Generation and evolution of siliceous high magnesium basaltic magmas in the formation of the Permian Huangshandong intrusion (Xinjiang, NW China)
Generation and evolution of siliceous high magnesium basaltic magmas in the formation of the Permian Huangshandong intrusion (Xinjiang, NW China)
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DOI：
10.1016/j.lithos.2013.01.002
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发表时间：
2013-03-01
期刊：
影响因子：
3.5
通讯作者：
Zhou, Mei-Fu
中科院分区：
文献类型：
--
作者：
Gao, Jian-Feng;Zhou, Mei-Fu
中亚造山带南缘二叠纪大量富含斜方辉石的镁铁质-超镁铁质岩体侵位于造山后环境。黄山东镁铁质-超镁铁质岩体是中国造山带东天山最大的岩体，由一个层状岩体单元和一个块状岩体单元组成。层状单元由二辉橄榄岩、橄榄闪长岩、橄榄辉长岩、角闪石辉长岩、辉长辉长岩和闪长辉长岩组成，块状单元由辉长辉长岩和橄榄辉长辉长岩组成。该单元的岩石具有初始Sr-87/Sr-86比值（0.7031-0.7043）和Nd（Nd）值（+3.4-+7.1），而斜长石的初始Sr-87/Sr-86比值范围为0.70010 - 0.71569。块状单元的橄榄石具有相对较低的Fo值（59至70）和较高的NiO和MnO。该单元的岩石具有相对较低且均匀的初始Sr-87/Sr-86比（0.7030）和高epsilon（Nd）值（+6.0-+7.5），并含有具有相对较低初始Sr-87/Sr-86比（0.70042至0.70520）的斜长石。这两个单元的橄榄石都具有低的CaO和Cr2 O3。这两个单元都是由硅质高镁玄武质岩浆形成的，来自含水的亏损地幔源。形成层状单元的岩浆在侵位前经历了较早的硫化物去除，而硫化物饱和则是由于地壳物质的加入而引起的。形成块状单元的岩浆经历了橄榄石+/-铬尖晶石的分离结晶。硅质高镁玄武岩浆作用是造山带的一个重要特征，它是由贫水地幔源熔融而产生的。(C)2013爱思唯尔有限公司版权所有。
Numerous Permian orthopyroxene-rich mafic-ultramafic intrusions in the southern margin of the Central Asian Orogenic Belt (CAOB) have been emplaced in a post-orogenic environment. The Huangshandong mafic-ultramafic intrusion is the largest in the eastern Tianshan Orogenic Belt of the CAOB and consists of a layered unit intruded by a massive unit. The layered unit consists of lherzolite, troctolite, olivine gabbro, hornblende gabbro, gabbrodiorite and diorite, whereas the massive unit is made of gabbronorite and olivine gabbronorite.Olivine from the layered unit has Fo values of 75 to 84 and contains low NiO and MnO. Rocks from this unit have initial Sr-87/Sr-86 ratios (0.7031-0.7043) and epsilon(Nd) values (+3.4-+7.1) while plagioclase has initial Sr-87/Sr-86 ratios ranging from 0.70010 to 0.71569. Olivine from the massive unit has relatively low Fo values of 59 to 70 and high NiO and MnO. Rocks from this unit have relatively low and uniform initial Sr-87/Sr-86 ratios (0.7030) and high epsilon(Nd) values ( +6.0-+7.5) and contain plagioclase with relatively low initial Sr-87/Sr-86 ratios (0.70042 to 0.70520). Olivines from both units have low CaO and Cr2O3.Both units formed from siliceous high magnesium basaltic magmas were derived from a hydrous, depleted mantle source. Magma forming the layered unit experienced earlier removal of sulfides before emplacement, with the earlier sulfide-saturation caused by the addition of crustal material. The magma that formed the massive unit has undergone fractional crystallization of olivine +/- Cr-spinel. Siliceous high magnesium basaltic magmatism, produced by melting of a hydrous depleted mantle source, may be an important feature of orogenic belts. (C) 2013 Elsevier B.V. All rights reserved.