【摘要】：北祁連東段毛藏寺鉬(銅)多金屬礦床是中國建筑材料工業(yè)地質(zhì)勘查中心甘肅總隊在進行“甘肅省天�？h毛藏寺礦區(qū)螢石礦詳查”工作過程中發(fā)現(xiàn)的。截止目前,對該礦床的研究程度較低。礦區(qū)位于北祁連加里東期造山帶東段冷龍嶺地區(qū)毛藏寺背斜的近軸部。礦體主要賦存于中奧陶統(tǒng)中堡群(O2z)變質(zhì)砂巖與似斑狀二長花崗巖體(ηγπ)的接觸部位,以接觸帶外側(cè)的礦化明顯。礦體呈似層狀、透鏡狀、脈狀平行排列。礦石呈脈狀、細脈浸染狀、斑雜狀、網(wǎng)脈狀。圍巖蝕變大致具分帶性:巖體中可粗略的分為鉀化帶、黃鐵-絹英巖化帶、青磐巖化帶;變質(zhì)砂巖中發(fā)育角巖化。礦區(qū)礦石礦物樣品S同位素δ34S測定值較集中,變化于0±3‰范圍之間,說明了硫來源于深部巖漿。不同礦物間δ34S平均值呈現(xiàn)出輝鉬礦→黃鐵礦→黃銅礦的遞減序列,與硫同位素平衡狀態(tài)下δ34S值在硫化物中遞減序列一致,可大致認為該礦床中的輝鉬礦、黃鐵礦、黃銅礦處于S同位素平衡狀態(tài)。樣品Pb同位素測定值:206Pb/204Pb比值為:18.274~19.472;207Pb/204Pb比值為:15.594~15.747;208Pb/204Pb比值為:38.397~40.096。相關(guān)圖解表明鉛來源比較復(fù)雜,可能來自巖漿并且加入了上地殼成分的混染,與造山作用有關(guān)。主成礦階段形成的石英中流體包裹體的巖相學特征與顯微測溫結(jié)果表明,原生流體包裹體可分為富液兩相包裹體、富氣兩相包裹體、含CO2三相包裹體三種類型。成礦流體為中-低溫(集中在175℃~315℃)、低鹽度(3~5wt%NaCleqv)、中密度(0.7~0.9g/cm3)的H2O-NaCI-CO2(CH4)流體體系。成礦壓力集中在15MPa~28MPa之間,對應(yīng)的成礦深度為為0.39km~1.06km,屬淺成礦床。H-O同位素測試結(jié)果表明,成礦流體主要來自于巖漿水,后期加入大氣降水的混合。與成礦作用關(guān)系密切的似斑狀二長花崗巖,為鈣堿性系列,強烈富集大離子親石元素Rb、Th、U、K,而Nb、Ta、P、Ti明顯虧損;輕稀土元素相對富集,重稀土元素相對虧損。似斑狀二長花崗巖具高Si埃達克質(zhì)巖石特征。很可能起源于俯沖洋殼部分熔融,并與地幔橄欖巖發(fā)生了一定程度的相互作用,源區(qū)主要殘留物為石榴石(±角閃石)。鋯石U-Pb測年表明賦礦巖石(似斑狀二長花崗巖)成巖年齡為(440.9±1.8)Ma,侵入時代為晚奧陶世。輝鉬礦Re-Os同位素模式年齡為(423.3±6.7)Ma,為中晚志留世,稍晚于似斑狀二長花崗巖體的形成時代(晚奧陶世)。毛藏寺鉬(銅)多金屬礦床應(yīng)屬典型的與淺成斑巖體有關(guān)的中-低溫熱液礦床。形成于晚奧陶-早志留時期北祁連洋洋殼俯沖-陸陸碰撞轉(zhuǎn)換階段洋殼的持續(xù)俯沖作用。
[Abstract]:The Mozangsi molybdenum (copper) polymetallic deposit in the eastern segment of North Qilian was discovered in the course of "detailed investigation of Fluorite deposits in Maozangsi Mining area, Tianzhu County, Gansu Province" by Gansu General team of China Building Materials Industry Geological Survey Center. So far, the degree of research on the deposit is relatively low. The mining area is located near the axis of the Maozangsi anticline in the Lenglongling area of the eastern section of the Caledonian orogenic belt in North Qilian. The orebody mainly occurs in the contact site between metamorphic sandstone and porphyry monzogranite (畏 緯 蟺) in the Middle Ordovician Zhonghu Group (O _ 2z), and the mineralization outside the contact zone is obvious. The orebodies are layered, lenticular and veined parallel. The ore is veined, variegated and reticulate. The alteration of the surrounding rock is roughly zonation: the rock mass can be roughly divided into the potash zone, the Huang Tie-sericite zone, the Qingiranlitization zone, and the keratology developed in the metamorphic sandstone. The S isotope 未 34 S values of ore samples in the mining area are concentrated and vary in the range of 0 鹵3 鈥，

本文編號：2165182