Low-δ18O rhyolites from the Malani Igneous Suite: a positive test for South China and NW India linkage in Rodinia
Low-δ18O rhyolites from the Malani Igneous Suite: a positive test for South China and NW India linkage in Rodinia
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马拉尼火成岩组中的低δ18O流纹岩：对罗迪尼亚华南和印度西北部联系的积极测试
DOI：
10.1002/2017gl074717
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发表时间：
2017
影响因子：
5.2
通讯作者：
Zhao Jun-Hong
中科院分区：
文献类型：
--
作者：
Wang Wei;Cawood Peter.A;Zhou Mei-Fu;Manoj P;it.K;Xia Xiao-Ping;Zhao Jun-Hong
位于印度西北部的马拉尼火成岩套（MIS）是保存最完好的大型火成岩省之一。MIS的大量熔岩在~780-750 Ma之间爆发。流纹岩和英安岩熔岩中的锆石颗粒具有氧同位素组成，包括亏损（δ 18 O = 4.12--1.11 ‰）和富集（δ 18 O = 8.23-5.12‰）的特征。低δ 18 O锆石颗粒具有高放射成因Hf同位素组成（δ Hf（t）= +13.0 ~+3.6），表明上层年轻镁铁质地壳的高温整体自食作用是产生低δ 18 O长英质岩浆的重要机制。英安岩中的捕晶锆石颗粒具有高δ 18 O和低δ Hf（t）值，其岩浆年龄大于800 Ma，反映了印度西北部在800-780 Ma期间构造热体制的剧烈转变。中国南部和马达加斯加岛也发生了同步转变，这表明一个空间上相互联系的地球动力系统。印度西北部和中国南部以及马达加斯加和塞舌尔要么沿着Rodinia的外围，要么位于超大陆的外侧，会聚板缘岩浆活动的时代与超大陆的裂解相吻合。
The Malani igneous suite (MIS) in NW India represents one of the best preserved silicic large igneous provinces. Voluminous silicic lavas of the MIS erupted between ~780–750 Ma. Zircon grains from rhyolite and dacite lavas have oxygen isotopic compositions that include depleted (δ18O = 4.12 to −1.11‰) and enriched (δ18O = 8.23–5.12‰) signatures. The low‐δ18O zircon grains have highly radiogenic Hf isotopic compositions (ƐHf(t)= +13.0 to +3.6), suggesting high‐temperature bulk cannibalization of upper level juvenile mafic crust as an essential mechanism to produce the low‐δ18O felsic magma. Xenocrystic zircon grains in dacites have high δ18O and low ƐHf(t)values for magmas older than 800 Ma, reflecting a dramatic transition in tectono‐thermal regime in NW India during 800–780 Ma. A synchronous transition also occurred in south China and Madagascar, suggesting a spatially linked geodynamic system. NW India and south China together with Madagascar and the Seychelles lay either along the periphery of Rodinia or outboards of the supercontinent with the age of convergent plate margin magmatism coinciding with breakup of the supercontinent.