(1. 中南大學(xué)有色金屬成礦預(yù)測教育部重點實驗室，長沙 410083；
2. 中南大學(xué)地球科學(xué)與信息物理學(xué)院，長沙 410083)
摘 要: 老鴉嶺銅礦床是安徽省銅陵冬瓜山礦田內(nèi)的一個矽卡巖型礦床。礦體賦存于遠離主接觸帶的下二疊統(tǒng)到下三疊統(tǒng)大理巖地層中。原生成礦過程分為矽卡巖期的早矽卡巖階段(A1)、晚矽卡巖階段(A2)、氧化物階段(A3)和熱液期的石英硫化物階段(B1)、碳酸鹽階段(B2)。包裹體巖相學(xué)分析表明：石榴子石、透輝石、石英和方解石中發(fā)育著氣液兩相包裹體(Ⅰ型)和含子礦物包裹體(Ⅱ型)。顯微測溫結(jié)果顯示：早矽卡巖階段，包裹體均一溫度為434~579 ℃或者＞600℃，鹽度連續(xù)分布在20.80%~56.70%，顯示其成礦流體具有高溫、高鹽度的特征，體系處于超高壓環(huán)境；氧化物階段，流體減壓沸騰，最低沸騰溫度為298℃，包裹體具有不均一捕獲特征，地下水的混入導(dǎo)致鹽度從59.36%到3.76%顯著變化，由于處于開放體系，受靜水壓力影響，估算成礦壓力范圍為16~37 MPa，結(jié)合上覆地層的厚度判斷成礦深度約為1.6 km；石英硫化物階段，包裹體均一溫度集中于250~350℃，鹽度在3.92%到49.22%之間；碳酸鹽階段，包裹體均一溫度為160~193℃，鹽度為2.63%~4.39%，成礦流體顯示出從高溫到低溫、從高鹽度到低鹽度、從均一到不混溶分離的演化過程。基于以上研究，推斷老鴉嶺銅礦床的成礦流體以高溫、高鹽度的巖漿流體為開端，在上侵和沿大隆組地層快速運移過程中逐漸演化，伴隨沸騰作用和兩次地下水的混入，成礦流體溫度、鹽度、壓力不斷下降，最終在青山腳背斜軸部卸載成礦。
關(guān)鍵字: 流體包裹體；成礦流體；銅礦床；成礦作用；矽卡巖
（1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals, Ministry of Education,
Central South University, Changsha 410083, China;
2. School of Geosciences and Info-Physics, Central South University, Changsha 410083, China）
Abstract:TheLaoyaling copper deposit, located at the Dongguashan mining area, Tongling, Anhui Province, China, is a skarn deposit. The orebodies are mainly located in the marble of the Lower Permain to the Lower Triassic strata, which is far from the contact zone. The primary ore-forming process is divided into skarn period and hydrothermal period. The former period can be subdivided into early skarn stage(A1), late skarn stage(A2) and oxide stage(A3), and the latter period can be subdivided into quartz sulfide stage(B1) and carbonate stage(B2). The characteristic of ore-forming fluids and mineralization were discussed by petrographical and microthermometric data of the fluid inclusion. Two types of inclusions, gas-liquid two-phase aqueous inclusions(type Ⅰ) and aqueous inclusions with daughter mineral(type Ⅱ), are hosted in garnet, diopside, quartz and calcite. The inclusions of early skarn period homogenize at temperatures of 434-579 ℃ or ＞600℃and have salinities of 20.80%-56.70%, indicating that the ore-forming fluids in this stage have the characteristics of high temperature, high salinity, and ultrahigh pressure. The oxide period, owing to the decrease of pressure, ore-forming fluids started to boil at the lowest temperature of 298℃, which shows the characteristics of heterogeneous capture of inclusions, and changes the salinity from 59.36% to 3.76% obviously by inburst of groudwater. The system is affected by the hydrostatic pressure in the open system with metallogenic pressure changing from 16 MPa to 37 MPa, together with thickness of the overly strata, the metallogenic depth is deduced to be 1.6km. The inclusions of quartz-sulfide period homogenizing at temperature of 250-350℃ have salinities of 3.92%-49.22%, and in carbonateperiod homogenizing at temperatures of 160-193℃, the inclusions have salinities of 2.64%-4.39%. The results demonstrates that the ore-forming fluids evolve from high-temperature to low-temperature, from high-salinity to low-salinity and from homogenization to immiscible separation. The ore-forming fluid is originated from different evolutional stages of the primitive fluids derived from the magmatic intrusion, and started with characteristics of high temperature and high salinity. The ore-forming components were precipitated in Qingshanjiao anticline due to twice boiling and fluid mixing as well as the decrease in salinity, temperature and pressure of the fluids.
Key words: fluid inclusion; ore-forming fluid; copper deposit; metallogenesis; skarn
