中国东部冰长石—绢云母型低温浅成热液金矿

中国东部许多金矿床产在中生代火山岩中,前人将其归于火山热液型矿床,作者将其划为冰长石-绢云母型低温浅成热液矿床,并讨论了其主要特征.许多产在变质岩和花岗岩中金矿过去分别归于变质热液和岩浆热液或者统称中温或中低温热液矿床,其中一部分作者也将其归于冰长石-绢云母型低温浅成热液矿床.这种矿床斑岩型金矿在空间上叠加,在国外有例子,在国内虽有争议,但有可能存在.文中讨论了美洲西部太平洋岛弧与中国东部矿床类型组合类似,但成矿时代有所差别,并从板块构造角度对比进行解释.作者强调指出,由于我国东部成矿时代老,剥蚀作用使得我们对这种矿床认识产生困难,但只要努力一定能打开找矿新思路.

ON EPITHERMAL VEIN GOLD DEPOSITS OF ADUL ARIA-SERICITE TYPE EASTERN CHINA

Epithermal" is used in the sense of general conception at present existing textural and mineralogic characteristics of shallow emplacement (less than 1 km)and predominant meteoric water at slightly higher temperatures (200-300℃) and pressures of less than a few hundred bars that were present in these deposits. Generally, the volcanic-hosted hydrothermal gold deposits are referred to epithermal deposits, which are of adularia-sericite type mostly in Eastern China except gold-copper deposits of the Chinkuashih mine, Taiwan Province, which is of acid-sulfate type. Without mineral assemblage enargite+pyrite ± covellite and hypogene alunite, and with mineral assemblage adularia- seriate, the gold deposits in Eastern China showld be assigned to adularia-seriate type and different from acid-sulfate type. The gold deposits in Eastern China are characterized by textural and mineralogic features of shallow emplacement, assemblage of chalcopyrite, galena and sphalerite, ores occurring in complex enviropnments structurally , several generations of faults or fractures in two or more directions typically, the hosted rocks of various composition and in several different compositional units within a district, ore-forming temperature of between 360-180℃ and pressures of between 230×l05-250×l05Pa, and emplacement in late Jurassic to early Cretaceous (150-94 Ma) . Some epithermal gold deposits in Eastern China are hosted by Archean metamorphic rocks and granites such as in Jinchanggouliang-Erdaogou gold camp where three gold deposits , i.e. Jinchangouliang, Erdaogou and Xiaochanggao gold deposits were hosted by Archean grneisses, Mesozok voklcani rocks and Triassic granitiod respectively, and therefore, were belonged to metamorphic hydrothermal, Volcanic hydrothermal and magmatic hydrothermal deposits respectively before. Evidence of structure, mineral assemblage, hydrothermal alteration, ore-forming temperature, salinity and constituent of ore-forming fluid, lead isotopic composition of galena., and hydrogen and oxygen isotopic composition of mineral and rock show that there are no different in genesis among them and all belong to epithermal gold deposit of adularia-sricite type. Many vein-type gold deposits in North China Platform tend to be richer in base metal (Zn, Pd, Cu), to carry more crystalline quartz than chalcedony, to be accompanied with serisitic rather than adularia-seristitic alteration, and to possess a more intimate relationship with intrusive rocks in space. All can be compared with that in Western Pacific Island Arcs. Some gold deposits of adularia-seriate type in Eastern China occur round, or above or superimposed on the stocks of mineralized porphyry , shch as Jinchanggouliang-Erdogou gold camp of Liaoning, Tuanjiegou gold deposit of, Heilongjiang and Xiaoxinancha deposit of Jilin etc. Like the gold deposits in Western America and in Western Pacific Island Arcs, the adularia-seriate type of epithermal gold deposits of easten China occur, tectonicdy, in the margin of plate under a geoloical background of compression by subduction.