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笔者通过对“秦岭地轴”伟晶岩区的野外观察和室内研究后,认为花岗伟晶岩的成因,是由深熔花岗岩浆源分异的伟晶岩浆上侵结晶形成。深熔花岗岩浆源,是由上地幔物质上升,对地壳物质交代熔融而成,在压力降低的条件下,分异出伟晶岩浆独立上侵;上侵过程中,开始熔浆在相对高温高压下,对围岩发生交代、再结晶,形成混合岩(长英质混合岩)或伟晶状花岗岩、无矿伟晶岩;随着温度压力降低,熔体的挥发分发生分馏,因内外压力差,以流渗方式迅速向低温低压地段流动,形成各种脉状伟晶岩。此阶段对围岩交代作用不明显。当温度压力降低到超临界状态时,挥发分和水从熔体中分离,向围岩中扩散,形成各种近矿围岩蚀变带,同时硅酸盐熔体迅速结晶,停止向前流动,形成各种矿化伟晶岩。
Through the field observation and laboratory study of the pegmatite area in the “Qinling axis”, the authors believe that the genesis of the granitic pegmatite is formed by invagination and crystallization of the pegmatite magmas distinguished by the deep-melt granite magma. The deep-melting granite magma originates from the rising of the upper mantle and the melting of the crustal material. Under the condition of reduced pressure, the petrogenetic differentiation of the pegmatite independently occurs. During the process of intrusion, the melting of the magma begins at relatively high temperature and pressure , The replacement and recrystallization of the surrounding rock formed mixed rock (feldspathic mixed rock) or pegmatitic granite and oreless pegmatite. With the decrease of temperature and pressure, the volatilization of the melt fractionated due to internal and external pressure Poor flow to the low temperature and low pressure flow quickly to form a variety of vein pegmatite. This stage is not obvious to explain the surrounding rock. When the temperature and pressure are reduced to the supercritical state, the volatiles and water are separated from the melt and diffuse into the surrounding rock to form various alteration zones of the ore-bearing rocks. At the same time, the silicate melt rapidly crystallizes and stops flowing forward , Forming a variety of mineralized pegmatite.