高校地质学报2026，Vol.32Issue(2)：207-224,18.DOI:10.16108/j.issn1006-7493.2025035
北祁连大岔大坂地区辉长岩的矿物化学特征及其构造意义
Mineralogical and Chemical Characteristics and Tectonic Significance of Gabbro from the Dachadaban Area,North Qilian,China
摘要
Abstract
Gabbro is a major component of oceanic crust and is of great significance for understanding the magma processes beneath different types of spreading ridges and their corresponding relationships with tectonic settings.This study systematically investigates the petrology,mineralogical and geochemistry of the gabbro bodies in the Dachadaban ophiolite in the North Qilian Orogen.Petrographic results show that these medium-fine-grained gabbros are mainly composed of plagioclase(around 60 vol.%),clinopyroxene(around 35 vol.%)and orthopyroxene(around 5 vol.%).Geochemical characteristics inidcate that the gabbros exhibit high-Mg features(MgO=8.90%-11.33 wt.%,Mg#=76-80),with low-Ti(TiO2=0.36%-0.49 wt.%)and low-Si(SiO2=47.10%-47.94 wt.%)contents,while their CaO content is comparable to that of mid-ocean ridge basalt(MORB).Furthermore,these gabbros display extremely low rare earth element(REE)abundance with pronounced light REE(LREE)depletion,along with depletion in high field strength elements(HFSEs;e.g.,Zr,Hf,Ti)and enrichment in large ion lithophile elements(LILEs).The overall composition of these entire rocks is similar to that of the back-arc basins.In terms of mineral composition,clinopyroxenes belong to diopside(Mg#=78-80)with a distribution pattern of light rare earth element depletion,indicative of the differentiation products of MORB-type magma.The calculation of mineral equilibrium temperature and pressure yields that the crystallization temperature of gabbro is 1200-1246℃,the pressure is 5.6-8.9 kbar,and the corresponding depth is 15-29 km,indicating characteristics of a deep magma chamber.Together with the previous results,the study suggests that the Dachadaban gabbro was formed in a back-arc basin setting.关键词
大岔大坂/辉长岩/矿物学/单斜辉石/弧后盆地环境Key words
Dachadaban/gabbro/mineralogy clinopyroxene/back-arc basin分类
天文与地球科学引用本文复制引用
张治国,刘希军,龚小晗,唐国强,王佳婷,田昊,曹聿钊,顿海龙..北祁连大岔大坂地区辉长岩的矿物化学特征及其构造意义[J].高校地质学报,2026,32(2):207-224,18.基金项目
甘肃省教育厅博士基金项目(2023QB-084) （2023QB-084）
广西科技计划项目(桂科LT2600640017) （桂科LT2600640017）
张掖市市级科技计划专项项目(ZY2024BJ12) （ZY2024BJ12）
河西学院博士科研启动基金项目(KYQD2023010) （KYQD2023010）
广西研究生教育创新计划项目(YCBZ2024172) （YCBZ2024172）
广西第七批八桂学者项目(刘希军) （刘希军）
河西学院第十五批科技创新发明项目(Z25,Z85) （Z25,Z85）
甘肃省大学生创新创业项目(S202410740070 （）
S202410740008)联合资助 （）
