tectonic constraints on the emplacement processes of mafic dykes receive renewed interest world over, mainly because dykes represent former conduits of magma from deeper levels of the Earth to the surface. Moreover, dyke swarms give information about tectonic processes that deformed the lithosphere and also the spatio-temporal evidences for super continental reconstructions (Hou et al., 2005; Ray et al., 2008). Most of the geological researches in the South Indian shield are centered on the reworking of the Palaeo- supercontinent Gondwana (Anil Kumar et al., 2001; Joseph et al., 2009). The late Phanerozoic mafic magmatism has received vital attention as a major constraint in deciphering the evolution and reconstruction of Gondwanaland (Srivastava et al., 2000; Saha and Chakraborty 2003). Apart from the Deccan magmatic event, South Indian shield has been punctured also by a large number of mafic dyke swarms with relatively similar origin (Pande et al., 2001). The geologic records provided by these dykes are significant because they provide crucial evidences for magmatic and tectonic events that contribute to the incessant modification of the Southern Granulite Terrain (SGT). However, there is a dearth of data and models on the emplacement process of the dykes in different tectonic settings in South Indian shield and their temporal relations. The present paper embodies the results of the structural, geochemical and AMS analysis of mafic dykes from a shear zone in the SGT.
Geological Background The South Indian Shield is a composite continental segment, formed by the accretion of various crustal blocks during the mid-Archaean to Neoproterozoic (Radhakrishna 1989; Harris et al., 1994; Jayananda and Peucat 1996). This shield comprises relatively low-grade granite-greenstone assemblages (the Sargur group) juxtaposed against high-grade granulites which include the Charnockites and Khondalite group of rocks. Various thermo-tectonic events that operated in the evolution of different units of the shield have left their imprints in terms of deep crustal structure also (Radhakrishna et al., 2003; Chetty et al., 2006; Ajayakumar et al., 2006). SGT is dominated by granulite facies rocks with several regional en echelon Neoproterozoic shear zones dissecting the terrain into different Late Archaean and Proterozoic crustal blocks (Fig.1a). Moyar Shear Zone (MSZ), one of the prominent Proterozoic tectonic zones in the South Indian granulite terrain, provides the challenge of deciphering its kinematic evolution, which in turn can throw light on the crustal evolution. The ESE-WNW trending, 10 km wide and 200 km long Moyar shear zone, usually considered together with NE-SW trending Bhavani shear zone, marks a major crustal discontinuity in the SGT. Swarms of mafic dykes are common along the SGT of Peninsular India and are found intruding all the rock formations ranging from Archaean to early-middle Palaeocene. But the mafic dykes in the MSZ area represent the less extensively studied group of dykes in the SGT. The area selected for detailed analysis is located in and around the western part of the Moyar shear zone. The area is also characterised by the occurrence of several igneous plutons of felsic and mafic composition emplaced within the gneisses and schists. The schist–gneiss complex of the Kannur/Manathavady area extends for about 150 km in a WNW–ESE direction with an approximate width of 10–20 km. The movement picture along the MSZ is interpreted as dextral with possible multiphase reactivation (Naha and Srinivasan 1996; Meissner et al., 2002; Jain et al., 2003). The rocks in the region, except the syenite pluton and
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 gabbro/dolerite, are characterised by polyphase deformation fabrics. The most widely developed planar fabric is a penetrative foliation (S1), subparallel to the rarely preserved primary planar fabric (S0). The foliation, defined mainly by flakes of biotite, crystals of hornblende and flattened and elongated grains of quartz and feldspar, is closely spaced in sheared rocks. Structural analysis indicates formation of folds of different tectonic styles and orientations (Praveen et al., 2009). Precambrian crystalline rocks comprising hornblende- biotite gneiss, mylonitic augen gneiss, garnetiferous hornblende-biotite gneiss and amphibolite are punctured by magmatic activity (Fig.1b). Thin mylonite zones are common in the gneiss. Mylonitic augen gneiss, characterised by feldspar augens, is confined to the northern part. The syenite pluton occurs as an elongate body of about 20 km long and an average width of about 4 km. Gabbroic rocks occur as both massive pluton and dykes and bear considerable amount of differentiation signature. Mafic dyke intrusions cross cut the gneisses and mylonites, the syenitic pluton and the younger leucogabbrros (Fig.2.a & b). Mafic dykes show widespread occurrence with major strike directions of NE-SW, NW-SE, NNW-SSE and ENE-WSW and varying width from 30cm to 5m (Fig.2.c), while dykes wider than 10m also occur. There are small dyke veins less than 30cm occurring in the major dykes as dyke-in-dyke structure (Fig.2.d). The dykes show very sharp contact with the host rocks and do not show any signature of assimilation with them. Petrographically these mafic dykes vary from fine-grained basalt (samples from the dyke margin) to medium-grained dolerite (samples from the central part of the dyke) having very similar chemical compositions, which may be classified as quartz or olivine normative tholeiites.
Methodology The area for detailed study was selected using Survey of India toposheets and satellite images (Landsat image) with the help of GIS and remote sensing methods followed by detailed fieldwork. Samples of all the rock types including the Precambrian crystalline rocks and their sheared equivalents along with the younger acid to basic intrusives were subjected to detailed field and laboratory analyses. Representative samples were analyzed for their major, trace and REE contents using XRF spectrometry and ICPMS methods. Anisotropy of Magnetic Susceptibility (AMS) analysis was also performed on the samples for determining the magnetic fabrics. In the present study, oriented core samples from gneiss, mylonite, syenite and gabbroic/basaltic dykes were used for AMS analysis. Sampling was undertaken following the oriented block method. Each block was cored and cut into specimens of 2.5 cm diameter and 2.2 cm height by retaining their field orientations. A high-sensitivity Spinner version of the latest AGICO (Czech) MFK-1A Kappa bridge anisotropy meter at the Structural Geology Laboratory of the department of Geology, University of Kerala, was used to measure the AMS.
Petrography The general petrographic features of dolerite dykes display chilled margins consisting of an aphanitic groundmass of plagioclase microlite laths, together with granular Fe–Ti oxides and fine clinopyroxene needles aligned parallel to the wall–rock contact. Both melanogabbro and dolerites are composed essentially of plagioclase and clinopyroxene, with hypersthene, olivine, and iron-titanium oxides as the accessories. Plagioclase occurs both as phenocryst and
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 groundmass (typically andesine to labradorite) and shows strong compositional zoning and sericitization. The main mafic mineral is clinopyroxene, which is occasionally titaniferous and occurs as phenocryst clusters, indicating a cumulus phase. The Fe–Ti oxides are mostly magnetite and ilmenite occuring as elongated needles or subhedral grains distributed throughout the rock.
Geochemistry The mafic dykes of MSZ are homogenous in terms of their geochemistry. The samples fall in the sub-alkaline tholeiitic basalt field in major element diagrams, with the composition varying from olivine-normative to quartz-normative. These dykes are distinguishable petrographically from the older dykes of Late Proterozoic age, especially in the degree of alteration, as the older dykes have undergone alteration probably with the multiphase reactivation of MSZ whereas, the group of dykes considered here are less altered. These mafic intrusions show evidences of differentiation from border to the centre in the form of fine grained chilled margin and a coarse grained central zone with occasional presence of pseudotachylite in the border zone. Early petrogenetic models of MSZ dykes recommend a different degree of partial melting of a heterogeneous source (Radhakrishna et al., 1991; Prasannakumar et al., 2008). The basalts that form the mafic dykes of the MSZ area are typically tholeiitic with general enrichment in silica, low K2O, Na2O and MgO with normative quartz/olivine. The concentration of major oxides in these basalt have SiO2 ranging from 45.15 to 49.71 wt %, Al2O3 from 13.32 to 15.97 wt %, CaO from 8.44 to 11.79 wt % and total alkalies (K2O+Na2O) from 2.23 to 4.85 wt % exhibiting its tholeiitic nature in the AFM diagram (Fig.3). Trace element discrimination diagram of MSZ dykes gives a clear picture of the tectono- magmatic settings. The Ti-Zr-Y diagram (Fig.4) is the most effective one to discriminate between within plate basalts, i.e. ocean-island or continental flood basalts and other type basalts. In this diagram MSZ dykes show an affinity towards border zone of MORB and within plate basalts with more affinity towards the latter. The discrimination based on the immobile HFS elements like Th-Hf-Ta (after Wood 1980) of MSZ dykes shows enrichment in elements relatively similar to N-MORB (Fig.5). Primordial mantle-normalized multi-element and chondrite-normalized rare-earth element patterns were also plotted (Fig.6) to examine the supplementary geochemical characteristics of the MSZ dyke samples. From these patterns, it is observed that in all the plotted elements there are alternate enriched and depleted concentrations, both in the primordial mantle and the chondrite values. The large-ion lithophile elements (LILEs) are comparatively more depleted than the high-field strength elements (HFSEs). Overall flat patterns are observed from the LILE to HFSE and prominent negative anomalies are observed for Ba, Nb, Pb, Sr and Yb and positive anomalies for Hf and Zr in the primordial mantle spidergram. Similarly, the slightly enriched light rare-earth elements (LREEs) show strong depletion in Pr and the heavy rare earth elements (HREEs) are depleted in Tb and Yb (Tm), hence the REE pattern shows gentle slope. A less prominent negative Eu anomaly is observed on the REE patterns, probably precluding the possibility of plagioclase fractionation. Comparable geochemical
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 characteristics and similar spider patterns are reported in some part of the Deccan flows (Sheth 2005) and elsewhere (Shukla et al., 2001; Sano et al., 2001).
Magnetic Susceptibility AMS data of dykes show normal magnetic fabrics nearly parallel to their trends, but with variably plunging magnetic lineation. The mean susceptibility (Km) values for dykes show a range with higher and lower limit of 10620 µSI (10-5SI) and 83.43 µSI (10-5SI) respectively. -5 In contrast the mylonite generally shows low Km values, ranging from 1569.533 µSI (10 SI) -5 to 9.453 µSI (10 SI). The high Km in dykes are mainly due to the higher percentage of ferromagnetic (titanomagnetite and clinopyroxene) minerals while the relatively low susceptibility values of mylonite (shear zone) suggest that either the magnetite was destroyed or the composition was different for the opaque minerals in this zone. The distribution of ellipses, at 95% confidence level, for each mean principal susceptibility directions and orientation of magnetic minerals for both dyke and mylonite are presented in figure 7. Figure 7a represents the distribution of the Kmax>Kint>Kmin (K1>K2>K3) axes for the dykes where samples consist of varying amounts of scatter in orientation of tensors and 7b shows the preferred orientation of magnetic fabric which is in WNW-ESE direction. The principal directions for shear zone rocks which show significant clustering and the preferred orientation of mylonites which is more or less E-W and the corresponding macroscopic field foliation are presented in figures 7c and 7d respectively.
Discussion Magnetic fabric data of the rocks are described using the Jelinek (1981) parameters P and T. The magnetic foliation trajectories of the syenite pluton in the MSZ have a sigmoidal shape and curve into the shear zone to the north of the pluton suggesting a dextral sense of shear. Both the magnetic foliation and the measured field foliation have similar orientation, indicating that the magnetic fabrics in the pluton were influenced by the regional tectonic events that controlled fabric development in the region. Systematic analysis of magnetic fabrics of the rocks of the shear zone and the pluton has indicated that the pluton also has been deformed by the last phase of reactivation of the shear zone (Praveen et al., 2009). However, the mafic dykes post date the shear zone and the pluton emplacement. The classical interpretation of dyke emplacement, in general, is that they form perpendicular to the minimum principal stress direction although the flow of magma inside fractures is one issue of basic importance in understanding how continental swarms developed (Raposo, 1995). While magma flow directions are traditionally investigated by petrographic fabrics, oriented vesicles and fingers, grooves or lineations (Wang and Jin 2006), among the AMS data, the Kmax in flows is often considered as parallel to the direction of flow (Khan 1962). Therefore, consistency in alignment of Kmax is a good proxy for determining magmatic flow directions. Among the samples M21a which is located at the centre of the Maximum Concentration
Cluster (MCC) of the dyke swarm shows a confident vertical orientation (0/90) for Kmax. In all other locations, away from the junction of dykes, Kmax shows a near vertical to horizontal orientation. The samples from M3a, M5a, M10 and M69a show near vertical to inclined flow directions while those from locations M2a, P30, P32, T1 and T2 indicate inclined to sub- horizontal flow directions. Inclined flow directions dominate in this swarm because the
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Conclusion The major and trace element geochemistry of the MSZ dykes, mostly basalts, show evidences for fractional crystallization of magma with an enriched mantle source. The mafic dykes of the MSZ area, formed contemporaneous with the Deccan Continental Flood Basalts, show similar geochemical concentrations, which can be considered as an indication of continued plume interaction with the intrusion. On the basis of the geochemical characteristics, it can also be suggested that the low-K mafic dykes encountered in the MSZ area are With-in-Plate continental tholeiitic N-type MORB with considerable amount of fractionation. The magnetic foliation and lineation trajectories in the deformed metamorphic rocks and syenite pluton indicate a dextral sense of shear in agreement with the megascopic and microscopic structural fabrics. However, the magnetic fabrics in mafic dykes and gabbro are of post tectonic character. Thus, while the fabric development in the syenite pluton indicates Pan-African tectonic reactivation of the MSZ, the mafic dykes indicate a late stage crustal dilation due to up-warping of crust caused possibly by a plume activity in the early formed crust of Southern Granulite Terrain. The younger isotopic age of the dolerites of the north Kerala can be interpreted in terms of Reunion mantle plume and consequent rifting which gave rise to the great Deccan basalts. The magmatic emplacements in MSZ are mainly controlled by the reactivated stress and hence the magnetic fabrics of these intrusives are of great tectonic significance in characterizing the South Indian crustal evolution.
Acknowledgement: VPK is thankful to the Department of Science and Technology, Govt. of India, New Delhi, for providing financial assistance through project number ESS/16/284/2006 for the work.
References 1. Ajayakumar, P., Kurian, P.J., Rajendran, S., Radhakrishna, M., Nambiar, C.G. and Mahadevan, T.M., 2006, Heterogeneity in crustal structure across the Southern Granulite Terrain (SGT): Inferences from an analysis of gravity and magnetic fields in the Periyar plateau and the adjoining areas, Gondwana Research, v.10, p.18-28. 2. Anil Kumar, Gopalan, K., Rao, K. R. P. and Nayak, S. S., 2001, Rb–Sr ages of kimberlites and lamproites from Eastern Dharwar Craton, South India, Journal of the Geological Society of India, v.58, p.135–142. 3. Chandrasekharam, D., Melluso, L., Cucciniello, C.,Mathew, B. and Perini, G., 2008, Petrogenesis of E-W Trending Dykes from Kalyadi, Dharwar Craton, Southwestern India, In: R.K. Srivastava, C. Sivaji and N.V. Chalapathi Rao (Eds.), Indian Dykes: Geochemistry, Geophysics and Geochronology, Narosa Publishing House Pvt. Ltd., New Delhi, p.199-214.
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4. Chetty, T. R. K., Fitzsimons, I., Brown, L., Dimri, V. P., and Santosh, M., 2006, Crustal structure and tectonic evolution of the southern granulite terrain, india: Introduction, Gondwana Research, v.10, p.3-5. 5. Delaney, P.T., Pollard, D.D., Ziony, J. and Mckee, E.H., 1986, Field relations between dikes and joints: emplacement processes and paleostress analysis, Journal of Geophysical Research, v. 91, p.4920–4938. 6. Devaraju,T.C., Viljoen, R. P. , Sawkar, R. H. and Sudhakara, T. L., 2009, Mafic and ultramafic magmatism and associated mineralization in the Dharwar craton, southern India, Journal of the Geological Society of India, v.73, p.73-100. 7. Ernst, R.E. and Baragar, W.R.A., 1992, Evidence from magnetic fabric for the flow pattern of magma in the Mackenzie giant radiating dyke swarm, Nature 356, p.511–513. 8. Ernst, R.E., Buchan, K.L, West, T.D and Palmer, H.C., 1996, Diabase (dolerite) dyke swarms of the world: first edition, Geological Survey of Canada Open File 3241. 9. Fahrig, W.F., 1987, The tectonic settings of continental mafic dyke swarms: failed arm and early passive margin, In: Mafic Dyke Swarms (eds) H C Halls and W F Fahrig Canada: Geol. Assoc. Spl. Pap. 34, p.331–348. 10. Harris, N.B.W., Santosh, M. and Taylor, P.N., 1994, Crustal evolution in South India: constraints from Nd isotopes, J. Geol., v.102, p.139-150. 11. Hou, G.T., Li, J.H., Jin, A.W., and Qian, X.L., 2005, The Precambrian basic dyke swarms in the western Shandong Province, Acta Geologica Sinica, v.79, p.190-199. 12. Jain, A.K., Sandeep Singh and Manickvasagam, R.M., 2003, Intra Continental Shear Zones in the Southern Granulite Terrain: Their kinematics and Evolution, In: Ramakrishnan, M., (Ed.) Geological Society of India, Memoir. 50, p.253–255. 13. Jayananda, M. and Peucat, J.J., 1996, Geochronological framework of Southern India, Gond. Res. Group Mem. 3, p. 53-75. 14. Jelinek, V., 1981, Characterization of magnetic fabrics of rocks, Tectonophysics,v. 79,p 63-67. 15. Joseph, M., Perrin,M., Radhakrishna,T., Camps, P., Balasubramonium, G. and Punoose J., 2009, Mafic Dykes from the Southwest Coast of India: Palaeomagnetism and tectonic implications, Geophysical Research Abstracts, EGU General Assembly 2009, v.11. 16. Khan, M. A., 1962, Anisotropy of magnetic susceptibility of some igneous and metamorphic rocks, Journal of Geophysical Research,v. 55,p 2873-2885 17. Kuno, H., 1968, Differentiation of basalt magmas. In: Hess, H. H. and Poldervaart, A. A. (eds) Basalts: The Poldervaart Treatise on Rocks of Basaltic Composition, 2. New York: Interscience, p. 623–688. 18. LeCheminant, A.N. and Heaman, L.M., 1989, Mackenzie igneous events, Canada, middle Proterozoic hotspot magmatism associated with ocean opening, Earth Planet. Sci. Lett.,v.96, p.38– 48 19. Mallikharjuna Rao, J., Poornachandra Rao, G. V. S., Widdowson, M., and Kelley, S. P., 2005, Evolution of Proterozoic mafic dyke swarms of the Bundelkhand Granite Massif, Central India, In Curr. Sci., v. 88, No. 3, p.502–506.
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20. McDonough, W. F. and Sun, S.-S., 1995, The composition of the Earth. Chemical Geology, v.120, p.223-254. 21. Meissner, B., Deters, P., Srikantappa, C. and Kohler, H., 2002, Geochronological evolution of the Moyar, Bhavani and Palghat shear zones of southern India: implications for east Gondwana correlations, Precamb. Res., v. 114, p. 149-175. 22. Morgan, W. J., 1971, Convection plumes in the lower mantle, Nature 230, p.42–43. 23. Murthy, N.G.K., 1987, Mafic dyke swarms of the Indian Shield, In: Mafic Dyke Swarms (eds) H C Halls and W F Fahrig (Canada: Geol. Assoc.) Spl. Pap. 34, p. 393–400 24. Naha, K. and Srinivasan, R., 1996, Nature of the Moyar and Bhavani shear zones, with a note on its implication on the tectonics of the southern Indian Precambrian shield, Proc. Ind. Acad. Sci. (Earth and Planet. Sci), v.105, p.143-189. 25. Nair, M.M., Vidhyadharan, K.T., Pawar, S.D., Sukumaran, P.V. and Murthy Y.G.K., 1976, The structural and stratigraphic relationship of the schistose rocks and associated igneous rocks of the Tellicherry–Manantoddy area, Cannanore district, Kerala India Mineral, v.16, p.89–100. 26. Oliveira, E. P., Tarney, J. and Joao, X.. J., 1990, Geochemistry of Mesozoic Amapa and Jari dyke swarms, northern Brazil: plume-related magmatism during the opening of the central Atlantic, In: Mafic Dykes and Emplacement Mechanism (eds) A J Parker, P C Rickwood and D H Tucker (Rotterdam: A A Blakema), p. 173–183. 27. Pande, K., Sheth, H. C. and Bhutani, R., 2001, 40Ar/39Ar age of the St. Mary’s Islands volcanics, southern India: record of India–Madagascar break-up on the Indian subcontinent, Earth and PlanetaryScience Letters, v.193, p.39–46. 28. Pearce, J.A. and Cann, J.R., 1973, Tectonic setting of basic volcanic rocks determined using trace element analyses, Earth Planet. Sci. Lett., v.19, p.290–300. 29. Prasannakumar, V., Pratheesh, P. and Praveen, K.R., 2008, Geochemical constraints and temporal evolution of dykes in the Moyar-Bhavani shear zone, Kerala, South India, 33rd International Geological Congress, Oslo. 30. Praveen, K.R., Prasannakumar, V. and Manish, A. Mamtani, 2009, Time Relationship Between Regional Deformation and Fabric Development in the Peralimala Pluton, South India –Inferences from Magnetic Fabric, Geol. Soc. India., v.73, p.803-812. 31. Radhakrishna, B.P., 1989, Suspect tectono-stratigraphic terrane elements in the Indian subcontinent, J. Geol. Soc. India, v.34, p.1–24. 32. Radhakrishna, M., Kurian, P.J., Nambiar, C.G. and Murty, B.V.S., 2003, Nature of the crust below the Southern Granulite Terrain (SGT) of Peninsular India across the Bavali shear zone based on analysis of gravity data, Precambrian Res., v.124, p.21–40. 33. Radhakrishna, M., Kurian, P.J., Nambiar, C.G. and Murty, B.V.S., 2003, Nature of the crust below the Southern Granulite Terrain (SGT) of Peninsular India across the Bavali shear zone based on analysis of gravity data, Precambrian Res, v.124, p.21–40. 34. Radhakrishna, T., Balasubramonian, G., Mathew Joseph and Krishnendu, N. R., 2004, Mantle Processes and Geodynamics: Inferences from Mafic Dykes of South India, Earth System Science and Natural Resources Management, CESS Silver Jubilee Compendium, p.3-25.
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35. Radhakrishna, T., Gopakumar, K., Murali, A.V. and Mitchell, J.G., 1991, Geochemistry and petrogenesis of Proterozoic mafic dykes in north Kerala, southwestern Indian shield- primary results, Precambrian Res., v.49, p.235-244. 36. Raposo, M.I.B. and Ernesto, M., 1995, Anisotropy of magnetic susceptibility in the Ponta Grossa dyke swarm (Brazil) and its relationship with magma flow direction, Physics of the Earth and Planetary Interiors, v.87, p.183-196. 37. Ray, R., Shukla, A.D., Sheth, H.C., Ray, J.S., Duraiswami, R.A., Vanderkluysen,L., Rautela, C.M. and Mallik, J., 2008, Highly heterogeneous Precambrian basement under the central Deccan Traps, India:direct evidence from xenoliths in dykes, Gond Res, v.13, p.275–285. 38. Saha, D. and Chakraborty, S., 2003, Deformation pattern in the Kurnool and Nallamalai groups in the northeastern part (Palnad area) of the Cuddapah basin, South India and its implication on Rodinia/Gondwana, tectonics, v.6, p.573-584. 39. Sano, T., Fujii, T., Deshmukh, S. S., Fukuoka, T. and Aramaki, S., 2001, Differentiation Processes of Deccan Trap Basalts: Contribution from Geochemistry and Experimental Petrology, Journal of Petrology, v.42, p. 2175-2195. 40. Sheth, H.C., 2005, Were the Deccan flood basalts derived in part from ancient oceanic crust within the Indian continental lithosphere?, Gondwana Research, v. 8, p. 109-127. 41. Shukla, D., Bhandari, N., Kusumgar, S., Shukla, P. N, Ghevariya, Z. G.,. Gopalan, K and Balaram, V., 2001, Geochemistry and magnetostratigraphy of deccan flows at Anjar, Kutch, Journal of Earth System Science, v.110, p 111-132. 42. Srivastava R.K. and Sinha A.K., 2004, Geochemistry and petrogenesis of early Cretaceous sub- alkaline mafic dykes from Swangkre-Rongmil,East Garo Hills, Shillong plateau, northeast India.Proc. Indian Acad. Sci. (Earth Planet. Sci.), v. 113, No. 4, p. 683–697. 43. Srivastava, R. K., Singh, R.K. and Verma, R ,2004, Juxtaposition of India and Antarctica During the Precambrian: Inferences from Geochemistry of Mafic Dykes, Gondwana Research,v.3, p.227- 234. 44. Srivastava, R. K., Singh, R. K. and Verma, R., 2000, Juxtaposition of India and Antarctica during the Precambrian: inferences from geochemistry of mafic dykes, Gondwana Research, v.3, p.227- 234. 45. Sun, S.-S. and McDonough, W.F., 1989, Chemical and isotopic systematics of oceanic basalts: Implications for mantle composition and processes, Geol. Soc. London, Spec. Publ., v.42, p.313- 345. 46. Tarney J., 1992, Geochemistry and significance of mafic dyke swarms in the Proterozoic, In: Proterozoic Crustal Evolution (ed) K.C. Condie Elsevier, New York, p.151–179. 47. Wang, C. and Jin, A., 2006, Mechanism of the Mafic Dyke Swarms Emplacement in the Eastern Block of the North China Craton. In: (Ed.) Guiting Hou, and Jianghai Li, Precambrian Geology of the North China Craton, Journal of the Virtual Explorer, Electronic Edition, ISSN 1441-8142, v.24, paper 3. 48. Wood D.A., 1980, The application of a Th-Hf-Ta diagram to the problems of tectonomagmatic classification and establishing the nature of crustal contamination of basaltic lavas of the British Tertiary volcanic province, Earth and Planetary Sciences., v.50, p.151–162.
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Fig.1. (a) Tectonic map of South India with disposition of shear zones (b) Geological map of the Study area.
Fig. 2. MSZ dykes showing crosscutting relationship with (a) syenitic rocks (b) leucogabbrro (c) dykes with width varying from few centimeters to few meters (d) dyke in dyke intrusion.
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Fig. 3. AFM diagram (after Kuno 1968) of MSZ dykes showing tholeiitic affinity.
Fig. 4. Ti-Zr-Y discrimination diagram for basalts (after Pearce and Cann 1973).MSZ dykes fall in the margin of MORB and within plate basalt (WPB), mostly in WPB.
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Fig. 5. Th-Hf-Ta discrimination diagram for basalts (after Wood, 1980), in which the MSZ dykes fall in the field of N-Type MORB.
Fig. 6. (a) Primordial mantle-normalized spider diagrams for MSZ dykes (after McDonough & Sun 1995) showing low/depletion in Ba, Pb and Yb and peaks in Hf and Zr, indicating fractionation (b) Chondrite normalized REE pattern (after Sun & McDonough 1989) for Moyar dykes, indicating relative enrichment of LREE with local depletion of HREE and a negative Eu anomaly.
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Fig. 7. Distribution of 95% confidence ellipses for each of the mean principal susceptibility directions and orientation of magnetic minerals for both dyke and mylonite. (a) distribution of Kmax>Kint>Kmin (K1>K2>K3) axis for the dykes, all dyke samples consist of varying amounts of scatter in orientation of tensors (b) preferred orientation of magnetic fabric which is WNW-ESE. (c) principal directions for shear zone rocks (d) preferred orientation of mylonite fabric which is more or less E-W and in agreement with the macroscopic field foliation.
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Fig. 8. Spatial distribution of magnetic foliation and Kmax in the MSZ dykes.
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Natural Gas Management of Bangladesh: Future Powerhouse of South-East Asia?
AKM Eahsanul Haque
University of Dhaka
Abstract Already Bangladesh has proven to be a natural gas giant in the region and to the energy producing community of the world. The Bangladesh sub-surface is according to the present knowledge mainly gas prone, with some potential for future oil discoveries. Within the 1,44,549 sq km of its political territory, Bangladesh has 23 gas fields with some more fields yet to be declared officially as gas fields. Total of 67 exploratory wells including 13 in offshore area have been drilled so far in Bangladesh. The success ratio till now is very encouraging 1:3. In the present energy policy, the present onshore and offshore area of the country has been divided in 23 exploration blocks. Under national and international seismic surveys already three new gas fields have been discovered with high reserve of gas and condensate. The energy management of the country is thus become most vital for efficient use of its energy resources and the present energy management has been tested to be fruitful for future exploration, production, demand and supply. This sector therefore merits the more attention and importance in the planning of the country compared to any other sector. Under the present energy policy, the gas demand and supply forecast for the short, medium and long-term scenarios playing the “key role” in development of a gas field. Short and medium term gas demand would be normally met from gas fields close to the trunk lines that would call for a minimum project cost and time, while the long term customers would require dedicated large volume of reserves, field production facilities and transmission pipeline. Development plan of a gas field is based on the initial evaluation of field reserves, well deliverabilities, reservoir fluid and reservoir driver. The essence of a gas field development and productions is to ensure maximizing recovery in a cost effective manner. That is why each field or reservoir is handled in an “asset management” approach during its life cycle right from discovery till its abandonment. In this southeast region, Bangladesh is comparatively in suitable position in terms of natural gas discovery and production that is powerful enough to lead a nation to gain economic boost. From the middle-east energy scenario, Bangladesh is determined to take important lessons to learn continuing its search for energy and to utilize the vast amount of energy resources that it has in a planned and systematic way. This paper will show the ways to develop long term plans for effective management of the present and incoming gas fields of Bangladesh and will emphasize on the techniques to follow for proper development with time.
Introduction Bangladesh is a country of opportunities, and the petroleum industry is one of the major sectors. Stable political climate, countrywide well established infrastructure, advanced telecommunication facilities, growing middle-class with substantial economic capacity and fast growing need for power have attracted International Oil Companies (IOC) to invest in the petroleum sector of Bangladesh. Bangladesh constitutes the largest deltaic basins of the world with up to 20,000 m of sediments deposited and has proven its ability to generate significant hydrocarbon resources through the discoveries of 23 gas fields Fig.1 and 1 minor oil field.
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Since 1984 several international oil companies were active in both onshore and offshore areas. In addition to the state owned companies, Shell Bangladesh Exploration and Development B.V. (SBED) is producing gas from the offshore Sangu Gas Field. Occidental of Bangladesh (Oxy), a subsidiary of Unocol Corporation, is producing the Jalabad Gas Field. During the 2000-01 fiscal years SBED's average production was 129 Mmcfd and for Oxy the average production rate during the same year was 83 Mmcfd. In Bangladesh there is currently a well- developed system of pipelines for transport of gas in the northeastern and eastern part of the country. The total transport of gas through the country's pipeline system was in one year approximately 332 Bcf. The block system was firstly introduced in Bangladesh in 1974 when six offshore blocks were awarded to six companies. They acquired 31,000 km (approx.) of seismic and drilled 7 wells. At present 9 National and International Oil Companies are working efficiently in the offshore blocks of Bangladesh.
Exploration History The exploration activity of petroleum products is over 100 years old in Bangladesh first exploration activity started with some topographic maps of Chittagong Hill Tracts and some simplified surveys were done. The first exploration started from 1914 to 1933 by Burma Oil Company (BOC). The second of phase petroleum exploration began after partition of Indian subcontinent. Three international oil companies and the state owned oil company (OGDC) were active in different part of the country. During phase II, Shell Oil discovered the most successful drilling operation; Rashidpur, Kailashtila, Titas, Habigonj and Bakhrabad gas fields were discovered. After the independence of Bangladesh in 1971, the petroleum exploration gathered pace. In this period, the first offshore gas field, Kutubdia was discovered. The country was first divided into 23 major blocks including offshore area. During 1995-2000, the foreign companies Fig.2 drilled 10 exploratory wells and discovered 1 offshore gas field (Sangu in 1996 by Cairns Energy) and two onshore gas fields (Bibyana in 1997 and Moulovibazar in 1998). After some more successful drilling by Tullow Oil, Bangura gas field was discovered in 2004. BAPEX, (Petrobangla exploratory subsidiary) drilled two wells and discovered two gas fields, i.e. Shahbazpur in 1995 and Saldanadi in 1996. BAPEX drilled one well in late 2004 and announced discovery of Srikail gas field in Comilla in January 2005. It is very interesting data that the national oil companies of Bangladesh have a discovery success rate over 80% Fig.3 compared to the multinational oil companies. Digital multi fold seismic data acquisition started in 1977, when Prakla was engaged under the German technical Assistance Program. In 1978 Petrobangla started acquiring multi fold analog seismic data, Fig.4 but in 1979 it moved into the digital domain. During 1986-87 Shell recorded over 1,500 km of multi fold data and these are available in BAPEX Data Center.
Geological Development The geological history of Bengal Basin is related to the rifting and separation of the Indian Plate from the Gondwanaland. The separation of east Gondwanaland, comprising India,
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Australia and Antarctica, took place in three major stages. During Paleocene/Eocene the present day Bengal Basin was part of a major basin streching from the Shan Massif in the east to the Indian Craton in the west. The initial collision with the Burmese Plate, probably during Late Eocene, resulted in rising of an Eocene island arc. This event created two basins; Errawady Basin in the east and Bengal Basin in the west.During Late Oligocene/Early Miocene the Bengal and Brrawady basins were finally separated. From then Fig.5 onward due to subduction of the Indian Plate beneath the Burmese Plate and anticlockwise rotation, the basin started closing in the northeast and gradually turned into a remnant ocean basin. The presence of source rocks is very crucial for any petroleum system, and in Bangladesh source rocks are present in Late Cretaceous through to Miocene strata. The discovery of the many gas fields in Bangladesh, testing of oil in a few, together with geochemical analysis of rocks, oil, condensate and gas, indicate that the sedimentary basin has passed through at least two phases of oil and gas generation. However, in two wells drilled in West Bengal just west of Meherpur-Chuadanga area of Bangladesh, the TOC content of Cretaceous sediments was 1.04-1.5%. The Cherra (Jalangi) Formation, deposited during Paleocene to Early Eocene, is considered to be a good source rock for the western region. However, in the vicinity of the Singra-Kutchma-Bogra, the unit has a good source rock potential, but is immature. TOC varies between 1 and 10%, and seismic data indicate that the sequence gradually dips down towards southwest, where it is expected to be mature and may generate hydrocarbon. TOC is 1-5%. The Miocene Bhuban Shale is widely developed over the Bengal Basin, including the Eastern Foldbelt, and is probably the youngest source rock unit capable of generating gas. The sequence is poor to lean in terms of source rock potential, with TOC values averaging from 0.2-0.7%. Proven reservoir rocks are known from wells drilled in the eastern folded belt of Bangladesh and they are all sandstone (clastic) reservoirs. The majority of these reservoir sandstones are Middle to Late Miocene of age, with porosities ranging from 15-33% and with permeability in the order between 20-330 md. In one gas field the permeability range between 1 and 4 dercy. These reservoir sandstones were deposited under generally coastal plain to shallow marine conditions, forming fluvial and tidal channel sandstones, tidal flat sands and sand bars, mostly wave dominated shore face deposits. In the eastern part the folded belt, upper part of the Upper Miocene sequence shows sandstone unit which is gas bearing in several fields. The oldest reservoir rocks that can be considered prospective in Bangladesh are the Gondwana sandstones of Jurassic to Carboniferous age. The deposits also comprise subordinate clays and coal seams, the thickness of individual seams range up to 45 m or more. The Lower Gondwana succession was deposited in fluvio-deltaic environment and contains a high proportion of sandstones. The Upper Gondwana sandstones, deposited within a deltaic to shallow marine environment, can be regarded as a prospective reservoir rock.
Fields and Discoveries At present 23 gas fields and 1 minor oil field have been discovered in Bangladesh of which 16 have been developed and set into production. The list below shows field, company and year of discovery of currently producing fields.
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Sylhet (PPL,1955) Rashidpur (Shell,1960) Titas (Shell,1962) Kailas Tila (Shell, 1962) Habiganj (Shell,1963) Bakhrabad (Shell,1969) Beani Bazar (Petrobangla,1981) Jalalabad (Scimitar,1989) Narsingdi (Petrobangla,1990) Meghna (Petrobangla,1990) Salda Nadi (BAPEX,1996) Sangu (Cairn,1996;offshore) Bibiyana (Oxy/Unocal,1998)
In addition to the producing fields above, another seven are discoveries not yet in production, and these are:
Semutang (OGDC,1969) Kutubdia (Union,1977;offshore) Begumganj (Petrobangla,1977) Fenchuganj (Petrobangla,1988) Shahbazpur (BAPEX,1995) Moulovibazar (Oxy/Unocal,1997)
The suspended fields are:
Chatak (PPL,1959) Kamta (Petrobangla,1981) Feni (Petrobangla,1981) At present gas is being produced from 13 fields in Bangladesh: Titas, Sylhet, Rashidpur, Kailas Tila, Habiganj, Bakhrabad, Beani Bazar, Bibiyana, Jalalabad, Narsingdi, Meghna, Salda Nadi and Sangu. Three national and two international companies are now operating the fields: Bangladesh Gas Fields Company Ltd.,Sylhet Gas Fields Ltd., Bangladesh Petroleum Exploration and Production Company Ltd., Occidental of Bangladesh and Shell Bangladesh Exploration and Development B.V. The current daily average gas production is approximately 1245 Mmcf. All the gas fields produce some some condensate. The condensate production ratio varies from field to field within a range of 0.1-3.9bbl/mmcf except for Beani Bazar, Kailas Tila and Jalalabad Gas Fields. During 2000-01 Kailas Tila Gas Field produced 557,310 bbl condensate. The condensate/gas ratio is about 17.8 bbl/mmcf. Jalalabad is also rich in condensate and it produces at a rate of 12.3 bbl/mmcf. During 2000-01 condensate production was 337bbl/day or 1.231 mmbbl. Condensate reserves of the country were estimated 57 mmbl.
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The gas production in Bangladesh has been increased significantly over the decades, driven by the domestic demand for production of electric power and further the needs of the fertilizer industry. The power industry is currently the major consumer, and the burning of natural gas produces 90% (approx.) of all electric power in Bangladesh. Gas consumption in other major industries; e.g. Cement, paper, tea states, pharmaceuticals, steel, brick fields are also steadily increasing, parallel to a distinct increase in the use of natural gas as a domestic fuel. At present Fig.6 power industry consumes 48%, fertilizer 27%, other industries 13%, domestic fuel 10% and other system loss 2%. The production of natural gas in Bangladesh commenced in 1961, when Chatak Field started production to supply gas to Chatak Cement Factory. This was followed by similar gas production from Sylhet Field in 1962, supplying Fenchuganj Fertilizer Factory with natural gas. In 1968 Titas Gas Gield started production, supplying gas to the Siddhirganj Power Station. During these years the gas production has increased in manifolds; from 6 Bcf till 1970 to 4.3 Tcf till 2001. Bibyana gas Field is the latest to join in the production of gas fro discovered field. It is now producing at a rate of 220 Mmcf natural gas daily and expected to be doubled the production very soon.
Natural Gas Reserves Natural gas reserve has been estimated by various companies or consultants for most of the gas fields of Bangladesh over the last two and half decades. Generally each field is evaluated upon its discovery and/or initial appraisal works. The working groups went through the SPE/WPC/AAPG adapted system as well as the CCOP system and prepared a proposal for Resources Classification System in Bangladesh. Of these works the IKM (Canada) study which was conducted during 1989-1992 constitutes the most comprehensive set of work. Natural gas is presently playing the most vital role in the economic development of the country. The country so far has discovered 24 gas fields including two offshore ones. The total initial reserve in the 22 fields has been estimated almost 17 Tcf. The reserves of two gas fields discovered in the late 2004-early 2005 respectively are yet to be estimated (expected to be in the range of 0.2 Tcf –0.5 Tcf each). Cumulative gas produced till December 2003 is about 5.3 Tcf leaving a remaining gas reserve of 11.3 Tcf in the 22 gas fields. Because of the increasing use of natural gas, the dependence on oil for electricity generation and other sectors has declined drastically over the past decade that saves a large amount of foreign exchange. During FY 2003, the 3.5 million ton oil import bill was about $600 million (Tk. 3600 crore). In this period consumption of gas was about 9.5 million-ton oil equivalent. If natural gas were not discovered, the country’s oil import bill would have increased by another $1600 million (Tk. 9450 crore). For the high potential of reserve yet to be discovered in the subsurface in Bangladesh, it has attracted several foreign investors in the hydrocarbon exploration sector and a number of International Oil Companies (IOCs) are active at present. These companies along with the national petroleum exploration company tend to express a seeming overoptimistic impression that Bangladesh is sitting on a huge natural gas reserve. For this the image of Bangladesh to the energy community of the world is changing from being a nation of too little wealth to one of the prospective natural gas province.
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Gas reserves: Over the last few years, updating of the gas reserve of the country have been undertaken by more than one organization or government appointed body. The government appointed committee of experts, the “National Committee for Gas Demand Projection and Determination of gas Reserve and Resource Potential in Bangladesh”, has done one of the comprehensive compilations of the up to date reserve data. In June 2002 the committee concluded its report and declared that the initial reserve (proved + probable) in 22 gas fields of the country is between 16.64 Tcf and 20.42 Tcf. The gas reserve of Bangladesh by gas fields is shown in this table, which is 16.64 Tcf (proved + probable). By December 2003, after consuming 5.31 Tcf of gas, the remaining gas reserve of the country, according to the estimate, stands at about 11.33 Tcf. A second estimate shows an initial reserve of 20.15 Tcf. By December 2003, after consuming 5.31 Tcf of gas, the remaining gas reserve of the country, according to the estimate, stands at about 14.84 Tcf. The gas fields of Bangladesh may arbitrarily be divided into three size groups. Of the twenty four gas fields fields of Bangladesh, five are large fields (Titas, Habigonj, Kailashtila, Rashidpur and Bibiyana) each having initial reserve in excess of 1 Tcf gas and these, cumulatively contain about 68% of the total initial gas reserve of the country. According to the international classification of gas field by size (tiratsoo 1979) the Titas gas field falls in the ‘Giant’ class (at least 3.5 Tcf gas reserve by definition). Bangladesh has a proved gas rich province in the eastern part. How much gas still remains undiscovered, has been a subject of much speculation and there have been several Fig.7 studies by oil companies to suggest that. Among those studies two of the recent and widely publicized ones are: I) USGS-Petrobangla joint assessment of undiscovered gas resource and II) Hydrocarbon Unit-Norway Petroleum Directorate (HCU-NPD) joint assessment of undiscovered gas resources of the country. I) Undiscovered resource estimate by USGS-Petrobangla: In 2000, an USGS-Petrobangla joint team of geoscientists conducted a 21 month long study to assess the undiscovered potential gas reserve. The report submitted by the team stated that Bangladesh has 95% possibility of finding 8.4 Tcf of yet undiscovered gas reserve. Of the above total undiscovered gas, 6.0 Tcf is assigned to the onshore area and about 2.4 Tcf is assigned to the offshore. The study also suggests a mean (50%) probability of finding 32.1 Tcf of yet undiscovered gas resource in the country. II) Undiscovered resource estimate by HCU-NPD: In 2001, a join team of geoscientists from Hydrocarbon Unit (HCU) of Bangladesh and Norway Petroleum Directorate (NPD) conducted a gas assessment job on Bangladesh. Based on their study, the team suggested that the total undiscovered recoverable gas resource of the country at 90% possibility is 18.5 Tcf of which 10.6 Tcf is assigned to hypothetical estimate and 7.8 Tcf is assigned to speculative estimate. The study also suggested a mean (50%) possibility of finding 41.6 Tcf undiscovered gas resource of which hypothetical estimate on mapped prospects include 16.9 Tcf and speculative estimate of unmapped prospects include 24.7 Tcf.
Gas Sector Demand and Supply Forecast Demand projection is usually based on certain assumptions on the variables related to that projection which requires developing a statistical model based on demographic data. National
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Energy Policy of Bangladesh has forecasted energy demand for twenty-five years from 1996- 2020. In Bangladesh primary commercial energy provides approximately 35% of the total energy need. Natural gas accounts for 65% of commercial energy use (excluding biomass) and about 90% of electricity generation. Total consumption of gas in 2000 was 332 Bcf (2.8 Mcf/person/yr, total population 126 million). Estimated consumption of different type of petroleum products in 2000 was about 3.3 million tons (25.8 kg/person/yr). Estimated total consumption of electricity was approximately 16549 Gwh (130 Kwh/person/yr). This may be compared with the projection made Fig.8 by National Energy Policy (NEP), 1995. Titas Gas T & D Co. Ltd. is the largest marketing company operating in the districts of greater Dhaka, Mymensingh and part of Brahmanbaria. Till June 2000 about 2.7 Tcf gas was consumed in TFA, which is 71% of country's total gas consumption. Ashuganj, Ghorasal, Haripur, Haripur barge-mounted, Siddhirganj and Mymensingh RPCL's power stations, and ZFCL, UFFL, PUFF and JFCL fertilizer plants Fig.9 are the major consumers under TFA. There are over 0.74% million customers of various categories under TFA currently consuming about 755 Mmcfd which is about 68% of total national demand. Moreover new IPPs such as AES Haripur 360 MW, AES Meghnaghat 2X450 MW (1st and 2nd phases), Siddhirganj 210 MW and 100 MW, Tongi 80 MW and new peaking duty power plants are the most likely power plants coming on stream in the short run. Bakhrabad Gas Systems Ltd. is the second largest company covering the districts of greater Comilla, Noakhali and Chittagong. It supplies gas to Sikalbaha and Rauzan Power Plants, CUFL and KAFCO fertilizer factories, Karnaphuli Paper Mills, Usmaina Glass Sheet Industry, TSP, Chittagong Steel Mill and Eastern Refinery. This company shares about 17% of total consumption of the country. Currently it supplies about 225 Mmcfd gas to over 0.2 million customers. Gas consumption in present Jalalabad Gas T & D Systems area began in the early 1960s by supplying gas to Chatak Cement Factory and Natural Gas Fertilizer Factory (NGFF), Fenchuganj, JGTDSL covers the districts under greater Sylhet, Fenchuganj, Kumergaon, and Shahbazpur power stations NGFF, Chatak Cement Factory, Sylhet Pulp and Paper Mill and significant numbers of tea-estates are the major customers under JGTDSL. Till June 2000 a total of 0.43 Tcf gas was consumed in this franchise area which is about 12% of the country's total consumption. Present daily requirement of gas is about 75 Mmcfd and total customer numbers are about 65 thousand. Shahjalal fertilizer factory, which will replace NGFF by 2004, Lafarge-Surma Cement by 2003 and new peaking duty power plants will be the most likely new customers in short term. The newest marketing company is WESGAS which began gas supply to the west of the river Jamuna and in late 1999. WESGAS's daily current gas requirement is 45 Mmcf and total number of customers 835. It will be responsible to cater gas to the northwestern districts. Major customers are BPDB's Baghabari 71 MW and Westmont's Baghabari Barge Mounted 90 MW powr plants. New plants such as BPDB's 100 MW, IPP's 170 MW, upcoming fertilizer factory at Sirajganj and Iswardi Export Processing Zone would be the major consumers of natural gas in the short run. Gas Sector Development Strategy Development of a gas field encompasses a wide variety of activities. Thses include geological and engineering characteristics of the field, estimates of its proved gas reserves and upside
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 potential, prospect of liquids recovery etc. This also takes in to account well planning, surface facilities and markets, compatibility with conservation and environmental regulations, and of course an economic evaluation. Development of a gas field is primarily guided by the gas demand and supply forecast for the short, medium and long term scenerios. Short and medium term gas demand would be normally met from gas fields colse to the trunk lines that would call for a minimum project cost and time, while the long term customers would require dedicated larger volume of reserves, field production facilities and transmission pipeline. Development plan of a gas field is based on the initial evaluation of field reserves, well deliverabilities, reservoir fluid and reservoir driver. This is why each gas field or reservoir should be handled in an “asset management” approach during its life cycle right from the discovery till its abandonment. A field development plan should be taken up covering,among others, Reservoir development plan, reserves and production profiles; well and drilling engineering plan; production and process facilities plan; hook-up and commissioning plan; project execution plan; reservoir management plan; operation and maintenance plan; field abandonment plan and development budget and economic analysis. Infrastructure development is an integral part of the sector. This involves the pipeline network, the associated installations and a proper monitoring and safety system. The existing pipeline system of Bangladesh is adequate for the national demand for only the current situation. This network requires expansion and upgradation to ensure that supply can be matched with the demand side. The current pipeline network of Bangladesh needs extensive modifications which needs national and foreign investments. The pipeline needs massive expansion. On the demand side new areas need to be connected to provide economic energy to the industry, on the supply side additional pipelines are necessary to carry extra gas as well as to have gas supply across Jamuna Bridge. A major transmission network supplemented by an extensive distribution system will be required to bring this region at par with the eastern region in respect to across to natural gas. Distribution lines in the main metropolitan and industrial areas should be replaced with higher capacity network to provide security of supply and to arrest methane emission. Where possible, all major metropolitan and industrial load centers should be brought under a distribution ring main with radial supply mains to ensure normal pressure. The sector plan for the development of oil and gas industry is conveniently laid down in the five-year plans. Since the sector was opened to the private sector, such plan has become more conceptual than functional. However, the sectoral objectives and their implementation strategies have remained more or less unaffected. The mainstays of the objectives and policy supports are as below: # To substitute imported oil by indigenous fuel, mainly natural gas, to the extent possible and feasible; # To meet most part of increased demand for commercial energy through the development of indigenous gas; # To make a balanced development of the different components of gas activities, namely exploration, transmission and distribution etc;
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# To involve private sector in oil and gas development activates, particularly in exploration under product sharing contract (PSC), transportation and sale of gas based liquids LPG, condensate (diesel/motor spirit/kerosene) etc; # To build a national gas grid for equitable regional distribution; # To conserve energy resources and help maintain the ecological balance; # To conduct geological and geophysical surveys in order to explore and discover new sources of indigenous energy resources; # To strengthen research and development in the energy sector.
Gas Sector Marketing Strategy It has been opined by the IOCs and some agencies that given the location, volume, price and situation involved, the best option for Bangladesh gas is pipeline export. This again is based mainly on the end user parameters without addressing the gas price and economics thereof. The logic is that LNG is not viable due to short distance and stiff competition from middle- east and south east Asia. Gas to wire is also considered to be not attractive, though there has been unconfirmed news of such propositions. Presence of extremely large associated and non associated gas reserve in middle-east, which is priced at a very low level for different reasons, would preclude Bangladesh gas to be a major input in the global urea industry. A recent attempt by India to finance a urea project in middle-east for export to India failed due to reluctance of lead bank citing unfavorable economics. In this circumstance, a pipeline to Jagdispur in India is being touted as only viable option. This option is based on the presumption that Bangladesh gas absolutely requires an external market, and that the gas price will be based on the end user tariff. This is rather cursory assumption, which assumes that gas can be sold to power and fertilizer plants on the way which are now using fuels at about US $ 4.5 to 7.0 mmbtu. The important point neglected here is that the present production cost is subsidized under retention pricing system (RPS) and the payment capacity of the consumers is also suspect. This has been voiced by the IOCs also. At present Bangladesh is very much eager to develop mutual relationships and understandings with the middle-east energy giants. From now on it will be very vital to decide “where and how” the gas fields and exploration activites can be done by joint venture programs with large scale Oil companies of middle-east like Saudi Aramco, Qatar Petroleum, RasGas etc. If western companies like Chevron, Shell etc can exploit the resources of Bangladesh by involving their masterminds why the middle-east can not? It is perhaps a vital question which has rather a simple answer. It is responsibility of us to develop mutual agreements between our brotherly countries and it can be very beneficial for both the parties without any doubt. It is to be noted that if exploration and discovery activities between Bangladesh and the middle- east can make a way to begin, it will be a great boost for the Muslim nations altogether because by this way, we will be able to share our knowledge between us and can uplift the growth rate of the energy sector by incredible pace. Since the government has declared that adequate gas reserve must be retained for the country's 50 years demand before any external marketing is considered. It is advisable to look for the market at home catering to the domestic demand. This might entail a slower growth in production and sales than is anticipated by the IOCs. However the question of natural security must get priority. Considering the governments goal of electricity to all by the year 2020, and
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 making the country food surplus, there is a vast future market within the country. This expansion will also require massive investment and will have to be supported by proper gas pricing. If the future power plants are all run on combined cycle and, where possible, power plants are integrated with fertilizer/steel plants, major savings in investment with resultant gain in IRR may be made. Diversification of gas use will be another major gap. In this respect large scale conversion of vehicles to CNG and introduction of cost effective technology to convert gas to liquids (GTL) will be important. This will decrease the import of liquid fuel providing energy stability and also contribute towards expansion of gas market.
Future Fifty Years of Gas Demand Scenerio Energy experts always have different opinions on the energy demands with respect to the energy growth. Experts have predicted that as coal was the fuel of 19th century, oil in the 20th century, so natural gas has a great possibility to make its way as the primary fuel of the 21st century. The take off point for solar energy and other renewables as a mean of large scale energy source will be delayed and will not take position until 2050. Nuclear power and renewable energy sources will double their present contribution to global energy use by2050 from about 100 Gtoe to about 215 Gtoe but their share will still be not more than about 18% of the total global energy use. In a recent report of the IAEA, it has been pointed out that oil will retain its position as the single most important source until about 2040 after which natural gas will be the near universal fuel. They forecasted that conventional natural gas use would peak around 2050 following which the use of natural gas will exceed that of oil and coal together. The analysis showed that the world natural gas use is foreseen to expand from about 50 Tcf in 1984 to around 123 Tcf by 2020 and thereafter this level will sustain for the following years to 2060. However the battle between gas and renewable energy will begin in earnest about 2060, and after 2070, the battle will swing in favour of the renewable energy including solar energy because of the cost reductions. Gas demand for power sector for the next five decades has been estimated, and the projection indicates that about 40 Tcf gas would be required to generate electrical power from the years 2001 to 2050. As on 27.07.2000 the maximum generation was 2823 MW. The GOB's vision is to supply reliable electricity to all by 2020. To achieve and sustain expected growth of 6- 7% per annum. Accordingly for the period from 2003 to 2015 PSMP's high demand forecast and for 2016-2050 an average annual growth rate of 3% have been used. As projected, demand for electricity would increase to about 16,808 MW by 2020 and 35,143 MW by 2050. The above projection is made based on 60% system load factor as stipulated in PSMP. This forecast uses energy efficient 450 MW capacity combined cycle and 150 MW capapcity gas turbine power plants. The plan includes also 250 MW coal based power plant at Barapukuria and 330 MW hydroelectricity at Karnafuli. It is estimated that 90% of electricity generation would be gas based and remaining 10% would be non-gas based. The industrial sector includes Fig.10 all industries except fertilizer. It is indicated by an analysis that industrial gas consumption will grow from 54.6 Bcf to 229.1 Bcf over the period of 2000-2020 at an average annual rate of 7%. Gas consumption in domestic, commercial, seasonal and tea-estates have Fig.11 been lumped together. It is auumed that the gas network would not be extended to rural areas for
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 domestic/commercial purposes, and besides seasonal brick fields, scope of expansion of tea gardens would also be very limited. As such, only urban areas particularly Dhaka metropolitan area and district towns would be important growth centers for gas consumption. Annual gas consumption growth rate of 4% has been estimated to forecast gas consumption to 2020 and thereafter 2%, 1% and 1% growth rates for the next three decades have been assumed.
Recommendations #As a country of great future energy prospects, Bangladesh should have to take effective and efficient measure for conducting systematic exploration activity in the country. It can easily be said that we have not been acted according to our vast energy resources because there still remain a large amount of reserve for petroleum resources of Bangladesh. As the same time one can not loose sight of the fact that exploration is “high capital intensive” and risky venture. It should be remembered that the energy resources that we have, is far more capable of uplifting the energy status and overall the economic status of the country if proper action to explore and distribute are taken in time. #Till now all development of gas fields had taken place separately. A decision for a national gas grid should be taken and development of gas fields undertaken on the basis of this national gas grid demand. A gas pipeline grid like the power grid is necessary for optimal utilization of facilities of the four systems i.e; Bakhrabad, Titas, Bibiyana and Jalalabad. Programs for this have been initiated but it should be much accelerated. #Gas supply scenario indictates the urgency of intensifying exploration anddevelopment. GOB's current policy for participation of IOCs in this sector must be strengthened. Findings of the recent Natural Gas Assessment Study conducted by Petrobangla/USGS (mean of 32 Tcf undiscovered natural gas reserve) should be investigated (Hydrocarbon Unit of Bangladesh and NPD, Norway have shown 42 Tcf of reserve) through future development activities and joint research programs specially with the Persian Gulf countries. # Collaborative research activities within the OIC state universities could be proved very fruitful for the sector. Activities within the universities of Bangladesh and Middle-East should have a strong impact on the scenario. It is to be noted that Geology department of D.U. is playing one of the supreme roles in exploring and discovering undiscovered energy resources of Bangladesh. There are research works which are being conducted by universities in the western world and they are getting innovative ideas from the greater student community. So we can surely achieve something very significant if this can be done in our own innovative ways and it should be done in order to progress rapidly. Moreover it will certainly strengthen the brotherly relationships between the Muslim Nations and OIC can play a key role to organize the idea. #Reserve growth potential of the existing fields must be examined by employing new technology. Gas reserves of the existing fields must be updated on regular basis in order to allow more realistic gas supply forecast and overall sectoral planning. To do that Reservoir Study Divisionof Petrobangla must be manned with adequate manpower and equipped properly. Appropriate training of the officials and staffs is a must in order to gain maximum work efficiency.
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#Alternate source of primary energy, and/or energy mix would provide secured supply of electricity. Bangladesh has enormous potential for solar, wind and wave energies. Some recent feasibility studies have proved the high potential wind energy production capability of Bangladesh. For that Research and Development (R & D) activities should have to be taken seriously to make new ways of energy sources in order to achieve energy security. #Gas consumption for power sector would be reduced at least by 10% if Bangladesh pursue over 50% energy efficient combined power plants or even further if technology improves. Demand of natural gas for power sector will be lower than the forecasted one if capital investment for power generation, transmission and distribution could not be made available. This could, however, be achieved if ongoing power sector reform and restructuring policy of GOB continues. #Gas demand for fertilizer sector will also be dependent on capital investment in fertilizer sector. The forecasted demand will be lower than the normal if international market price of urea falls and/or subsidy on natural gas price for fertilizer is withdrawn. #Natural gas demand as forecasted for industrial and domestic/commercial/other sectors will require huge investment for network expansion in the north, west and southern districts of Bangladesh. Regulatory body for gas sector would encourage private sector inverment in transmission and distribution system. #Gas price must be rationalized and set at its commercial value based on the production cost of gas. #Nepal and Bhutan have tremendous potential for hydroelectric power. Regional and sub-regional cooperation will allow Bangladesh to have access into regional and sub-regional electric grid system. Extensive energy cooperation within SAARC countries may be an alternative option to follow.
Acknoledgements I would like to thank my departmental teachers specially Prof. Dr. Woobaidullah to help to work out this work. I should also mention my deepest gratitude for Prof. Dr. Syed Humayun Akhter who always have given me support in every of my technical works. Last but not the least, thanks to the organizers of IAGC 2010 to give me this grand opportunity to publish my work.
References 1. Imam, Badrul; Energy Resources of Bangladesh (2005), University Grants Commssion. 2. Khan, F.H.; Geology of Bangladesh. 3. Reimann, K.U.; Geology of Bangladesh. 4. Juddson, Kauffman; Physical Geology. 5. Levorsen, A.I.; Geology of Petroleum. 6. Kingston, John; Undiscovered Petroleum Resources of South-Asia, Open-File Report. 7. Hossain, Mosharraf A.K.M.; Energy Sector of Bangladesh, (Newspaper article)
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8. Huq, M. Moinul, et. al.1995; Contribution to the stratigraphy of the Bengal Geosyncline, A New Concept from Bengal Basin (Bangladesh). 2nd South Asian Geological Congress (GEOSAS II), Columbo, Abstract Vol. 9. Government of People's Republic of Bangladesh & Bangladesh Oil, Gas & Mineral Corporation (Petrobangla); “Petroleum Geology and Hydrocarbon Potential of Bangladesh”. 10. USGS and petrobangla; “Cooperative Assessment of Undiscovered Natural Gas Reserves of Bangladesh”, January. 11. Petrobangla; National Gas Demand and Supply Forecast: Bangladesh, FY 2001-2050. M.A. Aziz Khan, 15 March, 2001. 12. Hydrocarbon Unit (HCU) and Norwegian Petroleum Directorate (NPD); Bangladesh Petroleum Potential and Resource Assessment,2001. 13. Ministry of Power, Energy and Mineral Resources; Report on Sectoral Plan and Vision Statement of Bangladesh's Energy Condition. 14. Bangladesh Power and Energy Today. Status of Hydrocarbon Exploration and Development in Bangladesh. Paper presented by M. Mosharraf Hossain on 29th April at National Defense College, Dhaka.
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Abbreviations
OXY OccidentalOil
BAPEX Bangladesh Petroleum Exploration and Production Company Ltd.
bbl/day Barrel per day
Bbl/MMcf Barrel per Million Cubic Feet
Bcf Billion Cubic Feet
BGFCL Bangladesh Gas Fields Company Ltd.
BGSL Bakhrabad Gas Systems Ltd.
BMEDC Bangladesh Mineral Exploration and Development Corporation
BODC Bengal Oil Development Company
BPC Bangladesh Petroleum Corporation
CNG Compressed Natural Gas
D.U. Dhaka University
E & P Exploration and Production
GIIP Gas Initially In Place
HCU Hydrocarbon Unit
IKM Interkomp Kanata Management
JGTDCL Jalalabad Gas Transmission and Distribution Company Ltd.
LPG Liquefied Petroleum Gas
mmbbl Million Barrel
MMcf Million Cubic Feet
NPD Norwegian Petroleum Directorate
OGDC Oil and Gas Development Corporation
ONGC Oil and Natural Gas Corporation
PPL Pakistan Petroleum Ltd.
PSC Product Sharing Contract
PSOC Pakistan Shell Oil Company
RPGCL Rupantarita Prakitik (Converted) Gas Co. Ltd.
SBED Shell Bangladesh Exploration and Development B.V.
SGFL Sylhet Gas Fields Ltd.
SPE Society of Petroleum Engineers
SVOC Standard Vacuum Oil Co.
Tcf Trillion Cubic Feet
TGTDCL Titas Gas Transmission and Distribution Co. Ltd.
TOC Total Organic Content
UMC United Merdian Corporation
UNOCAL Unocal Bangladesh Ltd.
WESGAS Pashchimanchal (Western Region) Gas Co. Ltd.
WPC World Petroleum Congress
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Fig.1- Energy blocks of Bangladesh Fig.2- Different operators working in the energy blocks
hase Wells drilled Gas Discovery Success Ratio ...... Onshore Offshore Total Onshore Offshore Total Onshore Offshore Total
1908-33 6 - 6 ------
1947-71 21 1 22 8 - 8 1:2.63 0 1:2.75
1972-2001 27 12 39 12 2 14 1:2.25 1:6.5 1:2.78 (+1 Oil)
Total 54 13 67 20 2 22 1:2.70 1:6.5 1:3.07 (+1 Oil)
Petrobangla/BAPEX/ OGDC 20 NONE 20 10 - 10 1:2.00 - 1:2.00
IOCs 34 13 47 10 2 12 1:3.4 1:6.5 1:3.92
Fig.3- Exploration History
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Operator Period Area Energy Source Line Km Recording type
OGDC 1963-71 Onshore Dynamite 971 Single fold,Analog
Petrobangla 1973-77 Onshore Dynamite 2065 Single fold,Analog
Petrobangla 1976-78 Onshore Dynamite 3606 Single fold
Petrobangla 1978-82 Onshore Dynamite 2151 6/12 fold,Analog
Petrobangla 1979-87 Onshore Dynamite 3809 12/24 fold, Digital
Petrobangla 1977-86 Onshore Dynamite 3658 12 fold, Digital
Petrobangla 1983-86 Onshore Dynamite 2646 12/24 fold, Digital
Petrobangla 1984-86 Onshore Dynamite 1961 24 fold, Digital
BAPEX 1990-97 Onshore Dynamite 2587 12/24/30 fold, Digital
Total 23454
SVOC 1956-59 Onshore Dynamite 900 Single fold,Analog
PSOC 1960-71 Onshore Dynamite 7600 Single fold,Analog
INA-Nafthalin 1974-76 Offshore Aquapulse 2957 24 fold, Digital
Union Oil 1974-76 Offshore Airgun/D.mite 4926 48/24/12/6 Digital
Ashland 1974-76 Offshore Airgun 5345 12/24 fold, Digital
ARCO 1974-76 Offshore Airgun 3242 48 fold, Digital
BODC 1974-76 Offshore Airgun 8163 24/48 fold, Digital
CSO 1974-76 Offshore Airgun 6536 24 fold, Digital
Shell 1986-87 Onshore Dynamite 1506 24 fold, Digital
Occidental 1995-97 Onshore Dynamite 2317 Multi fold, Digital
Cairn/Shell 1996-97 Onshore/Offsh. Airgun/D.mite 2500 Multi fold, Digital
Okland Onshore Airgun/D.mite 925 Multi fold, Digital
UMC 1998-99 Onshore Dynamite 515 Multi fold, Digital
Total 47332
Grand Total 70786
Occidental 1995-97 Onshore Dynamite 226 Sq.km 3D
Fig.4- Seismic Survey Database of Bangladesh
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Fig. 5: Structural Elements of Bangladesh and Neighboring Areas
Sectorwise Gas Consumption
POWER 48% OTHERS 2% DOMESTIC 10% INDUSTRY 13% FERTILIZER 27%
Fig.6-Sector wise gas consumtion
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Resources Recoverable Reserves/Resources ...... Proved+Probable(2P) Proved+Probable+Possible(3P) Discovered Resource a. Produced upto June 2001 4.3 4.3 (Reserved) b. Remaining in Fields 11.6 16.2
c. Not in Production 4.5 7.9
d. Remaining Reserves (b+c) 16.1 24.1
e. Total Discovered (a+b+c) 20.4 28.4
P90 Mean P10 Undiscovered Resource (Risked) f. Hypothetical (Mapped 11 17 24 Prospects)
g. Speculative (Leads/ Unmapped 8 25 40 Prospects)
h. Total Undiscovered (f+g) 19 42 64
Fig.7-Gas Resources of Bangladesh (Discovered+Undiscovered)
Factors 2000 2005 2010 2015 2020
Population(million) 130 141 153 165 177
GDP growth rate 6.4 7.2 7.7 8.2 8.7
Per capita GDP ($) 254 318 416 560 774
Energy coefficient 1.37 1.37 1.08 1.08 1.08
Energy growth rate 8.77 9.86 8.32 8.86 9.40
Per capita kgoe 94 131 194 269 384
Total energy (mtoe) 12 19 31 46 72
Fig.8-Energy consumption of Bangladesh
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Fig.9-Hydrocarbon Related Infrastructures
Year 2001-2010 2011-2020 2021-2030 2031-2040 2041-2050 Total
Industrial Gas 822 1684 2861 3788 4368 13522 Consumption (Bcf)
Fig.10- Gas consumption in industrial sector
Years 2001-2010 2011-2020 2021-2030 2031-2040 2041-2050 Total
Domestic/ 537 794 1051 1212 1339 4933 Commercial/ Others Gas Consumption (Bcf)
Fig.11- Gas consumption in Domestic/ Commercial/Others
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Mudbanks off South West coast of India - Role of Subterraneous Flow
Paimpillil Sebastian Joseph
Center for Earth Research and Environment Management, Cochin 17, India, [email protected]
Abstract The mudbanks along the south west coast of India is a unique geological phenomenon during the SW monsoons. The quiescence offered is on account of the increased viscosity of sea water due to the mud being in a colloidal suspension over a very loose and non-rigid clay bottom. A favorable combination of several factors like rainfall, sea water temperature, salinity and some other unknown factors - lead to the mudbank formation and decide its extent and duration. The recent findings of subterraneous discharges through the porous narrow sedimentary lime shell strip between the wetlands and Arabian Sea, forming pockets of low saline nutrient rich patches points the influence of such flows in the formation of mudbanks. A band of N/P > 15 funneling out from coastal region provided an indication of ‘external source’ of nitrogenous compounds. The long-term (decadal) trend of chlorophyll showed a “greening” of the near-shore waters. If the existence of subterraneous channels is proved, it might even re-construct the historical evidence that the subterraneous flow plays a decisive role in mudbank formation. The idea that land-use mosaic among sub-watersheds influences the coastal processes such as mudbanks may apply globally to any coastal regions hugged by wetlands and underlain with porous deposits and points towards the possibility of developing mudbanks like phenomena in such regions.
1. Introduction The Mudbanks (Chakara) off Alleppy (Southwest India) is a unique geological phenomenon serving very much as a natural harbor and is defined as transient accumulations of dense fine- sediment suspensions, which form sub-circular/elliptical depositional areas having dimensions from 2-5 km alongshore and 1.5 to 4 km offshore, occur yearly along certain stretches of the west coast of southern tip of India. Mudbanks nearly always occur shortly after the arrival of the southwest monsoon in late May/June. The remarkable characteristic of them is that they did not lead to any silting of the coast on which ships could have run aground. They protect both the incoming and outgoing ships during the heavy downpours and stormy winds of the South West monsoon. When active, they are noted for their wave damping effects that a 1.8 m high wave outside the mud bank is reduced to 0.5 m in the mud bank, within a distance of 1.1 km. This reduction can be 100% in a fully developed mud bank. The quiescence offered is on account of the increase in viscosity of the sea water due to the mud being in a colloidal suspension over a very loose and non-rigid clay bottom. The mud bank also provides protection to the coastal zone, by way of allowing accretion. The mudbank formation occurs within a week or so after the onset of the southwest monsoon. The occurrence is sporadic and erratic. This varies from year to year, in extent and duration. In some years they are not formed at all. They were also mobile, moving from place to place for long distances along the coast. A suitable combination of several factors like rainfall intensity and duration, temperature, salinity and some other unknown factors lead to its formation, its extent and duration of continuance. Apart from the beneficial to fishing
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 industry, the mudbanks have a role on the shore stability as mudbank accretes the coast behind. The present challenges are to predict mudbank formation, its artificial generation, precautions against down coast erosion, integrated management of mud bank areas taking into account the phenomena, coastal protection, socio-economics and infrastructure developments. Conventional understanding of coastal waters of southeastern Arabian Sea is that activation of mud banks by monsoon forcing triggers intense geochemical processes leading to high phytoplankton productivity. Recent studies as the one discussed here contradict these findings and show that even after the monsoon period, fresh injections of nutrients by hitherto unknown processes fertilize the coastal waters that are either permanent or quasi-permanent in nature. One of the major mudbank regions (Alleppy) of southwest coast of India was selected for observation that had indicated the introduction of nutrients into the coastal waters during periods when mud banks are passive.
2. Methods and materials During the hydrographic observations, sea water samples were collected from the coastal area (Fig.1g) using Niskin bottles from the surface, mid-depth (where the depth > 5m) and near bottom and were kept packed in iceboxes and brought to the shore laboratory. Nutrients were analyzed calorimetrically [1] and chlorophyll a by UNESCO procedure within 6 hours of collection.
3. Results and discussion The quality of coastal waters is coupled closely to the drainage of uplands. Primary attention has been given to river hydrography, but recent evidence shows that other transport mechanisms, particularly the discharge of groundwater, are important in areas covered by unconsolidated sediment or lime shell beds. Human activities on coastal watersheds seem to provide the major sources of nutrients to shallow coastal ecosystems. The human population along the coastal belt with more than 70 % of households (287 households/km2) without proper sanitation facilities had increased the use of septic tanks and the nutrient inputs to ground waters, particularly in the regions with limestone beds. The ground water quality of the region had shown that nitrate in sediment extract up to 12 µM, ammonia (in water) 8µM, urea (in water) 14 µM, urea (sediment extract) 15 µM [2] . As far as the chemical features of the coastal region are concerned, the general picture so far emerged out is that except during the monsoon periods, the southwest coastal waters remained oligotrophic and surface chlorophyll-a typically ranged from 0.1 to 5.3 mg.m-3, while primary productivity ranged from 100 to 360 mgC.m-2.d-1 .The present study in the post- monsoon season had revealed highest value of 14 mg/m3 for chlorophyll-a, approximately 3 times greater than the peak values reported so far from these waters. A band of N/P > 15 funneling out from coastal region provided an indication of ‘external source’ of nitrogenous compounds into the coastal waters (Fig 1b-f). The long-term (decadal) trend of chlorophyll had shown a “greening” of the near-shore waters. The present investigation represents the period when the mudbanks were not activated and the results showed a fertilization of the coastal water by injection of nutrients by hitherto unknown processes. The high nitrate-N, ammonia concentrations, enriched particulate organic carbon (> 3.5 mg/l) and Chlorophyll-a (14.8 mg/m3) at localized coastal regions had indicated clear near shore nutrient sources. It is difficult to point out a definite source for the high nutrient values as the fresh water discharge
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 was at its minimum. These sources of nutrients deserve identification as it was traced in a region far away from any river mouth and the injection of nutrients was observed during non- monsoon months, when mudbanks were passive. The productivity boosting in southwest coastal Arabian Sea can be partially attributed to the possibility of nutrient rich ground water discharges to the coastal sea across the narrow strip of porous lime shell bed separating the Vemabadu Lake and the sea. The necessary forcing for the ground water flow is gained when the fresh water level in Vembanadu Lake and the sea level reaching a critical value. With regard to the hydraulic mechanism, it would appear that apart from the trending faults and water level variations in the lake, existence of several passages depending on the thickness of the lime shell bed also contribute to the sub aqueous flow. It is likely that the subterranean flows during the present observations were very weak (ooze), it can be expected to be much larger during the southwest monsoon period, when the sea level is at its annual minimum and the water level of the lake, approximately 5 feet above than normal due to the increased river discharges. A head of 5 ft. of water exerting a pressure of 2 lb/sq.inch may be insufficient to push suspended solids [2], but is good enough to erode frictional resistance and force ground water flow into the coastal region [3]. It is ultimately this flow of brackish water through these passages that stratifies the water column (Fig 1a) and diverts the converging waves to unsettle the sediment. The increased fresh water input through these passages stratifies the coastal waters by forming a surface lid of low saline water, thereby diverting the incoming currents and wave energy to the bottom to disturb the bottom sediments. This can be the starting mechanism of mudbank formation. The periodicity and intensity of groundwater flows depend on the water level of the Vembanadu Lake, which depends on monsoon variability and frequency of floods. If the sufficient critical fresh ground water flow required to induce stratification in the coastal waters is available, the nutrient rich flow can also induce high primary productivity. The possibility of heavy rains and flash floods linked with cyclones is high with the ongoing climate variability, such critical conditions can occur during non-monsoon seasons and mudbank formations can shift to similar locations.
4. Conclusions The causative factors discussed are indicative of existence of a subterranean flow connecting Vembanadu Lake to the adjacent coastal waters through the submerged porous lime shell beds. Continuous nutrient entry through such process is bound to upset coastal water productivity pattern. The brackish ground water fluxes seems to stratify the coastal region and to induce the mudbank formation. The significance of this study is that subterranean flows could redefine the very concept of formation of mudbanks, which is presently recognized only as an oceanographic process. The formation of mudbank is not entirely forced by coastal processes; instead a remote forcing from the land involving a climate controlled subterranean flow through the submerged lime shell beds appears to be an initiative mechanism. If the existence of the subterraneous channels linking Vembanadu Lake to the adjacent coast is proved, it might even re-construct the historical evidence that the subterraneous flow plays a decisive role in the formation of mudbanks along this region. This assumption need further study to establish cause and effect mechanisms and quantify actual trends created by increased nutrient and brackish water loading.
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5. References 1-Grasshoff, K.. Ehrhardt, M & Kremling, K. (eds) methods of seawater analysis (Verlag Chemie, Weinheim, 1983). 2- Lizen Mathews(2000) Studies on the role of sediments on the nutrient dynamics and fertility of Kuttanad waters. Ph.D Thesis, CUSAT, 103 p. 3-Du Cane (1968) Report of the special committee on the movement of mudbanks, Cochin Govt.Press, 57. 4-Lapointe, B.E. & Clark, M.W (1992). Nutrient inputs from the watershed and coastal eutrophication in the Floriday Keys. Estuaries. 15(4), 465-476.
Fig 1b. Distribution of nitrate-N at the Fig 1c. Distribution of Phosphate at Fig 1a. Salinity distribution in coastal waters surface and bottom during October the surface and bottom - October (a,b), (a,b), February (c,d) & November (e,f) Feb (c,d) & November (e,f)
Fig 1d. Distribution of Ammonia at the Fig 1f. Distribution of nitrite-N at the Fig 1g. Map showing the study area surface and bottom during October (a,b), surface and bottom during October February (c,d) & November (e,f) (a,b), February (c,d) & November (e,f)
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
Using artificial intelligence to Prediction of permeability and rock type derived from fuzzy c -means clustering in uncored well in one of the Iran gas field.
mohammad Keshtkar*, seyedali moallemi
Corresponding author: NIOC.Exploration Directorate, Iran. E-mail address:[email protected]
Abstract Permeability, rock type and core facies are the most important parameters of the reservoirs and accurate reservoir simulation and management requires a quantitative model of the spatial distribution of reservoir properties. Geological and petrophysical survey has an important role in producing of really three-dimensional models of the reservoir. determination of permeability, and rock type are the challenge for reservoir scientist in uncored well.Rock type represent the certain facies with a defined range of porosity and permeability and play an important role in recognition of flow units and reservoir modeling.In this study Rock types were defined utilizing fuzzy c-means clustering from porosity and permeability of well cores.So that each obtained cluster was assigend to a special rock type. . It has been attempted in this study that Rock types and permeability are predicted indirect from electrical logs by using artificial intelligence like Backpropagation Neural Network(BPNN) and Fuzzy logic method.The section of Fuzzy logic in Geolog software is used in estimate Rock types and permeability from petrophysical logs. The results reveal a good match between the core data analyses and the intelligent technique determination of permeability and rock types.
Keywords: Artificial intelligence; Rock type; Fuzzy logic; BPNN; Fuzzy c-means clustering; Permeability;
1.Introduction In this paper, we highlight role of Soft Computing techniques for intelligent reservoir characterization,. Reservoir characterization plays a crucial role in modern reservoir management.The reservoir characteristics include pore and distribution and depositional environment.This paper suggests intelligent technique using fuzzy logic and Neural network to determine permeability and rock type in well where core data are not available, from wire- line logs data in one gas field of iran . The basic theory of fuzzy sets was first introduced by Zadeh (1965). Unlike classical logic which is based on crisp sets of "true and false", fuzzy logic views problems as a degree of "truth",or "fuzzy sets of true and false". Despite the meaning of the word "fuzzy", fuzzy set theory is not one that permits vagueness. It is a methodology that was developed to obtain an approximate solution where the problems are subject to vague description. In addition, it can help engineers and researchers to tackle uncertainty, and to handle imprecise information in a complex situation. During the past several years, the successful application of fuzzy logic for solving complex problems subject to uncertainty has greatly increased and today fuzzy logic plays an important role in various engineering disciplines. In recent years, fuzzy logic, and intelligent solution, has been applied extensively in many reservoir characterization studies. For example in Bois (1984), Baygun et
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 al.(1985), Baygun et al.(1985), Nordlund (1996), Cuddy (1997), Fang and Chen (1997) , Huang et al.(1999), Nikravesh and Aminzadeh (2000), Huang et al 2001, Saggaf and Nebrija 2003, the authors applied fuzzy logic and neural networks to solve number of reservoir characterization problems in several fields. 2.Method used 2.1.Fuzzy c-means Clustering Cluster analysis encompasses a number of different classification algorithms that can be used to organize observed data into meaningful structures. Fuzzy clustering partitions a data set into fuzzy clusters such that each data point can belong to multiple clusters. Fuzzy c-means (FCM) is a well-known fuzzy clustering technique that generalizes the classical (hard) c- means algorithm and can be used where it is unclear how many clusters there should be for a given set of data. FCM is based on minimization of the following objective function (Ozer 2005):
n c c 2 jm = ∑∑µ ij || xi − c j || i==11j (1)
1 ≤ m < ∞ where n is the number of objects to be clustered, c is the number of clusters, uij is the degree of membership of object i in cluster j, xi is a vector of h characteristics for object i, vj is a vector of the cluster means of the h characteristics for cluster jand c is the weighting exponent varying in the range [1,∞]. Equation (1) represents the sum of squared errors and is a goal function that the FCM algorithm tries to minimize.
2.2.BPNN(Back-propagation neural network) ANN is a new tool for solving complex problems in petroleum industry. A back propagation artificial neural network (BP-ANN) is a supervised training technique that sends the input values forward through the network then computes the difference between calculated output and corresponding desired output from the training dataset. The error is then propagated backward through the net, and the weights are adjusted during a number of iterations. The training stops when the calculated output values best approximate the desired values (Bhatt and Helle, 2002).
2.3. FUZZY LOGIC In recent years, it has been shown that uncertainty may be due to fuzziness rather than chance. Fuzzy logic isconsidered to be appropriate to deal with the nature of uncertainty in system and human error, which are notincluded in current reliability theories. The basic theory of fuzzy sets was first introduced by Zadeh (1965). Unlike classical logic which is based on crisp sets of "true and false", fuzzy logic views problems as a degree of "truth",or "fuzzy sets of true and false" [6]. Despite the meaning of the word "fuzzy", fuzzy set theory is not one thatpermits vagueness. It is a methodology that was developed to obtain an approximate solution where the problemsare subject to vague description. In addition, it can help engineers and researchers to tackle uncertainty, and to handle imprecise information in a complex situation. During the past several years, the successful application of fuzzy logic for solving
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 complex problems subject to uncertainty has greatly increased and today fuzzy logic playsan important role in various engineering disciplines. In recent years, considerable attention has been devoted to theuse of hybrid neural network-fuzzy logic approaches as an alternative for pattern recognition, clustering, andstatistical and mathematical modeling. It has been shown that neural network models can be use to construct11nternal models that capture the presence of fuzzy rules. However, determination of the input structure and number of membership functions for the inputs has been one of the most important issues of fuzzy modeling.Fuzzy logic provides a completely new way of modeling complex and ill-defined systems. The major concept offuzzy logic is the use of a linguistic variable, that is a variable whose values are words or sentences in a natural orsynthetic language. This also leads to the use of fuzzy if-then rules, in which the antecedent and consequents arepropositions containing linguistic variables.
3.Rock type classification The methodology is described as below: First, input porosity and permeability data was passed from the following function of Matlab,[center,U, obj f cn] = fcm (data, cluster n) where data (input matrix of porosity and permeability), cluster n (number of cluster to be derived) and fcm (Matlab’s fuzzy c-means clustering algorithm) are input arguments of the function. The output arguments are center (matrix of final cluster centres), U (membership function matrix) and obj fcn (values of the objective function during iterations). By specifying arbitrary values for cluster n, clusters were derived for the reservoir studied. Then each cluster was deemed as a unique rock type of the reservoir.in figure2 crossplot of ten rock type that detemined by permeability and porosity are shown. Statistic data of ten rock type are shown in table1. 4.Prediction rock type by fuzzy logic In this section, rock types were estimated from well log data using fuzzy logic. For this purpose, the distribution of well log data for the identified rock types was first investigated. According to figure1 which shows an example of the distribution of RHOB log values for the one rock types derived in previous stage, the data sets have been fitted by a Gaussian function(figure3). The normal distribution of data by a
Gaussian function is as below:
− ( x − c ) 2 σ 2 e P ( x , σ , c ) = (2) σ 2 π where f (x,σ, c) is the probability function that an observation x is measured in the data set by amean c and standard deviation σ. This curve was used to estimate relative probability or ‘fuzzy possibility’ that a data value belongs to each rock type. The methodology described here is similar to Cuddy’s approach (1998) for lithofacies estimation using fuzzy mathematics. Each log data value may belong to any FCM clustering derived rock type to a degree that can be calculated from a Gaussian membership function using equation (2). Each rock type has its own mean and standard deviation, namely, for n
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 number of rock types; there are n pairs of c and σ rock type. For example, the fuzzy possibility that a RHOB log data belongs to rock type 1 is obtained by substituting c rock type 1 and σ rock type 1 in equation (2):
− ( RHOB − c ) 2 σ 2 exp rt 1 rt 1 P ( RHOB ) = (3) σ 2 π rt 1 The ratio of the fuzzy possibility for each rock type with the fuzzy possibility of the mean or most likely observation is obtained by de-normalizing equation (3). The fuzzy possibility for mean of RHOB in rock type 1 is obtained by substituting RHOB by crock type 1 in equation (3):
−(c −c )2 σ 2 exp rt1 rt1 rt1 P (RHOB ) = = 1 σ 2π (σ ) 2π (4) rt1 rt1
The relative fuzzy possibility R(RHOBIrock type1) of a RHOB porosity RHOB belonging to rock type 1 compared to the fuzzy possibility of measuring the mean value crock type 1 is equation (3) divided by equation (4):
2 2 − ( RHOB − C rt 1 ) 2 σ rt 1 (5) R ( RHOB rt 1 ) = e
Each value derived from equation (5) is now indicated to possible rock types. To compare the relative fuzzy possibilities of this equation between rock types, equation (5) is multiplied by a coefficient named relative occurrence of each rock type i√n the reservoir interval. For rock type 1, it is noted as
− ( RHOB − C ) 2 2 σ 2 F ( RHOB ) = n e rt 1 rt 1 rt 1 rt 1 (6)
The obtained fuzzy possibility from equation (6) is based on RHOB log data only. This process should be repeated for other logs such as sonic (DT), neutron (NPHI), . . . at this point. This will give F(DTrock type1), F(NPHIrock type1), . . . for rock type 1. These fuzzy possibilities are combined harmonically to give a final fuzzy possibility:
1 1 1 = + + .... C F ( RHOB ) F ( DT ) rt 1 rt 1 rt 1 (7) This process is repeated for other rock types and all derived fuzzy possibilities are combined harmonically. Then, the rock type with the highest combined fuzzy possibility is taken as the most possible rock type at that point. A comparison between FCM clustering derived and fuzzy predicted rock types versus depth for the test well that was not used to model construction is shown in figure 4. The fuzzy Possibilities in fuzzy logic are combined harmonically, whereas, statistical methods such as Bayes theorem, combine probabilities geometrically. When comparing rock types that are equally likely, with similar probabilities,
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 the harmonic combination emphasizes any indicator which suggests the lithology selection is unlikely. Secondly, fuzzy logic weights the possibilities by the square root of the proportion in the calibrating data set, whereas Bayes uses the direct proportion (Cuddy 1998).in the next section permeability estimated by neural network and fuzzy logic figure 5 show comparison beetwen core permeability and fuzzy predicted permeability and crossplot of this comparison.
Table1:Rock types(1-10) derived by the FCM clustering method in this rock type porosity and permeability are important and show production potential and (xpl,×23.6) ,
Rock type1(cluster1)
k(md) (%) φ Min 0.01 0.1 Max 1.41 3.89 Mean 0.10 1.30 St.Dev 0.21 0.97 Rock type2(cluster2) k(md) (%)φ Min 0.07 4.85
Max 2.43 10.64
6.89 Mean 0.54٠
St.Dev 0.72 1.62
Rock type3(cluster3)
k(md) (%)φ
Min 3.93 17.81 Max 10.27 21.64 Mean 6.90 19.73 St.Dev 1.71 1.28 Rock type4(cluster4) k(md) (%)φ Min 0.346 23.94 Max 3.18 31.09 Mean 1.21 25.93
St.Dev 0.86 1.69 Rock type5(cluster5)
k(md) (%)φ
Min 4.20 22.11 Max 9.17 26.99 Mean 6.81 23.86 St.Dev 1.61 1.33
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Rock type6(cluster6) k(md) (%)φ Min 0.25 18.44 Max 3.71 2.66 Mean 1.494 21.66 St.Dev 0.96 1.402 Rock type7(cluster7)
k(md) (%)φ
Min 11.739 19.43
Max 16.22 22.02
Mean 14.21 21.05 St.Dev 2.27 1.41 Rock type8(cluster8) k(md) (%)φ Min 9.61 13.79 Max 9.61 13.79 Mean 9.61 13.79 St.Dev Rock type9(cluster9) k(md) (%)φ Min 20.01 22.16 Max 25.51 24.65 Mean 23.81 23.28
St.Dev 2.60 1.11 Rock type10(cluster10)
k(md) (%)φ
12.41 Min 0.19٠
Max 4.85 15.36 Mean 1.41 14.15 St.Dev 2.28 1.24
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
Figure1:distribution of RHOB log of one rock type derived by fcm by Gaussian function
Figure2:ten rock type derived from porosity and permeability by fcm method
Figure3:Gaussian membership
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
Figure4:Acomparison between clustering derived and fuzzy predicted rock types versus depth
Figure5:A comparison beetwen core permeability and fuzzy predicted permeability and crossplot of this comparison
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
5.Conclusions Intelligent systems including fuzzy logic and BPNN have been successful to predict for rock type and permeability in gas field in iran. Fuzzy c- means clustering is good technique to rock type definitation. Fuzzy logic based on the fuzzy possibility concept is efficient tool to prediction rock type derived by fcm clustering. A comparison between measured and predicted permeability and rock type versus depth are good agreement for the two intelligent techniques.
Acknowledgments I thank the reservoir geology department of Research Institute of Petroleum Industry (RIPI) of Iran for data preparation.
Reference 1-Baygun et. al, 1985, Applications of Neural Networks and Fuzzy Logic in Geological Modeling of a Mature Hydrocarbon Reservoir, Report# ISD-005-95-13a, Schlumberger-Doll Research. 2-Bhatt A and Helle H B 1999 Porosity, permeability and TOC prediction from well logs using a neural network approach 61 ST EAGE, Conf. (Helsinki, Finland) pp 1–4 3-Bois, P., 1984, Fuzzy Seismic Interpretation, IEEE Transactions on Geoscience and Remote Sensing, Vol.GE-22, No. 6, pp. 692-697. 4-Cuddy, S.: “The Application of Mathematics of Fuzzy Logic to Petrophysics,” SPWLA Annual Logging Symposium (1997), paper S 5-Cuddy S J 1998 Litho-facies and permeability prediction from electrical logs using fuzzy logic 8th Abu Dhabi International Petroleum Exhibition and Conference SPE 49470 6-Fang, J.H. and Chen, H.C.: “Fuzzy Modelling and the Prediction of Porosity and Permeability from the Compositional and Textural Attributes of Sandstone,” Journal of Petroleum Geology (1997) 20, 185-204. 7-Fuzzy logic Toolbox, Matlb Software CD-Room,2001.By the math works,Inc. 8-Huang, Y., Gedeon, T.D. and Wong, P.M.: “A Practical Fuzzy Interpolator for Prediction of Reservoir Permeability,” Proceedings of IEEE International Conference on Fuzzy Systems, Seoul (1999). 9-Huang Y, Gedeon T D and Wong P M 2001 An integrated neural-fuzzy-genetic-algorithm using hyper-surface membership functions to predict permeability in petroleum reservoirs J. Eng. Appl. Artif. Intell. 10-Saggaf M M and Nebrija Ed L 2003 A fuzzy approach for the estimation of facies from wireline logs AAPG Bull. 87 1233–40. 11-Nikravesh, M. and F. Aminzadeh, 1999, Mining and Fusion of Petroleum Data with Fuzzy Logic and Neural Network Agents, To be published in Special Issue, Computer and Geoscience Journal, 1999-2000. 12-Nordlund, U.: “Formalizing Geological Knowledge – With an Example of Modeling Stratigraphy using Fuzzy Logic,” Journal of Sedimentary Research (1996) 66, 689-698. 13-Ozer M 2005 Fuzzy c-means clustering and Internet portals: a case study Eur. J. Oper. Res. 14-Zadeh, L.A., 1965, Fuzzy sets, Information and Control, v8, 33353.
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Porosity Evolution In Carbonate Reservoir Rock Of Sarvak Formation, Zagros Basin, Iran
Parisa Gholami Zadeh*2, Mohamd Hosein Adabi3
Abstract The Sarvak Formation with middle Cretaceous age (Albian- Turonian) is the second major oil carbonate reservoir rock in Zagros area. Thickness of the Sarvak Formation is 285 meters in well No. 8 of Kuh-e Mond. For investigation of microfacies and effect of diagenetic process on the porosity evolution of this formation are studied 329 thin sections colored with red Alizarin, core data. Based on petrographical studies, 15 microfacies were recognized. These microfacies were deposited in lagoon, back reef (leeward), reef, fore reef (seaward), shallow open marine and deep open marine settings. Six major transgressive– regressive sequences are interpreted in the Sarvak Formation. In this study, porosity types were divided into primary and secondary porosity groups that affected by sedimentary environment, diagenetic process and tectonic. In high energy microfacies, primary porosity (interparticle and intraparticle types) was formed that interparticle porosity was decreased, but moldic and vugy porosities were increased in primary diagenetic stage (eogenetic). In mezogenetic stage, cementation lead to decrease porosity, but dissolution process, dolomitization and tectonic process lead to form vugy, intercrystalin and fracture porosities. The dissolution of unstable minerals (mainly aragonite) is the major process that improves porosity and then permeability by enlarging pores and pore throats. The best reservoir quality occurs in the upper parts of the regressive systems tracts, which contain primary grainsupported intervals or dissolution porosity. The studies show that porosity evolution controlled in sequence stratigraphy framework (A combination of depositional environment and diagenesis) in carbonate sequence of Sarvak Formation.
Keywords: Porosity evaluation, Sarvak Formation, reservoir characterization, sequence stratigraphy
1. Introduction Generally, there are several porosity systems which let to heterogeneous Petrophysic properties in the carbonate reservoir rocks [19]. Therefore, the relative percentage and type of pores and their distributions strongly is effective in production indexes and carbonate reservoirs simulation (e.g. [15], [3], [14] [12], [27]). Pore types in the carbonate rocks can generally be classified on the basis of the timing of porosity evolution [5 ]: 1) primary pores (or depositional porosity), which are pores inherent in newly deposited sediments and the particles that comprise them; and 2) secondary pores, which are those that form as a result of later, generally post-depositional dissolution. Primary porosity is substantially reduced by cementation and compaction during post-depositional burial Due to the natural tendency in most carbonate sediments [10], many workers would argue that most porosity in limestone and dolomite reservoirs has secondary origin [19]. Exceptions to this statement are cases where primary porosity is preserved because of the early influx of hydrocarbons into pores [8]. Today, the subaerial meteoric diagenetic (freshwater) model is highly used to describe porosity change in carbonate, especially in sequence stratigraphic-related diagenetic studies of
2 - Ms.c from Shahid Beheshti University, +989173125118, [email protected] 3 - Shahid Behesh University, +982129902617, [email protected]
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 reservoirs. [9], [16]. This model presupposes that if porous carbonate rocks are present beneath unconformities, then that porosity must have been created by freshwater dissolution during subaerial exposure. But this porosity may be occluded during later burial.
2. Location Of The Study Area The study area is located in Tangestan, south-eastern of Bushehr, southern Zagros Basin. Subsurface section (a well of Mond Oil Field) is located at 100 kilometers southeast of Bushehr city (Khormoj).
3. The Study Method In the petrographic studies, all thin sections (329) are colored with Red-s alizarin for recognizing dolomite and calcite mineralogy. Then, thin sections are named by Dunham method [7]. After Diagenetic studies, the relationships between Diagenesis and reservoir properties were compared with Core data.
4. Porosity Evaluation In The Sarvak Carbonate Reservoir Rock Primary Porosity: Pelloidal microcrystalline cement is observed in the reefal setting that covered by the coarse scalenohedral crystals. Also, isopachous radial fibrous cement is distinguished in some reef pores shows undulose distinct. Primary framework growth porosity between rudist skeletal has decreased due to early isopachuos cementation and filling with internal sediments. Syntaxial cement over the crinoid’s fragments can significantly reduce the interparticle porosity [27] and occluded throat pores. Other processes that will reduce porosity in the reef cavities are internal sedimentation (regardless of its origin). Core analyses of these parts show 8.7 percent total porosity. Figure 1 shows sedimentary porosity distribution (primary porosity) through the Sarvak Formation in the study area.
Secondary Porosity Beneath Unconformities (The Subaerial Meteoric Model) Dissolution degree of carbonates depends on the mineralogy of the sediments or rocks [17], [23]. At the beginning of this phase, dissolution of aragonite particles created moldic porosity. With increased saturated water by calcium carbonate, carbonate cement fills the porosity. Dissolutions that observed in these sections more depends on rock Fabric (moldic porosity). There are a few vuggy pores that do not depend on the Fabric. Secondary porosity in the Sarvak Formation result of dissolution after the sedimentation and including developed inter- and intraparticle porosities that all shows selective texture. For example, rudist bearing grainstones in the upper part of Sarvak Formation have been deposited in a high energy environment and have high interparticle porosity and permeability. In the facies that are formed in the Lagoon environment, only grains were dissolved, so samples have porosity and no permeability. But fractures in the reservoir rock have connected porosities and increased permeability. Average value of core porosity is 8.51% and for permeability is 3.02 md. Figure 1 shows meteoric porosity distributions. In this, meteoric porosities are limited to beneath of the sequence boundaries.
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Alternative Origin Of Secondary Porosity (The Mesogenetic Model) Since the late 1970s-early 1980s, geologists began to suspect that not all secondary dissolution porosity in carbonate rocks forms or formed solely beneath unconformities by freshwater dissolution in either the eogenetic or telogenetic environments [1], [26], [4], [23]. Choquette and Pray [4] referred this to as the mesogenetic environment. In the wackestone and packstone facies, dolomites as rhombohedral crystals with different sizes (between 10 to 220 microns) are distinguished that is floating in the Matrix. Mainly, along the pressure dissolution zone (Stylolites) have been gathering fine grain dolomites. This evidence shows that dolomites were formed in mesogenetic environment and they have increased intercrystalline porosity. The average value of porosity is 14% (totally intercrystalline, fractures and moldic porosities) and the average value of permeability is 8.44 md. Dolomite formations along the stylolites suggested that they have acted as conduits for movement of fluids in the shallow burial conditions. Petrographic studies of Sarvak carbonate Formation show that some porosity has not related to discontinuity surfaces, so their origin cannot be considered meteoric fresh water. They more were vuggy porosity that are seen in the deep marine facies and formed low percentage of porosity. A few feet below these samples were observed large vuggy porosities that were filled with coarse blocky or poikilitic cements. In addition, some cement that is probably formed in the burial diagenesis is seen in the open fractures and stylolites. Production of carbon dioxide, hydrogen sulfide and large quantities of organic acids during maturation of organic material in the buried hydrocarbon source rocks caused subsurface dissolution. As these gases and organic acids are expelled from the source rock, the evolved CO2 combines with subsurface water to produce carbonic acid and the H2S similarly combines with water to produce sulfuric acid. Together, these acids and associated organic acids can migrate great distances laterally as well as vertically [11]. Burial carbonate dissolution only in the upper part is done. Likewise, once the acids are spent, subsurface fluids can then precipitate carbonate cements, which is why many examples of such cements contain hydrocarbon inclusions [2]. Secondary dissolution porosity formation can alternate with cementation [24], [21], [20], [23]. The detailed petrographic Study of Sarvak Formation has shown that porosities along and associated with stylolites or which cuts across stylolites, pores that cut across cements that contain hydrocarbon inclusions and pores that cut across or which are intimately associated with pyrite must be the result of mesogenetic dissolution [24], [6], [13], [23], [21], [22]. Figure 1 shows burial porosity distribution through Sarvak Formation in this study. As can be seen this type of porosity does not depend on sequence boundaries.
Microporosity And Chalky Porosity The term microporosity refers to any very small pores that can be recognized only with the aid of a high-powered binocular microscope or thin-section [5], [25] and included intraparticle pores within small particles and intercrystalline pores between dolomite crystals or between calcite cement crystals in this study. Chalky porosity is a term that refers to microporosity that commonly forms in highly weathered or otherwise highly diagenetically altered carbonate rocks [18]. Average value of core porosity is 3.63% and for permeability is 0.001 md in the mudstone and wackestone facies. microporosity and specifically chalky porosity were formed beneath unconformities as well as in deeply buried rocks in the Sarvak
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Formation, and as such, their presence does not necessarily imply the existence of a stratigraphically-nearby unconformity.
5 - Conclusions In this study, different porosities are divided into primary and secondary that affected by the sedimentary environment, diagenesis and tectonic processes. In the high energy microfacies (Shoal and reef microfacies), primary porosity (Inter- and intraparticles) were formed that early cementation has decreased interpartile porosity, but dissolution has increased vuggy and moldic porosities during the early diagenesis stage (Eogenese). In the Lagoon and the open marine facies that have been affected by meteoric diagenesis, aragonite grains have been resolved and have created moldic porosity. Tectonic fractures in this facies are increased permeability. In the mesogenese stage, cementation cause to decrease porosity, but dissolution, dolomitization and tectonic processes has led to form vuggy, intercrystalline and fracture porosities. Generally, important factor in to being reservoir of Sarvak Formation is porosities that was formed in the meteoric diagenesis stage and increased by tectonic fractures. As a result, porosity evaluation in the Sarvak carbonate is controlled by sequence stratigraphy. The type of Porosities that formed in mesogenese is the same in the eogenesis and telogenesis stages. So that should point to that only with determining porosity types cannot distinguish diagenetic environments.
6 - Appreciation The authors would like to thank the Research & Development Department of the National Iranian Oil Company (NIOC), for data access and financial support of this study.
7- References [1] Bathurst, R.G.C., 1980, Deep crustal diagenesis in limestones, Revista Instituto Investaciones Geologicas: University of Barcelona, v. 34, p. 89-100. [2] Burruss, R.C., Cercone, K.R., and Harris, P.M., 1985, Timing of hydrocarbon maturation - evidence from fluid inclusions in calcite cements, tectonics and burial history, in N. Schneidermann and P.M. Harris, eds., Carbonate Cements: SEPM Special Publ. 36, p. 277-289. [3] Chilingarian, G.V., Torabzadeh, J., Rieke, H.H., Metghalchi, M., and Mazzullo, S.J., 1992, Interrelationships among surface area, permeability, porosity, pore size, and residual water saturation, in G.V. Chilingarian, S.J. Mazzullo, and H.H. Rieke, eds., Carbonate Reservoir Characterization: A Geologic-Engineering Analysis, Part I: Elsevier Publ. Co., Amsterdam, Developments in Petroleum Science 30, p. 379-397. [4] Choquette, P.W., and James, N.P., 1987, Diagenesis 12: diagenesis in limestones-3. The deep burial environment: Geoscience Canada, v. 14, p. 3-35. [5] Choquette, P.W., and Pray, L.C., 1970, Geologic nomenclature and classification of porosity in sedimentary carbonates: AAPG Bulletin, v. 54, p. 207-250. [6] Druckman, Y., and Moore, C.H., , 1985, Late subsurface porosity in a Jurassic grainstone reservoir, Smackover Formation, Mt. Vernon field, southern Arkansas: in P.O. Roehl and P.W. Choquette, eds., Carbonate Petroleum Reservoirs: Springer-Verlag, New York, p. 371-383.
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[7] Dunham, R. J., 1962, Classification of carbonate rocks according to depositional texture: Amer. Ass. Petrol. Geol. Mem., 1, p. 108-121. [8] Feazel, C.T., and Schatzinger, R.A., 1985, Prevention of carbonate cementation in petroleum reservoirs: in N. Schneidermann and P.M. Harris, eds., Carbonate Cements: SEPM Special Publ. 36, p. 97-106. [9] Friedman, G.M., 1964, Early diagenesis and lithification in carbonate sediments: Journal of Sedimentary Petrology, v. 34, p. 777-813. [10] Halley, R.B., and Schmoker, J.W., 1983, High porosity Cenozoic carbonate rocks of south Florida: progressive loss of porosity with depth, AAPG Bulletin, v. 67, p. 191-200. [11] Hanor, .S., 1987, Origin and migration of subsurface sedimentary brines: SEPM Lecture Notes, Short Course No. 21, 247 p. [12] Hendrickson, A.R., Thomas, R.L., and Economides, M.J., 1992, Stimulation of carbonate reservoirs: in G.V. Chilingarian, S.J. Mazzullo, and H.H. Rieke, eds., Carbonate Reservoir Characterization: A Geologic-Engineering Analysis, Part I: Elsevier Publ. Co., Amsterdam, Developments in Petroleum Science 30, p. 589-625. [13] Heydari, E., and Moore, C.H., 1989, Burial diagenesis and thermochemical sulfate reduction, Smackover Formation, southeastern Mississippi salt basin: Geology, v. 17, p. 1080-1084. [14] Honarpour, M.M., Chilingarian, G.V., and Mazzullo, S.J., 1992, Permeability and relative permeability of carbonate reservoirs, in G.V. Chilingarian, S.J. Mazzullo, and H.H. Rieke, eds., Carbonate Reservoir Characterization: A Geologic-Engineering Analysis, Part I: Elsevier Publ. Co., Amsterdam, Developments in Petroleum Science 30, p. 399-416. [15] Jodry, R.L., 1992, Pore geometry of carbonate rocks and capillary pressure curves (basic geologic concepts), in G.V. Chilingarian, S.J. Mazzullo, and H.H. Rieke, eds., Carbonate Reservoir Characterization: A Geologic-Engineering Analysis, Part I: Elsevier Publ. Co., Amsterdam, Developments in Petroleum Science 30, p. 331-377. [16] Land, L.S., 1967, Diagenesis of skeletal carbonates: Journal of Sedimentary Petrology, v. 37, p. 914-930. [17] Longman, M.W., 1980, Carbonate diagenetic textures from near surface diagenetic environments: AAPG Bulletin, v. 64, p. 461-487. [18] Mazzullo, S.J., 1994, Models of porosity evolution in Permian periplatform carbonate reservoirs (debrisflows and turbidites) in the Permian Basin: West Texas Geological Society Bulletin, v. 34, no. 1, p. 5- 12. [19] Mazzullo, S.J., and Chilingarian, G.V., 1992, Diagenesis and origin of porosity, in G.V. Chilingarian, S.J. Mazzullo, and H.H. Rieke, eds., Carbonate Reservoir Characterization: A Geologic-Engineering Analysis, Part I: Elsevier Publ. Co., Amsterdam, Developments in Petroleum Science 30, p. 199-270. [20] Mazzullo, S.J., and Chilingarian, G.V., 1996, Hydrocarbon reservoirs in karsted carbonate rocks: in G.V. Chilingarian, S.J. Mazzullo, and H.H.Rieke, eds., Carbonate Reservoir Characterization: A Geologic- Engineering Analysis, Part II: Elsevier Publ. Co., Amsterdam, Developments in Petroleum Science 44, p. 797-865. [21] Mazzullo, S.J., and Harris, P.M., 1991, An overview of dissolution porosity development in the deep-burial environment, with examples from carbonate reservoirs in the Permian Basin, in M.
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Candelaria: ed., Permian Basin Plays – Tomorrow’s Technology Today: West Texas Geological Society, Publ. No. 91-89, p. 125-138. [22] Mazzullo, S.J., and Harris, P.M., 1992, Mesogenetic dissolution: its role in porosity development in carbonate reservoirs: AAPG Bulletin, v. 76, p. 607-620. [23] Moore, C.H., 1989, Carbonate Diagenesis and Porosity: Elsevier Publ. Co., Developments in Sedimentology 46, 338 p. [24] Moore, C.H., and Druckman, Y., 1981, Burial diagenesis and porosity evolution, Upper Jurassic Smackover, Arkansas and Louisiana: AAPG Bulletin, v. 65, p. 597-628. [25] Pittman, E.D., 1971, Microporosity in carbonate rocks: AAPG Bulletin, v. 55, p. 1873-1878. [26] Scholle, P.A., and Halley, R.B., 1985, Burial diagenesis: in N. Schneidermann and P. M. Harris, eds., Carbonate Cements: SEPM Special Publ. 36, p. 309-334. [27] Wardlaw, N.C., 1976, Pore geometry of carbonate rocks as revealed by pore casts and capillary pressures: AAPG Bulletin, v. 60, p. 245-257.
Figure 1: distribution of porosity types in 8 well of Mond Oil field
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Lithostratigraphy of Nigeria An-Overview
Shitta Kazeem Akorede*,
Corresponding author: Geotech Nigeria Limited, KLM 8/9 Podo New Garage, Old Lagos Bye-Pass, Ibadan, Oyo-State,Nigeria . E-mail address: [email protected] (K.A Shitta).
Abstract Nigeria lies very close to the equator (hot country) West coast Africa between latitude 4° N and 14° N degree and longitude 2° E and 15° E degree. The country is located at the Northern end of Eastern branch of west coast of Africa rift system. Nigeria geological set up comprises broadly sedimentary formation and crystalline basement complex, which occur more or less in equal proportion all over the country. The sediment is mainly Upper Cretaceous to recent in age while the basement complex rocks are thought to be Precambrian. The studied area lies between latitude 12.4° and 11.11°W and longitude 13.81° and 14.13° S. The studied area is underlain by Precambrian basement complex of southern western Nigeria .The major rock in the area is charnokite and granite rock. The granite rock which is member of the older granite suite occupies about 65% of the total area .The principal granite is petrographic variety are recognized .The fine grained biotite-granite medium-coarse, non porphyritic biotite -hornblende granite and coarse-porphyritic biotite -hornblende granite. Also three main textural type of Charnokitic rock are also distinguished are coarse grained, massive fine grained and gneissic fine grained .The mode of occurrence of rock is three (1) core of the granite rock as exemplified by study area and few smaller bodies (2) Margin of the granite bodies as seen in Ijare and Uro edemo-idemo Charnokitic bodies and (3) Discrete bodies of the gneissic fine grained Charnokitic rock within the country gneisses as seen in Ilaro and Iju and Emirin village. All the charnokite in the region are dark-greenish to greenish-gray rocks with bluish quartz and greenish feldspar.
Keywords: Geology of the study area; Occurrence; Textural; Petrography; Colour;
1. Introduction Water is known to be a universal solvent. It is also one of the natural resources tapped by man, animals and plants to meet their needs for life sustenance. The world’s water resources include the entire range of natural waters on earth, either in vapour, liquid or solid form. Water is classified as surface water or groundwater. Surface water include rain water collected into rivers, lakes, reservoirs and oceans while groundwater include natural springs, well and boreholes. Groundwater is commonly understood as water occupying the voids within a geologic stratum, groundwater is free from suspend matter and bacteria. It can be said to be pure, clear and colourless. Groundwater has greater quality than surface water. About 495,000 children die annually of various diseases due to drinking of water that are not properly safe and sanitize (sea, stream e.t.c.), even as population increases and industries required all over the world, most people generally required about 2.5 litres of water everyday for direct consumption. The average amount of water used domestically each day by every person is about 190 litres (Hamill and Bell, 1986). Generally, industries require approximately one quarter to one third of the public water supply under normal condition the easiest and most convenient way to meet the public demand for
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 water is to utilize surface water resources, but unfortunately, water such as river, lake, stream e.t.c. are less plentiful than can be imagined. It can be recorded that surface water resources account for less than 2 percent of the world’s fresh water. The latter fresh water available however is unevenly distributed while the sources that are available have been either contaminated or polluted. (Hamill and Bell, 986).Groundwater accounts for about 98 percent of the world’s fresh water and is fairly evenly distributed throughout the world. It provides a reasonable constant supply which is not completely susceptible to drying up under natural condition unlike surface water (World water balance and water resources of the earth UNECO Copyright 1978). All over the globe, groundwater has been a very good and important source of water supply. It has been of continuous and tremendous use in irrigation industries and urban centers, as well as in rural communities. It is conveniently available at point of use and possesses excellent quality that requires little or no treatment in most cases.
2. Occurrence of Groundwater The concept which explains the ultimate destination of rainwater is the sea either directly through run off or indirectly be infiltration and subsurface flow. A system of water movement in the atmosphere or rainfall, dews, hailstones or snowfalls over land as run off. Vertical and horizontal movement underground as infiltration or subsurface and continuous movement of all forms of water is the hydrogeology cycle. In the atmosphere, water vapours condense and may give rise to precipitation. However, not all this precipitation will reach the ground surface; some are intercepted by vegetation cover or surface of building and other structures and then evaporate back into the atmosphere. The precipitation that reaches the ground surface may flow in to stream, lake and ocean, where it will either be evaporated or form seepages intruding in to the ground likewise soil moisture and further percolate downward to underline aquifer where it may be held for several years longer. Groundwater in Nigeria is restricted by the fact that more than half of the country is underlain by crystalline basement rock of pre-cambian era. The main rock types in this geological terrain include igneous and metamorphic rock such as migmatites and granite gneisses.Generally in their unaltered form, they are characterized by low porosity and permeability. Porosity in basement rocks is by induction through weathering while secondary permeability induces by tectonic activities which manifest in form of that often act as conduct path facilitating water movement. In other words, aquiferous zones in the basement terrain include fractured/weathered rocks. The yielding capacity of well, drilled within such rock are always very enormous.
Research Methodology (1) Literature Review: All available geological/hydrological information were collected through the reading of journal, reference seminar paper (Olorunfemi M.O., 1990) (2) Data Gathering: All vertical electrical sounding data were collected from water section of the Federal Ministry of Agriculture and Water Resources Abuja, Wenner array was used in collecting the date.
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(3) Data Analysis: The data were interpreted by using partial curve matching technique. Computer was then used to interpret the results, from the result obtained geoelectric sections were generated. (4) Interpretation of Results: Result obtained from each VES station were completed and interpreted in order to determine the best location for groundwater development in the study.
2.1.1Geology of the Study Area Akure south Local Government falls within the basement complex region of Nigeria. The studied area lies between latitude 12 o 04 o and 11 o 11 o W and 13 o 81 o and 14o13 o. and is underlain by precambian basement complex rocks of South Western Nigeria.Several part of Africa is underlain by crystalline basement complex rocks. The major types of rocks in Akure are granite rocks and charnokite. The granite rocks which are member of the older granite suit occupy about 65% of the total area of Akure. Three principal petrographic varieties are recognized, the fine-grained biotite granite, medium to coarse grained, non-porphyritic biotite – hornblende granite and coarse – porphyritic biotite- hornblade granite. The classification is based largely on the textural characteristics. Also three main textural types of charnockitic rocks are also distinguished in Akure.These are the coarse-grained variety, massive fine grained and the gneissic fine-grained types. Unlike most of the older granite, the charnokite rocks do not occur in form of smooth rounded boulders and only a few low hills all forming oval to sub-circular and elongated bodies. The charnockitic rocks appear to have three modes of occurrence in the area, the first occurrence is within what seems to be the ‘core’ of the granite rock as exemplified by Akure body and few smaller bodies.The second is along the margins of the granite bodies as seem in Ijare and Uro Edemo-Idemo charnockitic bodies. The first two modes of occurrence are mainly shown by the coarse-grained charnockitic variety. The last mode of occurrence is represented by the discrete bodies of the gneissic fine-grained charnockitic rocks within the country gneisses as seen in Ilara and also near Iju and Emirin villages.All the charnockitic in the region are dark-greenish to greenish-gray rocks with bluish quartz are greenish feldspars (V. O. Olarewaju, 1997).
2.1.2 Hydrogeology of the Study Area The major river in Akure in Ondo State is Ero River,this river originates from Igbara Oke road, about 16-18km distance to Akure town.Osun River is the major source of water runoff in Akure town, there are other smaller rivers such as Owuruwu River which is about 60m distance from Apex Nursery and Primary School, Oba Adesida, which is the Ves location. This river flows to meet Osun River at Akure road, the other rivers such as Otenre River, Omi Atamo, are smaller rivers that serve as runoff in the town; they meet Osun River at a point known as Osun Amon.Osun River flows from the Eastern part to Western part of the town and then flows to Ise town to meet a bigger river called Ogbese in Ondo State.
2.2Result and Discussion The interpretation of field resistivity data are in terms of resistivities and dept to the bedrock and interfaces across which a strong electrical exists.The analysis and interpretation of the
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 surveyed data shows four geoelectric layers. These layers are top soil which consists of the various rock types from clayey sand to sandy clay to compact sand. The second is the fresh/highly resistive basement. The fresh basement is characterized by high and infinite resistivity value and could not be contended on for groundwater, but the weathered zone and fractured basement which have lower resistivity value constitute good water zone
2.2.1.Geoelectric Section The quantitative interpretation of the VES data resulted in the production of numbers of geoelectric section. The section provides composite information along lithologic depth, the geoelectric section revealed four subsurface geoelectric layers.The top layer which consists of (clayey sand and sandy clay) has resistivity value ranging from 700hm-m to 5800hm-m, the maximum layer thickness is 3.0m. The top soil contributes to the development of groundwater, this layer is called the layer of aeration, and the water in this layer is called sub-surface water or zone of aeration. This zone is subdivided into three namely; soil water, intermediate belt and capillary belt. The water that infiltrate into the soil from precipitation and in general ranges to all water present in the sub soil, or (in lithosphere). It may be evaporated from the soil, may be absorbed by plant root (soil water) and then transpired or may percolate downward to groundwater reservoir (intermediate). It occurs in a zone extending from the ground surface to the lower limit of porous water bearing rock formation (capillary) and designated s zone of the rock fracture. The difference in compaction of the clayey sand is responsible for the variation in the resistivity values. The resistivity of the second layer (Weathered zone) ranges from 30ohm-m to 193ohm-m while the thickness varies between 3m to 15.0m2. The third layer is the fractured basement which has layer thickness varying from 17.5m – 29m with resistivity value ranging between 90ohms-m to 240ohms-m. The layer will be good for groundwater accommodation if the fractures are interconnected and permeable. The fresh basement which is the fourth layer is characterized by high resistivity value up to 6650ohm-m. The fresh basement is made up of infinitely resistivity rock in all the stations which form the bedrock.The rock in this zone is hard, with no permeability and no water bearing. In fresh, non-fractured rock, the porosity is often less than 2%, as a result, run off is high and infiltration rate is very low in this zone. The geoelectric section shows that the depth to the bedrock varies across the sounding station.
2.2.2. Overburden Layer The thickness of the overburden is an important hydrogeologic consideration in groundwater development in the basement terrain (Ajayi & Hassan 1990, Olorunfemi & Idonigie, 1992). Because water gets into the saturated zone through the overburden , the thickness of the overburden ranges from 23.30m to 36.60m in the study area. The variation in the overburden is due to degree of composition.
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2.2.3. Weather Layer. The weathered zone thickness shows the thickness of the weathered layer beneath in all the sounding station established across the study area, with VES 5 having the highest of thickness of about 13m and VES 1 having the lowest with about 2m.deriving from this, the thickness of the weathered layer here has, is sufficient enough for groundwater accumulation and therefore recommended for location of a borehole. The variation in the weathered layer is due to the degree of weathering.
2.2.4. Fractured Layer The weathered layer thickness shows the thickness of the fractured layer beneath in all the sounding stations established across the study area, with VES 1 having the higher thickness of about 15m and VES 2 having the lowest with about 1.80m and the variation of this layer is due to degree of fracturing. VES 5 and VES 1 are the location that will be recommended for groundwater, because they have the highest thickness of both weathered zone and fractured zone respectively which are good for groundwater accumulation. VES 5 is recommended as priority location for sitting borehole, because it has thick sequence of both weathered zone and fractured basement, which are good for groundwater accumulation. If the fractured are interconnected and hence permeable, the thickness of the weathered zone in this section confers advantage on this over others. The location will be good for optimum groundwater development, because of its availability in the study area; it will also be the only safe source of untreated water in Akure and also the cheapest source of good quality water supply, and its development can take in small crement rather than with relatively large scale financial investment which is the case of dams. VES 5 has an advantage over VES 1, because the cost of drilling through VES 5 (weathered zone) will be cheaper than drilling through VES 1 which is of harder rock (fractured basement) and more difficult to drill. VES 1: This location will be good for groundwater development if the fractures in this zone are interconnected and have permeable. The problem with this section is that to drill through fractured basement is very difficult and hard, it can damage the drilling bit. VES 2: In this location, groundwater yield could be high bit, will not be up to that of (VES 1 and VES 5) so it can not be recommended for groundwater because the dip of the location and also the thickness of the area could affect its yield. VES 4 will produce minimum groundwater yield, because of its dip and thickness of weathered zone which is small, it ranges between 1.70m to 7.0m. VES 3: This location has the lowest thickness and the lowest probable groundwater yield, this location could be poor for groundwater yield and it is not recommended because of the thickness and dip as it can be seen in the geoelectric section.
3. Conclusion The result of a quantitative interpretation of the VES data obtained in a geophysical survey over part of Akure, on a location opposite Apex Nursery and Primary School, Oba Adesida Road, Akure in Ondo State. The interpreted results obtained from the study area are represented by a geoelectric section which shows the sequence and relationships between the
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 subsurface lithologies. The weathered layer and the fractured zone have been identified as the aquiferous in the area. The weathered layer is thicker in VES 5 and lowest in VES 1, while the fracture basement is thickest in VES 1. The 2 VES stations have been identified as the most suitable location for groundwater development in the area, with VES 5 being more prolific than others.
4. References Adegoke Anthony O. W. & Ajayi (1988): Groundwater Prospects in Basement Complex Rock of South Western Nigeria. Journal of African Earth Sciences, Vol. 7, No. 1. pp. 227-235. Akinloye (1983):Hydro-geological Investigation or Groundwater Development at Obada Oko, Abeokuta Technical Brink Zones and Company Ltd. Ibadan pp. 10. David L. M. & Ofrey D. (1983): An Indirect Method of Estimating Groundwater Level in Basement Complex Regolith Resources. Vol 1, No. 2, pp 161 – 164. Griffiths O. T. & King R. F. (1981): Applied Geophysical Geophysics for Geologists and Engineers. (The Element of Geophysical Prospecting) 2nd Edition, pp. 1, 88, 105 – 107. Hamill, L. & Bell F. U. (1986): Groundwater Resources Development. Britain Library Cataloguing in Publication Data London. pp. 151 – 158. Jones M. J. (1985): The Western Zone Aquiferous of the Basement Complex Area of African, Quarterly Journal Engineering Geology. pp. 161 – 164. Kelly E. W. (1985): Geoelectric Sounding for Delineating Groundwater Contamination. pp.6. Olorunfemi M. D. & Olayinka A. I. (1992): Alteration of Geoelectric in Okene are and Implication for Borehole Sitting. Journal of Mining and Geology, pp. 403-411. Olorunfemi M. O.(1990): The Hydrogeological Implication of Topographic Variation with Overburden Thickness in Basement Complex. Area of South Western Nigeria. Journal of Mining and Geology. Vol 26, No. 1. Olorunfemi M. O. & Oloruniwo M. A. (1985): Geoelectric Parameters and Aquifer Characteristics of Some Part of South Western Nigeria. Journal of Mining and Geology. Olorunfemi, M. O. & P.K. Emikanselun (1999): Direct Current Resistivity Sounding for Groundwater Potential in Basement Complex Area of North-Central Nigeria. Journal of Applied Science, Vol. 2, No 1, pp. 31-34. Rahaman M. A. (1976): Review of the Basement Geology of South Western Nigeria in Geology of Nigeria. Elizabithan Publishing Company, Nigeria. pp. 41-58. Schwartz F. W. & M. C. Clymont, G. L. (1977): Application of Surface Resistivity Method Groundwater. pp. 197-200.
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Table 1: Summary of Layer Thickness of Resistivities Table 2: Resistivity in Sounding Station
VES Thickness Resistivities (Ohms-m) Overbur Town Location VES No Curve Type Num dened AKURE AKURE, 11, Opposite 1 HA ber Thicknes Apex Nursery and 2 HA s-EH(M) Primary School, Oba 3 H L h1 h2 h3 e1 e2 e3 e4 Adesida Road, Akure. 4 H 1 1.2 2.9 19.0 580 193 613 5400 23.76 5 HA 0 8 8
2 3.0 8.3 11.1 500 167 2470 6650 22.40
0 0 0
3 1.7 2.5 - 265 80 2565 - 4.25
0 5
4 1.1 6.7 - 170 30 - 7.85
5 0
5 1.8 14. 19.5 570 63 594 2660 36.66 0 58 8
Table 3: Classification of VES Curves QM ELECTRODES SPACING VES Thickness Thickness Thickness Depth of Weathered Resistivity Station of 1st of 1st of 1st Bedrock Layer of the Layer (m) Layer (m) Layer (m) (m) Thickness Weathered Overburden (m) Layer Thickness (ohm-m) * 1 1.70 2.98 19.08 23.70 19.08 613 2 3.00 8.30 11.10 22.40 11.10 247 3 1.70 2.55 - 4.25 2.55 86 * 4 1.15 6.70 - 7.85 6.70 30 5 1.80 14.58 19.00 35.38 19.00 594 * * * = CURVE * * = RESISTIVITY VALUES E1 = 550
ELECTRODES SPACING QM VES 1
*
* * * * * *
R2 = 167 R1 = 500
LOCATION ELECTRODES SPACING QM
* * * * * * * *
= CURVE R2 = 86 = RESISTIVITY VALUESR1 = 265
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
LOCATION ELECTRODES SPACING QM VES 5
* *
* *
* * * * * *
R2 =63 = CURVE R1 = 570
LOCATION:AKURE
* * * * * * * *
R2 =30 = CURVE R1 = 170
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
Geology of Precambrian Rocks in Central Iran, as Evidence of Metallogenic province and Metallogenic Epoch for Metallic Deposits.
Mollai Habib
Department of geology, Faculty of sciences, Islamic Azad University - Mashhad Branch Rahnamaei Avenue, Mashhad, Iran. Phone No:+985118408008 Fax No. +985118446361 Email: [email protected] ABSTRACT The sequences of low to high grade metamorphic rocks of Precambrian age with the thickness of about2000 meters exposed in Central Iran. The Precambrian rocks of Iran can be divided in to tow main groups. The first one is the metamorphic complex which are called the basement rocks of Precambrian overlay disconformities by of Katangan rock, and the second one which are more as marginal continent, they deposited after the Katangan Orogeny , are called late-Precambrian rocks. Most of these rocks are igneous of continental origin and some of them are oceanic origin. The most important metallic deposits of Iran occurred in the Precambrian rocks of Central Iran. The main parts of these deposits occurred in the metamorphosed rocks of Saghand–Chador Malou and Bafque regions. These deposits constitute the most largest and important economical deposits of Iran. The Chador Malou, Choghart , Golgohar, Sechahoun and Gelmandeh Iron Ore deposits, Kushk lead – sphalerite mines ,Saghand and Narygan Uraniume deposits and Esfordy phosphate, deposits are the some of these examples. Based on new investigation it is suggested that the separation of ore rich melt and the ensuing hydrothermal processes dominated by alkali metasomatism were both involved to different degrees in the formation of ore deposits in Central Iran. Because of high concentration of various and largest deposits in this limited area of Precambrian age we can call the Precambrian of Central Iran as metallogenic province and metallogenic epoch.
Key words: Precambrian rocks, central Iran, metallogenic, ore deposit
Introduction One of the most important and interesting geological structure occurrences in Iran is the Orogenic movements, which is comparable with the occurrence of Katangan in Gondwana land and Baikalian in the Eurasian continent. Paleozoic vertical movements took places during the Cambrian and caused sudden change in litho logy or short break in sedimentation (Eftekhar Nezhad 1975). From tectonic point of view Iran can be divided into two marginal active fold-belts located in the NE that is Kopeh Dagh and in the SW which called Zagros Zone resting on the Hercynian terrain and the Precambrian Arabian plate respectively. Between these marginal fold belts are the Central Iran, Alborz, Zabol-Baluch and Makran units (Stocklin and Nabavi 1973 ). The geologic structure of various tectonic zones is essentially the result of Alpine Orogeny of Tertiary age.The Precambrian rocks occupy more than half the Ardekan Quadrangle map in Central Iran and may reach 10000m in exposed thickness ( Haghipour 1977). The Precambrian rocks of Iran can be divided in to tow main groups. The first one is the metamorphic complex which are called the basement rocks of Precambrian overlay disconformities by of Katangan, and the second one which are more as marginal continent, they deposited after the Katangan Orogeny , are called late-Precambrian rocks.
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
Geology of the Area: The basement complex is used here to set of rocks underlying the pan African unconformity and comprising mostly metamorphic or igneous rocks with the age of the bottom of the related rock cover being variable, ranging in most case from 570 t0 550 ma. Central Iran in a broad sense, comprising the whole area between the North and South Iranian ranges . The rocks which are called Precambrian rocks in Iran are exposed in the zonal structure of Central Iran, Alborz, Lut and Zagross. The sequences of low to high grade metamorphic rocks of Precambrian age with the thickness of about2000 meters exposed in Central Iran. According to Haghypour (1974) and Aghanabaty (2004) based on metamorphism process and Stratigraphy events, these rocks can be divided in to four groups as follow 1) Earlier Series , (2) Chapedony Complex,(3) Bonehshuro Complex and (4)Tashk Formation. The Chapedony complex with about 4000 meters thickness and the highest grade of metamorphism is the oldest Precambrian rock in Saghand – Posht Badam region of Central Iran. The Precambrian Chapedony and Poshte Badam formation of east Central Iran consist of meta-greywacke, meta-diorite meta-andesite ,amphibolites, pyroxenites, serpantinite and calc- alkaline intrusive island arc (,Haghipour 1974,1977,Berbarian and King 1981). The sequences of low to high grade metamorphic rocks of Precambrian with the thickness of about 2000 miters exposed in central Iran. The metamorphism in the central Iran is due to tectonic activities of the area In the Chapedony Complex granitization has more important role, because at least two phases of migmatization very well can be recognized.. The first phase has been cut by the second one (Darvishzadeh 1992). The megascopic structure of the gneisses in the field can be seen in microscopic thin section also as microstructure. The major part of Chapedony Complex is occupied by banded gneisses which consist of light band of quartz and feldspar and dark band made up of biotite along with amphibole
Metallogenic of the Area: The most important metallic deposits of Iran occurred in the Precambrian rocks of Central Iran. The main part of these deposits occurred in the metamorphosed rocks of Saghand– Chadormalou Regions. These deposits constitute the most important and economical deposits of Iran .The Chador Mmalou, Choghart , Golgohar, Sechahoun and Gelmandeh Iron Ore deposits. , Koshk lead – sphalerite mine, Saghand and Narygan Uraniume deposits , Esfordi phosphate and Salt Diapers deposits are the some of these examples, The a banded mine of Narygan Manganez also can be added to these deposits . Therefore the mineralization of this epoch and province can be categorized in to (1) Iron ore, for example, Choghart was a prominent iron oxide deposit in the Bafq mining district of Iran. 800miters length and 300 miters width , standing 150m above the surrounding plain and 1257 m above sea level. (2) Lead –Sphalerite deposit (3) Uranium and (4) Salt Diapers deposits without considering the Narygan Manganese in which the last two. Each of these deposits is one of the largest and important deposits in Iran (.5) The Esfordi apatite-magnetite deposit is situated in the Bafq district of central Iran. is the most P rich deposits in that Iran and is hosted by a sequence of early Cambrian rhyolitic volcanic rocks and intercalated shallow-water sediments. Bafgh Mishidovan refractory is a potential of the refractory group minerals.
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
Conclusion The Precambrian basement complexes in the Saghand region along the Chapedony and Posht e Badam faults as the oldest rocks o f the Iranian micro plate and considers that they were emplaced during Palaeo-to Mesoproterozoic time with consolidation concentrated between 2400 Ma and 2100Ma. The greenstone belts, paleo-suture zones and ophiolitic rocks around the high-grade metamorphic rocks of central Iran confirm that an island-arc type cratonization occurred here .The presence of Neo proterozoic volcanic here is also an indication of stretching of the Arabian–Iranian continental crust during an extensional phase of Pan– African orogeny. The host rocks of these deposits various from sedimentary to high grad metamorphic rocks (dolomite, meta greywacke slate, shale, quartezite, amphibolites and gneiss and also extrusive and intrusive ((rhyolite pyroxenite and, pegmatite) rocks .Most of them have been cut by late magmatic activities especially this is very common phenomena in the Bafgh iron ore deposit. The various mineralization in the Precambrian rocks of Central Iran indicate the potential resources of different geological activities and mineralization processes which have been occur in these areas. From the events of the above four categorized ore deposits, one can easy conclude that, the Precambrian age in Central Iran is one of the most metallogenic epochs and Province in Iran.
References
-AGHANABATY ,A.(2004). Geology of Iran. Published by geological survey of Iran.586p.-- BERBERIAN, M.AND KING,G.C.P.(1981): Towards a paleogeography and tectonic evolution of Iran . Canadian jouranal of Earth sciences .Vol.18,.No.2,pp210-265 -.Balkema, Rtterdam, pp 631- 634
- DARVISHZADEH, A.(1992): Geology of Iran .Amirkabir Publication ,Tehran,Iran 901p.
-EFTEKHAR –NEZAHD.J. (1975): Brief description of Tectonic history and structural development of Azarbaijan.Geological Survey of Iran
- HAGHYPOUR. A (1974.) Etude geologique de la region de Biabanak-Bafgh (central Iran). petrologie et tectonique de socle Precambrian et de sa Couverture. These,Universite Scientifique et Medicale de Greoble ,France,403p.
1-MOLLAI HABIB AND TORSHIZIAN HABIB ALLAH (2005). Petrology of Precambrian rocks of Chapedony complex in Central Iran. “International Conference on Precambrian Continental Growth & Tectonism"February 22 – 27, 2005 at the Bundelkhand University, Jhansi, India.
.-STOCKLIN, J AND NABAVI, M.H. ( 1973) Tectonic Map of Iran 1:2500000 Geological Survey of Iran
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
Figure1: Ore locations in Central Iran.
Figure2: Typical metamorphic texture in Metamorphic rocks of Central Iran.
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
Physico Chemical condition of Mazreah Skarn North of Ahar ,North West of
Mollai Habib
Dept. of Geology,. Islamic Azad University Mashhad Branch, Mashhad (Iran) Phone: +985118408008. Fax:+985118446361 E-mail:[email protected] Abstract Principal Skarn deposits along the northern margin of the Ahar batholith from west to east include Mazraeh, Vine and Gowdoul skarn deposits. Among these skarn deposits, the Mazraeh Cu-Fe Skarn deposit is the most typical skarn deposit in the NW Iran. The main mineral constituents of the skarns are garnet, magnetite, calcite, chalcopyrite, epidote, hematite and pyroxene, accompanied by quartz, pyrite, bornite, coevalite, chalcocite, plagioclase and chlorite.This investigation presents and interprets fluid inclusion data of different lithological units of the copper skarn deposits in the north of Ahar NW Iran. The results provide an assessment of the P-T conditions and mineral-fluid .Various fluid inclusions present in Mazraeh show homogenization to different phases. The overall homogenization of inclusions with daughter-bearing fluid inclusions ranges from 157o to 520oC. The total salinity of salt bearing inclusions varies from 31.4 to 63.0 wt.% NaCl equiv. The salinity of biphase inclusions, based on their final ice melting temperature in different samples, vary between 10.
2 to 20.8 wt.% NaCl equiv. The inclusions formed at low pressure. Th vs. salinity plots of Mazraeh inclusions show that the salinity of the fluids correlates positively with temperature.
Key words:physico chemical condition , Skarn deposit, Fluid inclusions, Azarbayjan, Iran,
Introduction In the Alborz unit, Precambrian basement rocks are of Gondwanan affinity. Tectonic movements in the Late Precambrian caused significant uplift in Azarbaijan and locally formed angular disconformities .A thick Triassic to Upper Cretaceous sedimentary- volcanic sequence was subsequently folded during Late Cretaceous-Early Tertiary orogenic movement (Eftekharnezhad, 1975). The late Eocene-Oligocene plutonic activity of northern Iran (the Gharah Dagh - Tarom plutonic belt) has a NW–SE trend (Pourhosseini, 1981). Late Eocene-Oligocene (mainly Oligocene) plutonic activity was reported by Khain (1975) from the Lesser Caucasus to northern Azarbaijan ( Stockline and Eftekharnezhad, 1969; Pourhosseini, 1981). Fluid inclusion studies have become vital to understanding the genesis and exploration of ores. Several workers have studied skarn deposits as well as those linked with granites to understand fluid evolution that resulted in ore deposition (Einaudi and Burt 1982; Ahmad and Rose, 1980; Sato, 1980; Kwak, 1986; Meinert, 1992; Mollai, 1993; 1996; and Calagari, 2004). This investigation presents fluid inclusion data for different lithological units of the Mazraeh copper deposits. Our results were used to the exploration parameters and for an assessment of the P-T conditions for mineral-fluid evolution.
The Ahar Batholith This Ahar batholith extends E–W for about 30 km and is 3–10 km wide (Fig.1). In general, the rock is fresh except at few places. The pronounced structure of the granodiorite body is cross jointing striking NNE-SSW and NNW-SSE with spacing of joints from a few centimeters to a meter. In some places, veins of aplite, pegmatite and quartz fill the joints and some joint planes are coated by malachite. The granodiorite pluton has intruded Cretaceous subvolcanic and sedimentary rocks along a plunging antiformal structure. In the host rocks, skarn
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 deposits are developed, as well as silicification, recrystallization of limestone, and production of spotted schist and hornfels. From west to east, the following are the principal skarn deposits:
Geological and Minera logy of copper skarn deposit Major rock types of the copper skarn deposit include metasedimentary and metavolcanic country rocks, and intruding plutonic rocks that have developed a metasomatic zone at the contacts with Cretaceous limestone. The whole structural set up of the Mazraeh mine is in an elliptical shape with the major axis striking E-W for a strike length of about 1.5 km and the minor axis lies in N-S direction with a width of almost 1 km. The whole meta-volcanic sedimentary sequence occurs as a mega- enclave within the granodiorite The country rock is nearly pure recrystallized limestone interbedded with the aluminosilicate layers. This argillaceous limestone consists of angular calcite, subordinate biotite, feldspar and quartz exhibiting low-grade regional metamorphism and metasomatism. To the north of the copper mines, hornfels have developed after the metasomatism of cataclastic rocks. They are very fine-grained, hard and usually black in colour. The southern periphery of the elliptical body comprises siliceous recrystallized limestone layers, which have a sharp contact with skarn whereas the contact between limestone and pelitic rocks is transitional. The main skarn zone varies in width from 2 to 50 meters. The Mazraeh iron-copper skarn deposit can be classified on the basis of petrology into endoskarn, exoskarn and ore skarn. Each of these types can be further divided on the basis of predominant primary skarn minerals assemblage, as follows: I. Endoskarn, II. Exoskarn ,:III. Ore skarn
Physico- Chemical Condition of Skarn Deposit Method of study Doubly polished plates (0.05-0.1 mm thick) were prepared for microthermometric measurements. These sections were scanned microscopically for inclusions and small chips (0.5cm2) containing inclusions were broken of mounting in the heating/freezing stage. Photographs were taken from each microscope field for re-identification of individual inclusions. Fluid inclusions were examined using a petrographic microscope to determine the size, shape, abundance, distribution and type of inclusion present in the rock samples before commencing the freezing/heating experiments. In addition to ice melting temperatue (Tm) and homogenization temperature (Th), individual inclusions were studied for their approximate size and the relative phase volumes using the spherical approximation (Roedder, 1984)
Fluid inclusion types and petrography Characteristics of fluid inclusions in different minerals from the Mazraeh skarn deposit are shown in Fig. 3. Five inclusion types can be classified on the basis of observable phase at room temperature and their paragenesis. The important of inclusions have been observed in the studied samples are as follow:- Type A inclusions: These are multiphase inclusions (Fig.3A ) that essentially consist of a liquid, a vapor phase and at least two daughter crystals.Type B inclusions: Type B inclusions are primary liquid–vapour inclusions containing one or two fine-grained daughter crystals (Fig.3 B). They are similar to Type A inclusions in shape, size and distribution. The gas / liquid ratio varies with liquid from 50–60 vol% and the vapor bubble from 30–50 vol%. They exhibit subhedral to equant grains shapes.Type C inclusions: These are liquid-rich biphase inclusions that may include solid crystals and an opaque mineral (Fig. 3C). Their liquid-vapor ratio is usually 8:2. The size of these inclusions ranges from 15 to 30 µm. They are isolated subrounded to irregular in shape with an average population density of 30 to 40 inclusions per square cm. Type D inclusions: These are gas-rich
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 biphase inclusions with about 80 vol % to > 90 vol % vapor phase . They usually vary from 5 to 15 µm in size, are irregular in shape, and occur in trails.
Microthermometry A summary of fluid inclusion data is shown in Tables 1-3. Freezing and heating experiments were also restricted to the primary fluid inclusions of types A-D. Stretching of inclusions as described by Bodnar and Bethke (1984) and Singoyi and Khin Zaw (2001) was noted during heating of large fluid inclusions in garnet and quartz from mineralized quartz veins, but smaller inclusions(<2 µm) provide reproducible homogenization temperatures. In such samples homogenization temperature ranges from 369 -420oC (n=10). Various inclusions present in the Mazraeh show homogenization at a) halite melting temperature b) vapour disappearance temperature and c) liquid disappearance temperature. These results in homogenization of different fluid inclusions to liquid as well as to vapour phase. The sylvite melting temperature is from 157o to 190oC and the halite dissolution temperature ranges from 200o to 520oC. Of these temperatures, the highest values are recorded in the mineralized veins followed by the skarn and the lowest in the granodiorite. Barren veins do not have any solid crystals as inclusions.
Conclusions Various fluid inclusions present at the Mazraeh deposit show homogenization by (a) halite melting, (b) gas disappearance and (c) liquid disappearance. Sylvite melting temperature vary from 157o to 190oC. The homogenization range of salt bearing inclusions in mineralized quartz veins varies from 295o to 520oC. The total salinity of salt bearing inclusions varies from 31.4 to 63.0 wt.% NaCl equiv. The salinity of biphase inclusions, based on their final ice melting temperature, varies between 10. 2 to 20.8 wt.% NaCl equiv., whereas the salinity of fluid in barren quartz veins varies from 10.2 to 17.9 wt.% NaCl equiv. The early stage ore fluid was produced at the late to post granitic stage under low pressure and at 0 0 temperatures < 500 C, below the granite crystallization temperature of 698 to 754 C. Th vs salinity plots show that most inclusions positioned above NaCl saturation curve are from mineralized vein quartz. The salinity of the fluids and the temperature values are positively correlated. Early highly saline, high temperature fluids were late to post granitic as they are not only abundant in ore veins intruding granite but also present in the granite itself. It is interpreted that the mineralization occurred at temperatures above 350oC, before mixing of the fluids.
References Ahmad, S.N., Rose, A.W. 1980. Fluid inclusions in porphyry and skarn ore at Santa Rita. New Mexico. Econ. Geol. v. 75, pp. 229-250. Bodnar, R.J. 1992. Can we recognize magmatic fluid inclusions in fossil systems based on room- temperature phase relations and microthermometric behaviour? Rept. Geol. Surv. Japan, No. 279, pp. 26-30. Calagari, A.A. 2004. Fluid inclusion studies in quartz veinlets in the porphyry copper deposit at Sungun, East-Azarbaidjan, Iran. Journal of Asian Earth Sciences, v. 23, pp. 179-189. Eftekharnezhad, J. 1975. Brief Description of Tectonic History and Structural Development of Azarbayjan. Internal report to the Minestry of Mines. Geological Survey of Iran. p.10. Einaudi, M.T., Meinert, L.D., Newbery, R.J., 1981. Skarn deposits. Economic Geol. 75th Ann. pp. 317-391. Kwak, T.A.P. 1986. Fluid inclusions in skarn (carbonate replacement deposits). J. Metamorp. Geol. v. 4, pp. 363-384.
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Khin Zaw, Hutson, D.L., Large, R.R., Hoffman, C.F. 1994. Microthermometry and geochemistry of fluid inclusions from the Tennant Greek gold copper deposits: implications for ore deposition and exploration. Min. Deposita, v. 29, pp. 288-300. Mollai, H. 1994. Geology, Mineralogy and Benefication of Jajarm Bauxite, NW of Mashhad, Iran. International symposium, Recent Trend Beyond 2000AD, Nagpur, India. Mollai, H., Dave,V.K.S., Darvishzadeh, A., Yaghobpour, A. 1998. Distribution and role of fluid inclusions in Iron-Copper skarn deposit, North of Ahar, N-W of Iran. Proceeding of the 2nd Symposium of Geological Society of Iran 18-20, Aug. Ferdoosy University Mashhad, Iran, pp. 60- 62. Pourhosseini, F. 1981. Petrogenesis of Iranian plutons: a study of the Natanz and Bazman Intrusive complex. Geological Survey of Iran, report no. 53 Roedder, E. 1984. Fluid inclusions. Reviews in Mineralogy, Miner. Soc. America, v. 12, 644 p. Singoyi, B. and Khin Zaw, 2001. A petrological and fluid inclusion study of magnetite-scheelite skarn mineralization at Kara, Northwestern Tasmania: implications for ore genesis. Chemical Geology, v.173, pp. 239-253. Stokline, J., Eftekharnezhad, J. 1969. Explonatory text of the Zanjan quadrangle Map, 1/250,000. Geological Survey of Iran. Table.1. Fluid Inclusion data of Mazraeh samples Mineralized Veins Skarn Granodiorite Temp. of sylvite diss. ( oC) 155 to 190 162 to 185 155 to 182 Temp. of halite diss. (oC) 260 to 520 240 to 385 200 to 370 Homogen. temp.of Type A inclusions 312 to 520 325 to 460 230 to 495 (oC) Homogen. temp of Type B inclusions 274 to 470 400 to 460 340 to 465 inclusions (oC) (oC)
Th of type C&D 172 to 370 200 to 395 180 to 490 Final melting temp. of biphase -5.2 to -18.0 -4.0 to -17.0 -4.2 to -18.0 inclusion (oC) 10.4 to 58.7 (wt.% NaCl Salinity range 11.0 to 63.0 10.2 to 59.1 equiv.) Both liquid & gas(mostly Both liquid & Both liquid & gas(mostly Homogenization phase liquid) gas(mostly liquid) liquid)
Fig. 1. Regional tectonic map of Iran (after Nabavi 1976) showing location of area under study. and Geological map of Ahar batholith (Modified after Mollai 1993).
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
Fig.2- Microphotographs of different types of fluid inclusions observed in the Mazraeh samples
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
Genetic Issues of Some of the Non Metallic Minerals in Lesser Himalaya
Rajesh Sharma1*, Prabha Joshi2 and Priti Verma1
1Wadia Institute of Himalayan Geology, Dehra Dun (India)
2 Geology Department, Kumaun University, Nainital (India) *Corrosponding author e-mail: [email protected]
Abstract A brief account of the representative and workable industrial minerals namely magnesite, talc and barite in Lesser Himalaya, is presented here emphasizing their genesis. Deposits of magnesite and talc are found associated with Neoproterozoic, plateform type, shelf-slope limestone-dolomite host rocks from inner Lesser Himalayan sequences. Field, textural, geochemical signatures and fluid inclusions trapped in dolomite and magnesite reveal within basin processes, in an increased burial- diagenetic environment responsible for formation of magnesite replacing dolomite. Talc is formed at the expense of magnesite and silica, and with limited dolomite involvement at transition conditions from diagenetic to metamorphism. Barite deposit is hosted within Neoproterozoic Nagthat quartzite rocks of outer Lesser Himalaya, wherein its textures, fluid inclusion, sulfur and strontium isotopic studies helped in genetic understanding.
Introduction The reserves and prospects of non metallic minerals from Himalaya are significant not only because such materials are fundamental requirement of many industries and essential to infrastructure development, but also because their study help in understanding the geological environment and evolution. Among the four broad geotectonic divisions of Himalaya viz. Lower Himalaya, Lesser Himalaya, Central Himalaya and the Tethys Himalaya, much of the economic minerals are located in the Lesser Himalaya which is largely formed of the Precambrian elements of the Indian shield (Valdiya, 1995). The non metallic minerals in Himalaya are particularly hosted within the sedimentary sequences with only graphite occurring in the crystallines. Present discussion briefly focuses on magnesite, barite and talc from the sedimentary sequences of Lesser Himalaya emphasizing their formation and evolution. Various studies including incident light and scanning electron microscopy, geochemical work, fluid inclusions microthermometry and Raman spectroscopy has been vital for this purpose.
Regional Geology The Lesser Himalaya, demarcated by the Main Boundary Thrust (MBT) in the south, and Main Central Thrust (MCT) in the north, represents a distinct lithotectonic unit of the Himalaya. This is broadly divisible into Inner Lesser Himalaya and the Outer Lesser Himalaya, having basement of the crystallines representing Indian cratonic rocks. The Lesser Himalayan sequences were deposited from Paleoproterozoic to Cambrian age in marine conditions on the passive margin setting of Indian continent (Valdiya, 1980; Srivastava and Mitra, 1994; Ahmad, 2000, Miller 2000; Celerier, 2009). The Inner Lesser Himalaya
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 sediments are the lower flysh and quartz arenites with basic volcanics, and the upper carbonate shale assemblages. The 1800 ma old Berinag Formation constitute the lower most sequence of the Inner Lesser Himalaya (Miller, 2000), overlain by Chakrata and Rautgara Formation, Neoproterozoic Deoban Formation- mainly the carbonates and above them Mandhali Formation consisting slate and carbonates. The outer Lesser Himalaya is folded sequence of sedimentary rocks comprising 850 ma turbidites of Chandpur Formation, overlain successively by Nagthat quartzites, Blaini conglomerates, Neoproterozoic Krol Formation which is largely calcareous, and above it Cambrian age clastic sediments of the Tal Formation. A number of the klippen of the crystalline rocks present in Lesser Himalaya are result of the thrusting of basement rocks over the sedimentary succession. Present focus is on the magnesite-talc which is hosted within the carbonates of the Deoban Formation, and on the workable barite mineralization occurring in the Nagthat quartzite host rocks . The Deoban Formation is a thick succession of stromatolite bearing, siliceous dolomite and dolomitic limestone with intercalated bands of blue limestone and grey slates.
Magnesite-Talc Mineralization Deposits of magnesite are found associated with Neoproterozoic, plateform type limestone- dolomite host rocks from inner Lesser Himalayan sequences, although minor magnesite occurrences are associated with ophiolitic suits in Indus Suture Zone. Sizable talc deposits are also found at various places in the Deoban Formation, hosted within high Mg carbonates. Their mining by open pit method is operational particularly in Kumaun Himalaya. Earlier work (Valdiya, 1968; Safaya, 1986; Sharma and Joshi, 1997) carried out studies on the carbonate hosted magnesite from Almora mainly for its depositional environment and genesis. However, the origin of these magnesite deposits has been variously discussed as synsedimentary, biogenic, hydrothermal and syndiagentically replaced mineralisation. Updated data has helped to comprehend the origin of this magnesite. Thick bands, lenses and pockets of dirty white to pink colour, fine to very coarse grained stellate magnesite are found within the dolomite of the Deoban Formation. In addition, minor chert, carbonaceous material, and sometimes iron and sulphides are associated with magnesite and dolomite. The stromatolites are inevitably associated with magnesite, inferring that they facilitated the precipitation of magnesium carbonates with a rise in total Mg2+ in restricted water. Petrographic observations show that magnesite blades are either randomly oriented , or crystallized into spherulitic texture. The magnesite and dolomite exhibit a general sharp contact, but the irregular contacts are not uncommon wherein replacement of dolomite by magnesite is seen. Successive replacement from calcite to magnesite is also noticed elsewhere (Radvanec et al., 2001). Fine grained vein magnesite, infilling fractures and observed at few places is result of later recystallization. Talc occurs as irregular patches or pockets in these carbonate host rocks, showing close association with magnesite and restricted with dolomite. Bands, intercalations and pockets of talc also occur at the contact of dolomite and magnesite. The magnesite, quartz and talc are intimate partner in an assemblage, which shows development of talc at the expense of magnesite and silica. Chert flakes and the talc flakes are interleaved. Further details of the grain relations are evident in SEM study. The fluid inclusion microthermometry was carried out at the fluid inclusion laboratory of Wadia Institute of Himalayan Geology, Dehradun, and using calibrated LINKAM THMSG 600 stage
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 fitted onto the Nikon E600 microscope. Fluid inclusions calculations are based on Flincor program of Brown (1989), and the salinity estimates on the tables of Bodnar (1993). The fluid inclusions have been studied in dolomite, magnesite and gangue quartz. Fluid inclusions are abundant in clusters and trails. Fluid inclusions trapped in dolomite and magnesite, are biphase aqueous inclusions. A systematic increase in estimated salinity from about 7.5 to 19 NaCl wt% eq., is result of increased burial and longevity of the residence of fluids in the basin. This was linked to Mg enrichment and magnesite formation. The studied trapped aqueous brines represent remnants of basinal fluids having composition of H2O-NaCl±KCl± MgCl2± CaCl2. The range of the salinity from about 2 to 17 wt% NaCl eq. is identified for basinal fluids (Radvanec et al., 2001; Huraiova et al., 2002). It is known that saline fluids are invariably present in most of the sedimentary basins, and majority of mineral resources in such basins have been affected by these basinal fluids. The relation between final melting temperatures and the homogenization temperatures are poorly systematic (Fig. 1), these are interpreted to represent mixing of the basinal fluid with meteoric water, though partly reset of early inclusions can not be completely ruled out. Localized flux of the CO2 occurred because of mineral reaction forming talc after magnesite/dolomite and quartz (Slaughter et al., 1975). The geochemical signatures in magnesite and talc do not invoke any external flux of Mg carrying fluid in talc formation (Sharma et al., 2008), this is also substantiated by the fluid inclusions data of dolomite and magnesite suggesting within basin processes.
Barite Mineralization Barite mineralization in Himalaya invariably occurs in sedimentary formations, much of it in the Lesser Himalaya with only limited barite reported from the Tethyan sediments. The barite in Tethyan sedimentary rocks from Kumaun Himalaya is suggested to be structural controlled hydrothermal mineralization (Sinha, 1977), as corroborated by the minor sulphide mineralization associated with it. Majority of barite is found in the Nagthat Quartzite, Krol- Tal Formations of Lesser Himalaya, and minor barite occurs in the Great Limestone. These barites are not associated with large scale sulphide mineralization, although at a few locations barite is found as gangue in an assemblage consisting minor sulphides in veins. Workable barite occurs in veins, beds, lenticles and pockets in the Nagthat quartzite rocks wherein its concordant as well as discordant relation are seen with the hosts. The host Nagthat quartzites are medium to fine grained texturally and mineralogically mature sandstones which represent moderately sorted, subarkosic to sublithic arenite with subordinate amounts of fine- grained quartz arenite and quartz wacke. The geochemical evidences coupled with paleo-current direction suggest that the source for the host Nagthat siliciclastics were possibly southerly situated Banded Gneissic Complex of Aravali- Bundelkhand craton (Islam et al, 2002; Verma and Sharma, 2007). The depositional characters of various Lesser Himalayan barites and a general absence of igneous activity in their neighbourhood are matching for their genetic environment. The quartz grains show bimodal distribution with common presence of detrital quartz porphyroclasts and the finer recrystallized polycrystalline grains. The euhedral to subhedral grains of barite also show varied degree of recrystallization and formation of fine grains. Sutured marginal contacts between the grains of barite and host rock infer sharing of the depositional history. Fluid inclusion study carried out on barite show that the primary inclusions in barite grains are filled with saline aqueous fluid. Both monophase and biphase
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 inclusions are noticed. Their final ice melting temperatures correspond to a salinity < 15 wt NaCl eq., and the homogenization to liquid phase occurred at 170± 40º C. Fluid inclusion study support participation of moderately warm, saline aqueous fluid in barite deposition. Strontium isotope ratios in barite are useful in understanding its genesis (Barbeiri et al., 1984; Marchev et al., 2002). The abnormally high 87Sr/ 86Sr ratios: 0.720448± 0.000034 to 0.728637± 0.000039, are obtained for the Tons valley barite (Sharma et al., 2003) suggesting participation of the material from highly radiogenic crustal source. The material derived from gneissic rocks of BGC is also likely to be enriched in radiogenic strontium isotope because weathering products of Precambrian shield areas are rich in radiogenic strontium, with 87Sr/86Sr ratios varying from 0.712 to 0.730 (Holland, 1984). The strontium isotope geochemistry of the barite mineralization present in quartzites of Aravali Super Group overlying BGC also show high 87Sr/ 86Sr contents (Deb et al., 1991). We have also carried out sulphur isotope analyses of the barite. Obtained high δ34S values in barite substantiate absence of magmatic fluid participation in initial barite formation. These probably points to the participation of Proterozoic sea water in barite formation (Nielsen 1979; Schidlowski 1988). It is interpreted that the leaching of Ba from K- feldspar of the source BGC rocks possibly supplied Ba2+ for barite formation. During the fractional crystallization of igneous melts, Ba2+ gets mainly confined to K-bearing minerals because of the similarity in the ionic radii of these two elements. Therefore, feldspars and micas are enriched in Ba2+ (Barbeiri, 1989), thereby granites usually contain 400- 10,000 ppm of Ba content and the K- feldspar in granites may consists upto 6% Ba in its structure. Hence, the consideration of various parameters infer fluid mixing model for the initial barite formation (Fig. 2). They recommend mixing of the marine and crustal material and participation of saline aqueous fluids in barite formation, may be linked with diagenesis of host sedimentary rocks.
Acknowledgement: Director, Wadia Institute of Himalayan Geology is thankfully acknowledged for providing facilities to carry out this work and for the encouragements. PJ thanks the Head, Geology Department, Kumaun University for support.
References Ahmad, T., Harris, N., Bickle, M., Chapman, H., Bunbury, J., and Prince, C., (2000) Isotopic constraints on the structural relationships between the Lesser Himalayan Series and the High Himalayan Crystalline Series, Garwhal Himalaya: Geological Society of America Bulletin, v. 112, pp. 467–477. Barbeiri, M., Masi, U. and Tolomio, L. (1984) Strontium geochemical evidence for the origin of the Barite deposit from Sardinia, Italy. Econ. Geol., v. 79, pp.1360-1365.
Bodnar, R. J. (1993) Revised equation and table for determining the freezing point depression in H2O- NaCl solutions. Geochim. Cosmochim. Acta, v. 57, pp. 683-684. Brown, P. E. (1989) Flincor: a microcomputer program for the reduction and investigation of fluid inclusion data. Am. Mineral., v. 79, pp. 1390-1393. Celerier, J., Harrison, T.M., Webb, A.A.G. and Yin A. (2009) The Kumaun and Garhwal Lesser Himalaya, India: Part 1. Structure and Straitigraphy. Geol. Soc. Amer. Bull., v. 121, pp. 1262- 1280.
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Deb, M., Hoefs, J. and Boumann, A. (1991) Isotopic composition of two Precambrian stratiform barite deposits from the Indian shield. Geochim. Cosmochim. Acta., v. 55, pp. 303-308. Holland, H.D. (1984) The chemical evolution of the atmosphere and oceans. Princeton Univ. Press, Princeton, N.J., 582 p. Huraiova, M., Vozarova and Repcok, I. (2002). Fluid inclusion and stable isotope constraints on the origin of magnesite at Burda, Ochtina, Lubenik and Ploske deposits (Slovakia, Western Carpathians). Geologica Carpathica, v.53, pp.98-99. Islam, R., Ghosh, S.K. and Sachan, H.K. (2002) Geochemical characterization of the Neo-Proterozoic Nagthat siliciclastic rocks, NW Kumaun lesser Himalaya: implications for source rock assessment. Jour. Geol. Soc. India, v. 60, pp. 91-105. Marchev, P., Downes, H., Matthew, F. and Thirlwall, R.M. (2002) Small-scale variations of 87Sr/86Sr isotope composition of barite in the Madjarovo low-sulphidation epithermal system, SE Bulgaria: implications for sources of Sr, fluid fluxes and pathways of the ore-forming fluids. Mineral. Deposita, v. 37, pp. 669-677. Miller, C., Klotzli, U., Frank, W., Thoni, M., and Grasemann, B., 2000, Proterozoic crustal evolution in the NW Himalaya (India) as recorded by circa 1.80 Ga mafic and 1.84 Ga granitic magmatism: Precambrian Research, v. 103, pp. 191–206, Nielson, H. (1979) Sulphur isotopes. In Jagar, E. and Hunziker, J.C. (eds.) Lectures in isotope geology. Springer-Verlag, Berlin, pp. 283- 311. Radvanec, M. and Prochaska, W. (2001) Successive replacement of Upper Carboniferous calcite to dolomite and magnesite in Dubrava magnesite deposit, Western Carpathians, Slovakia. Mineralia Slovaca, v. 33, pp. 517-525. Safaya, H.L. (1986) Magnesite deposits of Kumaun Himalaya, Uttar Prades-Depositional environment, genesis and economic utility. Geol. Surv. India Misc. Pub. 41(VI), pp. 150-178. Schidlowski, M. (1988) A 3800-million year isotopic record of life from carbon in sedimentary rocks. Nature, v. 333, pp. 313-318. Sharma, Rajesh and Joshi, M.N. (1997) Fluid of magnesitization : Diagenetic origin of Bauri magnesite, Kumaun Lesser Himalaya, Curr. Sci., v. 9, pp 789-792. Sharma, Rajesh, Verma, Priti and Sachan, H.K. (2003) Strontium isotopic constraints for the origin of barite mineralisation of Tons Valley, Lesser Himalaya. Curr. Sci., v. 85, pp. 653-656. Sharma, Rajesh, Joshi, Prabha and Pant, P.D. (2008) The role of fluids in the formation of talc deposits of Rema area, Kumaun Lesser Himalaya. Jour. Geol. Soc. India, v. 73, pp.237-248. Sinha, A.K. (1977) A discovery of barite and associated polymetallic mineralization in Tethyan zone of Higher Garhwal and Kumaun Himalaya. Him. Geol., v. 7, pp. 456-463. Slaughter, J., Kerrick, D.M. and Wall, V.J. (1975) Experimental and thermodynamic study of
equilibria in the system Cao-MgO-SiO2-H2O-CO2. Am. Jour. Science. v. 275, pp.143-162. Srivastava, P., and Mitra, G., 1994, Thrust geometries and deep structure of the outer and lesser Himalaya, Kumaun and Garhwal (India): Implications for evolution of the Himalayan fold-and- thrust belt: Tectonics, v. 13, pp. 89–109, Valdiya, K.S. (1968) Origin of the magnesite of southern Pithoragarh, Kumaun Himalaya, India. Econ. Geol., v. 63, pp. 924-934.
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Valdiya, K.S. (1980). Geology of Kumaun Lesser Himalaya. Wadia Institute Himalayan Geology, Dehra Dun, 288 p. Valdiya, K. S. (1995) Proterozoic sedimentation and Pan- African geodynamic development in the Himalaya. Precambrian Res., v. 74, pp 35-55. Verma, P. and Sharma, Rajesh (2007). Primary to re-equilibrated fluids and geochemical signatures for the evolution of Nagthat Siliciclastics in Tons valley, Lesser Himalaya, India. Jour. Asian Earth Sci., v. 29, pp. 440-454.
Figure 1: Tm vs Th plots of the aqueous biphase fluid inclusions in dolomite and magnesite.
Figure2: Diagram illustrating mixing of the two fluids for the barite formation as deduced from Sr and S isotope signatures.
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TECHNO–ECONOMIC EVALUATION OF CARROUSEL SYSTEM FOR DAIRY WASTEWATER TREATMENT
By Hadi Pourdara*4 , T. Arun Kumar5 , S.D. Bhattacharya6 and Arvind Kumar7
Abstract The carrousel system is a promising modification of well-known Pasveer oxidation ditch for treating larger wastewater flow to attain high quality effluent along with significant savings in land. However, its efficiency depends solely on proper design of its aeration system. Suitable mechanical designs of impeller, rotational speed and impeller submergence have significant bearing on the mass transfer efficiency for synthesizing an optimal aeration system. The paper deals with a study on performance of twelve different configurations of impeller design through a laboratory scale model of the carrousel ditch system for treating dairy wastewaters. Impeller speed ranges from 30 -200 rpm, with immersion depth between 10- 30 mm have been investigated to study their effect on mass transfer efficiency of the system. Rational scale up criteria have been adopted to transfer laboratory results to prototype design for evaluating techno-economic justification of carrousel ditch as compared to oxidation ditch and conventional activated sludge system.
Keywords: Carrousel, Techno, Economic, dairy, Treatment
Introduction Dwars, Heedrik, and Verhey NV (DHV) patented the carrousel system in Holland, 1968. Basically carrousel ditches are deep oxidation to economize in land requirements. It has been found that carrousel system can be designed to require only two-third of the land required for the oxidation ditches. Reduction in land requirement in carrousel system is brought about by providing deeper ditches (2.5to5m), as compared to 1-1.5 m in oxidation ditches. Aeration is concentrated at one point only in carrousel as compared to distributed over the length of the oxidation ditch. This enhances oxygen transfer, which makes up the dissolved oxygen deficit from saturation. Vertical shaft aerators provided in the carrousel system impart a spiral flow mixing pattern. This transfers angular momentum to the liquid, which is deflected into the channel by the dividing wall and provides turbulent flows over the entire cross section of the channel. The velocity of the mixed liquor in the channel is usually 0.2 – 0.5 m/s, depending on the submergence and rotational velocity of the aerators. Thus, all the solids are kept in suspension. Earlier pilot plant studies on Carrousel systems have revealed that the liquid depth in the aeration zone should be at least equal to the aerator diameter (zeeper, 1970 and Arceivala, 1981). However, some carrousel systems have been designed with aeration zones deeper than the reactor channel (Zeeper, 1970). The carrousel plant at ASHVALE has an effective depth varying from 2.4 m to 3.4 m in aeration zone (Mandt, 1982). The minimum level of dissolved
4.Assistant Professor, Director, Research Center of Water and Environment Protection, University of Yazd, Yazd, Iran. [email protected] 5 . Post Graduate student, Civil Engg. Deptt., IIT, Roorkee, 247667, India. 6. Professor, Chemical Engg. Deptt., IIT, Roorkee, 247667, India. 7. Professor, Civil Engg. Deptt., IIT, Roorkee, 247667, India.
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 oxygen (DO) actually required in the extended aeration system is of the order of 0.5 to 2 mg/l (exact value depending upon the need of nitrification) (Arceivala, 1981). Ditch geometry, aerator design and mode of aeration are key considerations for providing efficient oxygen mass transfer rates and mixing of aeration basins (Mandt et.al., 1982). Only a portion of power required for aeration is generally used to generate channel flow. With all the aerators at one end of the reactor basin only, very high power intensity normally occurs in aeration zone, which is mostly used in improving the oxygen transfer efficiency. Only a prudent aeration system for continuous loop carrousel reactor shall make it capable of providing a high quality effluent with minimum energy needs. Therefore, there is always a need to provide better aerator designs and aerator modes, which could make the system feasible alternative for treating larger wastewater flow economically. This is the intent of the present work. The paper deals with the study on aeration performance of twelve different impeller configurations in a carrousel system. Significant design considerations taken into account include rotational speed and impeller submergence, which have significant bearing on mass transfer efficiency. Best impeller selected among the 12 is used for scale up process for treating dairy wastewater through carrousel ditch (CD) and compared for its cost effectiveness with other alternatives viz. activated sludge process (ASP) and oxidation ditch (OD). Experimental Model Figures 1 show the details of the laboratory experimental model of carrousel system. The power supply from AC mains was taken through a stabilizer and AC-DC converter to operate the motor on 220 V and 4A. The power was measured by a wattmeter. The AC-DC 746 watt motor was coupled to the impeller shaft through a V belt and pulley arrangement. Depth of water maintained was equal to the diameter of the impeller. Width to water depth ratio of 1.5 has been used. Experimental work done is brought out in two phases.
Scheme of Experimentation Phase I of the study was carried out to identify the best configuration which could affect maximum mass transfer. The experimentation involved twelve impellers, which were fabricated based upon configurations given by Nagata (Nagata, 1975). These impellers were operated with different speeds of rotation at varying depths of immersion. To begin with the run, tap water was filled to a required height and DO brought to zero by addition of Sodium Sulphite and Cobalt Chloride. DO measurements were done with a DO digital meter employing a DO probe. The measurements were calibrated with standard
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Winkler’s method (Standard Methods, 1989). For each impeller varying values of rotational speed and immersion depths were fixed to evaluate oxygen transfer rate. As is was not possible to run the studies under temperature control at 20ºC, oxygen transfer coefficient (kLa)20 was computed on the basis of equations (Arceivala. 1981, Eckenfelder, 1970 and ASCE Manual, 1988) as below : dc = (k a) (c − c ) and (k a) = (k a) /θ T −20 dt L T s t L 20 L T
The measurement of power consumed (P) has been done with a recalibrated wattmeter, which provides for instantaneous power readings and cumulative power utilization. Oxygenation capacity (G) defined as the rate of oxygen transfer during aeration, at the time when the water is completely deoxygenated and at a specified temperature, either 10ºC or 20 ºC, can be obtained from the transfer coefficient (KLa) using the relationship (Arceivala, 1981 and ASCE Manual, 1988). dc G = = (K a) (c − c )V dt L 20 s t and, oxygen transfer efficiency (OTE) shall be
OTE = (K L a) 20 (cs − ct )V / P
Where cs = 9.28 mg/l at 20 ºC Aeration Results: Best impeller among the 12 impellers has been identified on the basis of two approaches: P/V (Tatterson, 1993), and Ognean’s criteria (Ognean, 1993). The intent was to compare the approaches as well as identifying best impeller design.
P/V criteria: From the observations, (KLa)20 and oxygen transfer efficiency values were calculated with different depths of immersion and speeds of rotation employed. From the data it was clear that lowest and highest ranges of mass transfer coefficient values were available for impeller 2 and 7 respectively. However, in general, the mass transfer coefficient increased with increase in submergence and speed of rotation. Also, oxygen transfer trend is of increasing nature with increasing values of speeds of rotation. There is mixed trend in case of changing immersion depths. Maximum OTE values were observed at 30 mm immersion for all the 12 impellers considered. It will appear that it is possible to identify useful configuration of impellers up to a rotational speed of 150 rpm only. At 200 rpm the values are less likely to prove useful, since it was found that over splashing takes place at this high speed. Table 1 shows the G, OTE and specific power values for al the 12 impellers employed in the study at 30 mm immersion. From the data, the maximum OTE values 2.921, 3.151 kg
02/kWh correspond to impeller configurations 3, 7 and 12 respectively attained at 150 rpm speed and 30mm depth of immersion. Figure 3 shows the variation of oxygen transfer efficiency with specific power for all the 12 impellers. A clear inference can be drawn that at specific power values greater than 37 W/m3, 3, 7 and 12 impellers gave higher OTE. Further from the figure, it can be concluded that impeller 12 at a speed of 150 rpm provides maximum oxygen transfer efficiency with lower specific power.
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Ognean’s approach: According to this approach, aerators having same diameters and the same rotational speed, but different geometrical shape, can be compared on the basis of To (efficiency number) and Fr* (Froude number) value. To and Fr* are given by 1/ 2 3 3 / 2 5 / 6 3 / 2 1/ 3 −1 1/ 2 3 / 2 1/ 2 To = (Gs / Ps )(1/ P )(d n )(g p v ∆ ) Fr* n3/ 2P /(g p d ) Figure 4 present the variation between To and Fr*. An increase in the To number can generally be noticed as Fr* increases. Although for the tested aerators, a simple relationship between To and Fr* cannot be established. The profile of the curve tends to flatten in the location To > 5x10-5. Other workers have obtained similar results, but the flattening of curve was observed in the location To > 4x10-3. The difference can be attributed to the fact that the analyzed range (Fr = 0.004 - 0.17) was smaller than the analyzed range of other workers (Ognean, 1993) (Fr = 0.08 - 1.5), and also that the values of all the parameters are stated at 20ºC in the present work, as against 10ºC in the literature. Impellers 12 showed the maximum values of To (9.98 x 10-5) and further this impeller is said to have maximum power consumption. So impeller 12 is said to be the best one among the 12 impellers.
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Both approaches provide similar results. However, P/V approach has been utilized for techno- economic study.
Treatment Efficiency In the Phase II studies on the treatment of synthetic dairy wastewater on the laboratory model were done and then a comparative study with existing carrousel system, an activated sludge process and oxidation ditch was carried out. The results obtained from the experimentation are shown in Table 2.
Scale Up Many scale-up criteria are adopted in mixing applications, including equal impeller tip speed, equal torque volume, equal power per unit volume, and equal solids suspension (Tatterson,
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1993). Therefore following criteria has been adopter for scale-up of carrousel system laboratory data for prototype design. 3 2 3 5 3 2 (P /V )m (ρn d )m P = ρn d P /V = ρn d ≡ 3 2 ≡ 1 (P /V ) p (ρn d ) p Cost formulations: Major decisive variables in the selection of a treatment system for wastewater from the alternatives may include (Arceivala, 1981). a) Land cost and its availability; b) Desired effluent quality; and c) Capital and OMR cost for the treatment system. Plant costs are stated as capital cost and annual costs which are made of various components as sated below. (a) Capital costs : Include all the initial costs incurred such as civil costs, land purchase, and equipment costs, Civil costs include cost of steel, concrete, earth work for excavation, and shuttering. In the present case structural design of aeration tanks, sedimentation tanks and aerobic digester have been done as per IS 3370-1967 (P35) and IS 3370 – 1975 (II) code. Costing has been done at 2001 rates as shown in Table 3. Equipment cost includes Cost of aerators and Cost of return sludge pumps. Power cost for both aerators and return sludge pumps.
Manufacturing costs collected form the fabricators (EMICP-K. C.P. Pvt Ltd) have been analyzed and a best – fit regression curve fitted as shown in figure5.
(b) Annual costs : These include costs incurred after construction of the plant Interest charges on capital borrowings (loans), Amortization of loans, Depreciation of plant, Insurance of plant, Operation and maintenance of plant (including minor repairs) as follows : i) Amortization: Fund raising has been considered on full amortized basis as per normal international standards with interest rates of 7.5% (World Bank) with repayment period of 20 years.
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Annual repayment of annuity (A1) has been considered as (Arceivala, 1981). Pi(1+ i) n A1 = (1+ i) n −1 Where P = Principle amount , i = annual interest rates & n = design period ii) Depreciation can be calculated by different methods of which, sinking fund method is generally considered suitable for public works. Typical values of depreciation rates have been taken as per Table 4.
Annual amount (A2) required to set apart to produce a future sum F is given by Fi A2 = (1+ i) n −1 iii) Operation and maintenance (O and M): includes staff, chemicals, transport rentals and maintenance, which have been considered as a percentage of civil cost and electromechanical costs (equipment costs). Therefore, OMC = 1.5% of civil costs + 3% electromechanical costs. Now, Total Annual Cash Flow (TACF) is calculated as: TACF = Loan Amortization + Depreciation + Power cost. Systems Evaluated: Techno- economic efficacy of carrousel system for dairy wastewater treatment has been evaluated in comparison to conventional activated sludge process system (Fig 6.a) and oxidation ditch (Fig 6.b) for the same treatment efficacy and input characteristics. In the present work, a detailed design and estimation of activated sludge process, oxidation ditch and carrousel system for the treatment of dairy wastewater. Prototype design of carrousel system has been done on treatability results of model study on synthetic dairy wastewaters (Table 5) with a design period of 20 years.
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Results The results obtained by the design have been plotted figures 7 to 12. It can be seen that carrousel ditches are techno-economically superior to activated sludge system as well as oxidation ditches to treat dairy wastewater. Variations of oxidation ditch (OD) and carrousel ditch (CD) have been expressed as quotient of activated sludge process in Table 6. On average Total capital cost, Power cost, and Total annual cash flow for Carrousel system are 71%, 60% and 74% of activated sludge process and 89%, 83%, 92% of oxidation ditches for the same BOD removal efficiency.
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Conclusions The paper presents a laboratory treatability study on dairy wastewaters. The performance data on the lab scale has been scaled up for designing prototype system. A techno- economic study has been done to arrive at comparative feasibility of carrousel ditches vis-a-vis Pasveer oxidation ditch and activated sludge process. Carrousel system has been found to be better option than the other two. The results of the study can be extended to similar biodegradable wastewaters also which will go a long way in providing a prudent effluent treatment system for them.
References 1. Arceivala, S.J. (1981), "Wastewater Treatment and Disposal – Engineering and Ecology in Pollution Control”, Marcel Dekker, Inc., New York. 2. Arceivala, S.J. (1988). Wastewater Treatment for Pollution Control, Tata McGraw Hill publishing Co. Ltd., New Delhi, India. 3. ASCE- Manual and Reports on Engineering Practice (1998). No. 68, American Society of Civil Engineers, New York. 4. Eckenfelder, W. W. (1970). Water Quality Engineering for Practice Engineers, Barnes and Noble, Inc., New York. 5. Indian Standard: Guide for Treatment and Disposal of Effluents of Dairy Industry, IS: 8682-1977. 6. Mandt, M. G., Bell, B.A. (1982). Oxidation Ditches in Wastewater Treatment, Ann Arbor Science, Michigan.
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7. Nagata, S. (1975), Mixing: principles and application, John Wiley and Sons, New York. 8. Ognean, T. (1993), “Aspects Concerning Scale – Up Criteria for Surface Aerators”, Water Research, Vol. 27, No. 3, pp. 477 – 487. 9. Standard Method for the Examination of Water and Wastewater (1988). APHA AWWA, WPCF, 19th Edition. 10. Tatterson, G.B. (1993). “Scaling Based Upon Process Similarity and Scale Matching Concepts, Process Mixing: Chemical and Biochemical Applications”, AICHE Symposium Series 293, Vol 89. 11. Zeeper, J. and DeMan, A. (1970). “Large Oxidation Ditch, Carrousel Fifth Congress, Inst. Assoc. on water Poll. Res., San Francisco, California.
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Zonnation of western Alborz zone based on geomorphic indices
Z. Mehrjerdi A. A.
Islamic Azad University of Meybod Branch
Ghayoomiyan J.
Institue of Soil and water preservation
Abstract western Alborz between located between 30 longitude from 50 to 49 E within the two Caspian plain in the north and south of Qazvin and in place trend change in West and Central Alborz. Movements of the earth's crust is one of the most important factors shaping the perspective of land so that affected movement on the ground morphology and related complications. Some of these include the quantity of Sinus Mountain Front ,River Gradient, Zone of Deep Valley , Asymmetry channel and curves of the 30 hypsometry Sinus which have been studied in 30 Basins watershade .The above indices have been activated in three categories which include high activity, moderate and week activities .The results indicate that thirteen Basin area located in active basins and are energetic , while the other fourteen watershed basins can be categorizes as moderate and the other basine and watersheds are inactive
Keywords: western Alborz, indicators of tectonic form, zone scheme, qezel ozene
Introduction Rastagh Area is located in 35 kilometers northwest of Yazd and south of Meybod .This area is in between 54º 10˝ longitude 30º 12΄ 54˝ Eastern and latitude 31º 56΄ 30˝ to 32º 10΄ 15˝ North with an altitude of 1218 meters from sea level. This region with more than 13 villages in the Yazd plain - Ardakan is located along the main road. The alluvial fields of south of Meybod and particularly in the Rastaq region within 20 years the land subsidized between 50 t0 120 Cm . The result of this subsidizing is very devastating in the region. For example of these damaging include : the destruction of casing water wells and subsequently drying the wells, and thus change the slope of valley and surface drainage, destroying the agriculture land , loss of aquifer sides, creating left and deep on the ground and in cases where damage to structures and ways to achieve communication in the study area many factories and manufacturing units in the structure of industrial towns or are under construction, and these will be more and more in futures .In addition the cities of Meybod and Ashkzar locating in this area. The networks of water pipe supplying , gas, electricity and telephone widely extending in these area and all of the are under crisis condition.
Methods In the first stage of this research we have collect the pervious information .In the next stage during the field work we had studied the land development within the study area as well as gender and alluvial development is largely determined well derailing . For better understanding the structural complications such as precision faults, joints and cracks in
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 ground type faults, the mechanism of displacement movements initially was determined separately for each features. All the sampling points was recorded by most GPS Then by using Schmidt diagram its pole drawing and determine their status and fracture by analysis software WINTEK Point Dipole moment diagram into contour line. For better distribution along the joint show in the region, the software diagram Dips 3.3 was used , and derive the Rose diagram s for this fracture. The different level of sediments with differents characteristic were studied by the help well logging of water wells drilled by Regional water of Yazd province . The different samples were studied and analyzed by XRD & XRF method. The information of soil Mechanic Laboratory of Yazd transportation was used for clay shrinkage
Discussion The main strike of YAZD-ARDAKAN Plane is, North West-South East which are following the main strikes of regions. The Yazd active fault passing along the NW-SE from the center and has displaced the young alluvium in the aria .The biggest and the best water table in Yazd province which is used for agriculture, drinking and industry cities of Yazd, Meybod, is located in the Yazd-Ardakan plain. Operation of the table simultaneously through the aqueduct and deep wells will be done. This table depth based on excavations made in the region has been proven to 400 meters, but the final location Contact stones at least 500 meters following main plain is estimated. Underground water table Rastaq large part of the plain table Yazd – Ardakan, Mahriz that the input and output wells in the North Ardakan is better. Mentioned in the groundwater table to the south are moving north. Because this motion differences between the beginning and end table height to Mahriz If the altitude 1400 m and 990 m in height Afzal well above sea level is located. This means that there is about 410 m level difference between end of two Yazd-Ardakan table. Due to height difference, water damage to the operating table to over flow and underground water flow with relatively high speed and deep to the main table join is plain. However, this slope is not uniform and its value is different in different parts. Mahriz-Yazd and gets to the slope 5/3 in a thousand is better wells K output table is considered, is the slope of 1 in a thousand. In the Yazd Province, about 3000 deep wells and semi-deep wells is in operation , out of these 1700 wells are deep ranging from 1700 and 1300 wells are semi deep . The deepest wells with 400 m .depth located in Rastaq Chah kharkhab. At the initial stage the level of water was only at the depth of 60 meters deep but after 20 years fall done up to 80 meters,that means change of 20 meters within 19 years. This fluctuation is to much for such short period. Figure 1 shows linear hydrographyi changes of water level for 2005 -2004. Table 2 shows deep variation of water deuring 20 years in the Rastaq region
Conclusion Increased productivity of water resources or decrease water table in the Rastaq region cause hydraulic pressure reduction and thus reduce tensions and create land settlement. Ratio water table in the Rastaq area during 20 years ago was 15/4 m. Soil in this region is silt and clay. Available cracks have a lot of depth in this broader and deeper gaps have been formed . The silt cause soil evaporation humid in deeper region and clay-ciliate forming underground water table Rastaq than to coarse grain sand areas more affected by the creation of effective by the
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 density forces. In addition to low groundwater levels also increase the thickness of sediments above water table, and both factors, rate of settlement produce intensity in Rastaq region. catching from the water table of pyzometric Rastaq reduced pressure is 3 meters in this cause pressure on the balance of eating and increasing pressure from high sediment table has been modified so that the porosity sediments matching of this decline and increase in density, is the result of subsidence and pillar of the Rastaq Abad specially around the exploitation wells with casing apparent growth. The aqueduct can not create such a dimension to depression. In the other hand to create and karsts dissolution cavities in the constructor of geology in the region and particularly no bed rock. Analysis of influencing factors and possible role of tectonic faults in the formation of subsidence, the total study shows that some of the fractures orientation Yazd-Ardakan plain is due to tectonic factors which affected the region. Excessive with drawal of groundwater level decline and stagnation are caused mostly stretching type and the radial and have no particular trend. Excessive withdrawal of water can be allowed a lack of proper management of water resources in the harvest and other losses as a result of massive water additional extraction for the propose agricultural and industrial use or drinking . As a long-term solution based on experience in other countries no choice but to reform water management practices there and the time remaining to be moving towards it. But for immediate and urgent solution ,we should stop unauthorized users of drilled wells and venture stressed.
References - Zareh Mehrjerdi, Ahmad Ali. 1996 Study of Dehshir fault as geotourism phenomena. Msc thesis, faculty of Sciences Tarbiyat Modaress University. - Zareh Mehrjerdi, Ahmad Ali, 2004. Tectonic Model of Western Alburz ,unpublished PhD thesis .Center Research and Sciences Islamic Azad university Tehran. - Zare Mehrjerdi, Ahmad Ali, Eslami zade, Ezat, Samani Rad, Shahram, 2006 , The study of Subsidence in the South of Rastaq regions south of Meybod twon to understand the reasones of subsidences and method of determination and controlling.
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Tabl.1 :Variation of water table of studies wells in Charkhab region2004-2005 (Yazd –Ardekan plain)
81.95 81.79 81.72 81.72 81.5 ﻋﻤﻖ ﺳﻄﺢ ﺁب از ﻧﻘﻄﻪ ﻧﺸﺎﻧﻪ
1186.3 1186.3 1186.3 1186.3 1186.3 1186 1104.35 1104.465 1104.6 1186.3 1104.58 1104.8 ارﺗﻔﺎع ﻡﻄﻠﻖ ﺳﻄﺢ ﺁب ﺑﻪ ﻡﺘﺮ
moon Sep. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May Jun. Jul. Ago.
Figure 1 :Hydrograph showing linear changes of the level of underground water between 2004— 2005 (after water organization of yazd)
Figure 2-Histogram of hydrograph for changes of water leveling underground water of Rastaq region 1985-2005
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Table2 : quality analysis of borhole water from area under studied
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
Importance of Dinosaur Remains (Mostly Footprints) for Science Tourisms in the National Park Brijuni Islands (Istria, Croatia)
Zlatan Bajraktarević & Aleksandar Mezga
Geological Department, Faculty of Science, University of Zagreb, Horvatovac 102 a, 10 000 Zagreb, Croatia, Tel: ++38514606098; E-mail: [email protected], [email protected]
First research on the dinosaur footprints, of the Brijuni Archipelago began in 1925, with the paper of the Austrian industrialist Bachofen-Echt, who described two types of footprints. After him few others were interested in the same region. Today's territory of Istria with the Brijuni Archipelago made up a part of the larger paleogeographic unit, so-called Adriatic-Dinaridic carbonate platform, more or less isolated within the known Mesozoic Tethys ocean. However, it should necessarily be presumed that there existed some sort of connection between the platform and the continent since numerous fossil footprints are autochthonous, so that the platform was raised above the sea level and partially under shallow seas and inhabited by mainland vertebrates. Such continental phases – emersions in the evolution of the platform enabled the existence of dinosaurs in these areas. The presumption and the question of whether the platform was connected to the African continent still need to be answered (judging by the similarity of the faunas) although there were temporary isolations during the Cretaceous period (Albian-Cenomanian stages). The Brijuni Archipelago is today certainly one of the most attractive tourist destinations in Croatia. The paleontological findings of the dinosaurs are undoubtedly one of the prime issues of the so-called scientific tourism.
The results of geologic and sedimentologic research indicate that the Adriatic-Dinaridic carbonate platform in its continental phase very probably had the shape of a numerous flat islands surrounded by tidal flats, shallow bays and lagoons. The arrangement of the oceans and continents in the period of dinosaurs was completely different from today, so that the look of our planet Earth differed from today. Thus, during the Cretaceous period, the area of the Adriatic was partially dry land and partially shallow sea area (the so-called carbonate platform), divided from the former Tethys ocean by numerous islets. Proofs of the existence, behavior, locomotion and diet of the dinosaurs in Istria and the Brijuni Archipelago, like in the rest of the world, are related to the findings of their skeletons and fragmentarily preserved bones, and, especially in Istrian area, of their footprints, which can be preserved either as individual footprints or as a sequence of footprints (trackway). Based on such findings, we can decipher their characteristics: were they qudrupedal or bipedal dinosaurs; were they walking by means of leaning on the entire foot or on toes only, what was the shape of feet and number of toes, the existence of claws, as well as the possibility of estimating the size of individual animals. The trackways help us “read” whether the animal ran or moved slowly, lived alone or in herds, and similar. According to the size of footprints, we can estimate the size of dinosaurs, whereas the distance between the sequences of footprints made by the same leg indicates the speed of dinosaurs. Such estimates are based on the ratio between the stride length and the hip height. Dinosaur footprints are usually found within sedimentary rocks, in layers deposited at depths lower than 3 meters and on shoals what is proved with the other fossils whose life indicates such shoals such as various fossil calcareous algae (Salpingoporella melatae, S. genevensis, S.
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010 urladanasi) foraminifera (Nezzazata isabellae Arnaud-Vanneauj & Sliter ., Scandonea aff. phoenissa Saint-Marc, Pseudonummoloculina aurigerica Calvez, P. heimi (Bonet); as well as indicative sedimentary structures – ripple marks. Dinosaurs that moved across Istrian area, judging primarily by reconstructions based on the footprints and fossil bones, compared to similar dinosaur fauna of Africa and Eurasia, as we have already stated, had smaller dimensions. This fact (in case the specimens were not juvenile or sub-adult) proves the biologic thesis that large specimens in isolated areas (islands) become smaller, dwarfish, and endemic in a relatively short period (e.g. elephants on Channel Islands, California became smaller during Pleistocene over the period of thousands of years). On the other hand, the same period was not that short in geologic sense for dinosaurs; it could have lasted for several millions of years. In terms of time, it would correspond to the middle part of the Cretaceous period (between about 110 million years and 90 million years ago). Herbivorous dinosaurs that lived in the area ate leaves from large trees (various conifers, ferns, cycas, gingko and other angiosperms of the period), while carnivorous dinosaurs fed on all what they would catch, including herbivorous dinosaurs. Dinosaur footprints can be preserved in the form of ichnofossils in the case they moved across soft soil thus leaving traces. The traces could be preserved if the footprints were covered with sediment relatively quickly. The covering sediment had to be different from the surface into which the footprints were imprinted and they had to remain untouched until the diagenetic processes lithified the sediment transforming it into consolidated rock. We know that when we walk on the beaches and leave our footprints in wet sand or mud, they get washed away by waves or by tides and rains. It is thus easy to conclude that the probability of the preservation of footprints is quite exceptional, so that fossil tracks of dinosaurs are relatively rare and thus quite valuable. Austrian industrial Bachofen-Echt discovered the first dinosaur traces on Veliki Brijun Island in 1925 [1]. Bachofen-Echt assigned the tridactyl footprints to the Iguanodon species. We now know with certainty that the prints nevertheless belong to “some” carnivorous dinosaur from the group of Theropoda. In subsequent periods, footprints were also documented by Polšak [2], Velić & Tišljar [3], and others. First substantial and intensive paleoichnologic research began in the 1990s, as a global trend of the so called "dino-tracking". The research was undertaken by the Italians, especially by F.M. Dalla Vecchia and his team of the Paleontology Museum in Monfalcone [4], as well as by the authors of this text [5].
Localities with dinosaur footprints on Veli Brijun island Four localities with nicely recognizable dinosaur footprints have been discovered on the island of Veli Brijun. The localities are situated on promontories Pogledalo/Barban, Ploče, Kamik/Plješivac, and Trstike/Debela Glava (Fig. 1). There are more than two hundred single footprints as well as numerous trackways. 61 footprints of a large bipedal carnivore have been found on the Pogledalo/Barban promontory (Fig. 2). Based on footprint length, the length of dinosaurs has been estimated to 7.5 - 8 m. The diversity of dinosaur footprints is related to different sediment consistency.
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They are of Late Barremian age, and we presume that these dinosaurs were most similar to alosaurid theropods. The remaining three localities are found in sediments of the Upper Albian stage. 60 footprints of small bipedal carnivore whose lengths have been estimated to 3 - 4 m (Fig. 3) were found on the Ploče promontory, which would most probably indicate the fact that they were small ‘coelurosaurian’ carnivores, very aggressive and agile predators. About sixty footprints have been found on the Kamik/Plješivac promontory. They belong to large bipedal herbivores and small bipedal carnivores (Fig. 4). Bipedal herbivores attained the length from 6 – 6.5 m, and the carnivora the length of 3.5 m. Herbivores probably belonged to the iguanodontid dinosaurs, and the carnivora like the already mentioned representatives of the ‘coelurosaurian’ dinosaurs. The locality Trstike/Debela Glava has about thirty footprints of four-legged herbivorous dinosaurs. Their lengths have been estimated to about fifteen meters, and they were most probably representatives of the Sauropoda group. It is assumed on the basis of calculated parameters that the speed of dinosaurs inhabiting these localities ranged from 2 – 2.5 km/h for sauropod dinosaurs (herbivores), (which equals the speed of slow walk) and from 5 – 7 km/h, even up to 10 km/h for theropod carnivorous dinosaurs. Along with these four localities, individual tracks can be seen immediately upon leaving the ship and stepping on the main pier of the port of Veli Brijun island. In the one of the limestone block which was brought there, one can see a tridactyl footprint, probably belonging to a large carnivorous dinosaur of the Theropoda group. Together with Veli Brijun Island, we can find remnants of dinosaur locomotion and their trackways also in the rest of the Brijuni archipelago (Vanga, Galija and other islands).
References: 1- Bachofen-Echt, A., 1825, Iguanodon Fährten auf Brioni: Palaeontologische Zeitschrift, v.7, p.172- 173. 2- Polšak, A., 1965, Geologija južne Istre s osobitim obzirom na biostratigrafiju krednih naslaga. (Geologie de I’Istrie meridionale specialement par rapport e la biostratigraphie des couches cretacees): Geološki Vjesnik, v. 18, p. 415-509. 3- Velić, I. & Tišljar, J., (1987), Biostratigrafske I sedimentološke značajke donje krede otoka Veli Brijun i usporedba s odgovarajućim naslagama jugozapadne Istre. (Biostratigraphic and sedimentologic characteristcs of the Lower Cretaceous deposits in SW Istria): Geološki Vjesnik, v. 40, p. 149-168. 4- Dalla Vecchia, F.M., Vlahović, I., Posocco, L., Tarlao, A. & Tentor, M, 2002, Late Barremian and Late Albian (early Cretaceous) dinosaur tracksites in the Main Brioni/Brijun Island (SW Istria, Croatia), Natura Nascosta, v. 25, p. 1-36. 5- Mezga, A., & Bajraktarević, Z., 2004, Cretaceous dinosaur and turtle tracks on the island of Veli Brijuni, Istria, Croatia: Geologica Carpathica, v. 55/5, p. 355-370.
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FIGURES:
Figure 1: Localities with dinosaur footprints on the Veli Brijun Island.
Figure 2: Footprint of the theropod dinosaur on the Pogledalo/Barban promontory (Late Barremian)
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
Figure 3: Footprint of the theropod dinosaur Figure 4: Footprint of the theropod dinosaur from the Ploče promontory (Late Albian). from the Kamik/Plješivac promontory (Late Albian).
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
Seismic geotechnic and soil fundamental period In Saghez city Nw of Iran
Ahmad Adib1 , Naser Ebadati2
1.Islamic Azad University, South Tehran Branch, Tehran .Iran
2.ZaminKav Research Center, Tehran. Iran
Abstract The earthquake is a natural disaster that always causes fear and fright .it usually accompany with hurting people’s life. The safety against earthquake disasters needs envisage site feature and building’s safety. The safety of sites relates to geotechnical properties of sites. In this paper, we study geological engineering & geotechnical of Saghez city. Combining geotechnical and seismic borehole data in one step show a nice evaluation of seismic characteristics and response in the place of Saghez city. All the data have been interpreted with one dimensional linear method. On the basis of the obtained results in this site, the amplification coefficient is approximately around the frequency of 2 (Hz). So it seems that the amplification with the first peak is not reasonable in the frequency of 9 (Hz). The exception is alluvial terraces in north and northwest of city and also stream margin. The minimum amounts of SPT were found in northeast and southwest of city that increase toward city center gradually. The maximum amounts of Gs in east and west of city and the minimum amounts in north and southeast were recorded.
Keywords: Earthquake; Geotechnic ; Site effect; Saghez
INTODUCTION In seismic geotechnical survey for Saghez city that has been done with average precision, geotechnical data, earth classification on the basis of geological data and shear wave velocity profiles are used. In most of the similar studies, the focus is just on one or two of these methods will be used. For example Dikmen (1984), analyzed the stress function for seismic response of a site. Finn (1991), also just discussed about the geotechnical aspects of the seismic microzonation.
SEISMIC GEOTECHNICAL ANALYSIS Prior to study one dimensional equivalent linear analysis (Aki, 1988), Obtaining an appropriate image from ground motion (which is recorded on a station plugged in a rocky formation) is essential. For this purpose, the nearest station with respect to the area is used. With respect to the survey area and the length and magnitude of Tabas earthquake, 1979, it is also used as the reference earthquake of the survey. In preparing the describing models for Layers, achievable data of the borehole from various areas are specially noted too. Equivalent shear wave velocity of 750 (m/s) is applied in analysis of seismic bed rock depth in these boreholes.
Table (1) - Maximum acceleration of seismic bed rock in the borehole
Returning period(year) 100 200 475 Acceleration versus g 0.159 0.183 0.22
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
In digging borehole, various examinations such as shear wave velocity determination, density of formation, Special weight determination, grain size, SPT and compressional velocity of the layers is conducted. Table 1 shows the maximum of earth acceleration in this seismic bed rock in the place of borehole. Four different models with respect to grain size and type, shear wave velocity and special weight introduced. All the profiles recorded with three accelerator coordinates placed on the Deihouk station. The results are shown for the Tabas earthquake with 100 year returning period. Geotechnical profile of the soil including shear and compressional wave's velocity is listed in Table 2. Figure 1 shows Fance diagram of subsurface soil type in Saghez city.
Table (2) - Characteristics of soil profile in the well place
Vs(M/S) VP(M/S) density Class Sample 196.9 448.5 1.71 Silt 1 244.8 564.3 1.43 Silt 2 1.44 clay 3 3371 777.8 1.14 G.Sand 4 1.58 Gravel 5 400.9 913.6 1.75 Gravel 6 Gravel 7 449.2 1015.5 1.4 M.Sand 8 M.Sand 9 494.2 1100.9 Gravel 10 M.Sand 11 490.9 1112.5 1.4 M.Sand 12 M.Sand 13 506.2 1148.6 M.Sand 14 M.Sand 15 521.8 1177.3 G.Sand 16 1.5 Silt 17 536.2 1200.7 M.Sand 18 M.Sand 19 548.4 1220.1 M.Sand 20 G.Sand 21 568.9 1250.5 Gravel 22 G.Sand 23 584.3 1263.6 1.6 Gravel 24 G.Sand 25 602.1 1287.5 Gravel 26 Gravel 27 621.1 1314.9 Gravel 28 Gravel 29
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
Fig. 1, Fance diagram of Subsurface soil type in Saghez city
Figure 2 shows some profiles of the model. Response spectrum of the model to the Tabas earthquake with the returning period of 100 years for various depths is shown in figure 3, 4 and 5.
Fig. 2. Model 1. Maximum shearing coefficient profile changes, shear wave velocity and density in the borehole
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Figures 6, 7, 8 and 9 shows the second model and its results when applying Tabas earthquake acceleration. The third model and its analysis are shown in figures 10, 11, 12 and 13 introduced the forth model and their results.
Fig. 3. Spectral acceleration on earth surface With respect to period (First model).
Fig. 4. Maximum ground motion acceleration on various depths for period of 100 years (first
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
Fig. 5. Shear wave amplitude diagram in terms of frequency from ( first model )
Fig.6. Model 2. Maximum shearing coefficient profile Changes, shear wave velocity and density
Fig. 7. Spectral acceleration on earth surface .(with Respect to period (ُSecond model
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
Fig. 8. Maximum ground motion acceleration on various depths for period of 100 years (Second model).
Fig. 9. Shear wave amplitude diagram versus Frequency (Second model).
Fig. 10. Model 3. Maximum shearing coefficient Profile Changes, shear wave velocity and density
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The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
Fig. 11. Spectral acceleration on earth surface .(With Respect to period (ُThird model
Fig. 12. Maximum ground motion acceleration on various depths for .(period of 100 years (ُThird model
Fig. 13. Shear wave amplitude diagram versus .(frequency (Third modelُ 1970
The 1 st International Applied Geological Congress, Department of Geology, Islamic Azad University - Mashad Branch, Iran, 26-28 April 2010
Table 3- Amplification frequency and coefficient Resulting from four proposed models analysis.
Amplification Amplification model coefficient frequency No 1 1.300 2.000 No 2 1.583 1.800 No 3 1.622 1.600
INTERPRETATION AND CONCULSION With respect to the results, apart from the first model which describes the maximum amplification coefficient about 9 Hz, the other models with a little deviation, shows the amplification coefficient around 2 (Hz). Regarding the situation of the area from the viewpoint of sedimentation, it is thought that the 9 (Hz) components are not reasonable. So as the other models proved, the second peak of amplification is occurred in the frequency of 2 (Hz). Table 3, shows the frequency, wave amplitude amplification coefficient in the four models. For the conclusion of the survey, the average coefficient and amplification frequency from resulting models is used. So in the above borehole, shear wave amplitude in the frequency of 1.8 amplified with the coefficient 1.5.
Table 4- Maximum acceleration of ground motion on the surface versus (g) Return period (years) 100 200 475 Model 1 0.176 0.201 0.239 Model 2 0.196 0.226 0.272 Model 3 0.178 0.205 0.246
REFERENCES 1-Aki, K., 1988, Local site effects on strong ground motion. Proceedings, Earthquake Engineering and Soil Dynamics II- Recent Advances in Ground Motion Evaluation, ASCE, Geotechnical Special Publication, 20, 103-155. 2-Bard, P.Y., and Gariel, J.C., 1986. The seismic response of tow-dimensional sedimentary deposits with large vertical velocity gradients, B.S.S.A, 76, 343-356. 3-Dikmen, S.U., and Ghaboussi, J., 1984, Effective stress analysis of seismic response and liquefaction, theory, Journal of Geotechnical Engineering, ASCE, 110, 5, 628-644. 4-Finn, W.D.L., 1991, Geotechnical engineering aspects of microzonation, Proceedings, 4ht International Conference on Microzonation, Earthquake Engineering Research Institute, Stanford University, Palo Alto, California, 1, 199-259. 5-King, J.L.,and Tucker, B.E., 1984, Dependence of sediment-filles valley response on the input amplitude and the valley properties, B.S.S.A, 74, 1, 153-165
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6-Rial, J.A., Saltzman, N.G., and Ling, H., 1992, Earthquake-induced resonance in sedimentary basins, American Science, 80, 6, 566-578. 7-Sanchez-Sesma. F., and Campillo M., 1993, Topographica effects for incident P, SV, and Rayleigh waves, Tectonophysics, 218, 1-3, 113-125. 8-Schnabel, P.B., Lysmer, J., and Seed, H.B., 1972, 9-SHAKE: a computer program for earthquake response analysis of horizontally layered sites, Report EERC 72-
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