武当山十堰地区二叠纪E-MORB型玄武岩识别及构造意义
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本文为中国地质科学院基本科研业务费项目(编号:YK1701, K1615)和国家青年自然基金项目(编号:41402180)的成果。


Identification of the Permian E- MORBType Basalts and Their Tectonic Significance from Shiyan Area, Wudang Mountain
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    摘要:

    大比例尺构造—岩相填图和测试分析研究显示南秦岭武当山并非统一前寒武纪基底组成,在十堰和两郧断裂之间的黄龙—方滩及丹江口银洞山等地区识别和厘定出一套中生代混杂岩带,开展混杂岩带内物质组成和成因研究对正确认识武当山造山作用和区域构造演化有重要意义。本文重点对武当山十堰黄龙—方滩地区混杂岩带内玄武岩块体岩石成因及时代进行研究,岩石地球化学显示玄武岩块体为亚碱性拉斑玄武岩系列,具有中等Ti、Zr、Hf、Nd含量、弱轻稀土富集重稀土亏损的EMORB(Enriched Midocean ridge basalt, 富集型洋中脊玄武岩)特征,其岩浆为尖晶石二辉橄榄岩低压、高度部分熔融形成,源区可能受富集地幔或俯冲作用等影响导致富集高场强不相容元素;锆石U-Pb测年表明其为中二叠世火山作用产物;区域地质特征及岩石成因研究共同指示该套E-MORB形成于洋中脊或附近海山环境。综上,武当山十堰地区中—晚二叠世存在洋盆,该成果为理解十堰黄龙—方滩混杂岩带成因机制和正确认识南秦岭显生宙构造属性提供了基础资料。

    Abstract:

    Abstract: Detailed Large- scale lithofacies and structure field mapping and systematic test analysis reveals the Wudang Mountain is not unified Precambrian basement composition in South Qinling Orogeny, a suit of Mesozoic mélange were identified and determined in Huanglong—Fangtan and Yindongshan of Danjiangkou regions, which are located in between Shiyan and Liangyun faults. To further carry out the research on the mélange composition and their genesis directly affect the understanding of the Wudang Mountain orogeny and evolution. This study focuses on the genesis and epoch of the basalt block form Huanglong—Fangtan mélange. Whole rock geochemistry of these basalt blocks indicates they are subalkaline tholeiitic series with typically characterized by middle concentrations of Ti, Zr, Hf, and Nd and Enriched midocean ridge basalt (E- MORB)- like rare earth element distribution patterns, trace element spider diagrams. In addition, the samples appear to have all originated from the lowpressure and high degree of partial melting of spinel lherzolite and undergone the affected by enrichment of the mantle or subduction, ultimately resulting in an enrichment of highfield incompatible elements provenance. Zircon U- Pb dating of basalts indicates a Middle Permian magmatic age. Most importantly, in combination with its regional geological characteristics and petrogenesis, the E- MORB type basalt blocks are constrained to a midocean ridge or seamount environment. Thus, an ocean basin exists in Shiyan area Wudang Mountain on Mid—Late Permian, which provides the basic information for reunderstanding the origin of Huanglong—Fangtan mélange and the tectonic attribute of the Phanerozoic in South Qinling Orogeny.

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王刚,张晗,王宗起,武昱东,王东升,王嘉玮.2019.武当山十堰地区二叠纪E-MORB型玄武岩识别及构造意义[J].地质论评,65(1):65-84,[DOI].
WANG Gang, ZHANG Han, WANG Zongqi, WU Yudong, WANG Dongsheng, WANG Jiawei.2019. Identification of the Permian E- MORBType Basalts and Their Tectonic Significance from Shiyan Area, Wudang Mountain[J]. Geological Review,65(1):65-84.

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  • 收稿日期:2018-02-26
  • 最后修改日期:2018-11-21
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  • 在线发布日期: 2019-01-19
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