贵州碳酸盐岩风化壳中晶体石英的硅同位素组成及硅质来源探讨  

Silicon Isotopic Composition and Silica Source of Quartz Crystals in the Weathering Crusts of Carbonate Rocks,Guizhou Province

作　　者：姜立君[1,2] 王世杰[1] 刘秀明[1] 田世洪[3,4] 

机构地区：[1]中国科学院地球化学研究所环境地球化学国家重点实验室,贵阳550002 [2]中国科学院研究生院,北京100039 [3]中国地质科学院矿产资源研究所,北京100037 [4]国土资源部同位素地质开放重点实验室,北京100037

出　　处：《地球与环境》2009年第1期20-27,共8页Earth and Environment

基　　金：国家重点基础研究发展计划项目(2006CB403200);国家自然科学基金(40371012)

摘　　要：本文报道了黔北、黔东地区三个碳酸盐岩风化壳剖面中晶体石英的δ^30Si值,利用硅同位素作为示踪剂,通过分析剖面中晶体石英的硅同位素组成来判别其硅质来源。结果表明：晶体石英的δ^30Si值在0.8‰~1.7‰范围内,具有较高的同位素组成特征,与火山和热液（水）作用产物的δ^30Si值不同,结合已有的资料证明晶体石英与火山或热液（水）作用无直接关系,而是来自碳酸盐岩酸不溶物中含硅物质风化产生的硅质流体,其中以硅酸矿物风化释放的硅质流体为主。利用植物岩中Ge/Si很小的特点来验证植物作用对研究剖面中硅质流体的影响,结果表明植物作用的贡献相对较小,但在表土层植物作用的影响可能不容忽视。Reported in this paper are the δ^30Si values of quartz crystals in three weathering crusts of carbonate rocks in northernand eastern Guizhou Province. The source of silica for the quartz crystals was estimated based on their 33~Si values. The δ^30Si values of quartz crystals range from 0. 8‰ to 1.7‰, differing from those of samples resultant from volcanism and hydrothormalism. It is suggested that the source of silica can not be directly related to volcanism and hydrothermalism. The silica may have been derived from the dissolution of ＂insoluble＂ constituents in the parent rocks, mainly from feldspars and other silicate minerals. Ge/Si ratios were used to study biogenic silicon in the profiles, which suggest that except that biogenic silicon in the top soil may have little contribution to the silica source of quartz crystals in the work orofiles.

关 键 词：风化壳 晶体石英 硅同位素 硅质来源 

分 类 号：P597[天文地球—地球化学]