Petrogenesis of Cenozoic basalts in central-eastern China: Constraints from Re-Os and PGE geochemistry
Petrogenesis of Cenozoic basalts in central-eastern China: Constraints from Re-Os and PGE geochemistry
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中国中东部地区新生代玄武岩的岩石成因：Re-Os和PGE地球化学的制约
DOI：
10.1016/j.lithos.2017.01.022
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发表时间：
2017-05-01
期刊：
影响因子：
3.5
通讯作者：
Guo, Jinghui
中科院分区：
文献类型：
--
作者：
Chu, Zhuyin;Yan, Yan;Guo, Jinghui
为了进一步约束中国中东部新生代玄武岩的成因，我们提供了Re-Os和PGe(铂族元素)，并结合主量元素、痕量元素和锶-钕同位素数据。玄武岩包括低钙碱性、高钙碱性和拉斑玄武岩。大多数低钙碱性玄武岩具有非放射性成因的Os-187/Os-188(大多为0.4)，表明参与了硫化物/PGE合金分凝-AFC(同化-分馏-污染)过程。大多数拉斑玄武岩和高钙碱性玄武岩具有相对较高的Os含量、高度可变的超软体Os同位素组成、较高的Pd/Ir比值和富集锶、钕同位素组成。模拟结果表明，这些玄武岩中的Os同位素变化不能归因于上升过程中的地壳混染，而主要反映了源区的特征。结合其低CaO、低Mg-#、高FC3MS值(FeOt/CaO-3xMgO/SiO_2，均以wt%计)和高Fe/Mn特征，推测很大一部分辉石岩是地幔来源中的富集组分，以解释其高度超软体的Os同位素组成。辉石岩的形成可能是由于俯冲的含沉积物太平洋洋壳或扬子-中国地块与北中国地块碰撞形成的再循环下陆壳所致。(C)2017爱思唯尔B.V.保留所有权利。
We present Re-Os and PGE (platinum group elements), together with major-, trace-element and Sr-Nd isotope data, to further constrain the petrogenesis for the Cenozoic basalts in central-eastern China. The basalts include low-Ca alkali, high-Ca alkali and tholeiitic varieties. Most low-Ca alkali basalts have unradiogenic Os-187/Os-188 (mostly 0.4), indicating involvements of sulfide/PGE-alloy segregation-AFC (assimilation-fractionation-contamination) processes. Most tholeiites and high-Ca alkali basalts have relatively high Os concentrations, highly variable and suprachondritic Os isotopic compositions, high Pd/Ir ratios and enriched Sr-Nd isotopic compositions. Modeling results reveal that the Os isotopic variations in these basalts cannot be ascribed to crustal contamination during ascent but mainly reflect source characteristics. Combined with their low CaO, low Mg-#, high FC3MS values (FeOT/CaO-3 x MgO/SiO2, all in wt%), and high Fe/Mn signatures, a large portion of pyroxenite is inferred as an enriched component in the mantle sources to account for their highly suprachondritic Os isotopic compositions. The formation of the pyroxenites was probably due to the subducted sediment-bearing Pacific oceanic crust or the recycled lower continental crust resulted from the collision between the Yangtze and North China blocks. (C) 2017 Elsevier B.V. All rights reserved.