峨眉山苦橄岩原始岩浆成分反演及对地幔熔融条件的评估  

The Compositional Inversion and Evaluation of Melting Conditions for Primary Melt of the Emeishan Picrites

作　　者：于宋月[1] 蓝江波 陈琦 YU Song-yue;LAN Jiang-bo;CHEN Qi(State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院地球化学研究所,矿床地球化学国家重点实验室,贵阳550081 [2]中国科学院大学,北京100049

出　　处：《矿物岩石地球化学通报》2020年第6期1240-1255,共16页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家重点研发计划重点专项(2016YFC0600502);南方海洋科学与工程广东省实验室重大专项项目(GML2019ZD0202);国家自然科学基金项目(41573009);中国科学院西部青年学者A类项目;贵州省科学技术基金项目(黔科合J字[2010]2033号)。

摘　　要：为厘清峨眉山大火成岩省高钛、中钛和低钛岩浆的原始岩浆组成,定量评估地幔熔融的温度、压力及部分熔融程度,采用PRIMELT3软件反演了峨眉山苦橄岩的原始岩浆成分,定量计算了地幔潜能温度(tp)、起始压力(pi)、终止压力(pf)和熔体量。结果表明,高钛苦橄岩、低钛苦橄岩的原始岩浆组分分别表现为低Al2O3、Na/Ti和高Al2O3、Na/Ti的特征。高钛苦橄岩原始熔体的地幔潜能温度较高(1 525~1 620℃),低钛和中钛苦橄岩原始熔体的地幔潜能温度相对较低(1 500~1 550℃)。高钛苦橄岩浆的熔融终止压力较高(>3 GPa),低钛和中钛苦橄岩浆的熔融终止压力相对较低(2~3 GPa)。Although a large amount of research works on the genesis of the Emeishan large igneous province have been done previously, there are still some weak points in those research works. For example, there is a lack of clear understanding on primary compositions of the high-, medium-and low-Ti magmas, and a lack of quantitative evaluation on the temperature, pressure, and degrees of partial melting of the mantle. In this study, PRIMELT3 software was used to calculate compositions of the primary melts of the Emeishan picrites, and to quantitatively calculate their mantle potential temperatures, initial melting pressures, final melting pressures, and melt fractions. The calculated results show that the primary magma compositions of the Emeishan high-Ti picrites are characterized with low Al2O3 contents and Na/Ti ratios, whereas those of the low-Ti picrites are characterized with high Al2O3 contents and Na/Ti ratios. The calculated results show that the mantle potential temperatures for the primary melts of high-Ti picrites are slightly higher(1 525-1 620℃) than those for the primary melts of low-Ti picrites(1 500-1 550 ℃). The final melting pressures of the high-Ti melts(> 3 GPa) are higher than those of the low-and intermediate-Ti melts(2-3 GPa).

关 键 词：原始岩浆 峨眉山大火成岩省 苦橄岩 地幔熔融 地幔柱 

分 类 号：P581[天文地球—岩石学]