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6 (d) Oberkreide Spaltspurenalter wurden an Apatiten von Sedimentgesteinen tertiärer intramontaner Becken des Süd-Tien Shan bestimmt. Gleiche Alter erzielten Zirkone magmatischer Gesteine des nördlichen und südlichen Zentralpamirs. Diese Alter reflektieren möglicherweise schwache Exhumierung, verursacht durch die beginnende Unterschiebung des südöstlichen Pamirs unter den Südrand des Zentralpamirs und durch intrakontinentale Subduktion der Karakul-Mazar- und Jinsha-Lithosphäre unter den Nordrand des Zentralpamirs. Diese Einengung und Hebung wurde wahrscheinlich durch die flach einfallende Subduktion und Kompression entlang der Shyok Sutur zwischen den Karakorum und Kohistan-Ladakh Terranes ausgelöst. Mit der finalen Kollision von Indien mit Eurasien vor etwa 55 Mio. Jahren endete die lang andauernde Akkretionsgeschichte und der Pamir kam in eine intrakontinentale Position. Augenscheinlich schritt die post-kollisionale Deformation nicht kontinuierlich von Süden nach Norden voran, sondern hat sich in rheologisch geschwächten Zonen wie dem Zentralpamir konzentriert, wo wahrscheinlich intrakontinentale Subduktion entlang der Jinsha- und Bangong-Nujiang Sutur Deformation und Schmelzbildung erleichtert hat. Daher ist das stärkste Exhumierungsereignis in den Muzkol- und Sares- Domen des Zentralpamirs dokumentiert. Die Exhumierung der Dome bewirkte zwischen 25 und 15 Mio. Jahren die Aufheizung tertiärer intramontaner Becken entlang der Südseite des Doms. Ein Apatit-Spaltspurenprofil über den Karakul-Batholith ergab Alter von 56 bis 18 Mio. Jahren mit einer Verjüngung in Richtung Norden. Gleichzeitig mit der Dom-Exhumierung im Süden, wurde auch der nördliche Rand des Karakul- Mazar Gürtels entlang der dextralen, transpressiven Markansu-Störung exhumiert. Die frühmiozäne Exhumierung geht über in laterale Extrusion entlang großer (Karakorum, Markansu) und konjugierter (Südrand Tien Shan, frontale Pamirkette, Südrand Qiangtang Block) Seitenverschiebungen und kompensiert so die anhaltende Nord-Süd- Verkürzung zwischen Indien und Asien. Diese Lokalitäten sind seit mindestens 11-10 Mio. Jahren aktiv.
1 Introduction Until the 1990s, geological surveying of the Pamirs focused on Precambrian geology and ore exploration. At the same time, the neighbouring Himalayas and Tibet (Fig. 1.1) were studied applying modern mountain building theories. Despite the shortage of modern data, several scientists were successfully placing the Pamirs’ geologic history into a plate tectonic framework (e.g. Zonenshain et al. 1990, Burtman & Molnar 1993). In accordance with the tectonic history of other Central Asian regions, the Pamir crust amalgamated over several orogenic cycles during the Palaeozoic and Mesozoic. Although attempts have been made to correlate Palaeozoic and Mesozoic sutures in the Tien Shan and Pamirs with those in Tibet and Afghanistan, mapping of ophiolites and related rocks has not sufficiently highlighted the sutures. Likewise is the structural relationship, number, identity, and evolution of intervening blocks in the Central Asian region still poorly known. Attempts to correlate Palaeozoic and Mesozoic sutures from Tibet or Afghanistan across the Pamirs are problematic. This is by virtue of northward deflection of the Pamirs relative to the neighbouring areas in the east and west. Another difficulty arises from significant post-collisional shortening during the Cenozoic India-Asia collision. Although this collision occurred approximately 1000 km south of the Pamirs, it has dramatically reshaped the Pamirs until recently. Much of the research in Central Asia of the last two decades focused on Tibet and on the tectonic activity post-dating the India-Asia collision (e.g. Tapponnier & Molnar 1977; Dewey et al. 1989, Yin & Harrison 2000 and several others). By contrast, only little is published about the post-collisional history of the Pamirs (Arrowsmith & Strecker 1999; Burtman & Molnar 1993; Coutand et al. 2002; Ducea et al. 2003; Frisch et al. 1994a, 1994b; Hubbard et al. 1997, 1999; Pavlis & Hamburger 1997; Ratschbacher & Schwab 1999; Ratschbacher et al. 1996, 1997; Schwab et al. 1997, 1999, 2000; Strecker et al. 1994a, 1994b, 1995a, 1995b, 2003). Nevertheless, reconstructions of Cenozoic deformation resulting from the India-Asia collision are considered preliminary owing to insufficient knowledge of the pre-collisional geometry of Central Asia. Identification of pre- Cenozoic sutures can provide crustal markers which aid in unravelling Cenozoic shortening and displacements. This in turn facilitates understanding and reconstruction of tectonic events that were affecting the Pamirs. The aim of this study is to elucidate the Pamirs’ pre- and post-collisional tectonothermal evolution and to help understanding the development of the Pamir-Tibet orogenic setting, responsible for constructing one of the Earth’s largest mountain belts. Data collection was concentrated across E-W striking magmatic belts and along a N-S traverse from South Tien Shan (STS) through the eastern Pamirs. The following main questions are addressed: � What is the age and origin of the E-W striking magmatic belts and what was their role in the crustal formation of the Pamirs? � What are the eastern and western equivalents to Pamiran sutures and crustal blocks? � Where is intracontinental deformation, caused by the India-Asia collision, concentrated in the southern Tien Shan and eastern Pamirs? How does 7
Page 1: Institut für Geowissenschaften (IF
Page 4 and 5: Key words: Tien Shan, Pamirs, Tibet
Page 6 and 7: * Nr. 22 MESCHEDE, M. (1994): Tecto
Page 8 and 9: * Nr. 55 REINECKER, J. (2000): Stre
Page 13 and 14: The amalgamation of the Pamirs and
Page 15: Wer aber je auf Asiens Erdboden sch
Page 20 and 21: viii (1971). Black lines with arrow
Page 22 and 23: x sample locations and age distribu
Page 24 and 25: xii Swedish expeditions followed. I
Page 26 and 27: 2 postulated that the Safed Khers a
Page 28 and 29: 4 Zusammenfassung Die paläozoische
Page 32 and 33: 8 deformation propagate from the pl
Page 34 and 35: 10 source terrains, changes in the
Page 36 and 37: 12 Geochemisches Zentrallabor, Univ
Page 38 and 39: 14 mean UO+/U+ and Pb+/U+ value. Si
Page 40 and 41: 16 apatites and zircons were counte
Page 42 and 43: 18 number of simulation runs and th
Page 45 and 46: Two Palaeozoic sutures divide the C
Page 47 and 48: igneous and sedimentary rock sequen
Page 49 and 50: Triassic and the formation of an is
Page 51 and 52: 27 Lake Karakul The Lake Karakul ar
Page 53: 3.3.2 Major and trace elements Majo
Page 56 and 57: 32 of 26-40 for samples P2, P5, and
Page 58 and 59: 34 some of the zircons suffered Pb
Page 60 and 61: 36 fractions are situated close to
Page 65: 3.4.2 Rb/Sr dating The Rb/Sr minera
Page 69 and 70: 45 The Cretaceous plutons show mode
Page 72 and 73: 48 Thompson et al. (1984), who see
Page 74 and 75: 50 granites and have Sm-Nd model ag
Page 76 and 77: 52 associations in Afghanistan is f
Page 78 and 79: 54 Kara Kunlun or Mazar accretionar
Page 80 and 81:
56 Early Jurassic low-angle normal
Page 82 and 83:
58 Coward et al. (1988) pointed out
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60 oceanic crust for the consumptio
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62 Palaeogene volcanic rocks of cen
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64 3.7 Conclusions Based on new own
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4 Cenozoic exhumation history of th
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Southern Tien Shan One Permian gran
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Thermal modelling The results of th
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amphibole, white mica, and biotite
Page 101 and 102:
the zircon PAZ. The apparent apatit
Page 103 and 104:
elt likely operated as an out-of-se
Page 105:
ages from gneissic rocks within the
Page 108 and 109:
84 south to 18 Ma in the north; the
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86 Cretaceous plutons that intrude
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88 6 References Allègre C.J., Cout
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90 House, scale 1:2 000 000. Chen F
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92 Karakorum (Sinkiang, China); the
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94 Hurford A.J. and Hammerschmidt K
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96 without double spiking. Geochimi
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98 Geological Society of America, 2
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100 Zamoruyev A., 1995a. Neotectoni
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102 Ann. Rev. of Earth and Planetar
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104 this work, especially all membe
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II Appendix A Tab. A1 Sample descri
Page 134 and 135:
IV Tab. A2 continued Pamir frontal
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VI Tab. A2 continued Tertiary exten
Page 138 and 139:
VIII Tab. A3 continued Sample Miner
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X Tab. A6 Rb/Sr and Sm/Nd isotopic
Page 142 and 143:
XII Tab. A7 continued Apparent ages
Page 144 and 145:
XIV Tab. A9 U/Pb isotopic ratios fr
Page 146 and 147:
XVI Tab. A9 continued 207 Pb/ 206 P
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XVIII Tab. A9 continued 207 Pb/ 206
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XX Appendix B Plate B1 Cathodolumin
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XXII Plate B3 Cathodoluminescence i
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XXIV Plate B5 Cathodoluminescence i
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XXVI Tab. C2 Determination of the
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XXVIII
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XXX
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XXXII
Page 164 and 165:
XXXIV
Page 166 and 167:
XXXVI Tab. C5 continued Sample grai
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XXXVIII Tab. C5 continued Sample gr
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XL Tab. C5 continued Sample grain-n
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XLII Tab. C5 continued Sample grain
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XLIV
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XLVI Tab. C6 Zircon fission track a
Page 178 and 179:
XLVIII
Page 182 and 183:
LII
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LIV Tab. C7 Apatite and zircon fiss
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