本文選題：水銀洞金礦 + 載金黃鐵礦　； 參考：《成都理工大學》2017年碩士論文

【摘要】：卡林型金礦是于上個世紀六十年代在美國內(nèi)華達州卡林鎮(zhèn)被首次發(fā)現(xiàn)而命名的一種金礦類型。它的特點是金以“不可見金”形式賦存于載金硫化物之中。世界范圍內(nèi)的卡林型金礦集中分布在美國內(nèi)華達州和猶他州以及我國滇黔桂、陜甘川“金三角”中。目前,我國卡林型金礦探明金儲量已超過1000噸。貴州貞豐水銀洞金礦是滇黔桂“金三角”中最具代表性的超大型卡林型金礦床,具有極其重要的經(jīng)濟價值和科學研究價值。以往的研究已經(jīng)對礦床的基礎地質(zhì)特征、金的賦存狀態(tài)、流體特征等內(nèi)容進行過詳細的探討。但由于載金礦物——黃鐵礦顆粒細小,且黃鐵礦單礦物顆粒普遍發(fā)育環(huán)帶結(jié)構(gòu),這對傳統(tǒng)的分析測試技術提出了挑戰(zhàn)。本文在對貴州貞豐水銀洞金礦野外踏勘的基礎上,通過對礦石的顯微鏡下觀察和電子探針背散射電子圖像(BSE)分析,發(fā)現(xiàn)礦石中存在草莓狀黃鐵礦、自形黃鐵礦以及半自形-它形黃鐵礦。其中后兩者普遍發(fā)育環(huán)帶結(jié)構(gòu),即圍繞成礦前形成的黃鐵礦核部生長一到兩期次熱液環(huán)帶,表明水銀洞金礦床中黃鐵礦的形成是多期次地質(zhì)事件的產(chǎn)物。Au富集在黃鐵礦的富砷環(huán)帶之中。Nano-SIMS元素面掃描分析(Mapping)顯示黃鐵礦環(huán)帶相對富集Au、As、Cu元素,而Se元素則相對富集在核部,表明成礦流體具有富Au-As-Cu、貧Se的特征。Au在核部含量極低,暗示成礦前并未發(fā)生金的預富集作用。同時,即使在同一個增生環(huán)帶中微量元素也并非完全均勻分布,環(huán)帶之中有次一級環(huán)帶發(fā)育,表明熱液流體活動具有階段性和“脈沖式”特征。電子探針成分分析表明,黃鐵礦中As含量在0~10.884wt%,平均值為2.814wt%,屬砷黃鐵礦。黃鐵礦中除了含有Fe、S、As、Au元素之外,還含有Co(0.046~0.447wt%)、Cu(0~0.252wt%)、Cr(0~0.312wt%)等微量元素。元素相關性證實As-S呈負相關關系,證明As類質(zhì)同象置換了黃鐵礦中的S。在lgAu-lgAs圖上絕大多數(shù)測點落于金溶解度曲線之下,表明金主要以晶格金(Au+)的形式賦存于載金黃鐵礦之中。黃鐵礦的Co/Ni普遍大于1,暗示了成礦流體可能來源于巖漿熱液。原位微區(qū)硫同位素測試結(jié)果顯示黃鐵礦核部的δ34S值變化范圍為1.3‰~6.5‰,而富金環(huán)帶的δ34S值為-3.5‰~7.4‰。這些硫同位素特征顯示了巖漿硫特征,暗示了載金黃鐵礦的硫主要來源于深源巖漿硫,但不排除有部分沉積硫混入的可能。對比研究發(fā)現(xiàn),水銀洞金礦載金黃鐵礦的硫同位素特征與美國內(nèi)華達州典型的卡林型金礦硫同位素類似。綜合以上研究成果,本文提出水銀洞金礦的成礦模式,即受燕山期地殼伸展作用的影響,深源中酸性巖漿分泌的含Au-As-Cu-Si-S流體沿深大斷裂上升至地殼淺部,并沿構(gòu)造薄弱帶(區(qū)域不整合面和灰家堡背斜軸部)側(cè)向運移、充填、交代富Fe碳酸鹽圍巖成礦。在這個過程中,大氣降水的下滲和淋濾也在一定程度上有利于金礦化。
[Abstract]:Carlin gold deposit was first discovered in Carlin, Nevada in the 1960s. It is characterized by the presence of gold in gold sulphides in the form of invisible gold. Carlin gold deposits in the world are concentrated in Nevada and Utah in the United States, and in the "Golden Triangle" of Yunnan, Guizhou and Guangxi in China. At present, the proven gold reserves of Carlin gold deposits in China have exceeded 1000 tons. Zhenfeng Shuiyindong gold deposit in Guizhou is the most representative super large Carlin gold deposit in the "Golden Triangle" of Yunnan, Guizhou Province, which has extremely important economic value and scientific research value. Previous studies have discussed in detail the basic geological characteristics of the deposit, the occurrence state of gold and the fluid characteristics. However, due to the small particle size of pyrite, a gold bearing mineral, and the general zonal structure of pyrite single mineral particles, it is a challenge to the traditional analytical and testing techniques. On the basis of field exploration of Shuiyindong gold deposit in Zhenfeng, Guizhou province, through microscopic observation and BSEanalysis of electron probe backscattering electron image, it is found that strawberry pyrite exists in the ore. Self-shaped pyrite and semi-automorphic-it-shaped pyrite. The latter two generally developed zonal structure, that is, one or two stages of secondary hydrothermal ring formed around the pyrite core before mineralization. It is suggested that the formation of pyrite in the Shuiyindong gold deposit is the product of multiple geological events. Au is enriched in the arsenic-rich ring zone of pyrite. Nano-Sims elemental surface scanning analysis shows that the pyrite ring zone is relatively enriched in Au-As-Cu element, while the se element is relatively enriched in the nucleus. The results show that the ore-forming fluid is rich in Au-As-Cuand, and the content of au in the nucleus is very low, indicating that there is no pre-enrichment of gold before mineralization. At the same time, even in the same proliferative zone, trace elements are not uniformly distributed, and there is a secondary ring in the belt, indicating that the hydrothermal fluid activity has the characteristics of stage and "pulse". The electron probe analysis shows that the content of as in pyrite is 10.884wtand the average value is 2.814wt.The pyrite belongs to arsenopyrite. The pyrite contains not only the element of Fe ~ (2 +) S ~ (2 +) As-Au, but also some trace elements, such as: Co-0.046 ~ 0.447 wt ~ (4) ~ 0.252 wt ~ (2) ~ (2) ~ (2) ~ (2) ~ (2) ~ (2) ~ (2) ~ (2) ~ (2) ~ (2). The element correlation confirmed the negative correlation of As-S, which proved that the isomorphism of as replaced the S in pyrite. Most of the measured points on the lgAu-lgAs diagram fall below the gold solubility curve, indicating that gold mainly exists in gold-bearing pyrite in the form of lattice gold (au). The Co/Ni of pyrite is generally greater than 1, suggesting that the ore-forming fluid may originate from magmatic hydrothermal solution. The results of in situ sulfur isotope measurements show that the 未 34S values of the pyrite core vary from 1.3 鈥，

本文編號：1811509