中天山下石炭统马鞍桥组重结晶灰岩热水沉积成因的地球化学初步分析  

PRELIMINARY GEOCHEMICAL STUDY ON HYDROTHERMAL OF THE RECRYSTALLIZED LIMESTONE HOSTED IN MA′ANAIAO FORMATION OF LOWER CARB-ONIFEROUS IN MIDDLE TIANSHAN

作　　者：张志斌[1] 李忠权[2] 李朝阳[1] 叶霖[1] 李文铅[1] 

机构地区：[1]中国科学院广州地球化学研究所 [2]成都理工大学"油气藏地质及开发工程"国家重点实验室,四川成都610059

出　　处：《矿物岩石》2007年第2期70-77,共8页Mineralogy and Petrology

基　　金：国家自然科学基金(40373005;40573002);国家973重点基础研究发展规划项目(2001CB409805)

摘　　要：中天山下石炭统马鞍桥组中段的重结晶灰岩在Al-Fe-Mn和Fe-Mn-(Cu+Co+Ni)×10图解上的坐标落在热水沉积区内,为热水沉积形成。岩石中不同程度地富集金属元素Ti,Fe,Co,Cu,Zn,Pb和热液活动性元素As,Cd,Sb,Ba,F;显示沉积介质为海水和含金属热液的混合物。重结晶灰岩和与之共生的重晶石硅质岩的稀土分配模式具有轻稀土富集,弱的负Ce异常和强正Eu异常,为典型的热水沉积物的分布模式。其(Eu/Eu*)NASC值与现代大洋热水活动区的热水溶液相当,显示重结晶灰岩和重晶石硅质岩为在浅海热水喷口附近由高温热水溶液沉积而成,高温浅海条件下海水的沸腾导致了方解石的沉淀析出。重结晶灰岩和与火山岩中亲岩浆元素Co,Ni,Fe在Co/Y-P/Y,Ni/Y-P/Y及Fe/Y-P/Y图上呈良好的线性相关,显示重结晶灰岩的形成与岩浆气液有关,表明在发生碳酸盐岩沉积时海水中混入了大量含岩浆气液的热液。该套热水沉积碳酸盐岩是灰质沉积物由岩浆喷发间歇期含岩浆气液、富含金属成分的热液与海水混合而成的热水溶液中沉积所形成。The recrystallized limestone of Lower Carboniferous in Middle Tianshan,was hosted in organic reef limestones which were interbedded between two layers of volcanic rocks in middle section of Ma＇anqiao Formation. The plot of Al-Fe-Mn and Fe-Mn-（Cu＋Co＋Ni） ×10 triangle diagrams. Shows the recrystallized limestone lies in the areas of hydrothermal sediments. These rocks are enriched in metal elements of Ti,Fe, Co, Cu, Zn and Pb and hydrothermal active elements of As, Cd, Sb, Ba and F,indicating that the hydrothermal solution from which the limestone precipitated was a mixture of sea water and metalliferous hydrothermal solution. The rare earth elements distribution patterns of these rockes and the barite-silicalite show weak negative Ce and strong positive Eu anomalies, typical patterns of hydrothermal sediments. Their （Eu/Eu^＊）NASC values are equivalent to hydrothermal solutions in modern oceanic hydrothermal active area. It is suggested that the recrystallized limestone and barite-silicalite were precipitated from shallow sea hyperthermal solution near the hydrothermal vents by seawater boiling. The linear correlations of recrystallized limestone with the adjacent volcanic rocks on Co/Y-P/Y, Ni/Y-P/Y and Fe/Y-P/Y suggest that the formation of the limestone have some relations to magmatic gas. This hydrothermal carbonate suite was deposited from the mixed hydrothermal solution of seawater and the hydrothermal solution full of metal elements and magmatic gas, during the magmatic eruption interval.

关 键 词：中天山 下石炭统 马鞍桥组 热水沉积 

分 类 号：P588.2[天文地球—岩石学]