西秦岭李坝造山型金矿床围岩蚀变特征:基于高分五号02星(GF-5B)星载高光谱数据信息提取

Alteration characteristics of wall rocks in the Liba orogenic gold deposit,West Qinling:Based on information extraction from GF-5B spaceborne hyperspectral data

造山型金矿床蚀变范围广,是研究矿床热液蚀变分带的理想对象。由于距离矿体远近的差异,围岩存在不同的热液蚀变矿物组合。本文基于高分五号02星(GF-5B)星载高光谱遥感图像开展数据收集和蚀变信息提取工作,识别西秦岭李坝超大型造山型金矿床蚀变矿物组合。GF-5B高光谱遥感数据及近端光谱测量(Analytical Spectral Devices)结果表明,研究区蚀变类型主要有黄铁矿化、绢云母化、多硅白云母化、绿泥石化、碳酸盐化。依据野外实地考察、近端光谱测量调查方法验证,基于高光谱遥感提取蚀变信息结果较为准确。白云母与绿泥石短波红外光谱偏移通常与成矿过程中的温度压力条件有关,例如白云母矿物在2200nm附近的Al-OH组合吸收波长位置受矿石流体控制。本文根据2200nm附近的吸收位点将白云母矿物分为绢云母与多硅白云母矿物,二者蚀变模式对比鲜明。多硅白云母通常出现在接近矿体的围岩中,与成矿具有密切联系。绿泥石为远端蚀变,指示了成矿流体形成于酸性环境。二者均可作为示踪金矿化的理想光谱指示矿物。本文研究表明,高分02星星载AHSI高光谱数据在造山型金矿床成矿远景区预测中具有良好的应用效果和潜力。

Orogenic gold deposits have a wide range of alteration,especially for those hydrothermal-alteration-type.Due to variations in the distance from the ore body,different hydrothermal alteration mineral assemblages exist in the wall rocks.This study conducted data collection and alteration information extraction based on the GF-5B spaceborne hyperspectral remote sensing image,and identified alteration mineral assemblages of the Liba giant orogenic gold deposit in the West Qinling region.The results from the GF-5B hyperspectral remote sensing data and proximal spectral measurements(Analytical Spectral Devices)indicates that the predominant alteration types in the study area include pyrite mineralization,sericitization,phengitization,chloritization and carbonatization.Validation through field investigations and proximal wavelength measurements suggest the hyperspectral remote sensing can recognize the alteration information extration.The wavelength shift of the short-wave infrared between muscovite and chlorite is usually related to the temperature and pressure conditions in the mineralization process.For example,the absorption wavelength position of the Al-OH combination of muscovite minerals near 2200nm is controlled by the ore fluid.In this paper,based on the wavelength absorption features near 2200nm,minerals were classified into sericite and phengite.These two minerals exhibit distinct alteration patterns.Phengite typically appears in the wall rock close to the ore body and is closely associated with mineralization.Chlorite is indicative of distal alteration,pointing to an acidic environment of the mineralizing fluids.Both minerals can serve as ideal spectral indicators for tracing gold mineralization.This study verifies that High-Resolution 02 satellite s AHSI hyperspectral data has a good application effect and potential in predicting the ore-forming prospects of orogenic gold deposits.