Geochronological, geochemical and Sr-Nd-Hf isotopic constraints on the petrogenesis of Late Cretaceous A-type granites from the Sibumasu Block, Southern Myanmar, SE Asia
Geochronological, geochemical and Sr-Nd-Hf isotopic constraints on the petrogenesis of Late Cretaceous A-type granites from the Sibumasu Block, Southern Myanmar, SE Asia
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年代学、地球化学和 Sr-Nd-Hf 同位素对东南亚缅甸南部 Sibumasu 地块晚白垩世 A 型花岗岩岩石成因的限制
DOI：
10.1016/j.lithos.2016.11.005
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发表时间：
2017-01-01
期刊：
影响因子：
3.5
通讯作者：
Wei, Xiao-Peng
中科院分区：
文献类型：
--
作者：
Jiang, Hai;Li, Wen-Qian;Wei, Xiao-Peng
缅甸Sibumasu地块广泛发育晚白垩世-早第三纪花岗岩类，与锡钨矿化关系密切。然而，这些花岗岩类的确切时间，岩石成因和构造意义的制约很差，到目前为止。在这项研究中，我们提出了一个详细的地质年代学，元素和Sr-Nd-Hf同位素地球化学研究的Hermingyi和Taungphila在缅甸南部的花岗岩，目的是确定其岩石成因和构造意义。两个花岗岩中锆石的LA-ICP-MS U-Pb年龄为69-70 Ma，表明发生了晚白垩世岩浆事件。这些花岗质岩石是弱过铝质的，属于高钾钙碱性系列。它们均具有高SiO2、K2 O + Na 2 O、FeOT/（FeOT + MgO）和Ga/Al比值，低Al 2 O3、CaO、MgO、P2 O 5和TiO 2含量，富Rb、Th、U和Y，贫Ba、Sr、P和Eu，显示出A型花岗岩的亲和性。此外，它们还表现出明显的稀土元素四分体配分模式和非CHAAC微量元素行为，这在岩浆分异晚期具有强烈热液作用或深成蚀变作用的岩浆岩中很常见。花岗岩属A（2）型，可能形成于高温无水条件下。它们的锆石Hf（t）值为-12.4 ~-10.0，全岩Nd（t）值为-11.3 ~-10.6，Hf和Nd同位素的T-DM 2年龄为1741-1922 Ma。地球化学和同位素数据表明，这些A型花岗岩来自于部分熔融的古元古代陆壳为主的变火成岩与英云闪长岩花岗闪长岩成分，没有显着的输入幔源岩浆，随后的分离结晶。通过综合东南亚及邻近地区区域构造演化的所有可用数据，我们将晚白垩世A型花岗岩的形成归因于俯冲带后方腹地的弧后伸展，这是由平坦的新特提斯俯冲板片回滚引起的。大约。70马。(C)2016爱思唯尔B. V.保留所有权利。
The Late Cretaceous to Paleogene granitoids occur widespread in the Sibumasu block within Myanmar (SE Asia), which show a close association with tin-tungsten mineralization. However, the precise timing, petrogenesis and tectonic significance of these granitoids are poorly constrained so far. In this study, we present a detailed study on geochronology, elemental and Sr-Nd-Hf isotopic geochemistry for the Hermyingyi and Taungphila granites in southern Myanmar, with the aim of determining their petrogenesis and tectonic implications. LA-ICP-MS U-Pb dating of zircon grains from the two granites yield ages of 69-70 Ma, indicating a Late Cretaceous magmatic event. These granitic rocks are weakly peraluminous and belong to the high-K calc-alkaline series. They are both characterized by high SiO2, K2O + Na2O, FeOT/(FeOT + MgO) and Ga/Al ratios and low Al2O3, CaO, MgO, P2O5 and TiO2 contents, enriched in Rb, Th, U and Y, but depleted in Ba, Sr, P, and Eu, suggesting an A-type granite affinity. Moreover, they display prominent tetrad REE patterns and non-CHARAC trace element behavior, which are common in late magmatic differentiates with strong hydrothermal interaction or deuteric alteration. The granites belong to A(2)-type and probably formed at a high temperature and anhydrous condition. They have zircon epsilon(Hf)(t) values from -12.4 to -10.0 and whole-rock epsilon(Nd)(t) values from -11.3 to -10.6, with Paleoproterozoic T-DM2 ages (1741-1922 Ma) for both Hf and Nd isotopes. Geochemical and isotopic data suggest that these A-type granites were derived from partial melting of the Paleoproterozoic continental crust dominated by metaigneous rocks with tonalitic to granodioritic compositions, without significant input of mantle-derived magma and followed by subsequent fractional crystallization. By integrating all available data for the regional tectonic evolution in SE Asia and adjacent regions, we attribute the formation of the Late Cretaceous A-type granites to a back-arc extension in the hinterland behind the subduction zone, which is induced by the rollback of the flat Neo-Tethyan subducting slab around ca. 70 Ma. (C) 2016 Elsevier B.V. All rights reserved.