摘要:
斯弄多银(金)-铅-锌矿床是冈底斯南缘林子宗群火山岩中发现的首例低硫化浅成低温热液型矿床,其发现对于完善区域成矿系列,开拓区域找矿方向都具有重要的意义.本文采用遥感技术与短波红外技术相结合的方法,通过三维建模重现了地表-地下的蚀变矿物组合,形成了星-空-地一体化的三维蚀变填图.本文采用多光谱遥感ASTER数据提取了地表围岩蚀变信息,通过遥感波段比值算法的铁染指数(b2+b3)/b1、镁羟基指数(b6+b9)/(b7+b8)、铝羟基指数(b5/b8)+(b6/b9)分别圈定了矿区地表含有Fe3+、Fe2+,Al-OH和Mg-OH等基团的蚀变矿物信息;采用短波红外技术提取了岩心中的绢云母、蒙脱石和伊利石等矿物,并确定了地下的蚀变矿物组合.研究表明,(1)地表蚀变中的Al-OH蚀变信息与钻孔中绢云母的分布非常吻合,遥感的Al-OH信息可作为重要的找矿线索;(2)根据地下蚀变矿物的种类分布,能够确定地表铁染蚀变矿物主要表现为大量褐铁矿化(野外特征明显)、少量黄钾铁矾及绢云母;(3)绢云母形成环境的不同导致其二八面体结构发生变化:AlⅥAlⅣ?MgⅥSiⅣ和Fe?Mg,是Mg-OH基团与Al-OH信息在地表部分叠合的重要原因;(4)钻孔中伊利石反射光谱特征参数计算表明,伊利石结晶度(SWIR-IC)在钻孔中呈规律性变化,近矿部位SWIR-IC(1.1~1.4)值域较低,说明伊利石形成温度较低,可能是黏土矿物成岩过程中蒙脱石向伊利石的转化递进反应,远矿段SWIR-IC(1.6~2.1)值域较高,说明该矿物较近矿段而言形成温度相对较高,是绢云母伊利石化的具体反映.
Abstract:
The Sinongduo Ag (Au)-Pb-Zn deposit is the first low-sulfidation epithermal deposit discovered in the volcanic rocks of the Linzizong Group on the southern margin of Gangdise. This discovery is of great significance for perfecting the regional metallogenic series and expanding the regional prospecting. The authors used the method of remote sensing technology and shortwave infrared technology to reproduce the surface-underground alteration mineral assemblage by 3D modeling and form a three-dimensional alteration map of star-air-ground integration. The extraction of surface alteration mineral features was based on multi - spectral remote sensing ASTER data, whereas iron index (b2+b3)/b1, magnesium hydroxyl index (b6+b9)/(b7+b8), and aluminum hydroxyl index (b5/b8)+(b6/b9) were used to extract the mineral information of Fe3+, Fe2 +, Al-OH and Mg-OH groups on the surface of the mine. For underground alteration mineral information extraction, the authors used short-wave infrared technology, spectral matching, decoupling and other methods to extract the alteration information of the core minerals sericite, montmorillonite and illite. According to the characteristics of subsurface alteration mineral assemblage, some conclusions have been reached: (1) It is found that the Al-OH alteration on the surface is consistent with the underground sericite, and hence the remote sensing Al-OH information can be used as an important prospecting clue. (2) According to the distribution of underground alteration minerals, it is possible to determine the fact that the alteration of iron minerals on the surface is mainly manifested as a large amount of limonite mineralization (obvious field characteristics) and a small amount of jarosite and sericite. (3) The formation of sericite causes a change of its octahedral structure: AlⅥAlⅣ?MgⅥSiⅣ and Fe?Mg, which is an important reason for the superposition of Mg-OH groups upon Al-OH information on the surface. (4) The calculation of the characteristic parameters of illite in the drill hole shows that the crystallinity of illite (SWIR-IC) exhibits regular changes in the drill hole: that is, the SWIR-IC (1.1 ~ 1.4) in the near-mine area is lower, and the formation temperature of the illite is lower, indicating that it is probable that the conversion of montmorillonite to illite in the process of diagenesis of clay minerals is progressive, thus the SWIR-IC (1.6 ~ 2.1) is higher in the distant part, and the formation temperature of the illite is lower, indicating that the formation of the mineral in terms of relatively high temperature is relatively high, which is the specific reflection of sericite.
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