【摘要】：黃沙坪礦床是湘南地區(qū)最大的鉛鋅礦床。礦區(qū)內(nèi)巖漿活動復雜,礦化類型齊全,成礦元素多樣,是湘南地區(qū)斑巖-矽卡巖-熱液脈型Cu多金屬與W-Sn多金屬復合成礦作用的典型代表。礦區(qū)兩種巖體(石英斑巖和花崗斑巖)的成礦差異是礦區(qū)多金屬復合成礦形成的基礎(chǔ),且其較小的巖體出露卻造成礦區(qū)大規(guī)模成礦也一直備受關(guān)注,成礦物質(zhì)來源長期存在爭議。為初步查明礦區(qū)兩類成礦巖體的成礦差異原因、探討礦區(qū)成礦物質(zhì)硫的來源問題,此次分別從同位素年代學、同位素地球化學、元素地球化學及礦物微區(qū)等角度對礦區(qū)不同花崗質(zhì)巖石的年代學特征、巖石成因差異及硫同位素特征方面開展了相關(guān)研究工作。在成巖年代學方面,通過對黃沙坪礦區(qū)的不同類型花崗巖進行了系統(tǒng)的鋯石LA-ICP-MS U-Pb定年和Hf同位素組成研究顯示,英安斑巖、花崗斑巖和石英斑巖的侵位年齡分別為158.5±0.9 Ma、155.2±0.4 Ma、160.8±1.0 Ma,不同花崗質(zhì)巖石中鋯石的εHf(t)值為-3.2~-7.6,Hf同位素兩階段模式年齡為1.7~1.4Ga,即該區(qū)花崗質(zhì)巖漿主要源自中元古代的古老基底物質(zhì)部分熔融;結(jié)果表明黃沙坪礦區(qū)不同類型花崗質(zhì)巖石的鋯石年齡和Hf同位素特征表明,英安斑巖、花崗斑巖、石英斑巖可能是同源同時期不同階段巖漿演化的產(chǎn)物,與礦床成礦年齡(154~159 Ma)接近,反映其成巖成礦具有密切的時空聯(lián)系。在巖石成因與巖漿性質(zhì)方面,本文在前人研究的基礎(chǔ)上,從兩類成礦巖體的空間分布特征、巖石地球化學特征、主要特征礦物(長石、黑云母)和副礦物鋯石的微區(qū)特征等方面對比巖漿形成機制發(fā)現(xiàn),石英斑巖和花崗斑巖在空間侵位、巖漿分異演化程度和形成條件(溫度、氧逸度等)方面均存在差異。分析表明石英斑巖具有的高侵位特征、相對較高的氧逸度和較低的形成溫度可能是礦區(qū)Cu礦形成的關(guān)鍵,而高分異、還原性的高溫花崗斑巖巖漿可能是礦區(qū)W-Mo-Sn礦形成的重要原因。在成礦物質(zhì)來源方面,本次研究在已有工作的基礎(chǔ)上,對黃沙坪礦區(qū)石英斑巖和花崗斑巖進行了系統(tǒng)的全巖硫同位素分析,并與已有硫化物硫同位素數(shù)據(jù)進行了對比研究。結(jié)果顯示,礦區(qū)石英斑巖和花崗斑巖的δ34S范圍分別為+4.1‰~+7.5‰和+4.9‰~+11.4‰,與典型的S型花崗巖硫同位素組成基本一致,而明顯低于區(qū)內(nèi)礦石δ34S值(+2.3‰~+17.5‰)。綜合上述,我們認為礦區(qū)巖漿硫的同位素組成應接近或略低于花崗質(zhì)巖石全巖硫同位素組成,成礦物質(zhì)硫除部分來自巖漿外,很大程度上有地層或膏鹽層硫的加入,這可能是黃沙坪成為區(qū)域上最大鉛鋅多金屬礦床的重要原因。
[Abstract]:Huangshaping deposit is the largest lead-zinc deposit in southern Hunan. The magmatic activity in the mining area is complex, the mineralization type is complete, and the metallogenic elements are various, which is a typical representative of the composite mineralization of Cu and W-Sn in southern Hunan. The metallogenic difference between the two kinds of rock mass (quartz porphyry and granite porphyry) is the basis of the formation of multi-metal composite mineralization in the mining area, and the large-scale mineralization in the mining area has been paid more and more attention because of the emergence of its smaller rock mass. The source of metallogenic materials has long been controversial. In order to find out the reasons for the metallogenic differences between the two types of metallogenic rocks in the mining area, and to explore the source of ore-forming sulfur in the mining area, the isotopic chronology and isotopic geochemistry are respectively discussed. The chronological characteristics, genetic differences and sulfur isotopic characteristics of different granitic rocks in the mining area have been studied from the point of view of element geochemistry and mineral microarea. In the aspect of diagenetic chronology, the zircon LA-ICP-MS U-Pb dating and Hf isotopic composition of different types of granites in Huangshaping mining area have been systematically studied. The emplacement ages of granitic porphyry and quartz porphyry are 158.5 鹵0.9 Ma,155.2 鹵0.4 Ma,160.8 鹵1.0 Ma, respectively. The 蔚 Hf (t) values of zircon in different granitic rocks are-3.2 鈮，

本文編號：2484070