Zircon SHRIMP U-Pb Dating of Ultramafic Rock and Mafic Granulite from Qinglongyu in Yishui County, Shandong Province
详细信息
- 责任者：Zhao Ziran (Institute of Geology ; Chinese Academy of Geological Sciences ; Beijing 100037 ; China) ; Song Huixia
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(2)
- 关键词：麻粒岩 ; granulite ; 超镁铁质岩 ; ultramafics ; 杂岩 ; complexes ; 铀—铅计时 ; U-Pb dating ; 山东 ; Shandong Province
- 页码：p.551-563
- 图表：illus., 2 tables, 18 refs.
- 分类号：0801
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
This study is focus on zircon SHRIMP U-Pb dating of ultramafic rock and mafic granulite from Qinglonyu, Yishui County, Shandong Province. Ultramafic rocks occur in the form of xenoliths in Yishui complex, without developed spinifex structure. Its oxides with high MgO ultramafic komatiites rich CaO, low SiO2, TiO2, K2O and Na2O content is characterized. Its major mineral assemblage to clinopyroxene+olivine±orthopyroxene+chromite, and metamorphic mineral to hornblende+serpentine is characterized. The ultramafic rock have fairly low REE contents with high LREE/HREE ratios (3.35～4.40) and negative Ce and Eu anomalies. The trace element to Ba, Nb, Zr negative anomalies and Nd, Sm positive anomalies is characterized. Zircon SHRIMP U-Pb dating results indicate that the magmatic crystal zircon age of 2657～2702Ma and the metamorphic zircon ages of 2551～2585Ma. The ultramafic rock formed ages between 2585～2657Ma. The mafic granulites oxide compositions indicate its original rock is high Mg oceanic island tholeiite. The granulite facies-high amphibolite facies metamorphism related to the anatectic magma intrusion role of Neoarchean. The mineral assemblages with hypersthene+clinopyroxene±hornblende+plagioclase±garnet are characterized. The late alteration related to the intrusion of gabbro, diabase and quartz diorite. The late altered mineral assemblages include talc+sericite+chlorite etc. REE composition of light and heavy rare earth elements is no different and no Eu anomaly is characterized. Trace element compositions of Nb, Zr, P, Ti negative anomalies and Sr, K is abnormal for the characteristics. SHRIMP U-Pb zircon dating results show that the granulite facies-amphibolite facies metamorphism age of 2498.4±7.6Ma, leading to granulite facies-amphibolite facies metamorphic anatectic magma crystallization age of 2551±24Ma, and the late alteration age of 2231～2235Ma and 1850±19Ma.