矿物包裹体的研究在找寻斑岩铜(钼)矿床中的应用

THE INFORMATION OF THE INCLUSIONS IN THE MINERALS OF PORPHYRY COPPER (MOLYB DENUM) DEPOSIT AND ITS APPLICATION TO PROBE INTO DEPOSIT GENESIS AND PROSPECTING FOR ORE DEPOSIT

近些年来,矿物中包裹体的研究工作在揭示成岩成矿的物质来源和形成条件(特别是温度和压力)方面做出了贡献,并在国内、外已被广泛利用。但是,也有其未被全面认识的一面,如一提到矿物包裹体的研究,就常常被称为“包体测温”,当作一个方法、手段,而对其已发展成为一门新的学科——矿物包裹体学,尚未被充分认识,特别是对其在解决成岩成矿的理论和找矿工作中所起的作用,缺乏足够的重视。

The data of inclusion studies of porphyry copper (molybdenum)deposits in China, America, Russia, and Japan are summarized in the paper. On the basis of the discussion on the genesis of the deposit and the regularity of the nature of fluid inclusions in the deposit, the prerequisite and the indicator for prospecting and the foundation of evaluating the deposit are suggested.There exist three types of inclusions in minerals of porphyry copper (molyb-denum)deposit. polyphase fluid inclusion,gaseous inclusion, and liquid inclusion. The homogenization temperature of inclusions is Commonly from 400℃ to 250℃ .The salinity of inclusions is 26-62 wt%.The components in fluid inclusions involve Co2.Co.N2,Cl.F.K.Na,etc.besides H2O. 'Boiling inclusion group'is rich in host rocks and ore bodies .Polyphase fluid inclusions and gaseous inclusions are generally localized in ore bodies (especially in the shoot),the former being commonly around the interior, but the latter near the border and the contact zone. There is, in general, no copper mineralization if liquid inclusions occur in the rocks alone The inclusions with high solinity are distributed in the ore bodies. The salinity of inclusions is not less than 20 wt% even at the border of ore bodies or in the potassic altered rock zone Polyphase fluid inclusions closely related to mineralization are characterized by the existence of daughter minerals such as halite, sylvite, gypsum, pyrite, hemalite, and carbonates. When the inclusion contains only halite as daughter mineral, in general, there is no mineralization. The homogenization temperature, the salinity of inclusions,and the amount of polyphase fluid inclusions which contain daughter minerals decrease continuously from the center of porphyry or the core of ore body to the border.Ore-bearing hydrothermal solution was mainly derived from intermediate-acidie porphyry, which is proved by. the localization of ore bodies in the inner and outer contact zones of porphyryjthe gradual reduction of mineralizing temperature towards wall rocksjthe ore-bearing hydrothermal solution containing mineralizing agents such as F and Cljand the stable isotope composition of H and S. It can be infered that the elements of Cu and Mo were transported in the form of alkali halide and sulpho salt complexes in alkaline er weekly acidic hydrothermal solution.As the ore deposit is of the type of veinlet texture, and the 'boiling inclusion group'exists,it appears that ia the mineralizing terrain,tectonic movement developed frequently and the rocks fractured extensively so that the pressure decreased instantaneously, favouring the flow of the fluids and the release of the gases from the fluids. When ore-bearing solution flowed into a suitable environment, due to the falling of temperature and pressure, mixing with-ground waters, and reacting with wall rocks, the complexes dissolved so that ore minerals precipitated to form ore deposit.One of the prerequisites for the prospecting of porphyry copper (molyb-denum)deposit (ore-bearing porphyry is characterized obviously by inclusions) is the intemediate-acidic porphyry. There are three indicators for prospect-ing: ① the presence of 'boiling inclusion group', in which several kinds of daughter minerals must be included;② the high salinity of fluid inclusions(> 20wt%);③ homogenization (and decrepitation) temperature of 400℃-250℃.