Early Mesoproterozoic arc magmatism followed by early Neoproterozoic granulite facies metamorphism with a near-isobaric cooling path at Mount Brown, Princess Elizabeth Land, East Antarctica
Early Mesoproterozoic arc magmatism followed by early Neoproterozoic granulite facies metamorphism with a near-isobaric cooling path at Mount Brown, Princess Elizabeth Land, East Antarctica
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南极洲东部伊丽莎白公主地布朗山的早中元古代弧岩浆作用，随后是早新元古代麻粒岩相变质作用，具有近等压冷却路径
DOI：
10.1016/j.precamres.2016.08.003
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发表时间：
2016-10
影响因子：
3.8
通讯作者：
Song Biao
中科院分区：
文献类型：
--
作者：
Liu Xiaochun;Wang Wei-;Zhao Yue;Liu Jian;Chen Hong;Cui Yingchun;Song Biao
布朗山是普里兹湾和登曼冰川之间独特的内陆露头，为南极洲印度洋板块的构造演化提供了有用的见解。本区基岩以长英质正长岩为主，次含镁质麻粒岩、深熔质副长岩和伟晶岩脉。高分辨率离子探针（SHRIMP） U-Pb锆石测年揭示了约1490-1400 Ma时镁质麻粒岩和长英质正长岩原岩的侵位，约1250 Ma后副长岩前体沉积，约920-900 Ma时伴随部分熔融的高变质作用。这些早中元古代镁质-长英质火成岩的微量元素地球化学特征表明它们形成于大陆弧环境。Nd同位素组成的初始ε nd_2值在+2.8 ~ - 6.6之间，Nd贫化地幔模型年龄集中在2.4 ~ 1.7 Ga之间，表明古元古代存在明显的地壳形成。NC(K)FMASHTO [na20 - cao (-K2O) -FeO-MgO-Al2O3-SiO2-H2O-TiO2-Fe2O3]体系中基性麻粒岩和副长岩的岩相结构、矿物组成和压力-温度（P−T）拟剖面计算表明，早新元古代变质作用的峰值P−条件为830-870℃和7 - 8kbar，随后近等压冷却至760-830℃和7-8.5 kbar。布朗山地质事件的年龄谱和特征与雷纳杂岩相似，支持雷纳造山带向东延伸至威廉二世地。结合现有资料，我们推断印度克拉通和东南极洲（可能是Ruker克拉通）之间的漫长构造演化可能发生在大约600 Myr的时期，从大约1500-1000 Ma的长期海洋俯冲-增生到大约1000-900 Ma的最终碰撞。
Mount Brown is a unique inland outcrop between Prydz Bay and Denman Glacier that provides useful insights into the tectonic evolution of the Indian Ocean sector of Antarctica. The bedrock in this area is dominated by felsic orthogneisses with subordinate amounts of mafic granulites, anatectic paragneisses and pegmatite veins. Sensitive high-resolution ion microprobe (SHRIMP) U–Pb zircon dating reveals the emplacement of mafic granulite and felsic orthogneiss protoliths at ca. 1490–1400 Ma, sedimentation of paragneiss precursors after ca. 1250 Ma, and subsequent high-grade metamorphism accompanied by partial melting at ca. 920–900 Ma. The trace element geochemistry of these early Mesoproterozoic mafic–felsic igneous rocks indicates that they formed in a continental arc setting. Nd isotopic compositions for these rocks yield initial εNdvalues ranging from +2.8 to −6.6 and Nd depleted mantle model ages clustering between 2.4 and 1.7 Ga, implying a significant crustal formation in the Paleoproterozoic. Petrographic textures, mineral compositions, and pressure–temperature (P−T) pseudosection calculations for mafic granulite and paragneiss in the system NC(K)FMASHTO [Na2O–CaO(–K2O)–FeO–MgO–Al2O3–SiO2–H2O–TiO2–Fe2O3] system suggest that early Neoproterozoic metamorphism reached peakP−Tconditions of 830–870 °C and 7–8 kbar, followed by near-isobaric cooling to 760–830 °C and 7–8.5 kbar. The age spectra and characteristics of geological events at Mount Brown are similar to those in the Rayner Complex, thereby supporting an eastward continuation of the Rayner orogen to Wilhelm II Land. Combined with existing data, we infer that a protracted tectonic evolution between the Indian craton and East Antarctica (possibly the Ruker craton) might have occurred for a period of ca. 600 Myr from long-lived oceanic subduction–accretion at ca. 1500–1000 Ma to final collision at ca. 1000–900 Ma.
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影响因子：
3.8
作者：
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