| 南岭某些与锡多金属矿床有关的花岗岩体的稀土元素地球化学及其成因 |
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| 引用本文：.1987.Ree Geochemistry And Origin Of Some Granite Bodies Related To Tin Polymetallic Deposits In Nanling Region[J].Mineral Deposits,6(4):11~22 |
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| 中文摘要:南岭地区锡多金属矿床是由锡、铜、铅、锌、金、银（有时伴有铁、钨、钼）等成矿元素组合而成的，它分布比较广泛，是区内最重要的锡矿矿床类型。该类型矿床，与由钨、锡，铌，钽、铍（稀土）等成矿元素组合的矿床一样，常与酸性花岗岩体伴生在一起，因而长期以来中外许多矿床学家一直认为硅铝壳富锡带深熔作用形成的含锡花岗岩浆是原生锡矿（包括锡多金属矿床）的唯一来源。即其成因上与陆壳改造型（系列I、s型）花岗岩有关。本文根据区内与锡多金属矿床有关的花岗岩体的地质一地球化学特征的研究，并运用岩石中稀土元素定量模式的计算，首次提出区内与锡多金属矿床有关的花岗岩体是下部地壳玄武-安山质岩石和少量硅铝质岩石部分熔融，再经一定程度分离结晶作用演化后派生的酸性岩浆的产物。 |
| 中文关键词:锡多金属矿床 含矿花岗岩 稀土元素 岩石部分熔融 岩浆分离结晶作用 |
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| Ree Geochemistry And Origin Of Some Granite Bodies Related To Tin Polymetallic Deposits In Nanling Region |
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| Abstract:The tin-polymetallic deposits under discussion constitute the most important type of tin deposits in Nanling region. Many researchers both at home and abroad consider this type of tin deposits to be products of differentiation and evolution of the granitic magma formed by remelting of substances of continental crust and to be genetically related to the transformation type (series I, S-type) of granitoids. In this paper, the geological setting: petrology and REE geochemistry of tin polymetal-bearing granitic intrisive bodies have been dealt with in comparison with those of the granitoids associated with the copper (molybdenuin, tunrsten) polymetallic deposits and the tungsten-tin (niobium, tantalum) deposits in Nanling region. 1. The tin polymetallic deposits and their related granitic intrusive bodies are mainly distributed in some deep fault belts and in the coastal volcanic belt of southeast China. In the areas (or zones) where these deposits and their related granitic rocks are distributed, the granitic bodies are accompanied frequently by intermediate-acid intrusive bodies and/or their related copper (molybdenum, tungsten) polymetallic deposits. They show obvious evolutionary features in time and in geochemistry of such trace elements as tin and copper. 2. The intrusive bodies related to tin polymetallic deposits and tungsten, tin, niobium and tantalum deposits are unexceptionally granites; nevertheless, different kinds of ore-bearing intrusive bodies have different contents of some main rock-forming elements and trace elements. For example, the content of T1O2+MgO in the tin polymetallic granitic body is much higher than that in W, Sn, Nb, Ta-bearing granitic body, with the average value being 0.86% and 0.4% respectively. The biotite in the former body is rich in MgO (5-8%) and poor in Li2O (0.2-0.4%) while that in the latter is rich in Li2O (0.5-2%), Al2O3 and poor in MgO (<5%). 3. The chondrite-normalized REE patterns of the intermediate-acid rocks related to the copper (molybenum, tungsten) polymetallic deposits all show rightward sharply declining curves, suggesting an obvious enrichment of LREE and weak Eu anomalies (δEu=0.57-0.93). Genetically, granitoids of this type may be connected with partial melting of pre-existing intermediate-basic volcanic rocks in the lower crust. 4. The REE patterns of granitic rocks related to tin polymetallic mineralization are rightward declining curves with remarkable negative Eu anomalies (δEu=0.3-0.5) or slightly leftward declining V-shaped curves with extremely distinct negative Eu anomalies (δEu<0.1). The REE patterns of these kinds of ore-bearing granitoid indicate that with the advance of the differentiation, the REE concentration increases while δEu and LREE/HREE values decrease. 5. From the calculation of quantitative model for REE, it is obvious that the chondrite-normalized REE pattern of the melt resulting from 40-50% fractional crytallization of the initial melt represented approximately by Qiuba Subdacite porphyry (with the lowest value of REE) related to the copper (molybdenum, tungsten) polymetallic deposit is similar to that of Huangniushan medium-coarse-grained porphyritic biotite granite related to tin polymetallic mineralization. In view of the foregoing points, we may suggest that the tin polymetallic deposits and their related granitoids in Nanling region are probably the products of differentiation and evolution of acidic magma resulting from the partial-melting and fractional crystallization of pre-existing intermediate-basic volcanic rocks in lower crust. |
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