Diagenesis-metallogenic System And Metallogenic Prognosis Of Late Indosinian In Jinchang-laoheishan Area, Heilongjiang

Jinchang-Laoheishan study area is part of Taipingling Gold-Copper polymetallic mineralization belt, in which Jinchang gold deposit is an important large gold deposit. In recent years, because of decreasing reserves of mineral resources of Jinchang gold deposit, to achieve ore-search breakthrough in Jinchang mining area periphery becomes an urgent matter. At present, study on this area is dispersed and lack of comprehensive research. Based on the idea of metallogenic system, combined field investigation and a series of geochemical test,the paper carried out an in-depth study in the characteristic and evolution of igneous rocks, geological features, ore-fluid geochemistry, metallogenesis and metallogenic prognosis. The main results are as follows:The characteristics of trace elements and rare earth elements of magmatic rocks are basic consistent indicating the two stages of magma have the same sources in late Late Indosinian and Yanshannian period(including volcanic rocks in Late Indosinian) in Jinchang-Laoheishan study area. In addition, the trace elements of two stages of magma are characterized by enrichment of large ion lithophile elements suggesting that magma is original from enriched mantle, and furthermore, with relatively obvious negative Nb、Ta、P、Ti anomalies,respectively indicating that the two stages of magma is hybridized with upper crust matter during the magmatic evolution.Zr/Hf and Nb/Ta of the two periods Magmatic rocks are respectively close to the range of Zr/Hf and Nb /Ta of granite evolved from the mantle, Indicating that the two periods Magmatic rocks is deep-derived.The characteristics of petrography, mineralogy and rare earth element and trace element data shows that magma in the late Indosinian epoch evolves by the fractional crystallization. The fractional crystallization controlls the mineralization category: Jiufogou gold-polymetallic deposit is dominated by intermediate sub-volcanic rocks, and Yanghuidongzi copper deposit is dominated by acid ultra-shallow insrusion rocks.Researching on the H-O isotopic data shows that ore-forming fluids of two deposits are a mixture of primary magmatic and meteoric-hydrothermal water. Moreover, the author considers that two kinds of deposit belong to porphyry deposit(Yanghuidongzi deposit) and low temperature shallow-seated hydrothemal deposit(Jiufogou deposit), respectively. Two kinds of deposits forms mineralization in different temporal and spatial framework at the same volcanic-intrusion magmatism, which composes a diagenesis-metalogenic system in Late Indosinian.According to Three-Filed metallogenic prediction theory(material field, energy field and spatial field), the author carrys out metallogenic prognosis in three prospecting potential areas: Nanshajingou, Nantianmen and Laoheishan, and get 106 level Ⅰ prediction tagets and 143 level Ⅱ prediction taget, and point out the prospecting direction.