基底岩系和花岗岩类Pb-Nd同位素组成限制祁连山带的构造属性

张宏飞; 靳兰兰; 张利; 袁洪林; 周炼; 张本仁

Volume 31 Issue 1

Jan. 2006

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Article Navigation > Earth Science > 2006 > 31(1): 57-65

ZHANG Hong-fei, JIN Lan-lan, ZHANG Li, YUAN Hong-lin, ZHOU Lian, ZHANG Ben-ren, 2006. Pb and Nd Isotopic Compositions of Basement and Granitoid in the Qilianshan: Constraints on Tectonic Affinity. Earth Science, 31(1): 57-65.

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Pb and Nd Isotopic Compositions of Basement and Granitoid in the Qilianshan: Constraints on Tectonic Affinity

1.
State Key Laboratory of Geological Processes and Mineral Resources, china Univences, Wuhan 430074, China
2.
Key Laboratory of Continental Dynamics, Northwest University, Xi'an 710069, China

Received Date: 2005-09-23
Publish Date: 2006-01-25

Abstract

Abstract

The northwestern boundary of the Yangtze (South China) block has not been efficiently constrained yet. Pb and Nd isotopic compositions of the Qilianshan Precambrian basements and granitoids in the western segment of the Central Oro-genie System (COS) of China provide constraints on the northwestern boundary of the Yangtze block. Most samples from the Qilianshan Precambrian basement have mantle-depleted Nd isotopic model ages (T_DM)ranging from 0. 75 to 2. 5 Ga, with a peak value of -2. 1 Ga. The Qilianshan Paleozoic granitoids have T_DM values ranging from 1. 07 to 2. 14 Ga. They show that crustal growth of the Qilianshan mainly occurred in the Proterozoic, without significant Archean information. The Precambrian basement rocks and the Paleozoic granitoids are characterized by high radiogenic Pb isotopic composition. Most samples have ²⁰⁶Pb/²⁰⁴Pb > 18. 0, ²⁰⁷Pb/²⁰⁴Pb > 15. 5 and ²⁰⁸Pb/²⁰⁴Pb > 38. 0. The T_DM values and Pb isotopic compositions of the Qilianshan basement and granitoids are similar to those of the Yangtze block but distinct from those of the North China block, indicating that the crustal basement of Qilianshan has an affinity with the Yangtze block. It is suggested that the northwestern boundary of the Yangtze block is located along the north side of the Qilianshan belt. Since the Proterozoic, the Qilianshan belt had experienced lithospheric rifting and subsequent Qilian ocean opening. These tectonic events had thus happened within the Yangtze block.
- Qilianshan,
- basement,
- granitoid,
- Pb-Nd isotope,
- tectonic affinity

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References(31)

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