The source of A-type magmas in two contrasting settings: U-Pb, Lu-Hf and Re-Os isotopic constraints
The source of A-type magmas in two contrasting settings: U-Pb, Lu-Hf and Re-Os isotopic constraints
复制标题
DOI：
10.1016/j.chemgeo.2013.05.010
复制
发表时间：
2013-08
期刊：
影响因子：
3.9
通讯作者：
M. Pankhurst;B. Schaefer;S. Turner;T. Argles;C. Wade
中科院分区：
文献类型：
--
作者：
M. Pankhurst;B. Schaefer;S. Turner;T. Argles;C. Wade
比较了两种不同地球动力学背景下造山后A型岩浆的来源。的结束。南澳东南部514-480 Ma的Delamerian造山运动以约1000万年的双峰式A型岩浆活动为标志，受增厚岩石圈的对流迁移驱动。初始Os和Hf同位素比值记录了岩石圈地幔源区的不均匀性，并有部分来自地幔的输入。基性岩母熔体分馏产生花岗岩。与此相反，初始Os同位素比值的A型岩浆组成的ca。1598-1583 Ma中元古界高勒长英质大火成岩省，位于南澳中部，记录了下地壳的主要演化成分。然而，从这些样品的初始Hf同位素比值亏损，表明地幔来源的亲石元素。这种大量的双峰式岩浆活动持续了约1500万年，结束了瓦尔塔坎造山运动。在这两种情况下，化学（流变学）不均匀性的均匀化，继承了地形融合和造山增厚，加强了岩石圈。不均匀的地幔±地壳的同时期融合可能代表了一种共同的，稳定的影响岩石圈柱，无论构造岩浆背景。
The sources of post-orogenic A-type magmas from two distinct geodynamic settings are compared. The end of the ca. 514–480 Ma Delamerian Orogeny, southeastern South Australia, was marked by ~ 10 Myr of bimodal A-type magmatism, driven by convective removal of thickened lithosphere. Initial Os and Hf isotope ratios record a heterogeneous lithospheric mantle source, with some input from aesthenospheric mantle. Mafic parental melts fractionated to produce the granites. In contrast, initial Os isotope ratios of the A-type magmas that comprise the ca. 1598–1583 Ma Mesoproterozoic Gawler Felsic Large Igneous Province, central South Australia, record a dominant evolved lower crust component. However, initial Hf isotope ratios from these samples are depleted, indicating a mantle source for lithophile elements. This voluminous, bimodal magmatism lasted for ~ 15 Myr, and ended the Wartakan Orogeny. In both cases the homogenisation of chemical (rheological) heterogeneities, inherited from terrain amalgamation and orogenic thickening, strengthened the lithosphere. The contemporaneous fusion of heterogeneous mantle ± crust may represent a common, stabilising influence on the lithospheric column regardless of tectono-magmatic setting.