Yasmin Rizvi Et-Al GSP Information Release 924

Yasmin Rizvi et-al GSP Information Release 924

GOVERNMENT OF PAKISTAN Information Release No. 924 MINISTRY OF PETROLEUM & NATURAL RESOURCES GEOLOGICAL SURVEY OF PAKISTAN

PRELIMINARY PETROLOGICAL SUTDIES OF BASALTS, RANIKOT, AMRI BARA AND REHMAN DHORO AREA, (35O/13 & 35N/16) JAMSHORO AND DADU DISTRICTS, SINDH, PAKISTAN

YASMIN RIZVI SYED ANWAR HUSSAIN MUHAMMAD ATIQ MIR ANWAR HUSSAIN ALIZAI SHAHNAZ PYAR ALI

2010

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CONTENTS

ABSTRACT

INTRODUCTION -1-

Purpose and Scope Location and Accessibility Previous Investigations

Acknowledgments GENERAL GEOLOGY -2- Stratigraphy Pab Sandstone Khadro Formation

Bara Formation

PETROGRAPHY -3-

Ranikot Area Rehman Dhoro Bara Nai

GEOCHEMISTRY -5-

DISCUSSIONS -6-

RECOMMENDATIONS -7-

REFERENCES -8-

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ILLUSTRATIONS

Figure 1a : Geological Map of Ranikot Area showing locations of samples. (Part of Toposheet

35O/13)

Figure 1b : Geological Map of Rehman Dhoro & Bara Nai Area showing locations of samples

(Part of Toposheet 35N/16).

Figure 2: Major element discrimination diagrams for distinguishing Tholeiitic series rocks from alkaline rocks. FeO/MgO verses SiO2 diagram of Miyashiro. 1974.

Fig.3:(a) Plots of Ranikot, Rehman Dhoro & Bara Nai Basalts on the TAS Diagram. Dividing lines between alkalic & subalkalic fields proposed by Macdonald & Kastura (1964) and Irvine &

Baragar (1971). (b) A plot of Deccan Basalt of the western ghats on the same diagram.

Fig 4: (A) An AFM diagram of Deccan Basalt Western ghats, India Typical tholeiitic trend

(Thingmuli, Iceland) and Calc-alkaline trend (Cascades) are also shown along the boundaries between the two fields proposed by Kuno (1968) and Irvine and Baragar (1971). (B) An AFM diagram of our study area i.e; Ranikot, Rehman Dhoro and Bara Nai areas.

Tables:

Table 1. Stratigrahy of the area.

Table 2a. Chemical composition of Rock samples from Ranikot area (XRF results).

Table 2b. CIPW norms of Rock samples from Ranikot area.

Table 3a. Chemical composition of Rock samples from Rehman Dhoro area.

Table 3b. CIPW norms of Rock samples from Rehman Dhoro area.

Table 4a. Chemical composition of Rock samples from Bara Nai area.

Table 4b. CIPW norms of rock samples from Bara Nai area.

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Plates: Plate I a. Gypsum vein in altered vesicular Basalt at Ranikot Fort area. S-12; XPL. Bar Scale. b. Deformed texture of Tholeiitic Vesicular Basalt from Ranikot area. S-9; XPL, Bar Scale.

Plate II a. The amygdules latter filled by spherulitic aggregates of epidote; RD-7 Thoeliite Amygdaloidal Basalt. XPL. Bar Scale b. The amygdule latter filled by Iron stained carbonates as radial aggregates; RD-7 Thoeliite Amygdaloidal Basalt.

Plates III

a. The photomicrograph shows the glomeroporphyritic texture; cluster of glomerocrysts of Plagioclase (Pl) are visible RD-9: Pol Lt. Bar Scale. b. Vesicular carbonate with Zeolite grain: RD-9 Pol. Lt. Bar Scale.

Plate IV a. The photograph shows subophitic texture plagioclase laths embedded partly in pyroxene grain showing tapering ends; RD-10 XPL Bar Scale. b. Relatively large grain of Olivine with corrode boundries is visible at the centre. Rest of the field is occupied by plagioclase laths with intergranular clinopyroxene grains and smoky opaques. RD-10(5) XPL. Bar scale.

Plate V a. Pyroxene cross section with its typical two sets of cleavage. RD-10, XPL. Bar scale. b. Secondary aggregates of biotite. Rd-10. XPL Bar Scale.

Plate VI a. Fractured and partially altered olivine showing subophitic texture S-8. XPL. Bar Scale. b. Intergranular & subophitic texture alongwith Secondary amygdaloidal

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carbonates. S-9. XPL. Bar Scale.

Plate VII a. Clinopyroxene subophitically enclose lath of Plagioclase. The intergranular spaces between plagioclase laths are occupied by more than one grains of pyroxene & smoky opaques (titanium bearing Iron oxide) RD-10XPL Bar Scale. b. A group of clinopyroxene crystals are located at the centre or the field. Rest of the field is occupied by plagioclase laths with intergranular pyroxene finer grains. The rock is relatively fresh. RD-10 XPL Bar Scale.

Plate VIII a. Plagioclase grains embedded in the pyroxene in sub ophitic manner. Thoellitic Basalt: BA-2(8) XPL Bar scale. b. Clinopyroxene sub ophitically enclose laths of plagioclase with tapering ends. Thoelitic Basalt: BA-2(9) XPL. Bar scale.

Plate IX Photo 1: Representing different alteration, Rehman Dhoro. Photo 2: Showing the contact of limestone and basalt, Rehman Dhoro.

Plate X Photo 3: Showing the well developed exposures of basalt at Bara Nai. Photo4: showing the presence of subrounded quartz crystals at Rehman Dhoro.

Plate XI Photo 5: Lower contact of basalt with quartz crystals; Rehman Dhoro. Photo 6: Magnifying view of quartz grains at Rehman Dhoro.

Plate XII Photo 7: Basalt with inclined fractures; Rehman Dhoro. Photo 8: Paleocene and Eocene exposures at the Ranikot area, Sindh.

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ABSTRACT

Basaltic flow exposures within cretaceous- paleocene sedimentary rock sequence are reported from Laki Range southern Sindh. These flows are confined to Pab Sandstone of late cretaceous age, Khadro Formation of early Paleocene age and the Bara Formation of middle paleocene age. The exposures found at Bara Nai, Rehman Dhoro and Ranikot Fort area interbedded with the sedimentary rocks of above mentioned formations. The presence of these basaltic flows formed the basis of this report i.e. The Preliminary Petrological studies of Basalts of Ranikot Fort, Bara Nai and Rehman Dhoro, Jamshoro and Dadu District, Sindh, Pakistan.

The petrographic studies shows that the rocks from Rehman Dhoro and Ranikot are amygdaloidal Tholiitic Basalts . Texturally fine grained to very fine grained, intergranular and ophitic to subophitic, occasionally glomeroporphyritic and composed of Plagioclase (Labrodorite – Byotonite: where possibly measured) and Pyroxene (Pigeonite). Vesicles are occupied mostly by spherulitic calcite occasionally limonite and zeolites. The rocks from Bara Nai classified as amygdaloidal Tholeiitic Dolerites. The grain size is relatively coarser than other two localities and showing intersertal, intergranular and subophitic texture, however texture is commonly deformed. The minerals it composed are Pyroxene (Pigeonite) and Plagioclase. Amygdaloids are commonly occupied by spherulitic calcite. The major element geochemical studies of all three localities reflect that basalts are of tholeiitic in composition and belong to continental flood basalt. It is also depicted by various binary and ternary plots that all the samples fall in the tholeiitic field.

The CIPW norms calculated on the basis of chemical composition yield normative hypersthene and Quartz indicative of tholeiitic nature.

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INTRODUCTION

The indication of basaltic rocks from Dadu and Jamshoro District as reported by many geologists during geological mapping of that area (HSC, 1960; Abdullah,M.M,1980 etc). But no detail studies account from the publication Records. The present studies provides the basic insight on the basis of preliminary petrologic investigation from three localities i.e. Ranikot area, Rehman Dhoro and Bara Nai, Dadu and Jamshoro districts, Sindh..

Location and Accessibility:-

The studied first location lies in the middle part of the toposheet 35O/ 13 in the vicinity of Ranikot Fort (Fig 1a), Jamshoro District. The area is approximately 230 Km from Karachi and linked by both road and railway. The Rehman Dhoro and Bara Nai areas lie in the upper and middle part of the toposheet 35N/ 16. The areas are about 260 & 240 Km from Karachi and linked by road & railways both.

Previous Investigation:-

A number of workers reported the basalt exposures in the study area. Their contributions briefly in chronological order are as follows.

1. Blandford (1876) and later workers have reported the presence of traps (90 feet) in Paleocene rocks termed as Trap group which are equivalent to the Deccan trap of Peninsular India.

2. Farshori, 1972 referred as Trap rocks in northern part of the Laki Range. According to him these are mainly flows of basaltic composition interstratified with the sedimentary rocks i.e Pab Sandstone, Khadro Formation and Rehman Member of Ranikot group. These rocks occur at two horizons: 1. at lower level 300 feet above the base of Pab sandstone in Bara Nala 8 miles from Amri. 2. Upper flows occur just above the unfossiliferous sandstone of basalt Ranikot i.e. Dhapro beds (Nagappa, 1959).

3. Stratigraphy of Pakistan, 1977 reported a member of basaltic flows (at least two) in Khadro formation is present in the unit that is partly massive, amygdaloidal, brecciated and weathers black. In Bara Formation they termed it the volcanic debris.

4. Abdullah, 1980 reported during geological mapping of Amri Bara Quadrangle (35N/16) Lava flows of basaltic composition 0.1 to 1.5 meters thick in the middle part of Pab sandstone. As per his observations these flows are incidental and rare.

5. Shah, 2009 named the basaltic flows as the Khaskheli Formation overlies the cretaceous and are underlain by the Paleocene rocks.. These basalts are having the distinct

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Stratigraphic position in lower Indus basin encountered in most of the wells drilled in South Indus basin by the oil companies.

Acknowledgments:

Authors are grateful to Dr. Imran Khan, Director General and Muhammad Ali Tagar, Deputy Director General for their encouragement and interest in the present work. The valuable guidance & keen interest during digitization work of Mr. Ali Muhammad, Assistant Director is thankfully acknowledged. Thanks are also due to the Mr. Riaz Hussain Rajpar, Assistant Geophysicist,GSP Karachi for helping in installing Geochemical software used in geochemical calculations.

GEOLOGY

The investigated area represents the northern part of the Hyderabad Arch, a pre organic positive structure developed along the peripheral part of the Indus plain, West of the Indus River, where oscillatory movements has repeatedly occurred in the post Mesozoic period. The Arch includes the Laki and Kirthar ranges where the folded mountain belts are arranged echelons with curved axial traces plunging north-northwest ward in the northern part and southeast ward in the southern part. The Neogene and Paleogene sediments are exposed in Hyderabad Arch whereas the late periods of Indus plain are however, manifested mostly by subsurface lava flow comparable with the Deccan trap of India. Conspicuous post Paleocene sub-arid erosion marks a regional unconformity. (After Abdullah. M.M 1980).The generalized picture of the stratigraphical units present in the area is shown in Table 1. The area of investigation mainly comprises of rocks from cretaceous to recent. Oldest Fort Munro Formation exposed in the particular area of Bara Nai. It is exposed in the core of anticline which is faulted from east, and Fort Munro Formation is thrusted over the Laki Formation. In Rehman Dhoro there are two exposures of basaltic flows one at the contact of Pab Sandstone and Khadro Formation (shale) while the second at the contact of Khadro and Bara Formation. The younger exposures of basaltic flows are along the fault in the northeastern corner of Fig 1b (Plate IX Photo 1& 2). Here the well developed crystals of agate are present along the fault. (Plate X Photo 4; XI Photo 5,6) the basaltic flows are black to greenish black on fresh surface and brownish and reddish brown on weathered surface and commonly interbedded with mudstone and shale. At the contact of the Pab Sandstone and Khadro Formation along the fault at the Station 2 alteration into Iron oxides observed (Fig 1b) & (Plate IX photo 1 & 2). In Ranikot area basaltic flow are present in the Bara Formation in the core of anticline (Plate XIII Photo 8). Since the present work deals with the petrography of basaltic flows observed in Pab sandstone, Khadro formation and Bara formation, it is desirable to describe in detail only these three formations.

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Pab Sandstone:

Sandstone, subordinate siltstone constitutes the formation. Lava flows of basaltic composition, 0.1 to 0.5 meters thick in the middle part of the formation appears to be accidental and rare. The thickness of the formation range between 52 and 229 meters maximum at Bara Dhoro. Pseudolaterites developing at the contact with overlying Khadro formation of Ranikot group represent a disconformity.

Khadro Formation:

It represents the lowest division of Ranikot group. It consists of siltstone, sandstone and limestone. Basaltic flows are present in the unit (at least two) and top of the unit is marked by a volcanic flow.

Bara Formation:

Sandstone, siltstone and shale (at places carbonaceous) with two thin layers of basaltic flows are the predominant rock types in the Bara formation. The carbonaceous shale contains the coal lenses of variegated thickness.

PETROGRAPHY

The petrographic studies involve both megascopic and microscopic studies. The megascopic studies carried out under simple stereoscope with magnification upto 40x. The microscopic studies cover the study of thin sections under polarized microscope. The studies based on petrographic studies of selected samples from three localities i.e. Rani Kot area, Rehman Dhoro and Bara Nai.

Ranikot Area:

The samples collected from Rani Kot area are mostly intergranular and subophitic fine grained and vesicular/amygdaloidal. The texture is deformed and grains are mostly fractured (Plate IA & IB). Some samples show glomeroporphyritic texture. The major minerals are plagioclase and pyroxene; the angular spaces between plagioclase are occupied by one or more grains pyroxene ± opaque mineral. Pyroxene show subophitic and ophitic texture i.e. plagioclase grains are completely to partially enclosed – pyroxene.

Plagioclase is observed in two sizes; one is fine grained, lath shaped and twinned (combined Albite-calsbad) variably as angular arrangement and as glomeroporphyritic. Very few grains show clear figure i.e. biaxial positive. Most of the samples do not have suitable orientation to measure the extinction however where possible it shows range AW54-72 i.e. mostly Labrodorite and rarely Byotonite. The 2nd generation is very fine grained laths shaped and wedge shaped

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penetrated - pyroxene grains. These grains are twinned but due to unsuitable orientation extinction can not be measured. Plagioclase is moderately to intensely replaced by calcite.

Pyroxene is subhedral to auhedral commonly fractured colorless to pale green at places show very weak pleochroism. Extinction angle varies between 25° - 45º, interference figure is biaxial positive with small to very small 2v, intensely to moderately penetrated by plagioclase fine grains. Pyroxene is replaced by carbonates like in sample S-12 the ferromagnesians are almost completely replaced by carbonates. Intergranular aggregates of opaques, black colored, altered moderately to strongly into limonite however in some samples (S-11) altered mineral is smoky. Few grains with high relief and strong birefringence of olivine are present as colorless to greenish, medium to coarse grain, anhedral, figure not clear partly to completely altered into iddingsite and serpentine (Plate VIA). Gypsum vein is observed in one sample (S-12) (Plate IA) Zeolites tabular and colourless grains are also observed in (S-11). The rocks are highly to moderately vesicular and vesicles are filled mostly by spherulitic calcite, occasionally by zeolite and epidote. The rocks identified are altered vesicular tholeiitic Basalts.

Rehman Dhoro:

Megascopically the rocks are intergranular and vesicular; the vesicles are mostly infilled by calcite variably light olive gray to dark yellowish brown.

Microscopically these vesicular altered Basalts show intergranular ophitic to subophitic (Plate IVA) and glomeroporphyritic (Plate IIIA) (RD-9) with intergranular ground mass and very fine grained. The mineralogy is as follows: Plagioclase as glomeroporphyritic texture occurs as clusters of tabular grains, commonly zoned, extinction angle varies 24° to 29½ (An46 - 53) of Labaodorite composition, Biaxial positive, weakly to moderately altered to calcite along cores. Iron staining along fractures is also present, groundmass is very fine grained intergranular composed of Plagioclase and carbonates and altered opaques into limonite.

In other samples showing intergranular texture plagioclase observed as lath shaped, twinned, extinction can not be measured because appropriate orientation required for the measurement is not available, moderately altered to carbonates relatively fine grained randomly arranged chadocryst embedded partially to completely in pyroxenes showing the patchy appearance. This plagioclase occurs as lath shaped with wedge shaped ends. In most of the thin sections ferromagnesians are completely altered/replaced by biotite cholorite (Plate VB) carbonates and opaques where present are pyroxenes (Pigeonite). The pyroxenes occur mostly as clusters of tabular grains (Plate IV A & VA ) of light pale greenish color. Cross sections with 2 sets of cleavage are also present (Plate VA). Extinction angle varies from 15° to 39º and interference figure is biaxial positive with very small 2 V. No figure with

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moderate or high 2V observed, many grains show flash figure so most probably it is suggested that augite coexisted with Pigeonite. Rarely olivine grains are observed (Plate IV B) Opaques present as intergranular to Plagioclase of black colour and smoky appearance so most probably titanium rich (leucoxene) (Plate IV B). Rarely colourless tabular grains with weak birefringence of zeolites present (Plate IB). Vesicles are infilled by carbonates and epidote (Plate IIA & B), commonly oxidized or lined by opaques. Brown color glass is also observed (RD-10)

The rocks identified are altered vesicular tholeiitic Basalts.

Bara Nai:

Microscopically the rocks are fine grained relatively coarser than sample collected from Ranikot area and Rehman Dhoro. The texture is intersertal, intergranular and subophitic (Plate VIIIA). In mostly of the samples it is deformed. Plagioclase present as lath shaped grains, twinned (Combined Albite Calsbad), extinction can not be measured and figure is biaxial positive. Pyroxenes (Pigeonite): The pyroxenes are relatively more abundant than plagioclase occupied the spaces between plagioclase by grains (+ opaque grains), colourless light pale green coloured, extinction angle varies 23° – 41° and the figure is biaxial positive with small 2V. The grains subophitially enclosed plagioclase narrow lamellaes (Plate VIIIB). Opaques are black and smoky. Zeolite grains are colourless tabular, has low relief, very weak birefringence and biaxial positive observed as intergranular spaces between plagioclase. Vesicles are occupied by spherulitic calcite and opaques. Glass is common in samples (BA-5 and 9) and altered to yellow Palogonite. In some samples ferromagnesians are completely replaced by carbonates and Iron oxide. The texture is also deformed (for e.g. BA-4, 10).

The rocks identified are altered vesicular tholeiitic Dolerites.

GEOCHEMISTRY

Selected samples collected from the vicinity of Ranikot fort were analyzed by WD-XRF in Geoscience Lab. Islamabad for all the major elements using Pressed Pellet (I.Q + method), Loss on Ignition (LOI) at 1000° C (as reported by Geoscience Lab. Islamabad). The selected samples collected from Rehman Dhoro and Bara Nai were analyzed in Chemical Lab. Karachi by (wet chemistry) for major elements. SiO2 was determined by gravimetrically, Al2O3 by difference i.e. R2O3 (Fe2O3 + TiO2 + MnO), P2O5, TiO2 by calorimetric method, CaO and MgO

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by titration of EDTA, Na2O, K2O, FeO, and MnO by atomic absorption spectrophotometer, H2O was estimated by drying the rock powder at 105° C and ignition on loss was measured at 900° C.

Analytical results of Basalts from Ranikot fort, Rehman Dhoro and Bara Nai are shown in Tables 2a, 3a, 4a respectively. Cross, Iddings, Pirrson & Washington hence the acronym CIPW norms has been calculated by Geochemical data toolkit 2.3 software (GCD kit) and shown in the tables 2b, 3b, 4b.

All mineralogies reflect chemistry of the tholeiitic Basalts are hypersthene normative and alkali olivine basalts are olivine and nepheline normative. As indicated in the Tables 2b, 3b, 4b the rock samples from all three localities are hypersthene normative

The major element chemical data of the Basalts from Ranikot area, Rehman Dhoro as well as Dolerites from Bara Nai are used to plot binary and ternary diagrams.

Binary diagram plotted on the basis of major elements for distinguishing tholeiitic series rocks from alkaline rocks by using Total Iron (FeO)/MgO versus SiO2 (after Miyashiro, 1974). The plot shows that all the rock samples from Ranikot fort area, Rehman Dhoro and Bara Nai fall in the tholeiitic field (Fig.2).

The plots of all samples from three localities on TAS diagram are drawn (Fig.3a) and all the compositions restricted to Basalt and Picrobasalt in the field of subalkalic (tholeiitic) nature. Dividing lines between alkalic and subalkalic fields proposed by Macdonald & Kastura (1964) and Irvine & Baragar (1971) are also shown. The Deccan Basalts samples of the western ghats (after Sheth, H, last updated 2006) is also given in the Fig 3b for comparison. Deccan basalts lie in the field of Basalts and Andesitic basalts.

Triangular plot AFM diagram which illustrates the difference between differentiation trends in the calc-alkaline and tholeiitic series. Chemical analysis of the various rocks in the series is plotted in terms of F (Total Iron as FeO), M (MgO) and A (alkalies Na2O + K2O). Boundary between calc-alkaline field and tholeiitic field after Kuno (1968) and Irvine and Baragar (1971) as heavy lines for a typical tholeiitic sequence (Thingmuli volcano, Iceland (as filled circles from Carmichael, 1964). The rock samples from all three localities i.e. Ranikot fort area, Rehman Dhoro and Bara Nai showing the Fe enrichment trend typical of tholeiitic basalts (Fig.4a). Their comparison with Deccan Basalts (after Sheth, H, last updated 2006) is given in (Fig 4b) showing their restriction in the tholeiitic field however the samples from Ranikot, Rehman Dhoro and Bara Nai are more iron rich.

DISCUSSION

The presence of basaltic rocks from Dadu and Jamshoro District reported by geologist during geological mapping of that area has formed the basis of this report. This report is of preliminary nature based on petrological studies of very selective samples from three localities i.e. around Ranikot Fort area, Rehman Dhoro and Bara Nai.

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The rocks identified are Tholeiitic Basalt from Ranikot area and Rehman Dhoro and Tholeiitic Dolerite from Bara Nai.

The mineralogical data shows that the Tholeiitic Basalts from Ranikot Fort area and Rehman Dhoro are very fine grained intergranular, subophitic and vesicular and rarely glomeroporphyritic (RD-9). The basalts mainly composed of Plagioclase and Pyroxene. Two generations of plagioclase are observed. First generation is of Labrodorite and rarely Byotonite composition (An54-64) (where possibly measured due to the deformed texture and secondly unsuitable orientation). Pyroxene is of Pigeonite composition. (Extinction angle varies b/w 15 – 39° and biaxial positive with low 2v). The rocks are commonly vesicular/ amygdaloidal and commonly filled later by calcite. The mineralogical data of Tholeiitic dolerite from Bara Nai shows that the texture is intersertal, intergranular and subophitic and fine grained while most of the samples show the deformed texture. Grain size is relatively coarser than other two localities. The minerals it composed of are Pyroxene (Pigeonite) and Plagioclase and occasionally zeolites. The rocks are commonly vesicular and the vesicles are occupied by spherulitic calcite. Glass is common in samples (BA 5&9) and altered to yellow Palogonite. The CIPW norms calculated on the basis of chemical composition by GCD kit yield normative hypersthene and quartz. Both are indicative of tholeiitic nature (Table 2b, 3b & 4b). Major elements discrimination binary diagram (Fig.2) plotted by Total Iron (as FeO), MgO versus SiO2 (after Miyashiro 1974). The plot shows that all the rock samples from Rehman Dhoro, Ranikot area and Bara Nai fall in the tholeiitic field. Binary TAS plot of total alkalies versus SiO2 used to distinguish members of alkali olivine basalts and tholeiitic basalts. The plot indicates that all the points of three localities restricted to the field of tholeiites (Fig.3a). The TAS diagram of Deccan Basalts Western ghats (Fig 3b) is given (after Sheth, H, last updated 2006) for comparison. Both are falling in the similar fields i.e; tholeiitic. Triangular plot an AFM diagram plotted in terms of F (Total Iron as FeO),M (MgO) and A (alkalies Na2O+K2O) (Fig.4a). The rocks samples from all three localities i.e. Ranikot fort area, Rehman Dhoro and Bara Nai fall in the tholeiitic area. AFM diagram of Deccan Basalts Western ghats (after Sheth, H, last updated 2006) is also given (Fig 4b). Both are falling in the tholeiitic field however the samples from our study area are richer in iron (Fe). The petrographic studies and binary and ternary plots show that most probably these basalts emplaced at the time of Deccan flows but the classification based on major elements need to verify by the trace elements and REE elements geochemistry due to the post magmatic alterations and possible partial replacement of some minerals latter filled the amygdules.

RECOMMENDATIONS

The present report based on the preliminary petrographic studies and chemistry of major oxides of the rock samples collected from three localities i.e. Ranikot fort area, Rehman Dhoro and Bara Nai, Dadu and Jamshoro Districts Sindh.

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It is recommended that detail sampling of the area showing basalt presence be done to carry out the: 1. Petrographic studies 2. Chemistry of Trace elements 3. Age determination to correlate with the basalt exposures of other part of world especially the neighboring country India.

REFERENCES

Hunting Survey Corporation, 1960, Reconnaissance Geology of Part of West Pakistan, A Colombo Plan Cooperative Project, Toronto, Government of Canada for Government of Pakistan

Farshori, M.Z., 1972, The Geology of Sindh

Shah S.M. I., 1977, Stratigraphy of Pakistan, Memoirs of Geological Survey of Pakistan, Vol. 12, pp 60 – 61.

Abdullah, M.M., 1980, Geological Map of Amri – Bara Quadrangle, Dadu District, Sindh, Pakistan at 1:50,000 scale Map No. 8.

Raymond, L.A., 1995, Petrology: The study of Igneous, Sedimentary and Metamorphic Rocks. Wm.C. Brown Publishers pp 98 – 100.

Hatch, F.H., Wells, A.K, Wells, M.K, Petrology of Igneous Rocks: Text book of Petrology / Volume one, 1984, pp. 373

Rollinson, H., 1993, Using geochemical data: evaluation, presentation, interpretation: pp.77.

Akhtar, J, Rizvi Y, Muhammad Ali, 2009, Geological Map of Sindh, Pakistan (Unpublished)

Shah, S.M.I, 2009; Stratigraphy of Pakistan: GSP Memoirs Vol. 22, pp 247-249.

Sheth, H, last updated 2006; The Deccan beyond the plume hypothesis: www.mantleplume.org

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Table 1: Generalized Stratigraphy of the area.

Formation Age Lithology

Loose to semi-consolidated Recent deposits Recent boulders, cobbles, gravels and fine silty clays. Boulders, cobbles and pebbles of Dada conglomerate Pleistocene limestone.

Disconformity Sandstone, grit stone, clay and Manchar Formation Late Mio Pliocene conglomerate.

Gaj Formation Mio Pliocene Interstratified sand stone and clay.

Nari Formation Oligocene Sandstone and clay.

Middle Eocene to Kirther Formation Massive limestone. Early Oligocene Marl intercalated with limestone Tiyon Formation Middle Eocene and clay.

Limestone and basal lateritic clay Laki Formation Early Eocene with coal lenses. Unconformity

Lakhra Formation Late Paleocene Sandstone, siltstone and limestone. Sandstone, siltstone and shale with layers of basaltic flows & Bara Formation Middle Paleocene carbonaceous shale with coal lenses.

Siltstone, sandstone and limestone Khadro Formation Early Paleocene with occasional basaltic flows. Disconformity

Sandstone, subordinate siltstone Pab Sandstone Late Cretaceous with occasional basaltic flows Limestone and calcareous Fort Munro Formation Late Cretaceous sandstone

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Table 2a: Chemical composition of Rock samples from Rani Kot area. (XRF results from Geoscience Lab. Islamabad)

Sample S-8 S-9 S-11 Name % % % SiO2 45.37 42.50 45.77 TiO2 1.39 1.461 2.13 Al2O3 15.22 15.21 12.79 Fe2O3 13.02 13.83 16.25 MnO 0.134 0.31 0.13 MgO 6.84 4.600 5.91 CaO 10.27 14.22 8.567 Na2O 1.76 1.70 1.52 K2O 0.075 0.067 0.09 P2O 0.232 0.172 0.22 NiO 0.01 0.012 0.011 CuO 0.01 0.012 0.011 ZnO 0.010 0.015 0.015 SrO 0.015 0.023 0.017 Y2O3 0.0095 0.0095 0.0018 ZrO2 0.0057 0.0095 0.0075 WO3 0.020 0.00 0.015 Cl 0.132 0.201 0.117 LOI 4.23 5.14 5.49

Table 2b: CIPW norms of Rock samples from Ranikot Area.

S-8 S-9 S-11 Q 6.757 3.232 12.899 Or 0.443 0.396 0.532 Ab 14.893 14.385 12.862 An 33.407 33.673 27.810 Di 9.116 24.716 4.939 Wo 0.000 0.052 0.000 Hy 12.811 0.000 12.431 Il 0.287 0.663 0.278 Hm 13.020 13.830 16.250 Tn 3.042 2.730 4.870 Ap 0.550 0.407 0.521 Sum 94.326 94.084 93.391

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Table 3a: Chemical composition of Rock samples from Rehman Dhoro Tholeiitic Basalts

+ Sample L.O.I SiO2 Al2O3 Fe2O3 FeO TiO2 CaO MgO Na2O K2O P2O5 H2O No. % % % % % % % % % % ppm % RD-2 9.58 44.15 15.48 11.56 1.11 0.45 11.20 4.54 1.25 0.07 350 2.24 RD-3 16.75 32.58 16.98 9.88 0.86 0.36 15.60 5.04 1.14 0.08 400 2.96 RD-4 18.98 30.88 23.60 6.90 0.34 0.24 13.92 3.50 0.93 0.04 200 1.75 RD-5A 19.36 31.34 20.65 9.06 0.68 0.26 14.70 2.51 0.80 0.05 250 1.96 RD-7 18.76 30.94 24.35 7.10 0.28 0.25 13.80 2.95 0.94 0.06 300 2.20 RD-8 17.88 32.49 21.50 6.88 0.36 0.23 13.50 5.50 0.96 0.05 250 2.30 RD-9 7.69 50.25 20.65 7.10 0.50 0.30 8.95 2.70 1.13 0.04 250 2.46 RD-10 1.65 47.33 21.50 6.70 0.56 0.32 13.30 7.06 1.10 0.05 300 1.39

Table 3b: CIPW of Rock samples from Rehman Dhoro Tholeiitic Basalts

RD - 2 RD - 3 RD - 4 RD - 5A RD - 7 RD - 8 RD - 9 RD - 10 Q 29.843 18.129 20.1 22.753 20.845 18.515 39.499 30.215 C 13.348 15.018 22.027 19.28 22.739 19.867 18.748 19.636 Or 0.414 0.473 0.236 0.295 0.355 0.295 0.236 0.295 Ab 10.577 9.646 7.869 6.769 7.954 8.123 9.562 9.308 Hy 11.308 12.554 8.718 6.252 7.348 13.699 6.725 17.585 Mt 2.273 1.728 0.4 1.438 0.178 0.493 0.742 0.877 Il 0.855 0.684 0.456 0.494 0.475 0.437 0.57 0.608 Hm 9.992 8.688 6.624 8.068 6.977 6.54 6.588 6.095 Ap 20.145 28.059 25.037 26.44 24.821 24.282 16.098 23.922 Sum 98.755 94.979 91.467 91.79 91.691 92.252 98.768 108.542

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Table 4a: Chemical composition of Rock samples from Bara Nai Tholeiitic Dolerites.

Sample L.O.I + HO (%) SiO2 Al2O3 Fe2O3 FeO CaO MgO N2O K2O No. % 45°C 350°C % % % % % % % % BA-1/09 1.33 0.42 0.82 43.14 21.48 11.75 0.15 14.72 6.50 0.60 0.08 BA-2/09 1.09 0.38 0.93 43.40 19.98 12.05 0.12 15.42 7.00 0.44 0.07 BA-3/09 5.85 1.03 1.87 43.80 24.22 10.12 0.14 10.52 4.50 0.54 0.05 BA-4/09 13.84 0.66 1.82 39.58 24.45 7.48 0.12 10.12 3.50 0.58 0.06 BA-5/09 4.55 0.70 2.78 45.98 24.68 11.62 0.30 8.52 2.50 0.95 0.55 BA-6/09 35.65 0.18 2.10 5.08 10.35 12.80 0.15 32.42 3.00 0.27 0.03 BA-7/09 4.08 0.78 2.90 47.70 22.51 12.20 0.35 9.50 2.00 0.85 0.58 BA-8/09 5.21 0.85 3.32 45.85 24.35 11.98 0.26 8.25 2.00 1.22 0.45 BA-9/09 5.04 1.04 3.10 46.02 23.20 12.55 0.15 9.50 2.00 0.82 0.43 BA-10/09 4.71 1.00 3.30 45.88 24.45 12.90 0.14 8.50 2.50 0.38 0.26 BA-11/09 17.91 0.68 2.47 33.28 20.75 7.05 0.30 13.70 5.50 1.12 0.06 BA-12/09 8.98 0.99 4.44 45.28 16.85 10.45 0.95 11.50 4.50 1.15 0.07 BA-13/09 6.62 1.76 2.15 64.28 13.80 6.85 0.16 5.25 2.00 0.69 0.13 BA-13/09 5.34 0.95 2.40 46.88 25.95 10.58 0.18 7.80 2.00 0.85 0.08 BA-14/09 7.75 0.70 2.46 49.68 20.80 7.65 0.40 9.90 2.50 0.98 0.05

Table 4b: CIPW Norms of Rock samples from Bara Nai Tholeiitic Dolerites. Q C Or An Lo Kp Di Hy Ol Cs Mt Hm Sum BA-1 4.871 0 0.484 58.374 0 0 11.407 10.902 0 0 0.483 11.416 97.82 BA-2 4.445 0 0.414 54.31 0 0 17.273 9.428 0 0 0.387 11.783 98.04 BA-3 14.357 5.038 0.295 52.192 0 0 0 11.209 0 0 0.451 9.809 93.35 BA-4 12.446 5.985 0.355 50.207 0 0 0 8.718 0 0 0.387 7.213 85.31 BA-5 21.89 8.593 3.25 42.269 0 0 0 6.227 0 0 0.967 10.953 94.15 BA-6 0 0.000 0.000 28.152 86.024 62.44 0 0 6.236 41.07 0.483 12.466 63.83 2 4 BA-7 22.141 4.609 3.428 47.131 0 0 0 4.982 0 0 1.128 11.422 94.84 BA-8 23.467 8.863 2.659 40.93 0 0 0 4.982 0 0 0.838 11.402 93.14 BA-9 21.035 5.461 2.541 47.131 0 0 0 4.982 0 0 0.483 12.216 93.85 BA-10 22.943 8.714 1.537 42.17 0 0 0 6.227 0 0 0.451 12.589 94.63 BA-11 0 0 0.355 56.441 0 0 8.973 2.598 4.865 0 0 0.967 6.383 80.58 1 BA-12 16.097 0 0.414 45.77 0 0 8.783 7.137 0 0 3.062 8.338 89.6 BA-13 49.551 4.114 0.768 26.046 0 0 0 4.982 0 0 .516 6.494 92.47 BA-14 26.877 11.661 0.473 38.697 0 0 0 4.982 0 0 0.56 10.18 93.47 BA-15 24.547 2.745 0.295 49.116 0 0 0 6.227 0 0 1.289 6.761 90.98

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