The lithospheric mantle beneath the southwestern Tianshan area, northwest China

被引:50
作者
Zheng, JP [1 ]
Griffin, WL
O'Reilly, SY
Zhang, M
Pearson, N
Luo, ZH
机构
[1] China Univ Geosci, State Key Lab Geol Proc & Mineral Resources, Fac Earth Sci, Wuhan 430074, Peoples R China
[2] Macquarie Univ, GEMOC ARC Natl Key Ctr, Dept Earth & Planetary Sci, Sydney, NSW 2109, Australia
[3] CSIRO Explorat & Min, Sydney, NSW 2113, Australia
[4] China Univ Geosci, State Key Lab Geol Proc & Mineral Resources, Beijing 100083, Peoples R China
关键词
D O I
10.1007/s00410-006-0071-x
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 [地球物理学]; 070902 [地球化学];
摘要
A suite of spinel peridotite xenoliths in Mesozoic basalts of the Tuoyun basin in the Tianshan area of northwest China has a high proportion of amphibole/mica-bearing lherzolites, with high Cpx/Opx ratios (mean 0.74). Many aspects of mineral chemistry in the Tuoyun peridotites are intermediate between those of refractory Archean cratonic mantle and fertile Phanerozoic mantle. These include Ni/Cr and the contents of transition metals and Y in olivine and orthopyroxene and the abundances of elements such as Na, Al, Ti, Y, Sr and LREE in clinopyroxene. The data suggest that the mantle in Tuoyun is moderately depleted in basaltic components relative to both the refractory Archean mantle and the fertile Phanerozoic mantle. The wide variations in the CaO/Al2O3 (0.9-3.5) of whole rocks and LREE/HREE (0.8-14.2) and Ti/Eu (971-5,765) of clinopyroxenes in the Tuoyun peridotites are interpreted as the metasomatism of hydrous carbonatitic and potassic melt or the cumulative effects of mantle metasomatism by different agents (carbonatite and small-volume silicate melts) through time. The Tuoyun mantle shows closer affinity to the type of mantle found beneath the Proterozoic Cathaysia block, and especially to that beneath the East Central Asia Orogenic Belt (ECAOB), than to the mantle beneath the Archean North China Craton. This implies that the Tianshan subcontinental lithospheric mantle may have been generated during the accretion of the ECAOB. The high proportion of fine-grained microstructures, high Cpx/Opx ratio, obvious Ca enrichment and lower overall depletion in the Tuoyun mantle relative to that in other parts of the ECAOB reflect stronger mechanical and chemical modification of the Tuoyun mantle, near the translithospheric Talas-Ferghana strike-slip fault, which played a major role in controlling the strength of the mantle lithosphere and has channeled the upwelling mantle.
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页码:457 / 479
页数:23
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