Study On Metallogenetic Regularities And Ore-forming Forecast Of Epithermal Gold Deposits In Wanda Mountain And Taiping Mountain Belts In Southeast Of Heilongjiang Province

Epithermal gold deposit is a very important type of gold deposit to which deposit scientists pay a lot of attention. Epithermal gold deposit is an important type of gold deposit in Heilongjiang province, and dozens of epithermal gold deposits have been found in recent years. The Wandashan--Taipingling metallogenic belt, southeastern of Heilongjiang province, has a large number of epithermal gold deposits, such as the Sipingshan gold deposit and the Sishanlinchang gold-silver deposit. This metallogenic belt has a favorable condition for regional metallogeny, and a huge potential for both ore forming and ore prospecting. The widespread neutral-acid intrusive rocks of different stages can provide ore-forming fluid, ore-forming material and thermal power for the ore forming. The large-scale nappe structure and strike-slip shear and its secondary faults are the important channel for the ore-forming transport and the location where the metallogenic material precipitate. However, the surface mulching of the study area is rather severe and therefore the work degree is low. So the metallogenic regularity of this metallogenic belt is further analyzed based on the study of metallogenic characteristics and formation mechanism of the typical deposit in this metallogenic belt. The main results are as follows:1. The Sishanlinchang gold-silver deposit is mainly composed of auriferous quartz vein type ores. It has many kinds of sulfides and high gold grade. The Au has a close correlation with As, Pb, Ag and Cu; the REEs of the deposit relatively enriched in LREEs, which have a moderate or lower negative Eu anomaly; the sulfur isotopes are single and deep seated, and the lead isotopes indicate that the plumbum is from the earth's mantle and crust, mainly from the crust; the ore-forming fluid has a temperature of 215℃-350℃and a low salinity with a mixture of characteristics of magmatic hydrothermal and meteoric water; and the ore-forming age is 111.1-111.4 Ma. The deposit is formed through the mineralization and the precipitation of the metallogenic materials caused by the mixture of the magmatic hydrothermal fluid and meteoric water.2. The gold-bearing quartzite is the main type ore of the Sipingshan gold deposit. This deposit has a low gold grade and a low content of a few types of sulfides; the Au have a close correlation with Ag, Cu, Pb, As and Hg; the upper quartzite has a middle negative anomaly of Eu, and the lower quartzite has a positive anomaly of Eu, but the hot spring cemented conglomerate and rhyolite porphyry both have a negative anomaly of Eu; the sulfur isotopes have a feature of the mixture of the deep-source sulfur and terrestrial sulfate ; and the lead isotopes indicate that the plumbum is from the earth's mantle and crust, mainly from the crust; the ore-forming fluid has a temperature of 180℃-244℃, and it contains both magmatic hydrothermal and meteoric water; and the ore-forming age is 80~120Ma. The deposit is formed by the ore-forming fluid erupting from the structural belt onto the surface of the earth, causing the occurrence of the mineralization and the precipitation of the metallogenic materials.3. Although the Sishanlinchang gold--silver deposit and Sipingshan gold deposit are both epithermal deposits, they have different output area and formation mechanism. The former is the kind of deposit that the ore-forming fluid enriches the metallogenic materials by filling and metasomatism from 1 km underground; and the latter is the kind of deposit which is formed by the ore-forming fluid erupting out of the surface as a hot spring. These two deposits are the reflection of the epithermal system mineralizing at different locations in the vertical direction.4. The epithermal deposits in Wandashan-Taipingling metallogenic belt mainly formed in five concentration areas: (1)Sipingshan-358 highland; (2) Yuejinshan-Xianfengbeishan; (3)Xiangyang-Sishanlinchang; (4) Yanghuidong-Jinchang; (5)Shendong-Dongfenggou. The centers of the first two concentration areas are mainly for gold deposits, and the surrounding and deep areas are mainly for copper-polymetallic deposits. The centers of the last three concentration areas are mainly for gold-silver deposits, and the surrounding and deep areas are mainly for copper-lead-zinc sulfide deposits. Based on the summary of the prospecting criteria and metallogenic regularity, five ore prospecting areas of epithermal gold deposit are pointed out.