摘要
广西原生金矿有火山岩、硫化物、石英脉、超微细粒等类型。前三种主要集中在大瑶山凸起的轴部附近;后一种分布在红水河凹陷、由古生界和中生界组成的凌云、乐业等穹窿或短轴背斜内。 广西原生金矿床必须同时具备有中酸性岩浆岩,矿源层、有利岩性和构造三个成矿条件。寒武系和三叠系是广西原生金矿的矿源层,它们的岩石金的丰度普遍高。各类型原生金矿床之内或外围往往出露或隐伏有一般是含金的中酸性岩体或次火山岩体。JY超微细粒金矿载金矿物毒砂和黄铁矿的稀土元素含量较高,并随含金量增高而提高,这两种载金矿物与含金石英斑岩岩石的稀土元素组成特征和球粒标准化分布模式一致。火山岩、硫化物、石英脉和超微细粒金矿分别受近东西向和北西向深大断裂控制。
The primary gold deposits in Guangxi can be grouped into four types: volcanic rock,sulfide, quartz vein and supermicro-grained. Among them the first three are mainly distributed at or near the axis of the Dayaoshan Rise, whereas the last one is distributed in the Lingyun and Leye Domes(or short-axial anticlines), which consist of Paleozoic and Mesozoic strata and are located in the Hongshuihe Depression.
There are three indispensable ore-forming conditions for the primary gold deposits in Guangxi: intermediate-acidic magmatic rocks, source beds, and favourable lithology and structures.
The Cambrian and Triassic strata, which are commonly high in gold abundance, form the source beds of the primary gold deposits.
Auriferous intermediate acidic or subvolcanic rock bodies are generally exposed or concealed within the primary gold deposits of various types, or in the periphery of them. Arsenopyrite and pyrite, the carriers of the JY supermicro-grained gold, contain 37.0 to 473.06 and 1 to 31.45 g/t gold respectively; both of them are high in REE, which increases with increasing amount of gold. It has been found that the REE compositions and chondrite normalized distribution pattern of these two minerals are similiar to those of the gold-bearing quartz porphyry (located 10 to 20 km away from the gold deposit).
Gold deposits of such types as volcanic rock, sulfide and quartz vein are controlled by EW-trending deep faults in the basement. The distribution of supermicro-grained gold in northwetern Guangxi is mainly related to the deep fault which goes from Lingyun through Bama to Shanglin, and to the Youjiang deep fault, both of which trend northwest.
