变泥质岩递进部分熔融作用的构造物理学效应  

Progressive partial melting of metapelite and its tectonophysical effects

作　　者：曾令森[1] 高利娥[1] Jason B．Saleeby 

机构地区：[1]中国地质科学院地质研究所大陆动力学实验室,北京100037 [2]美国加州理工学院地质与行星科学系,加州帕萨迪纳91125

出　　处：《地质通报》2008年第12期1992-2000,共9页Geological Bulletin of China

基　　金：国家自然科学基金项目(编号:40673027);中国地质科学院科技行业业务基金项目(编号:20071120101125);中国地质调查局项目(编号:1212010610105)资助。

摘　　要：在南内华达岩基中,晚中生代花岗岩的侵位导致表壳岩广泛的变质及部分熔融,形成混合岩杂岩体。对伊萨贝拉湖南羊圈混合岩杂岩体构造的野外观测和应变测量表明:①变泥质混合岩和鹅卵石砾岩记录了类似强度的应变;②变泥质岩发生了递进部分熔融,表现为离羊圈花岗闪长岩岩体的距离越远,部分熔融程度越低;③随部分熔融程度的变化,变泥质岩的应变承载构造也逐渐从混合岩带的弱相承载构造(IWL)往强相承载构造(LBF)过渡;④在同岩浆构造作用中,浅色体的流变学性质与鹅卵石砾岩中泥质组分相当,为应变的主要承载体。该结果表明:在高级变质岩区中,部分熔融程度是否足够高及熔体能否形成互相链接的网络,是高级变质岩的流变学强度发生突降、深部岩石发生侧向流动的前提。Field observations and strain measurements on the migmatite structures in the Cretaceous petite unit and the fabric within the quartzite unit of the Isabella pendant, southern Sierra Nevada, California show that： （1） the migmatite had experienced similar magnitude of strain to that of the pebble conglomerates within the quartzite unit; （2） the Cretaceous pehte unit had undergone progressively increasing degrees of partial melting with the proximity of the Goat Ranch granodiorite; （3） and as a result, the loading framework of the Cretaceous pelite changed as a function of the distance away from the Goat Ranch pluton, e.g. from interconnected weak layer （IWL） structure to load-bearing framework （LBF） structure. This data presented here strongly support that formation of an interconnected network of melts in a partially molten rock is a critical point at which catastrophic rheology reduction can occur. Such a change would induce the collapse of an over-thickened mountain belts and lateral flow of deep crustal rocks, if relatively deep seated crustal rocks undergo progressively partial melting.

关 键 词：部分熔融 应变分解 混合岩 内华达岩基 

分 类 号：P588.22[天文地球—岩石学] P313[天文地球—地质学]