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Title of Thesis

Amanullah Laghari
Institute/University/Department Details
University of Peshawar, Pakistan / Department of National Centre of Excellence in Geology
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
nagar parkar granites, thar, dykes, granites, basement rocks, riebeckite-aegirine grey granite, biotite pink granite, acid dykes, riebeckite, aegirine, devitrified rhyolite, basic dykes

Covering 480 km, the Nagar Parkar area in southeastern Sindh is a part of the Thar Desert adjacent to the Runn of Kutch. Detailed petrology of the area, based on mapping, petrography, and major, trace, and rare-earth element geochemistry, has been studied during the course of this investigation. The area is occupied by a variety of magmatic rocks referred to as the Nagar Parkar igneous Complex. At least six phases are recognizable: 1) basement rocks (oldest), 2) riebeckite-aegirine grey granite, 3) biotite pink granite, 4) acid dykes, some of which contain riebeckite and aegirine, 5) devitrified rhyolite “plugs” , and 6) basic dykes (youngest). Of these, the last three are insignificant in volume. Radiometric dates are lacking, but the grey and pink granites are petrographically comparable to the Siwana and Jalalore plutons, respectively, emplaced in the Malani volcanic series that covers large areas in western Rajasthan. Based on these similarities and proximity, it is thus suggested that the phase 2 to 6 bodies in Nagar Parkar may belong to the late Proterozoic (720-745 Ma) Malani magmastism.

The basement (age unknown) comprises deformed and epidote-amphibolite facies metamorphosed rocks ranging from mafic to granodioritic composition. They appear to be the products of crystallization differentiation of a calc-alkaline magma of island are affinity. The phase 2 to 5 rocks, forming stock-size plutons to minor dykes and plugs, range from peralkaline (Most common) to peraluminous grabutes nucroigrabutes, rhyolite and trachyte. The display very similar trace element characteristics and classiy as typical within plate. A type “granitiod”. Their trace element patterns are akin to those of Mull (Scotland), Skaergaard (Greenland) and Sabaloka (Sudan) Granites, which are emplaced in attenuatedto normal continental crust.

The mafic dykes are divisible into hornblende-bearing (dioritic / lamprophric) and pyroxene+olivine-bearing (doleritic) types. Both are alkaline and show some chmical resemblance to continental alkaline basalts. Significantly, the mantle-normalized diagrams of the basic dykes are similar to those of the main granites except for relatively lower concentrations of trace and rare earth elements. This similarity provides a strong argument in favour of derivation of the parent magmas of phase 2 to 6 rocks from the upper mantle. However, during ascent, the magmas that produced the granitic rocks were contaminated with crustal material. In trems of tectonic evolution, the Nagar parkar region appears to be a composite terrance that developed initially as an island arc. It was accreted to other terrances to constitute a Precambrian continental crust. During the collision it may have experienced deformation and metamorphism in epidote-amphibolite facies. During the late Proterozoic, the terrance played host to continental magmatism related to epeirogenic uplift ((doming) and extension.

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4009.85 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
197.55 KB
2 1 Introduction
232.86 KB
  1.1 General Statement 1
  1.2 Climate, Flora and Fauna 3
  1.3 Previous Work 5
  1.4 Present Study and Objectives 7
  1.5 Methodology 8
  1.6 Laboratory Techniques 8
3 2 Local Geology of the Nagar Parkar Area 9
576.57 KB
  2.1 Local Geological Setting 21
  2.2 Physical Features 25
  2.3 Stratgiraphy 26
  2.4 The Basement Rocks 26
  2.5 Riebeckite-Aegirine Grey Granite 32
  2.6 Biotite Pink Granite 38
  2.7 Acid Dykes 42
  2.8 Rhyolite “Plugs” 42
  2.9 Basic Dykes 43
  2.10 Bartala Sedumentary Unit 44
  2.11 Dedhvero Laterite and Kaolin Deposits 45
  2.12 Late Quaternary Deposits 46
  2.13 Economic Mineral Deposits 50
4 3 Regional Geological and Tectonic Setting 52
263.97 KB
  3.1 Introduction 52
  3.2 anded Gneissic complex 54
  3.3 Proterozoic Fold Belt 57
  3.4 Late Proterozoic 62
  3.5 Nagar Parkar Igneous Complex 74
  3.6 Regional Tectonics 75
5 4 Field and Petrographic Studies 81
1805.71 KB
  4.1 Introduction 82
  4.2 The Basement Rocks 83
  4.3 Ribeckite-Aegirine Grey Granite 95
  4.4 Parodharo Granodiorite 108
  4.5 Biotite-Pink Granite 113
  4.6 Mottled Pink Granite 131
  4.7 Wadharai Adamelite/Quartz Monzonite 131
  4.8 Acid Dykes 133
  4.9 Rhyolite “Plugs” 141
  4.10 Sadorus Rhyolite 142
  4.11 Boodhar Rhyolite 144
  4.12 Basic Dykes 145
  4.13 Homblende-bearing Basic Dykes 145
  4.14 Pyroxene-bearing Basic Dykes 146
6 5 Geochemistry 154
1050.61 KB
  5.1 Introduction 154
  5.2 Whole Rock Geochemistry 154
  5.3 The Basement Rocks 155
  5.4 Grey Granites 170
  5.5 Pink Granites 202
  5.6 Acid Dykes 229
  5.7 Rhyolite Plugs 247
  5.8 Basic Dykes 264
7 6 Synthesis, Discussion and Conclusion 285
259.1 KB
  6.1 General Statement 285
  6.2 The Basement Rocks 287
  6.3 The Grey and Pink Granites 288
  6.4 The Minor Granitic and Mafic Bodies 292
  6.5 Regional Geological Correlation 294
  6.6 Concouding Remarks 296
  6.7 References 298