Kinematics of the Greater Himalayan sequence, Dhaulagiri Himal ...

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$Fayek & Kyser 2000 uraninite fractionations.pdf - Queen's University$

595 596 597 598 different metamorphic grade and structural character). While such a juxtaposition can be achieved even after significant translation along footwall and hanging wall thrust flats if throw along the corresponding ramps does not exceed the thickness of the lithotectonic unit, it may be interpreted as evidence for relatively moderate displacement across the mapped MCT. 599 600 601 602 603 604 605 606 607 608 609 610 611 612 Geochronologic constrains are key to elucidating the evolution of the MCT and strain within the Greater Himalayan sequence. 208 Pb/ 232 Th dating of monazite inclusions in garnet collected from successively lower levels of the Greater Himalayan sequence in other (some adjacent) portions of the Himalaya have been interpreted to record prograde metamorphism related to thrust motion ranging between 3.3 ± 0.1 Ma and 22 Ma (Harrison et al. 1997; Catlos et al. 2001, 2002, 2004; Kohn et al. 2001, 2005). The ages reported generally young down structural section, away from the migmatitic core of the Greater Himalayan sequence, and are thus consistent with the model of a downward migrating MCT. However, Bollinger & Janots (2006) have demonstrated that some young Himalayan monazite is a retrograde product from the breakdown of allanite at low temperatures (
617 618 619 620 621 622 623 624 625 (Figure 1b; Shrestha et al. 1987; DeCelles et al. 2001; Pearson & DeCelles 2005) that, based on balanced cross-sections, has accommodated ca. 120 km of post-initial India-Asia collision shortening (DeCelles et al. 2001; Pearson & DeCelles 2005; Robinson et al. 2006). The surface trace of the Ramgarh thrust in India and western Nepal has been inferred in numerous studies (e.g., Heim & Gansser 1939; Pande 1950; Gansser 1964; Valdiya 1980; Shrestha et al. 1987; Srivastava & Mitra 1994; DeCelles et al. 1998, 2001; Robinson et al. 2006), however, only in two localities has a fault surface been observed (Pearson & DeCelles 2005). Martin et al. (2005) and Pearson & DeCelles (2005) inferred the presence of the Ramgarh thrust in central and eastern Nepal on the basis of interpreted stratigraphic repetition. 626 627 628 629 630 631 632 633 634 635 636 637 638 639 In the Modi river drainage of central Nepal (Figure 1c), the location nearest to the Kali Gandaki valley where the Ramgarh thrust has been mapped, the thrust fault has been interpreted to be at the base of a thick layer of quartzites (Figure 13; Martin et al. 2005; Pearson & DeCelles 2005). These quartzites have been interpreted as being the lower Kunchha Formation and the overlying metapelitic rocks have been interpreted to be part of the upper Kunchha Formation. These interpretations are, however, inconsistent with the rock types described by Hodges et al. (1996) and Pearson & DeCelles (2005) in the Modi river drainage. The Kunchha Formation (Ranimata Formation; Figure 4b) is characteristically a chloritic or sericitic phyllite and phyllitic siltite with subordinate amounts of chloritic schist (DeCelles et al. 2001) that is entirely noncalcareous (Stöcklin 1980). The rocks stratigraphically above the quartzite in the Modi river, however, comprise graphitic phyllite intercalated with thin layers of dolostone and impure marble both near the base and the top of the sequence (Pearson & DeCelles 2005). There is no evidence for repetition of stratigraphic units. The strata in the Modi valley more closely resemble the lithotectonic sequence observed above the Kunchha Formation and its equivalents 29
Page 1 and 2: 1 2 3 4 5 Kinematics of the Greater
Page 3 and 4: 39 1. Introduction 40 41 42 43 44 4
Page 5 and 6: 84 85 86 87 88 provide new insight
Page 7 and 8: 129 130 131 132 133 134 135 The Dha
Page 9 and 10: 173 3.3 Greater Himalayan sequence
Page 11 and 12: 218 219 220 221 222 8 cm apart. In
Page 13 and 14: 263 quartzite and, locally, more im
Page 15 and 16: 307 308 309 310 311 312 In this stu
Page 17 and 18: 352 4.1 Quartz petrofabric analysis
Page 19 and 20: 398 399 400 401 402 403 404 405 406
Page 21 and 22: 443 444 445 446 447 448 449 maximum
Page 23 and 24: 488 489 490 491 492 the X-Z plane o
Page 25 and 26: 534 535 through the following equat
Page 27: 572 573 574 575 576 577 578 579 val
Page 31 and 32: 663 6.3 Flow kinematics 664 665 666
Page 33 and 34: 709 710 711 712 713 714 715 716 717
Page 35 and 36: 753 754 better understand the proce
Page 37 and 38: 765 766 References 767 768 769 770
Page 39 and 40: 830 831 832 833 834 835 836 837 838
Page 41 and 42: 900 901 902 903 904 905 906 907 908
Page 43 and 44: 970 971 972 973 974 975 976 977 978
Page 45 and 46: 1039 1040 1041 1042 1043 1044 1045
Page 47 and 48: 1107 1108 1109 1110 1111 1112 1113
Page 49 and 50: 1163 1164 1165 1166 1167 a leucogra
Page 51 and 52: 1205 1206 1207 1208 1209 plotted ag
Page 53 and 54: 1247 1248 1249 1250 1251 1252 1253
Page 55 and 56: 83˚ 30'E South Tibetan Detachment
Page 57 and 58: A Previous Studies (Central Nepal)
Page 59 and 60: SW NE NW SE A B W E W E C D
Page 61 and 62: 018 015 grain shape foliation 038 2
Page 63 and 64: SW A S Qtz C Qtz Ep Am Am Am Ms 200
Page 65 and 66: 10 percent pure shear 80 70 60 50 4
Page 67: (A) percent pure shear 60 50 40 30

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