斑岩铜矿高光谱短波红外勘查模型构建研究

Hyperspectral short-wave infrared technology is a new technique which is based on spectral absorption features of altered mineral to identify their types and, in order to extract prospecting information. It is significant to research and build the exploration model of porphyry copper deposits by hyperspectral short wave infrared technology. The researching and building of exploration model are influenced by altered mineral assemblages and metallogenic elements' distribution. Whether through altered mineral assemblages features can invert the fluid migration paths and their warm pressing geological conditions of porphyry copper deposits is the key point of the hydrothermal short-wave infrared technology that can be generalized in the geology field. This project intends to use American ASD spectrometric analyzer, which combines field testing with indoor analysis, using quantitative analysis methods that combines multivariate statistics with linear and nonlinear mathematics quantitative analysis methods, and also refers to classic model analysis of porphyry copper deposits, taking Jiama porphyry-skarn copper polymetallic deposit of Tibet as an example, and taking drill cores and rocks' hyperspectral short wave infrared signature as research objects, so that explores fine altered mineral regularities of distribution of porphyry copper deposits based on hyperspectral short-wave infrared technology, in order to invert the relationships between altered mineral assemblages and migration tracks of ore-forming fluid, and then builds exploration model of porphyry copper deposits upon hyperspectral short-wave infrared technology, putting forward the norm of prospecting information filtering and evaluating of the wall rock alteration, at last expands the breadth and depth of hyperspectral short-wave infrared technology in geology field.

高光谱短波红外技术是基于蚀变矿物的光谱吸收特征识别蚀变矿物类别，提取找矿信息的新技术方法。利用高光谱短波红外技术研判和构建斑岩型铜矿床的勘查模型意义重大。勘查模型的研判和构建受蚀变矿物组合、成矿元素分布等的影响，能否通过蚀变矿物组合特征反演斑岩型铜矿床的热液流体运移路径及其温压地质条件是高光谱短波红外技术能否在地质应用中推广的关键。本项目拟使用美国ASD便携式光谱分析仪，采用野外测试与室内分析相结合、多元统计与线性、非线性数学相结合的定量分析方法，参考斑岩型铜矿床的经典模型分析，以西藏甲玛斑岩-矽卡岩型铜多金属矿为例，以岩心、岩石光谱吸收特征为研究对象，探索基于高光谱短波红外技术的斑岩型铜矿床精细蚀变矿物分布规律，反演蚀变矿物组合与成矿流体运移轨迹间的关系，构建基于高光谱短波红外技术的斑岩型铜矿床勘查模型，提出围岩蚀变找矿信息筛选与评价的准则，拓展高光谱短波红外技术地质应用的广度和深度。

采用短波红外谱段对含有羟基的蚀变矿物进行识别，通过O-H键在短波红外区间引发的振动位置、频率等可以确定蚀变矿物类别、含量等相关参数。利用短波红外勘查技术（波长范围1300-2500 nm），可测量并反演出用于指示热液成矿体系的环境参数，提供找矿线索并指导找矿，而进一步研究其典型蚀变矿物的波长变化及矿物组合，对于构建勘查模型，指导矿床的深入研究具有重要意义。. 本研究采用美国ASD便携式光谱测量仪，对西藏甲玛斑岩-矽卡岩型铜多金属矿床及多龙整装勘查区的铁格隆南矿床（荣那矿段）进行了间距为2米的钻孔短波红外测量，共实测甲玛矿床26731米、荣那矿床3464米岩心。通过对蚀变矿物的识别，确定了两个不同类型矿床的蚀变矿物组合特征；通过采用非线性数学方法进行数据降噪及增强，达到了对微量蚀变矿物识别的目的；通过多元统计数学分析，以白云母的波长变化为基础，反演了甲玛矿床的热液流体的运移途径及其温压变化特征；通过详细的蚀变矿物分布特征分析，建立了不同类型矿床的勘查模型，并以此为基础构建了基于短波红外技术的斑岩型矿床短波红外综合勘查模型。.研究结果显示：甲玛矿床具有从铁（镁）绿泥石→高岭石、蒙脱石→白云母→黑云母、石膏的蚀变矿物分布特征，这是典型的斑岩铜矿蚀变矿物分布模式。钻孔中白云母广布，具有波长与铜矿体品位之间的正相关关系，同时波长变化也显示出一定的温压、PH值环境变化规律；铁格隆南矿床（荣那矿段）具有明矾石+地开石+高岭石蚀变矿物组合特征，同时横向和纵向蚀变矿物组合特征各异，明显形成了浅成低温热液型矿床叠加于斑岩型矿床之上的特点，这对于研究该区域的构造、流体演化、深部找矿奠定了重要基础。. 该项研究提出了利用短波红外技术快速筛查找矿信息的新方法，对于找矿及勘查评价也建立了基于蚀变矿物分布、波长变化等的新准则，同时研究成果拓展了高光谱短波红外技术地质应用的广度和深度。