Geochronology and isotopic character of ultrahigh‐pressure metamorphism with implications for collision of the Sino‐Korean and Yangtze cratons, central China

Tectonics - Tập 15 Số 2 - Trang 472-489 - 1996
Leslie Ames, Zhou Gaozhi, Xiong Baocheng

Tóm tắt

The collision zone between the Sino‐Korean and Yangtze cratons in central China is marked by subduction‐related metamorphic rocks composed of crustal protoliths. These range in metamorphic grade from ultrahigh‐pressure eclogite to low‐greenschist facies. The paragenesis of the ultrahigh‐pressure rocks (coesite and diamond‐bearing) indicates subduction to depths greater than ∼120 km as a result of continental collision. Despite extreme metamorphic conditions, zircons have not undergone Pb loss but rather illustrate two periods of growth: crystallization between 700 and 800 Ma and ultrahigh‐pressure metamorphism at 218 ± 2.5 Ma. Previous studies have predicted a time‐transgressive collision, but age data presented in this study indicate that the collision was approximately coeval along the length of the suture. U‐Pb zircon ages of these ultrahigh‐pressure metamorphic rocks are 218.4 ± 2.5 Ma and 217.1 ± 8.7 Ma for the Dabie Mountains and Shandong peninsula, respectively. The similar ages imply that the Tan‐Lu fault, which offsets the ultrahigh‐pressure metamorphic rocks, is a secondary feature not related to collision or subduction. Whole rock isotopic data show that both Rb‐Sr and U‐Pb were open systems during metamorphism but that Sm‐Nd probably remained closed. Nd initial isotopes display crustal signatures, indicating that the crust subducted as a coherent slab rather than becoming intercalated with mantle material at depth. Sm‐Nd data in conjunction with U‐Pb zircon dating indicate that the ultrahigh‐pressure rocks are not typical Yangtze craton basement (2.9 Ga) but that they originally crystallized in a rift environment between ∼700 and 800 Ma. Discrepancies between 40Ar/39Ar plateaus, Sm‐Nd isochrons, and U‐Pb zircon ages render calculation of a P‐T‐t path unrealistic.

Từ khóa


Tài liệu tham khảo

10.1130/0091-7613(1993)021<0339:TOCOTS>2.3.CO;2

10.1016/0012-821X(87)90158-0

Chen P., 1993, The Tancheng‐Lujiang Wrench Fault System, 105

Chen W., 1992, The cooling history of melange zone in north Jiangsu‐south Shandong region: Evidence from multiple diffusion domain 40Ar/39Ar thermal geochronology, Shiyou Xuebao, 8, 1

10.1130/0091-7613(1991)019<0710:ZRTDPM>2.3.CO;2

10.1130/0091-7613(1994)022<0601:AAGAEO>2.3.CO;2

Enami M., 1990, Quartz psuedomorphs after coesite in eclogites from Shandong province, east China, Am. Mineral., 75, 381

10.1111/j.1525-1314.1993.tb00174.x

10.1029/92JB00648

10.1016/0743-9547(91)90066-7

10.1007/978-94-010-9263-0_6

10.1111/j.1525-1314.1994.tb00057.x

Griffin W. L., 1985, REE, Rb‐Sr and Sm‐Nd studies of Norwegian eclogites, Chem. Geol., 52, 249

10.1017/CBO9780511573088.006

10.1029/95TC00932

Jagoutz E. Isotopic systematics of metamorphic rocksU.S. Geol. Surv. Circ. 1107 156 1994.

Jagoutz E., 1989, Workshop on D/amends, 32

10.1007/BF00374722

10.1029/92TC01788

Li S., 1991, Geochemistry of granitoids in Tongbaishan‐Dabieshan, central China

10.1016/0009-2541(93)90063-O

10.1016/0009-2541(94)90033-7

10.1098/rsta.1990.0091

Lin J., 1991, The origin of the Mesozoic associated multiseries granitoid magma in the Shandong peninsula, Dizhi Xuebao, 4, 153

Liu X., 1993, High‐P metamorphic belt in central China and its possible eastward extension to Korea, J. Petrol. Soc. Korea, 2, 9

Ludwig K. R. A plotting and regression program for radiogenic‐isotope dataU.S. Geol. Surv. Open File Rep. 91‐445 1992.

10.1038/317496a0

Mattauer M., 1991, Paleozoic and Triassic plate boundary between North and South China; new structural and radiometric data on the Dabie‐Shan (eastern China), C. R. Acad. Sci., Ser. 2, 312, 1227

Mattinson J. M., 1987, U‐Pb ages of zircons: A basic examination of error propagation, Chem. Geol., 66, 151

10.1038/293212a0

Metcalfe I. R. S.Nicoll Early‐middle Palaeozoic reconstructions of the India ‐ NW Australian Gondwanaland marginThe IGCP 321 ‐ Gondwana Dispersion and Asian Accretion Fourth International SymposiumSeoul Nat. Univ.Seoul Korea 1994.

Nie S., 1990, Paleozoic Palaeogeography and Biogeography, Geol. Soc. London, 397

10.1127/ejm/5/4/0659

10.1130/0091-7613(1992)020<0411:EFITRE>2.3.CO;2

10.1127/ejm/1/4/0595

10.1029/93TC01544

10.1139/e91-106

10.1016/0009-2541(93)90319-E

10.1016/0040-1951(90)90407-Y

10.1016/0016-7037(92)90364-O

10.1127/ejm/6/6/0995

10.1007/BF00307322

10.1144/GSL.MEM.1990.012.01.01

10.1007/BF00310465

10.1038/364299a0

10.1038/287366a0

10.1016/0016-7037(92)90138-9

10.1007/BF00307323

10.1111/j.1365-3121.1993.tb00221.x

10.1130/0091-7613(1991)019<0933:RUPCBE>2.3.CO;2

10.1016/0024-4937(90)90010-X

10.1086/629585

Xu J., 1993, The Tancheng‐Lujiang Wrench Fault System, 3

10.1016/0040-1951(87)90342-8

10.1126/science.256.5053.80

Yang Z., 1986, The Geology of China

10.1029/93TC00313

Zhai X., 1995, First Workshop on UHP Metamorphism and Tectonics, 23

10.1111/j.1525-1314.1993.tb00175.x

10.1111/j.1525-1314.1994.tb00012.x

10.1038/327141a0

10.1111/j.1525-1314.1993.tb00172.x

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Tectonics

Tập 15 Số 2

472-489

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