浙江青田石的岩石学特征及成因  

Petrological Characteristics and Genesis of Qingtian Stone in Zhejiang Province

作　　者：陈延芳[1] 喻学惠[2] 蒋亮智[2] 

机构地区：[1]中国地质大学珠宝学院,北京100083 [2]中国地质大学地球科学与资源学院,北京100083

出　　处：《现代地质》2011年第3期522-530,共9页Geoscience

基　　金：国家重点基础研究发展计划项目(2009CB42100);国家自然科学基金项目(40972049)

摘　　要：青田石主要是由叶腊石等粘土矿物组成的岩石,也是由气液交代变质作用形成的次生石英岩中的一个特殊品种。基于青田石的岩相学观察以及青田石的扫描电镜、X射线物相分析及全岩化学、稀土和微量元素地球化学分析,结合野外观察与前人研究成果,对青田石的岩石学特征、青田石的矿物成分与类型划分进行详细描述,论证了中酸性火山岩气液交代变质作用与青田石的成因。研究表明,青田石的矿物组合与原岩成分、交代流体的成分及交代变质作用的条件(如温度,压力)有关;青田石的颜色、质地(品级)及其矿物成分与显微结构及其所含的微量致色离子有关。在中—新生代中酸性火山岩分布区开展详细的野外地质填图和蚀变带的划分,是寻找高品级青田石的主要方法,也是评价与鉴定青田石中需要关注的问题。Petrologically,Qingtian stone is a kind of rock comprising clay mineral of pyrophyllites,which formed by hydrothermal metasomatism and metamorphism and is a kind of secondary quartzite.The present work focuses on petrography,mineral composition and varieties of Qingtian stone,suggesting that hydrothermal metasomatism and metamorphism of intermediate-acid volcanic rocks lead to the formation of the stone.Our investigations include petrographical observations,physical and chemical characteristics,geochemical compositions,field environments and reviews of previous papers of Qingtian stone.The studies show that Qingtian stone can be classified into several types,according to its main mineral components which are closely related to its protolith,features of the hydrothermal fluid,and temperature pressure conditions.Its color and quality are closely related to the mineral component,microstructure,and color-causing cations.High quality Qingtian stone had under-gone extensive metasomatism and metamorphism,whereas others with lower quality commonly had undergone slight metasomatism and metamorphism.It is suggested that determination of alteration zone of volcanic rocks of Mesozoic and Cenozoic Era by means of geological mapping is an effective way of looking for the high quality Qingtian stone,and must be concerned in the identification and subsequent evaluation of the stone.

关 键 词：青田石 交代变质作用 次生石英岩 浙江青田县 

分 类 号：P581[天文地球—岩石学] P588.3[天文地球—地质学]