介绍一种寻找隐伏岩体的好方法:岩浆热场法

隐伏岩体对于热液矿床找矿是非常重要的。寻找隐伏岩体的方法很多,其中以物探(磁法、电法、重力、地震等)方法应用得最广泛、效果最好。本文介绍的岩浆热场法,是专门寻找隐伏岩体的方法。岩浆热场法是地球物理方法的一种,它以感知温度场的差别为目的,没有多解性是它最大的优点。它以岩浆热场理论为基础,以各种能够恢复古温度场的方法为手段。能够感知岩浆热场温度的方法很多,本文介绍了其中的五种:接触变质带法、煤质和煤级法、伊利石结晶度法、牙形石色变度法和镜质体反射率法等。接触变质带是岩浆热场直接的具体的体现,传统的接触变质带范围有限(一般不超过1km)。但是,如果考虑到极低级变质作用,将大大扩展接触变质带的范围(达6~8km)。煤质和煤级是煤田地质部门应用得非常娴熟的方法,中国无烟煤分布区大多与岩浆热场有关,是隐伏岩体的良好指示剂。伊利石结晶度、牙形石色变度和镜质体反射率法是极低级变质作用研究中非常重要的三个指标。在上述各种方法中,笔者推荐镜质体反射率方法。该方法具有简单、精确、适用、经济、快速的特点。与物探方法比较,该方法有很多优点,但也有其局限性。如果能够将该方法从煤田和石油部门移植到岩石学和矿床学部门,与磁法、电法、重力法配合使用,可以提高寻找隐伏岩体的效果。

A good method for finding concealed rock: Magma-thermal field method

Concealed rock mass is important for a hydrothermal deposit prospecting. There are a lot of methods to look for concealed rock; the best of them is geophysical prospecting method(magnetic method, electric method, gravity, earthquake, etc.). Magma thermal field method is dedicated to find concealed rock. Magma thermal field method is a kind of geophysical methods, which to perceive the difference of temperature field, its biggest advantage is no multiple solution. It based on the magma thermal field theory; its means is a variety of methods to restore the ancient temperature field. This paper introduces the five of these methods, contact metamorphic zone method, coal quality and coal rank method, illite crystallinity method, conodont alteration index method and vitrinite reflectance method. Contact metamorphic zone is the concrete and direct expression of magma thermal field; the traditional contact metamorphic zone was limited(generally less than 1km). However, if considering the very low grade metamorphism, it will greatly extend the scope of the contact metamorphic zone(up to 6~8km). Coal quality and coal rank method is applied very adept in coalfield geology department. Illite crystallinity, conodont alteration index and vitrinite reflectance method is very important in the study of very low grade metamorphism. In the above methods, the author recommends the vitrinite reflectance method, which is simple, accurate, applicable, economic and fast. Compared with geophysical exploration methods, this method has many advantages, but also has its limitations. If it can be transplanted from coal and oil geology department into petrology and mineral deposits department, and couple it with magnetic method, electric method and gravity method, which can improve the effect of searching for concealed rock, advancing the prospecting practice of the deep concealed deposits.