| The Luoshan gold-silver deposit is situated in Dongyang City, central Zhejiang Pvovince. Tectonically, it is lacated between the Jiangshan-Shaoxing fault zone and the Lishui-Yuyao fault zone, it is also lacated in north-east of Chencai-Suichan uplift and south-east of the secondary structure Furongshan caldera. On the basis of the predecessors’ work, this paper has studied the geological characteristics, ore-forming fluid, geochemistry, metallogenic chronology and so on of the deposit, discussed the genetic types and established metallogenic model of gold-silver deposits.The deposit occurs in the Neoproterozoic basement metamorphic rocks and mixed rocks of Chencai Group, mainly controlled by NE-NEE structural fissures. The ore body mainly veinlike tends to SE and SSE, inclination 60-80°. The main ore type is quartz vein type, developmental hypothermia alteration types, such as silicification, sericite and carbonate and so on. Mining dikes widespread, there are links with the deposit space and causes closely. Mining acid intrusive rocks are peraluminous, high-K, calc-alkaline series rocks, the REE pattern enrich LREE and Eu negative anormaly is obvious, trace element spider diagram show “TNT” anormaly, characterized by island arc volcanic rocks of subduction zones, intrusive rocks provided hydrothermal metallogenic minerals and heat sourses. According to the field observation, the main metallogenic stage can be divided into three stages: pyrite-quartz stage, quartz-polymetallic sulfide stage, quartz-carbonate stage. The quartz-polymetallic sulfide stage is the main metallogenic stage of the deposit. Ore types of fluid inclusions in quartz to rich liquid inclusions, lack of CO2 and introncontaining crystal inclusion, homogenization temperature of concentrated in 140 ~ 220℃, fluid salinity 0.70~5.26%(Na Cleq), density for 0.738 ~ 0.955 g / cm3 and metallogenic pressure of 62.58 ~ 110.05 bar, metallogenic depth 0.23 ~ 0.53 km, fluid properties similar with epithermal-type, which properties are low temperature, salinity and density fluid, metallogenic fluid was based on ancient meteoric water. Ore lead isotopes in the 208Pb/204Pb-206Pb/204 Pb diagram mainly shows the orogenic belt(island arc) crust-mantle mixed lead characteristics, combined with previous data, it can be concluded into that the ore material mainly came from the metamorphic basement rocks and migmatites. Sulfur isotope characteristics show a deep source of minerals(lower crust or upper mantle). We made determination of LA-ICP-MS U-Pb isotopic age of intrusive rocks in system: diabase porphyrite diagenetic age is 129~130 Ma, diagenetic age of granite porphyry is 154.9 ± 2.9 Ma, diagenetic age of quartz porphyry is 131.2 ± 3.3 Ma, mixing rock age is 230.1 ± 2.4 Ma. According to the dikes and ore body spatial relationships and genetic relationship, we speculated metallogenic age: 129~230 Ma. The overall manifestation of the deposit is the epithermal gold-silver deposit. |
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