陕西商丹地区花岗伟晶岩型稀有金属矿产成矿规律初探
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摘要
陕西省目前发现的稀有金属矿床主要分布在秦巴地区,并且以伟晶岩型稀有金属矿产为主。其中研究程度最高的地区为北秦岭商丹伟晶岩密集区,前人研究表明该地区稀有金属主要为铷、铌(钽),其次为锂、锶、铍等;稀有金属成矿受区域构造位置、构造节理裂隙及围岩类型等条件制约。商丹地区伟晶岩型稀有金属矿产分布在北秦岭新元古代—早古生代构造带内;成矿期主要为早古生代;商丹地区内的多数伟晶岩在自身结构构造及宏观区域分布上都具有一定的分带性,都能找到伟晶岩的母岩体。通过对区内典型矿区对比研究,可知铷的矿化富集与伟晶岩的分带特征无太大的关系,与伟晶岩中的富铷长石、白云母关系较大;而其他锂、铌钽、铍等都有其独立矿物,却与分带特征息息相关,多分布在围绕母岩分异强、分布较远的边缘带中。因此母岩体特征、地质构造、岩石结构、矿物类型、蚀变、原生晕、化探重砂异常等为区内稀有金属矿的特征标志。
Rare metal deposits in Shaanxi are mainly in Qinba area,and the main metallogenic type is pegmatite type.Most of previous studies are focused on pegmatite concentrated area of Shangnan and Danfeng counties(Shangdan for short).The rare metals mineralizations in this area are mainly rubidium and niobium(tantalum),secondly lithium,strontium,beryllium,etc,and the metallogenesis of pegmatite type rare metals is controlled by the conditions of regional structural,structural joint fissures and its country rocks.The pegmatite type rare metal mineral deposits in Shangdan region are located in the southern margin of the North Qinling Orogenic belt.The mineralization period is mainly in the early Paleozoic.Most of the pegmatites in this area exhibit a certain extent of zoning features in their own structure and the regional distribution.Moreover,the parent rock of the pegmatites can be found.Through the investigation of the two typical ore deposits,it could be concluded that the mineralization and enrichment of rubidium has no relationship with the zoning characteristics of pegmatite,but it is closely related to Rb-rich feldspar and muscovite in pegmatites.While other rare metal mineral deposits including lithium,niobium,tantalum,beryllium,etc.have their own independent minerals and thus their mineralizations are closely related to the zoning characteristics,and are mostly distributed in the marginal zones or the surrounding areas of the parent rocks with strong differentiation.Thus,the characteristics of the parent rock,regional structure,rock type of host rock,mineral type,alteration,primary halo,geochemical and heavy placer mineral anomalies are the important indicators for the rare metal deposits in the Shangdan area of Shaanxi province.
Rare metal deposits in Shaanxi are mainly in Qinba area,and the main metallogenic type is pegmatite type.Most of previous studies are focused on pegmatite concentrated area of Shangnan and Danfeng counties(Shangdan for short).The rare metals mineralizations in this area are mainly rubidium and niobium(tantalum),secondly lithium,strontium,beryllium,etc,and the metallogenesis of pegmatite type rare metals is controlled by the conditions of regional structural,structural joint fissures and its country rocks.The pegmatite type rare metal mineral deposits in Shangdan region are located in the southern margin of the North Qinling Orogenic belt.The mineralization period is mainly in the early Paleozoic.Most of the pegmatites in this area exhibit a certain extent of zoning features in their own structure and the regional distribution.Moreover,the parent rock of the pegmatites can be found.Through the investigation of the two typical ore deposits,it could be concluded that the mineralization and enrichment of rubidium has no relationship with the zoning characteristics of pegmatite,but it is closely related to Rb-rich feldspar and muscovite in pegmatites.While other rare metal mineral deposits including lithium,niobium,tantalum,beryllium,etc.have their own independent minerals and thus their mineralizations are closely related to the zoning characteristics,and are mostly distributed in the marginal zones or the surrounding areas of the parent rocks with strong differentiation.Thus,the characteristics of the parent rock,regional structure,rock type of host rock,mineral type,alteration,primary halo,geochemical and heavy placer mineral anomalies are the important indicators for the rare metal deposits in the Shangdan area of Shaanxi province.
引文
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[21]郭正林,申茂德,郭旭吉,等.阿尔泰地区花岗伟晶岩稀有金属成矿机理及找矿标志浅析[J].新疆地质,2013,31(增刊):77-83.
[2]陕西省地质调查中心.中国区域地质志·陕西志[M].北京:地质出版社,2017:740-818.
[3] MENG Q R,ZHANG G W.Geologic framework and tectonic evolution of the Qinling orogen, central China[J].Tectonophysics,2000,323(3):183-196.
[4] MATTAUER M, MATTE P, MALAVIEILLE J,et al.Tectonics of the Qinling Belt:build-up and evolution of eastern Asia[J].Nature,1985,317:496-500.
[5] DONG Y,ZHANG G,NEUBAUER F,et al.Tectonic evolution of the Qinling orogen,China:Review and synthesis[J].Journal of Asian Earth Sciences,2011,41(3):213-237.
[6]RATS CHBACHER L,HACKER B R,CALVERT A,et al.Tectonics of the Qinling(Central China):tectono stratigraphy,geochronology,and deformation history[J].Tectonophysics,2003,366(1/2):1-53.
[7]XUE F,KRONER A,REISCHMANN T,et al.Palaeozoic pre-and post-collision calc-alkaline magmatism in the Qinling orogenic belt,central China,as documented by zircon ages on granitoid rocks[J].Journal of the Geological Society,1996,153(3):409-417.
[8] WU Y B,ZHENG Y F.Tectonic evolution of a composite collision orogen:An overview on the Qinling-Tongbai-Hong'anDabie–Sulu orogenic belt in central China[J].Gondwana Research,2013,23(4):1402-1428.
[9]WANG X L,ZHOU J C,WAN Y S,et al.Magmatic evolution and crustal recycling for Neoproterozoic strongly peraluminous granitoids from southern China:Hf and O isotopes in zircon[J].Earth&Planetary Science Letters,2013,366(2):71-82.
[10]LIU B X,Qi Y,WANG W,et al.Zircon U–Pb ages and O–Nd isotopic composition of basement rocks in the North Qinling Terrain,central China:evidence for provenance and evolution[J].International Journal of Earth Sciences,2013,102(8):2153-2173.
[11] WANG T,WANG X X,TIAN W,et al.North Qinling Paleozoic granite associations and their variation in space and time:Implications for orogenic processes in the orogens of central China[J].Science in China,2009,52(9):1359-1384.
[12]朱焕巧,李卫红,惠争卜,等.陕西丹凤三角地区花岗伟晶岩铀—稀有元素矿化特征及成矿作用分析[J].西北地质,2015,48(1):172-178.
[13]王江波,赖绍聪,李卫红,等.北秦岭东段宽坪岩体地质地球化学特征及其与铀成矿关系[J].地质与勘探,2015,51(1):98-107.
[14]张宗清,张国伟,刘敦一,等.秦岭造山带蛇绿岩、花岗岩和碎屑沉积岩同位素年代学和地球化学[M].北京:北京地质出版社,2016:204-337.
[15]宋公社,许锋,王明志,等.陕西丹凤地区资峪沟伟晶岩铷矿赋存状态[J].现代矿业,2015,31(10):106-109.
[16]LONDON D.The origin of primary textures in granitic pegmatites[J].The Canadian Mineralogist,2009,47:697-724.
[17]DAVID K.Teertstraetc,rubidium feldspar in granitic pegmatites[J].The Canadian Mineralogist,1998,36:483-496.
[18]陈西京,王淑荣,张秀颖,等.秦岭花岗伟晶岩基本特征或成矿作用[M].北京:地质出版社,1993:8-70.
[19]何玉良,黄岑杨.河南省卢氏地区伟晶岩型稀有金属矿成矿规律初步研究[J].科技资讯,2012,28:77-78.
[20]卢欣祥,祝朝辉,谷德敏,等.东秦岭花岗伟晶岩的基本地质矿化特征[J].地质论评,2010,56(1):21-30.
[21]郭正林,申茂德,郭旭吉,等.阿尔泰地区花岗伟晶岩稀有金属成矿机理及找矿标志浅析[J].新疆地质,2013,31(增刊):77-83.