| Petrology, Geochemistry and Tectonic Significance of the Metamorphic Peridotites from Longmuco–Shuanghu Ophiolitic Melange belt, Tibet |
| |
| 作者姓名： | WU Yanwang LI Cai XIE Chaoming WANG Ming and HU Peiyuan |
| |
| 作者单位： | College of Earth Science, Jilin University, Changchun 130061, Jilin, China |
| |
| 基金项目： | Our research is supported by the National Natural Science Foundation of China (Nos. 40872146, 41072166, 41272240), the Project of China Geological Survey (No. 1212011086064, 1212011221093). The authors would like to thank Enago (www.enago.cn) for the English language review |
| |
| 摘 要： | Taoxinghu metamorphic peridotite is a firstly reported mantle sequence of ophiolite since Longmuco–Shuanghu–Lancangjiang suture zone (LSLSZ) was proposed, and it is also an important discovered for ophiolite studying in central Qiangtang. Based on detailed analyses of whole–rock geochemistry of Taoxinghu metamorphic peridotites and contrast to metamorphic peridotites in typical ophiolites worldwide, the paper investigates their petrogenesis and geological implication. The petrologic results show that the protolith of Taoxinghu metamorphic perdotites have the mineral assemblage and texture characteristic of mantle peridotite. Most metamorphic peridotites hav near global abyssal peridotites major elements contents, while the few is similar to SSZ–type peridotites. They exhibit typically U–shaped REE patterns, characterized by slight enrichment of LREE and HREE relative to MREE and a low fractionated LREE to HREE segment. Trace elements contents are low and all samples are strong enrichment in Cs, U, Pb, weak enrichment in Ba and depletion in Th, but negative Nb anomalies are only observed in few samples. That suggests Taoxinghu metamorphic peridotites have depletion mantle and suprasubduction affinities. A two–stage evolution history is considered: Taoxinghu metamorphic peridotites originated as the residue from melting at a ridge with 7%–20% degree of fraction melting and were subsequently modified by interaction with mafic melt and aqueous fluid within mantle wedge on subducted zone. Combined with previous studies, we preliminarily propose Taoxinghu metamorphic peridotites may be the Products of initial rifting of palo–Tethys, forming at middle Ordivician–upper Cambrian, and they may be the direct evidences for spreading of palo–Tethys.
|
| 关 键 词： | geochemistry metamorphic peridotite Taoxinghu Longmuco–Shuanghu suture zone Tibetan plateau |
| 收稿时间： | 2012/5/20 0:00:00 |
| 修稿时间： | 2012/10/14 0:00:00 |
Petrology, Geochemistry and Tectonic Significance of the Metamorphic Peridotites from Longmuco-Shuanghu Ophiolitic Melange Belt, Tibet |
| |
| Authors: | WU Yanwang LI Cai XIE Chaoming WANG Ming HU Peiyuan |
| |
| Institution: | College of Earth Science, Jilin University, Changchun 130061, Jilin, China |
| |
| Abstract: | Taoxinghu metamorphic peridotite is a firstly reported mantle sequence of ophiolite since Longmuco‐Shuanghu‐Lancangjiang suture zone (LSLSZ) was proposed, and it is also an important discovered for ophiolite studying in central Qiangtang. Based on detailed analyses of whole–rock geochemistry of Taoxinghu metamorphic peridotites and contrast to metamorphic peridotites in typical ophiolites worldwide, the paper investigates their petrogenesis and geological implication. The petrologic results show that the protolith of Taoxinghu metamorphic perdotites have the mineral assemblage and texture characteristic of mantle peridotite. Most metamorphic peridotites hav near global abyssal peridotites major elements contents, while the few is similar to SSZ‐type peridotites. They exhibit typically U‐shaped REE patterns, characterized by slight enrichment of LREE and HREE relative to MREE and a low fractionated LREE to HREE segment. Trace elements contents are low and all samples are strong enrichment in Cs, U, Pb, weak enrichment in Ba and depletion in Th, but negative Nb anomalies are only observed in few samples. That suggests Taoxinghu metamorphic peridotites have depletion mantle and suprasubduction affinities. A two‐stage evolution history is considered: Taoxinghu metamorphic peridotites originated as the residue from melting at a ridge with 7%‐20% degree of fraction melting and were subsequently modified by interaction with mafic melt and aqueous fluid within mantle wedge on subducted zone. Combined with previous studies, we preliminarily propose Taoxinghu metamorphic peridotites may be the Products of initial rifting of palo–Tethys, forming at middle Ordivician‐upper Cambrian, and they may be the direct evidences for spreading of palo–Tethys. |
| |
| Keywords: | geochemistry metamorphic peridotite Taoxinghu Longmuco-Shuanghu suture zone Tibetan plateau |
| 本文献已被 万方数据 等数据库收录！ |
| 点击此处可从《Acta Geologica Sinica》浏览原始摘要信息 |
| 点击此处可从《Acta Geologica Sinica》下载免费的PDF全文 |
|
