| 石榴子石反应边及其地质意义——以大兴安岭第四纪火山岩为例 |
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| 引用本文： | 隋建立.石榴子石反应边及其地质意义——以大兴安岭第四纪火山岩为例[J].岩石矿物学杂志,2022,41(1):37-46. |
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| 作者姓名： | 隋建立 |
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| 作者单位： | 中国地震局地质研究所 |
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| 基金项目： | 国家自然科学基金面上基金(40972048)。 |
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| 摘 要： | 大兴安岭第四纪火山岩(包括诺敏河火山区和哈拉哈河-绰尔河火山区)地幔包体中含有少量石榴子石,普遍发育矿物反应边.根据显微照片和BSE图像特征,石榴子石反应边可分为3类:①冠冕状石榴子石反应边,包裹在石榴子石矿物外部,具有一期或者多期反应的特征,厚度通常为0.1～1 mm,反应边矿物组合为Opx+Glass、Cpx+Gl...
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| 关 键 词： | 大兴安岭 石榴子石反应边 电子探针 等化学分解 地幔演化 |
| 收稿时间： | 2021/5/21 0:00:00 |
Reaction rims of garnet and its geological significant:A case study on Quaternary volcanics in Da Hinggan Mountains |
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| SUI Jian-li.Reaction rims of garnet and its geological significant:A case study on Quaternary volcanics in Da Hinggan Mountains[J].Acta Petrologica Et Mineralogica,2022,41(1):37-46. |
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| Authors: | SUI Jian-li |
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| Institution: | (Institute of Geology,China Earthquake Administration,Beijing 100029,China) |
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| Abstract: | Mantle xenoliths,with minor garnets,have been found in the Quaternary volcanic rocks in Da Hinggan Mountains.Reaction rims,documenting significant records of mantle dynamic evolution,are common in most of the garnets.Optical photomicrographs and BSE pictures demonstrate three types of reaction rims of garnets,(1)coronal rims,a thin layer of 0.1~1 mm enclosing the relic garnet,with a typical mineral assemblage of Opx+Glass,Cpx+Glass or Grt+Sp;(2)vein rims,vein-like strips in several 100μm in width and several millimeter in length,with a typical mineral assemblage of Opx+Glass;(3)microfracture rims,very thin reaction rims of several to several ten micrometers thick along microfractures in garnet,with a typical mineral assemblage of Sp+Glass.On the aspect of petrogenesis,these reaction rims were divided into two types,(1)origin of magma/melt reaction with garnet:Some reaction rims have quite different bulk chemical composition from the precursor garnets.For example,K2O and Na2O compositions in garnet reaction rims are one or two orders of magnitude higher than those in precursor garnets,indicating that compositions from mantle melts or alkaline magmas were induced to the mineral assemblages of reaction rims;(2)origin of isochemical breakdown of garnet:The other reaction rims have nearly the same bulk chemical compositions as the precursor garnet,indicating isochemical breakdown of garnet without any significant chemical compositions from mantle melts or other minerals,especially the vein rims and microfracture rims.Hence two types of garnet reaction rims with quiet different origins were found in Quaternary volcanic rocks in Da Hinggan Mountains.These garnet reaction rims provide evidences of K2O-and Na2O-rich melt reactions and mantle refertilizing processes,as well as evidences of evolution of mantle p-T conditions.Studies on garnet reaction rims may light on further understanding on chemical evolution and thermal history of lithospheric mantle in Da Hinggan Mountains. |
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| Keywords: | Da Hinggan Mountains garnet reaction rim electronic probe analysis isochemical breakdown mantle evolution |
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