Heterogeneous and metasomatized mantle recorded by trace elements in minerals of the Donghai garnet peridotites, Sulu UHP terrane, China
Heterogeneous and metasomatized mantle recorded by trace elements in minerals of the Donghai garnet peridotites, Sulu UHP terrane, China
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DOI：
10.1016/j.chemgeo.2005.05.002
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发表时间：
2005-10
期刊：
影响因子：
3.9
通讯作者：
Jianping Zheng;R. Zhang;W. Griffin;J. Liou;S. O’Reilly
中科院分区：
文献类型：
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作者：
Jianping Zheng;R. Zhang;W. Griffin;J. Liou;S. O’Reilly
本文报道了苏鲁超高压变质带东海地区芝麻房二辉橄榄岩和徐沟方辉橄榄岩中矿物的原位微量元素数据。芝麻房二辉橄榄岩和徐沟辉橄榄岩分别具有变斑结构和等粒结构，由橄榄石（Fo 90.6 -92.4）、顽火辉石（En 92.0 -92.7）、石榴子石（Prp 63.2 -87.1）和透辉石（Mg #90.8 -95.7）组成，并含有少量金云母。两种橄榄岩中的石榴子石均表现出低LREE和负Ce异常，但芝麻房石榴子石的HREE丰度（（HREE）n=8- 15）高于徐沟石榴子石（（HREE）n=2-6）。这两种橄榄岩的透辉石具有低的Yb、Y和Ti丰度和低的Ti/Eu（517-1158），但具有高且可变的Sr/Nd（4800- 22，000）和（La/Yb）n（40-100）。岩石学和地球化学特征表明，东海石榴橄榄岩是由富含碳酸盐和含水组分的硅酸盐熔体交代形成的。考虑到这些天体在地幔和地壳中必须经历的复杂演化，可能发生了几次交代作用。芝麻房橄榄岩和徐沟橄榄岩的矿物化学特征（如橄榄石的Ni含量和Mg#，石榴石的Y、Al、HREE、Nd/Y和Sc/Y）的差异表明它们来自非均质地幔，芝麻房二辉橄榄岩的亏损程度小于徐沟橄榄岩。它们在插入俯冲大陆板片之前可能有不同的演化历史。
In situ trace element data for minerals in the Zhimafang lherzolite and Xugou harzburgites from the Donghai area of the Sulu UHP terrane are presented. The Zhimafang lherzolite and the Xugou harzburgite have porphyroblastic and equigranular textures respectively, and consist of olivine (Fo90.6–92.4), enstatite (En92.0–92.7), garnet (Prp63.2–87.1) and diopside (Mg#90.8–95.7) with additional minor phlogopite. Garnets from both peridotites have low LREE and show negative Ce anomalies, but Zhimafang garnet has higher HREE abundance ((HREE)n=8–l5) than Xugou garnet ((HREE)n=2–6). Diopsides from both peridotites have low abundances of Yb, Y and Ti, and low Ti/Eu (517–1158), but high and variable Sr/Nd (4800–22,000) and (La/Yb)n(40–100). The petrographic and geochemical characteristics suggest that the Donghai garnet peridotites were subjected to metasomatism caused by silicate-rich melts with both carbonate and hydrous components. Several episodes of metasomatism may have occurred, given the complex evolution these bodies must have undergone in the mantle and crust. The differences in mineral chemistry (such as the Ni content and Mg#of olivine, and the Y, Al, HREE, Nd/Y and Sc/Y of garnet) between Zhimafang and Xugou peridotites suggest that they are derived from a heterogeneous mantle, and the Zhimafang lherzolite was less depleted than the Xugou harzburgite. Probably they have had a different evolutionary history prior to insert into the subducted continental slab.