江西余干支家桥橄榄辉长岩矿物化学特征及其地球动力学意义  

Mineral Chemical Characteristics and Geodynamic Significance of Olivine Gabbro from the Zhijiaqiao Area,Yugan County,Jiangxi Province

作　　者：严文亚 郭国林 贾琳[1,2,3] 杨铃 陈缵诺 YAN Wen-Ya;GUO Guo-Lin;JIA Lin;YANG Ling;CHEN Zuan-Nuo(National Key Laboratory of Uranium Resources Exploration-Mining and Nuclear Remote Sensing,Nanchang 330013,Jiangxi,China;State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,Jiangxi,China;School of Earth Sciences,East China University of Technology,Nanchang 330013,Jiangxi,China)

机构地区：[1]铀资源探采与核遥感全国重点实验室,江西南昌330013 [2]东华理工大学核资源与环境国家重点实验室,江西南昌330013 [3]东华理工大学地球科学学院,江西南昌330013

出　　处：《华南地质》2025年第1期51-62,共12页South China Geology

基　　金：国家自然科学基金项目(42262009)。

摘　　要：橄榄辉长岩起源于岩石圈地幔,其中的造岩矿物的结构和成分特征与岩石成因密切相关,可以反映岩浆源区特征、结晶的物理化学条件以及地球动力学背景。本文对产于华夏地块的江西余干支家桥橄榄辉长岩开展了岩相学和矿物化学分析以探讨其形成的背景。该橄榄辉长岩的造岩矿物由单斜辉石、斜长石、橄榄石及少量角闪石和金云母等组成。橄榄石为他形粒状,边缘发育蛇纹石化,Fo=80.68~82.20,属贵橄榄石,CaO含量低于0.1 wt.%,指示其为地幔捕虏晶;单斜辉石为透辉石和普通辉石,Mg^(#)=82.52~85.95,矿物成分计算表明岩体的母岩浆为钙碱性玄武质岩浆,结晶温度为1173~1193℃,结晶压力为0.25~0.39 GPa。橄榄辉长岩中富含含水矿物及单斜辉石结晶时岩浆含水量(2.1%~2.7%)指示其母岩浆具有富水的特征,可能其岩浆源区受到过俯冲流体的交代改造。结合区域地质背景认为支家桥地区橄榄辉长岩可能是受俯冲流体交代过的岩石圈地幔在新生代伸展背景下发生减压熔融,形成橄榄辉长岩的母岩浆,母岩浆上升侵位于中下地壳的产物。Olivine gabbro originates from the mantle lithosphere,with the structural and compositional characteristics of its rock-forming minerals closely related to its petrogenesis,reflecting the characteristics of the magma source region,the physicochemical conditions of crystallization,and the geodynamic background.This paper conducts the petrographic and mineral chemical analyses on the olivine gabbro from the Zhijiaqiao area in the Cathaysia Block,to explore its formation background.The rock-forming minerals of this olivine Gabbro consist of clinopyroxene,plagioclase,olivine,and a small amount of hornblende and phlogopite.Olivine is xenomorphic granular and developing serpentinization alteration edge.With the Fo values of 80.68~82.20, it belongs to the chrysolite, CaO content is less than 0.1 wt.%, indicated as mantle xenocrysts.The clinopyroxene is composed of diopside and augite. with Mg^(#)=82.52~ 85.95. Mineral compositioncalculations indicate that the parent magma is calc-alkaline basaltic magma, with a crystallization temperaturerange of 1 173~1 193 ℃ and a crystallization pressure of 0.25~0.39 GPa. The richness in hydrous mineralsand the water content (2.1%~2.7%) of the clinopyroxene in the olivine gabbro indicate that its parent magmais water-rich, possibly due to metasomatism by subduction-related fluids in the magma source region.Combined with the regional geological background, it is believed that the olivine gabbro in the Zhijiaqiao areamay have originated from lithospheric mantle metasomatized by subduction fluids. Under the extensionaltectonic setting of the Cenozoic, this mantle has undergone decompression melting, forming the parentmagma of the olivine gabbro, which ascended and intruded into the middle-lower crust.

关 键 词：单斜辉石 橄榄石 含水量 地球动力学意义 支家桥 

分 类 号：P574.2[天文地球—矿物学]