青海尕林格铁矿床电气石矿物学、元素地球化学及成因研究  

Mineralogy, element geochemistry and genesis of tourmaline from Galinge skarn deposit, Qinghai Province

作　　者：于淼[1,2] 丰成友[1] 刘洪川 李定武 赵一鸣[1] 李大新[1] 刘建楠[1] 王辉[1] 

机构地区：[1]中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室,北京100037 [2]北京大学地球与空间科学学院,北京100871 [3]青海省有色地质矿产勘查局地质矿产勘查院,青海西宁810007

出　　处：《矿床地质》2016年第1期69-84,共16页Mineral Deposits

基　　金：国土资源部公益性行业科研专项经费项目(编号:201411025);青海省地质勘查基金项目(编号:201304);中国地质调查局地质调查项目(编号:1212011085528);中国地质调查局高层次地质人才培养计划(编号:201309);青年地质英才计划(编号:201112)联合资助

摘　　要：尕林格矽卡岩型铁多金属矿床位于青海东昆仑祁漫塔格造山带与柴达木盆地结合带中部。电气石作为矿区内普遍出现的矿物,部分呈半自形-自形粒状出现在正接触带矽卡岩化蚀变火山岩中(Tour-Ⅰ),也有呈他形粒状形式出现在外接触带变质砂岩中(Tour-Ⅱ)。因其生长化学行为与寄主岩石和流体的化学属性强烈相关,所以电气石的主、微量元素成分为研究热液体系背景下的流体演化及成矿物质来源提供了渠道。尕林格电气石的化学成分包括富Na-Mg的镁电气石和富Ca-Mg的钙镁电气石。Tour-Ⅰ中的环带电气石存在早期核部(Gen-1)被晚期边部(Gen-2)交代的不连续反应边特征。Gen-1为钙镁电气石,而Gen-2为镁电气石。由于镁铁质火山岩的缓冲作用,Gen-1更多地显示出原地寄主岩石的化学成分。随着流体的持续补充,Gen-2则更多地与流体成分保持平衡,显示出较窄的变化范围,与成矿密切相关。Gen-1比Gen-2更加富Fe,意味着流体中Fe浓度降低;而Na含量逐渐上升则暗示流体p H值的升高。尕林格绝大部分矽卡岩电气石都是在早期成核阶段结晶生长的,因为电气石在酸性和中酸性溶液中更加稳定。除此之外,部分Tour-I中还存在沿早期电气石颗粒边缘生长的增生边结构(Gen-3)。Gen-3比Gen-1更加富Ca,推测Gen-3是在相对封闭环境下颗粒间隙溶液作用下的产物。Tour-Ⅱ则既包括钙镁电气石,又含有镁电气石。在Tour-Ⅰ中,Fe和Mg的含量变化范围较大,这与实际观测的Tour-Ⅰ围岩为镁铁质中-基性火山岩密不可分。Tour-Ⅱ比Tour-Ⅰ更加富集B、Ti、Sc、V、Cr、Ga、LREE等元素,这与B的溶解度随流体p H值的升高而升高有关。随着岩浆演化流体p H值的升高,B在相对碱性溶液中大量富集,而大部分微量元素和LREE易与挥发分结合成络合物的形式迁移,因此,B含量高的溶液中部分微量元素和稀土元素含量也会升高。The Galinge skarn iron polymetallic deposit is located in the middle of the transfer zone between the Qimantag orogen and the Qaidam Basin, and the ore district is wholly buried by the Quaternary sediments with the average thickness of 200 m. Tourmaline is ubiquitous in the Galinge deposit and occurs as idiomorphic or hypidiomorphic granular structure in the altered mafic igneous rocks（ Tour-Ⅰ）, or as xenomorphic crystals in the metasandstone（ Tour-Ⅱ）. The tourmaline compositions include the Na-Mg rich dravite and the Ca-Mg rich uvite, and show a strong dependence on the chemistry of the host-rock and the magmatic fluid. The zoning tourmalines in the Tour-I contain the discontinued reaction rims in which the early stage cores are replaced by the second rims. Paragenetically the core compositions（ Ca-rich, Na-poor uvite） of the zoning tourmaline from the different samples are distinctively different from those of the discordant reaction rims（ Na-rich, Ca-poor dravite）. Ex., the content of Na is increased from the cores to the rims, which implies that the p H values of the fluid is increased. The cores contain much more content of Fe than the rims, which suggests that the Fe concentration of the fluid is decreased. The zoning tourmalines have recorded the meaningful information from the buffering of the host rock to the ore forming process of the fluid. Gen-1 reflect the local host rock composition because of the buffering of the country rocks, and the most of the tour-I are formed at the early stage because the tourmaline is considerably more stable in the acidic solution than the alkali solution. In contrast, Gen-2, which are more in equilibrium with the fluid compositions,display a narrow range due to the continual fluid influx, and are related to the main ore-forming event. Besides, a few of the Tour-Ⅰ tourmalines have a structure of overgrowth margin（ Gen-3） whose composition is distinctively more enriched in Ca. The Fe and Mg concentrations of Tour-Ⅰ show an intense modification, w

关 键 词：地球化学 电气石 不连续反应边 微区原位分析 流体演化 尕林格 

分 类 号：P618.31[天文地球—矿床学]