甘肃北山地区460金矿床植物地球化学异常形成的地学机制  

Formation Geo-mechanism of Botanogeochemical Anomaly of 460 Au Deposit in Beishan Area of Gansu

作　　者：宋慈安[1,2] 宋玮[3] 丁汝福[4] 雷良奇[1,2] 

机构地区：[1]桂林理工大学广西隐伏金属矿产勘查重点实验室,广西桂林541004 [2]桂林理工大学地球科学学院,广西桂林541004 [3]广东工业大学计算机学院,广东广州510006 [4]北京矿产地质研究院,北京100145

出　　处：《地球科学与环境学报》2016年第6期766-777,共12页Journal of Earth Sciences and Environment

基　　金：国家自然科学基金项目(41363003;40972220)

摘　　要：为探讨旱区荒漠植物地球化学异常形成的地学机制,选择甘肃北山地区460金矿床作为研究对象,进行了从基岩(矿)→覆盖层→植物的系统采样和多项目试验研究。结果表明:旱区荒漠覆盖条件下,金矿床地下水和土壤水携带的各种可溶性成分和成矿-伴生元素在外界潜在蒸发力、含水量及其变化梯度和植物吸收蒸腾等驱动力的作用下垂直向上运移;在垂向上,K、Na、Cl、Ca等元素淀积在上部,Au、Ag、Cu、Pb、Zn、As、Sb、Mo等成矿-伴生元素淀积在下部;在横向上,矿体及其上部覆盖层形成的相对氧化酸性环境形成了Au、Ag、Cu、Zn、As、Sb、Mo等元素相对高含量区,两侧基岩及其上部覆盖层形成的相对还原碱性环境形成了K、Na、Cl、Ca、Mg、Mn等元素相对高含量区;生长在矿体上部的植物吸收了较多的Au、Ag、Cu、As、Mo等元素,形成了植物地球化学异常;由于不同根深的植物吸取水分及元素的深度和基质类型不同,所以它们吸收的元素组合及含量也不相同;旱区荒漠覆盖条件下,植物地球化学异常的形成主要与地下水和土壤水将下部成矿-伴生元素搬运到上部植物根系所能达到的部位有关;不同根深的植物产生的地球化学异常元素组合、强度等特征具有一定的差异。In order to understand the formation geo-mechanism of botanogeochemical anomaly in arid desert,the samples were collected from bedrock（ore）,cover and plants of 460 Au deposit in Beishan area of Gansu,and the contents of water,pH and Eh values,element contents were measured,and the formation geo-mechanism model was built.The results show that a variety of soluble components,ore-forming and associated elements carried by groundwater and soil water move upward vertically by the action of driving forces including the external potentialevaporation,water content and its gradient,and absorption and transpiration of plants in Au deposit covered by arid desert;K,Na,Cl and Ca are vertically rich in the upper part,and the ore-forming and associated elements（Au,Ag,Cu,Pb,Zn,As,Sb and Mo,etc.）are vertically rich in the lower part;laterally,the ore body and its upper covering layers,which are relative oxydic and acidic,are relatively high content areas of Au,Ag,Cu,Zn,As,Sb and Mo,but the bilateral bedrock and its upper covering layers,which are relative reductive and alkaline,are relatively high content areas of K,Na,Cl,Ca,Mg and Mn;the plants in the upper part of the ore body absorb more elements（Au,Ag,Cu,As and Mo,etc.）,and the botanogeochemical anomaly is formed;the depths and matrix types of elements and water absorbed by plants with different depths of roots are not the same,so that the element association and contents absorbed by plants are different;the formation of botanogeochemical anomaly in arid desert is mainly related with the underground and soil waters which transport ore-forming and associated elements from the lower part to the upper part,so that the root of plant can absorb the elements;the element combination and strength of geochemical anomaly in the plants with different depths of root are different.

关 键 词：植物地球化学异常 金矿床 红沙 梭梭 地学机制 水盐运移 荒漠 甘肃 

分 类 号：P593[天文地球—地球化学]