摘要
浙江天目山地区的中生代火山岩由流纹岩、英安岩、安山岩组成,其喷发存在反序现象。笔者用带状岩浆房的模式解释了该区火山岩的特点,应用各种物理化学方法建立了岩浆房中存在的温度、密度和粘度梯度。主要元素及微量元素的行为及其定量模拟表明,分离结晶是导致岩浆成分变化的主要机理。然而,各种矿物在岩浆房中的沉降速度计算表明,尤其是酸性岩浆中,晶体的重力沉降是不可能的。因此,岩浆房中存在的分离结晶现象主要是通过对分离作用进行的。
The Mesozoic volcanic suite located in the Tianmushan Mount., northwestern Zhejiang Province, China, is, in ascending order, composed of rhyolite, dacite and andesite. A model of physically and chemically zoned magmatic chamber has been used for explaining this reversed compositional sequence. Gradients of temperature, density and viscosity in the chamber have been established according to some thermodynamic methods. Modeling for major and trace elements supports the idea that fractional crystallization is a main mechanism responsible for the chemical variation. The settling velocities of observed minerals in different magmas, which are estimated from Stocks' law, indicate that gravitative settle is impossible, especially in the acid magma. Thus, convective fractionation (Huppert et al., 1988) is considered most probably to be the process accounting for the fractional crystallization in the zoned chamber.
出处
《岩石矿物学杂志》
CAS
CSCD
1991年第4期289-300,共12页
Acta Petrologica et Mineralogica
关键词
火山岩
天目山
成因
岩浆房
带状
Tianmushan, volcanic rocks, zoned magmatic chamber
