本文選題：矽卡巖礦物 + 金的賦存狀態(tài)　； 參考：《中國地質(zhì)大學(xué)(北京)》2017年碩士論文

【摘要】：云南保山黑牛凹金礦床位于三江造山帶西側(cè),核桃坪礦集區(qū)西北側(cè)的一個金礦床。構(gòu)造位置為保山-永德褶皺束北段的核桃坪復(fù)式背斜核部,礦床主要受近南北向的F12、F3、F4次級斷層控制。礦體呈脈狀、似層狀賦存于上寒武統(tǒng)核桃坪組上段的構(gòu)造破碎帶及石英硫化物脈中。本文依據(jù)野外礦體穿插關(guān)系與鏡下觀測礦物共生關(guān)系,將金礦床成礦分為早期矽卡巖化階段、退化蝕變階段、石英-硫化物階段、石英-碳酸鹽化階段等四個階段。區(qū)內(nèi)早期矽卡巖礦物主要為石榴石、輝石,屬于鈣質(zhì)矽卡巖,分布較少。其中,石榴石主要為鈣鐵榴石-鈣鋁榴石系列,石榴石環(huán)帶中元素組分變化顯示,成礦環(huán)境由弱氧化、偏堿性環(huán)境→中酸性、偏還原環(huán)境。輝石為鈣鐵輝石,閃石族礦物為陽起石、鐵閃石、鐵陽起石、綠泥石等。綠泥石以鐵鎂綠泥石為主,形成于250℃~330℃,相對還原環(huán)境。黑牛凹金礦礦體中的金主要有以下3種賦存狀態(tài):(1)呈粒間金的形式與石英、磁黃鐵礦共生;(2)呈包裹金包裹于石英或硫化物中,載金礦物為石英、磁黃鐵礦和毒砂;(3)呈納米級自然金(Au0)的形式存在于黃鐵礦、閃鋅礦、磁黃鐵礦、毒砂等載金礦物中。對成礦前到成礦后3個階段的石英、方解石中的包裹體進行測溫,溫度變化范圍為:260-320℃、190-270℃、170-250℃,成礦溫度逐漸降低。主成礦階段的溫度變化范圍為230-280℃,平均為257℃,說明金礦結(jié)晶沉淀的溫度較低,為中溫環(huán)境。成礦各階段的流體鹽度變化較大,沸騰作用強烈,CO2的溢出作用隨著成礦作用進行逐漸減弱。隨著CO2的溢出,溶液pH值變高,加之溫度、壓力的下降,導(dǎo)致硫金絡(luò)合物穩(wěn)定性下降,可能是金的主要富集機制。礦區(qū)同位素結(jié)果表明:δDV-SMOW變化范圍是-132‰~-109‰,平均為-114.4‰;δ18O水值為1.89‰~3.79‰,平均為2.60‰,表明其成礦熱液可能來源于深部巖漿水與大氣降水的混合。δ13CV-PDB變化范圍為-3‰~1.5‰,平均-2.53‰,碳質(zhì)主要來源于深源巖漿,部分碳來源于碳酸鹽巖的熱解作。δ34SV-CDT的變化范圍為-0.9‰~2.7‰,平均為1.02‰,δ34S值的分布范圍很窄,集中在0±1‰,2-3‰之間,與核桃坪、金廠河鉛鋅礦中硫同位素總體分布范圍基本一致,反應(yīng)了成礦物質(zhì)主要來自于深部流體,可能與中酸性巖漿密切相關(guān)。
[Abstract]:The HeiNiuao gold deposit in Baoshan Yunnan is located in the west side of the Sanjiang orogenic belt and a gold deposit in the northwestern side of the Juzuping ore concentration area. The tectonic location is the Juzuping complex anticline in the northern segment of Baoshan-Yongde fold bundle, and the deposit is mainly controlled by the near north-south F12F3F4 secondary fault. The orebody is veined and stratiform in the structural fracture zone and quartz sulphide vein of the upper member of the Upper Cambrian Juzuping formation. Based on the relationship between the intercalation of ore bodies in the field and the mineral symbiosis observed under the microscope, the mineralization of gold deposits is divided into four stages: early skarn stage, degenerative alteration stage, quartz sulphide stage, quartz carbonization stage. The early skarn minerals in the area are mainly garnet and pyroxene, which belong to calcareous skarn. Among them, garnet is mainly composed of calcium iron garnet and calcium aluminite series. The change of element composition in garnet ring shows that the ore-forming environment is weakly oxidized, the alkalinity environment is slightly acidic, and the partial reduction environment is partial. Pyroxene is calcium ferroxene, amphibole group minerals are actinolite, iron amphibole, iron actinite, chlorite and so on. Chlorite is mainly iron and magnesium chlorite, formed at 250 鈩，

本文編號：1808361