Geochemical and Geochronological Investigations in the Southern Appalachians, Southern Rocky ...

160 Pages·2015·2.54 MB·English

by  Reshmi Das

Florida State University Libraries
Electronic Theses, Treatises and Dissertations The Graduate School
2006
Geochemical and Geochronological
Investigations in the Southern Appalachians,
Southern Rocky Mountains and Deccan
Traps.
Reshmi Das
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THE FLORIDA STATE UNIVERSITY

COLLEGE OF ARTS AND SCIENCES

GEOCHEMICAL AND GEOCHRONOLOGICAL INVESTIGATIONS IN THE
SOUTHERN APPALACHIANS, SOUTHERN ROCKY MOUNTAINS AND
DECCAN TRAPS.

By

RESHMI DAS

A Dissertation submitted to the
Department of Geological Sciences
in partial fulfillment of the
requirements for the degree of
Doctor of Philosophy

Degree Awarded:
Fall Semester, 2006
The members of the Committee approve the Dissertation of Reshmi Das defended on 1st
November, 2006.

____________________________________
A. Leroy Odom
Professor Directing Dissertation

____________________________________
Jeffrey Chanton
Outside Committee Member

____________________________________
Stephen A. Kish
Committee Member

____________________________________
Vincent J. M. Salters
Committee Member

____________________________________
James F. Tull
Committee Member

Approved:

_____________________________________________
Professor A. Leroy Odom, Chair, Geological Sciences

The Office of Graduate Studies has verified and approved the above named committee
members.
ii
To
my first geology teacher,
Dr. Mohan Chand Baral,
who
made me fall in love with Geology.
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ACKNOWLEDGEMENTS

Many people have contributed to the making of this dissertation. First and foremost I
would like to acknowledge Prof. Leroy Odom, my advisor who not only supported me
academically and financially for five years but also lent personal support whenever
required. This dissertation would have been impossible without him.
Prof. James Tull supervised my project on the southern Appalachian and words are
inadequate to express his contribution in development of this dissertation.
Prof. Stephen Kish always had an answer for my most difficult question and Prof.
Vincent Salters helped me with the modeling part of the chemical data.
Prof. Munir Humayun, Prof. Tapas Bhattacharyya and Dr. Michael Bizimis, though not a
part of my committee, supervised portions of my research. I am indebted to them for
their time, technical support and patience.
The field work required for this dissertation was partly funded by EDMAP component of
the National Geologic Mapping Act 2002.
The Isotope Geochemistry Division at the National High Magnetic Field Laboratory has
been a wonderful place to work, and I would like to thank Ted Zateslo and Afi Sachi-
Kocher for their technical support.
I would also like to thank all of the geochemistry graduate students for the long chats, the
little favors, and camaraderie along the way.
My parents made the greatest sacrifice of their life by letting their only child go ahead
with her life and providing the best educational opportunity.
Last but not the least is my best friend and husband Subhajit who inspired me to continue
my career in academia. His extremely active academic and intellectual presence kept me
going and will continue to do so.
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TABLE OF CONTENTS

List of Tables ................................................................................................ vii
List of Figures ................................................................................................ viii
Abstract ...................................................................................................... x

1. Geochemical and Geochronological Constraints on the Origin and Evolution of the Eastern
Blue Ridge, Southern Appalachians. .......................................... 1

1.1 Introduction........................................................................................... 1
1.2 Regional Overview............................................................................... 3
1.3 Study Area and General Description of Lithotectonic Units................ 4
1.4 Purpose of the Study............................................................................. 7
1.5 Analytical Techniques.......................................................................... 8
1.6 Results ................................................................................................ 10
1.7 Nd Model Age and Detrital Zircon Ages of the Metasediments of the Eastern Blue
Ridge .......................................................................................... 14
1.8 Mulberry Rock Gneiss.......................................................................... 15
1.9 Discussion............................................................................................. 16

2. Kilometers Scale Strontium Isotopic Homogenization During Metamorphism: A Case Study
in the Tres Piedras Granite, New Mexico.................................... 62

2.1 Introduction........................................................................................... 62
2.2 General Geology................................................................................... 63
2.3 Tres Piedras Granite.............................................................................. 64
2.4 Previous Work...................................................................................... 65
2.5 Results ................................................................................................ 69
2.6 Discussion............................................................................................. 70
2.7 Conclusion............................................................................................ 74

3. Trace Element and Lead Isotopic Studies of the Kutch Volcanics of Northwest India
................................................................................................ 87

3.1 Introduction........................................................................................... 87
3.2 Geological Setting................................................................................. 88
3.3 Deccan Stratigraphy.............................................................................. 89
3.4 Previous Work-Sr and Nd Isotopic Data.............................................. 90
3.5 Analytical Technique............................................................................ 91
3.6 Results ................................................................................................ 91
3.7 Comparison with the DVP.................................................................... 93
3.8 Discussion............................................................................................. 94
3.9 Conclusion............................................................................................ 95

APPENDICES ................................................................................................ 107

A Analytical Techniques.......................................................................... 107
B Sample Locations.................................................................................. 118
C Photomicrographs................................................................................. 120

REFERENCES ................................................................................................ 122

BIOGRAPHICAL SKETCH .............................................................................. 149

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LIST OF TABLES

Table 1.1: Major Oxide concentration in weight percent.................................... 26

Table 1.2: Trace Element and REE concentration (in ppm) of the Pumpkinvine Amphibolites
(PCF) and the Galts Ferry Gneiss (GFG)............................................................ 27

Table 1.3: Trace Element and REE concentration (in ppm) of the Hillabee Greenstones (HG) and
Hillabee Dacite (dacite)....................................................................................... 28

Table 1.4: Sr and Nd Isotopic Data...................................................................... 29

Table 1.5: Rb-Sr isotopic data for whole rock samples....................................... 30

Table 1.6: Nd Model Age of metasediments from eastern Blue Ridge............... 30

Table 1.7: U-Pb analysis of Galts Ferry Gneiss zircons by LA-MS-ICPMS...... 31

Table 1.8: U-Pb analysis of detrital zircons from meta-sandstone by LA-MS-ICPMS 33

Table 1.9: U-Pb analysis of Mulberry Rock Gneiss zircons by LA-MS-ICPMS 35

Table 1.10: REE concentrations of eastern Blue Ridge metasediments.............. 36

Table 2.1: Regional Geologic history of the north-central New Mexico............ 67

Table 2.2: Stratigraphic nomenclature and lithologic description of supracrustal Proterozoic
rocks of New Mexico........................................................................................... 68

Table 2.3: Chemical analysis, norm and modes of the Tres Piedras Granite...... 75

Table 2.4: Rb-Sr whole rock analysis of Tres Piedras Granite............................ 76

Table 2.5: Rb-Sr analysis of the mineral phases of the Tres Piedras Granite...... 77

Table 2.6: Tres Piedras Granite zircon analysis by LA-MC-ICPMS.................. 78

Table 3.1: Stratigraphic nomenclature and thickness of the southwestern Deccan Formations
................................................................................................ 97

Table 3.2: Trace element and Pb-isotope results................................................. 98

Table 3.3: Elemental ratios of Re'union type source at 65 Ma............................ 94

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LIST OF FIGURES

Figure 1.1: Generalized geological map of southern Appalachians ................... 37

Figure 1.1A: Generalized geologic map of eastern Alabama and western Georgia Blue Ridge
terranes ................................................................................................ 38

Figure 1.2: Bimodality of Hillabee Greenstone sequence and Pumpkinvine Creek Formation
................................................................................................ 39

Figure 1.3: Total alkali vs. silica diagram for the Hillabee Greenstone sequence and
Pumpkinvine Creek Formation ........................................................................... 40

Figure 1.4A: Hillabee dacite and GFG classification using Shand's index ........ 41

Figure 1.4B: HG and PCF amphibolite plotted on AFM diagram ...................... 41

Figure 1.5: Ti vs Zr plot of greenstones- dacites and PCF amphibolite - GFG .. 42

Figure 1.6: Co-variation diagrams of relatively immobile elements for HG and PCF amphibolites
................................................................................................ 43

Figure 1.7: Tectonic discrimination diagrams for the PCF amphibolites and HG 44

Figure 1.8: La/10-Y/15-Nb/8 diagram for the PCF amphibolite and HG .......... 45

Figure 1.9: Tectonic discrimination diagram for GFG and Hillabee dacite ....... 46

Figure 1.10: Spider diagram plot of PCF amphibolite and HG .......................... 47

Figure 1:11 CI chondrite normalized plot of PCF amphibolite and HG ............ 48

Figure 1.12: CI chondrite normalized plot of GFG and Hillabee dacite ............ 49

Figure 1.13: Initial Sr vs. epsilon Nd isotopic plot ............................................. 50

Figure 1.14: Rb-Sr isochron of GFG samples .................................................... 51

Figure 1.15: Two chemical groups of GFG defined by REE concentrations. .... 52

Figure 1.16: U-Pb ages of GFG zircons ............................................................. 53

Figure 1.16A: CL images of GFG zircons .......................................................... 54

Figure 1.17: Nd isotopic evolution diagram of the eBR metasediments ............ 55
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Figure 1.18: NASC normalized REE plot of the eBR metasediments ............... 56

Figure 1.19: U-Pb ages of the detrital zircons of eBR ........................................ 57

Figure 1.20: Rb-Sr whole rock age of Mulberry Rock Gneiss ........................... 58

Figure 1.21: U-Pb ages of Mulberry Rock Gneiss zircons ................................. 59

Figure 1.22: Epsilon Nd of Ordovician arc felsic magmas of the Appalachians. 60

Figure 1.23: Model for passive mechanism of lithosphere extension ................ 61

Figure 1.24: Model for accretionary orogen in southern Appalachians during Ordovician
................................................................................................ 61

Figure 2.1: Map of Proterozoic basement uplifts and associated major faults in north-central New
Mexico ................................................................................................ 80

Figure 2.1a: Map of Tres Piedras Granite sampling locations ........................... 80

Figure 2.2: Whole rock Rb-Sr isochron of Tres Piedras Granite ........................ 81

Figure 2.3: Rb-Sr mineral isochron of Tres Piedras Granite .............................. 83

Figure 2.4: U-Pb ages of Tres Piedras Granite zircons by LA-MC-ICPMS ...... 85

Figure 2.5: LA-ICPMS measurement of concentration ratios across a feldspar grain from Tres
Piedras Granite ................................................................................................ 86

Figure 3.1: Structural-tectonic features of southern Asia and Indian Ocean basin 99

Figure 3.2: Initial Nd vs. initial Sr isotope plot of the Kutch samples ............... 100

Figure 3.3: Trace element-REE plot of the Kutch basalts ................................. 101

Figure 3.4: La/Nb vs Ce/Pb and La/Sm vs Sm/Yb in the Kutch basalts ............ 102

Figure 3.5: Pb and Sr isotopic variation in Kutch Basalts .................................. 103

Figure 3.6: Melting model of garnet peridotite to produce the alkali basalts ..... 104

Figure 3.7: Mixing model for the Kutch tholeiites to generate the trace element-REE pattern
................................................................................................ 105
Figure 3.8: Mixing model for the Kutch tholeiites to generate the Sr and Nd isotope ratioserate
the trace element-REE pattern ............................................................................ 106

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