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 BY YASMIN RIZVI SYED ANWAR HUSSAIN MUHAMMAD ATIQ MIR ANWAR HUSSAIN ALIZAI SHAHNAZ PYAR ALI 2010 Yasmin Rizvi et-al GSP Information Release 924 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- Yasmin Rizvi et-al GSP Information Release 924 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. Yasmin Rizvi et-al GSP Information Release 924 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 Yasmin Rizvi et-al GSP Information Release 924 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. Yasmin Rizvi et-al GSP Information Release 924 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. Yasmin Rizvi et-al GSP Information Release 924 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 - 1 - Yasmin Rizvi et-al GSP Information Release 924 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.