浙江拔茅破火山岩浆作用:开放体系多机制复合演化  

Magmatism of Bamao caldera, Zhejiang province: Composite evolution of poly-mechanism in open system.

作　　者：薛怀民[1] 陶奎元[1] 杨祝良[1] 谢家莹[1] 谢方贵[1] 

机构地区：[1]国土资源部南京地质矿产研究所

出　　处：《岩石学报》2001年第3期403-412,共10页Acta Petrologica Sinica

基　　金：自然科学基金项目 (4 0 0 0 2 0 0 5 );国土资源部科技司自由探索项目 (2 0 0 0 40 6)资助

摘　　要：拔茅火山杂岩的成分变化范围广泛 ,包括玄武质、玄武粗安质、粗面安山质、粗面英安质、流纹英安质到流纹质和高硅流纹质岩石都有 ,它们不是由单一母岩浆演化而来 ,也不是由单一岩浆房喷发形成的 ,而是来自多种类型的岩浆房 ,并经历过复杂的演化过程 ,为开放体系多机制复合演化。其中早期双峰式基性端元是由上地幔部分熔融形成的 ,而酸性端元则是地壳物质边熔融边喷发 (分离熔融 )的结果。作为火山杂岩主体的粗面英安质岩石 ,其岩浆是在高位主岩浆房内由玄武质岩浆与流纹英安质岩浆混合形成的 ,发生混合的流纹英安质与玄武质岩浆的比例为 5 7∶ 4 3。而粗面安山质岩浆则是深部岩浆房内由玄武质岩浆分离结晶形成的。晚期侵出The Bamao volcanic complex is characterized by wide ranges in the composition including basaltic, trachy basaltic, trachyte andesitic, trachy dacitic, rhyodacitic, rhyolitic and high silica rhyolitic rocks. They did not evolved from single parental magma, and also did not extrude from single magma chamber, as came from poly types magma chamber, had undergone the processes of complex evolution, being composite evolution of poly mechanics in open system. The basic element of bimodal volcanism in early stage was formed by partical melt of upper mantle, while the acid element was the product of crust material immiscibility melt. The trachy dacitic rocks which are composed of the major part of the complex were formed by mixing of basaltic magma and rhyodacitic magma in high level major chamber. Trachyte andesitic magma was formed from basaltic magma by crystallization differentiation in deep magma chamber. The rhyodacitic dome and high silica rhyolite porphyry dike extrusion and intrusion in late stage represent major composition of high level proximate grade and its upper silica cap.

关 键 词：开放体系 复合演化 岩浆房 岩浆混合作用 拔茅破火山 火山岩 岩石学特征 

分 类 号：P588.14[天文地球—岩石学]