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首页 > 中国极地考察知识库 > 成果信息库 > 已审查 Late Neoproterozoic/Cambrian high-pressure mafic granulites from the Grove Mountains, East Antarctica: P–T–t path, collisional orogeny and implications for assembly of East Gondwana

Late Neoproterozoic/Cambrian high-pressure mafic granulites from the Grove Mountains, East Antarctica: P–T–t path, collisional orogeny and implications for assembly of East Gondwana

【标题】Late Neoproterozoic/Cambrian high-pressure mafic granulites from the Grove Mountains, East Antarctica: P–T–t path, collisional orogeny and implications for assembly of East Gondwana

【Title】Late Neoproterozoic/Cambrian high-pressure mafic granulites from the Grove Mountains, East Antarctica: P–T–t path, collisional orogeny and implications for assembly of East Gondwana

【作者】 刘晓春; 胡健民; 赵越; 刘小汉

【Author】 Liu Xiaochun ; Hu Jianmin ; Zhao Yue ; Liu Xiaohan

【期刊】Precambrian Research

【Journal】Precambrian Research

【期刊年份】2009

【卷】174(1-2)

【期】

【关键词】 East Antarctica; Prydz Belt; Late Neoproterozoic/Cambrian; HP mafic granulite; Collisional orogeny

【Keywords】 East Antarctica; Prydz Belt; Late Neoproterozoic/Cambrian; HP mafic granulite; Collisional orogeny

【摘要】The Grove Mountains are an inland continuation of the Late Neoproterozoic/Cambrian Prydz Belt of East Antarctica. In this paper we report high-pressure (HP) mafic granulites that occur in glacial moraines from this area. Petrographical textures, mineral compositions and P–T pseudosection calculations in the system NCFMASHTO (Na2O–CaO–FeO–MgO–Al2O3–SiO2–H2O–TiO2–Fe2O3) suggest that the HP mafic granulites record peak P–T conditions of 11.8–14.0 kbar and 770–840 °C. The post-peak evolution of these rocks involved near-isothermal decompression of ca. 6 kbar followed by a greenschist facies overprint. SHRIMP U-Pb zircon dating, coupled with the identification of mineral inclusion assemblage in zircons, reveals HP metamorphism occurred at ca. 545 Ma and subsequent retrograde reactions involving near-isothermal decompression at ca. 530 Ma. Garnet-clinopyroxene-whole-rock Sm-Nd isotopic analyses also yield Cambrian ‘isochron’ ages. This reflects collision at a convergent plate margin followed by extensional exhumation as the orogen collapsed during Late Neoproterozoic/Cambrian orogeny. Therefore, the occurrence of HP mafic granulites from the Grove Mountains provides evidence for a collisional tectonic setting for the Prydz Belt, which supports the notion that East Gondwana was not finally assembled until the Cambrian.

【Abstract】The Grove Mountains are an inland continuation of the Late Neoproterozoic/Cambrian Prydz Belt of East Antarctica. In this paper we report high-pressure (HP) mafic granulites that occur in glacial moraines from this area. Petrographical textures, mineral compositions and P–T pseudosection calculations in the system NCFMASHTO (Na2O–CaO–FeO–MgO–Al2O3–SiO2–H2O–TiO2–Fe2O3) suggest that the HP mafic granulites record peak P–T conditions of 11.8–14.0 kbar and 770–840 °C. The post-peak evolution of these rocks involved near-isothermal decompression of ca. 6 kbar followed by a greenschist facies overprint. SHRIMP U-Pb zircon dating, coupled with the identification of mineral inclusion assemblage in zircons, reveals HP metamorphism occurred at ca. 545 Ma and subsequent retrograde reactions involving near-isothermal decompression at ca. 530 Ma. Garnet-clinopyroxene-whole-rock Sm-Nd isotopic analyses also yield Cambrian ‘isochron’ ages. This reflects collision at a convergent plate margin followed by extensional exhumation as the orogen collapsed during Late Neoproterozoic/Cambrian orogeny. Therefore, the occurrence of HP mafic granulites from the Grove Mountains provides evidence for a collisional tectonic setting for the Prydz Belt, which supports the notion that East Gondwana was not finally assembled until the Cambrian.

【基金/项目】 十一五科技支撑南极环境变化预测与资源潜力评估技术 ; the Geological Investigation Project of the Chinese Geological Survey (Nos. 1212010511505 and 1212010711509) ; 东南极埃默里冰架东缘的构造属性及演化过程 ; 南极普里兹带构造格架、变形过程及大地构造意义 ; the National Key Technology R & D Program (No. 2006BAB18B08)

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