云南省金宝山基性—超基性杂岩体特征及找矿远景

发布时间：2018-10-10 17:00

【摘要】：云南省弥渡县金宝山铂钯矿是我国最大的独立铂族元素矿床,其矿床成因类型属典型的岩浆熔离型铜镍硫化物铂族元素矿床,该矿床主要赋存于金宝山基性-超基性杂岩体内,因此,对金宝山基性-超基性杂岩体的深入研究具有重要的理论意义和实际意义。金宝山杂岩体大地构造位于扬子地台西南缘,其西距哀牢山构造带不到5km。本文在野外区域地质调查、矿区地质调查、岩体实测地质剖面及系统的岩矿样品采集的基础上,结合室内镜下光薄片鉴定、电子探针分析、地球化学分析及SHRIMP锆石U-Pb测年等方法对金宝山基性-超基性杂岩体的岩体特征进行了深入研究。研究认为,金宝山杂岩体整体蚀变强烈,岩石类型主要包括基性岩和超基性岩两大类,基性岩主要为蚀变辉长岩和辉绿岩,超基性岩主要为辉石橄榄岩。铂族元素主要赋存于超基性岩中,而基性岩内几乎不含矿,因此本文侧重对金宝山杂岩体中的超基性岩进行了重点研究。金宝山超基性辉石橄榄岩矿物组成主要为橄榄石和斜方辉石,且以贵橄榄石(Fo分子百分数在84~86之间)和古铜辉石(En分子百分数在83~89之间)为主,其次为钙镁橄榄石、单斜辉石、透辉石、铬铁矿、角闪石、黑云母等,由于岩体蚀变强烈,岩体内还发育大量的叶蛇纹石、纤蛇纹石等。金宝山超基性岩主量元素分析结果显示,SiO2含量32.5%~40.52%,MgO含量29.95%~36.32%,TFeO含量7.31%~20.19%,Al2O3含量1.41%~5.90%,TiO2含量0.36%~1.53%,P2O5含量0.03%~0.17%,CaO含量0.14%~5.05%,K2O含量0.05%~0.22%,Na2O含量0.01%~0.51%,MnO含量0.09%~0.20%,m/f比值为3.06~5.98,属铁质超镁铁岩,主量元素特征显示杂岩体属亚碱性大陆拉斑玄武岩系列。岩石的固结指数(SI)56.87%~82.81%,镁铁指数(MF)16.79%~43.00%。其中不含矿的辉石橄榄岩与含矿的辉石橄榄岩相比,岩石的固结指数(SI)偏小,镁铁指数(MF)偏大。金宝山超基性岩稀土元素分析结果显示,岩体中稀土含量总体较高,其中LREE含量15.36×10-6~37.77×10-6,HREE含量2.32×10-6~4.86×10-6,轻重稀土Σw(Ce)/Σw(Y)比值为4.35~7.97,稀土元素配分图呈明显的右倾型,反映了岩浆作用晚期发生了较强烈的分馏作用。金宝山超基性岩δEu比值为0.43~1.11,平均比值为0.74,稀土元素配分图显示铕亏损明显,反映金宝山杂岩体负铕异常特征明显。[w(La)/w(Sm)]N比值为1.70~3.32,指示其岩浆来源为富集型地幔。微量元素分析结果显示,杂岩体中强不相容元素如Rb、U、Th、Ta、Nb、La、Ce等相对于弱不相容元素如Zr、Hf、Sm、Ti、Y、Yb、Lu等明显富集,而K、Ba、P、Y、Yb亏损明显,Sr亏损强烈,主要是斜长石的结晶分异造成。Nb/La比值为0.47~1.21,Nb/Ce比值为0.21~0.51,Lu/Yb比值为0.10~0.18,Zr/Hf比值为24.00~39.78,Nb/Ta比值为5.99~29.08,与原始地幔和MORB的相应比值对比差距较大,指示地壳混染程度较强。金宝山杂岩体形成时代约260Ma,原始岩浆上侵过程中遭受了地壳物质同化混染,并促进硫化物发生熔离。铂族元素硫化物矿物主要赋存于海绵陨铁构造、浸染状构造等岩浆熔离阶段形成的矿石中,因此岩浆熔离作用是导致铂族元素富集成矿的重要因素。金宝山超基性岩岩性为古铜辉石橄榄岩,且Fo与En相近,岩石含矿性总体较好。金宝山矿床中的铂族元素主要以硫化物形式赋存在岩体中,而超基性岩中MgO的含量特征显示其属高温无硫化物系列,岩体中硫化物含量较少,因此金宝山超基性岩中的铂族元素品位较低。金宝山杂岩体以西及哀牢山以东的德苴一带发育晚二叠世的中-基性火山岩带,带内玄武岩属于大陆拉斑玄武岩系列,与金宝山杂岩体地球化学特征一致,该火山岩带形成于晚二叠世哀牢山洋壳向西俯冲而诱发的后侧扬子地台边缘发生伸展作用所形成的扬子地台边缘裂陷槽,金宝山杂岩体微量元素特征显示金宝山基性-超基性杂岩体产于活动大陆边缘内的裂谷活动。因此,金宝山基性-超基性杂岩体与该陆缘裂陷槽具有成因上的关系。结合杂岩体的产状,本文认为其岩浆通道可能位于其西北侧的德苴中-基性火山岩带内。本文提出在金宝山矿区周围仍然具有较大的找矿潜力,同时金宝山杂岩体的岩浆通道与德苴裂陷槽有关,因此,在德苴一带仍有较大的找矿潜力。
[Abstract]:The gold polymetallic deposit is the largest independent platinum group in China, and its genetic type belongs to a typical magma-melting copper-nickel sulfide platinum family element deposit. It is of great theoretical significance and practical significance for the in-depth study of the Jinshajiang-super-rare-earth complex rock mass. The tectonics of the gold-bearing complex is located in the southwest margin of the Yangtze platform, and its west-to-west distance is less than 5km. On the basis of field geological survey, geological survey of mining area, geological profile of rock mass and sample collection of rock ore, combined with the identification of optical sheet under indoor mirror, electron probe analysis, Geochemical analysis and SHRIMP-U-Pb dating methods have been used to deeply study the characteristics of rock mass of the Jinshajiang-ultra-large-scale complex rock mass. According to the study, the rock type mainly consists of basic rock and ultrabasic rock, and the ultrabasic rock is mainly pyroxene peridotite. The platinum group element is mainly in the ultrabasic rock mass, while the basic rock salt contains little ore. Therefore, this paper focuses on the ultra-basic rock mass in the gold-bearing complex rock mass. The composition of peridotite peridotite is mainly olivine and orthopyroxene, and is mainly olivine and orthopyroxene, and is mainly composed of forsterite (the percentage of Fo molecule is between 84 and 86) and antique copper pyroxene (between 83 ~ 89%), followed by forsterite, pyroxene, diopside and chrome iron ore. hornblende, hornblende, etc., due to the strong rock alteration, the rock mass also develops a large number of leaves and the like, and so on. The results show that the content of SiO2 is 32. 5% ~ 40. 52%, MgO content 29. 95% ~ 36. 32%, TFeO content 7. 31% ~ 20. 19%, Al2O3 content 1. 41% ~ 5. 90%, TiO2 content 0. 36% ~ 1. 53%, P2O5 content 0. 03% ~ 0. 22%, Na2O content 0. 01% ~ 0. 51%, MnO content 0. 09% ~ 0. 20% and m/ f ratio of 3.06 ~ 5.98. It belongs to the iron-ultramafic-iron rock, and the main quantity elemental features show that the mixed rock mass belongs to the sub-basic continental tholeiite series. The consolidation index (SI) of rocks is 56. 87% ~ 82. 81%, and the magnesium iron index (MF) is 16. 79% ~ 43. 00%. The consolidation index (SI) of rock is too small, and the magnesium iron index (MF) is larger than that of pyroxene peridotite containing ore. The rare earth element analysis results show that the content of rare earth in rock mass is high, and the content of LREE is 15. 36% 10-6 ~ 37. 77% 10-6, the content of HREE is 2. 32% 10-6 ~ 4.86% 10-6, the ratio of light weight rare earth element w (Ce)/ ww (Y) is 4.35 ~ 7.97, rare earth element distribution diagram shows obvious right inclination. It reflects a strong fractionation effect in the late stage of magmatism. The ratio of the ratio of the ultra-base rare earth elements to the gold was 0. 43 ~ 1. 11, the average ratio was 0. 74. The distribution of rare earth elements showed a significant loss, which reflected the abnormal characteristics of the negative geochemical anomalies of the gold-bearing complex.[w (La)/ w (Sm)] N ratio is 1. 70 ~ 3.32, indicating that its magma source is enriched uranium deposit. The results of trace element analysis show that the strongly incompatible elements such as Rb, U, Th, Ta, Nb, La, Ce, etc. are obviously enriched with respect to weak incompatible elements such as Zr, Hf, Sm, Ti, Y, Yb, Lu, etc., while K, Ba, P, Y, Yb loss are obvious, Sr loss is strong, It is mainly caused by the crystallization of plagioclase. The ratio of Nb/ La is 0. 47 ~ 1. 21, the ratio of Nb/ Ce is 0. 21 ~ 0. 51, the ratio of Lu/ Yb is 0. 10 ~ 0. 18, the ratio of Zr/ Hf is 24. 00 ~ 39. 78, the ratio of Nb/ Ta is 5. 99 ~ 29. 08, and the corresponding ratio of Nb/ La is 5. 99 ~ 29. 08. In the age of 2260Ma in the formation of the gold-bearing complex rock mass, the original magma was subjected to assimilation and dyeing of the earth's crust during the invasion of the original magma and promoted the melting and separation of the sulfide. The platinum group element sulfide minerals are mainly hosted in the ore which is formed by the magmatism, disseminated structure and the like, so that the magmatism is an important factor in the enrichment and mineralization of platinum group elements. The lithology of the ultrabasic rocks of the gold deposit is the peridotite peridotite, and the Fo is close to the rock, and the rock content is generally better. The platinum group elements in the gold ore deposit are mainly in the form of sulfide in the rock mass, while the content of MgO in the ultrabasic rocks shows that it belongs to the high-temperature no-sulfide series, and the sulfide content in the rock mass is low, so that the grade of the platinum group in the gold-gold ore deposit is lower. The Mesozoic-Permian volcanic belt developed in the Late Permian in the area east of the Jinshao complex, west of the rock mass, belongs to the continental tholeiite series and is consistent with the geochemical characteristics of the gold-bearing heterorock. The volcanic belt is formed on the edge of the Yangtze platform formed by the extensional action of the late Permian Woraoshan oceanic crust to the west, and the margin of the Yangtze platform formed by the extension effect. The trace elements of the gold-bearing complex are characterized by the rift activity in the margin of the active continental margin. Therefore, the relationship between the gold and the super-small complex rock mass and the trough of the continental margin is found to have a genetic relationship. In combination with the occurrence of a complex rock mass, this paper holds that the magma passage may be located in the Carboniferous-Permian volcanic belt in the northwest side of the rock mass. This paper puts forward that there is still a large prospecting potential around the gold mining area, while the magma channel of the gold-bearing hybrid rock is related to the Defaultrift trough. Therefore, there is still a large prospecting potential in the area of Dejiang.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.12;P618.53

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