利用机载高光谱成像间接推断砷异常--对新西兰隆起和闪耀剪切带金矿勘探的启示

IF 3.4 2区 地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS
Rupsa Chakraborty , Gabor Kereszturi , Reddy Pullanagari , Dave Craw , Patricia Durance , Salman Ashraf
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引用次数: 0

摘要

在全球范围内,出露良好的矿藏非常稀少,目前潜在的富矿地点位于植被覆盖层和表土之下,这对于基于遥感的直接勘探技术来说并不理想。本研究旨在利用地下地质的地表表现,采用间接方法绘制砷(As)分布图,并将其与研究区域已知的金矿化联系起来。新西兰的Rise and Shine剪切带(RSSZ)大致属于奥塔哥片岩的一部分,其下至上部的绿色片岩岩相中蕴藏着中温金矿化。该地区有几处表层地质印记,将矿化区和非矿化区分开,但这些印记在高光谱数据中主要由地形崎岖、土壤湿度和植被(主要是草地/草丛)光谱组成。首先,使用递归特征消除法(RFE)进行波段选择。生成的波段与实地情况和对该地区的地质了解相吻合。然后,对产生的 85 个波段进一步进行正交总变异成分分析(OTVCA),将信息浓缩为 10 个波段。然后使用随机森林分类器对 OTVCA 输出进行分类,绘制出三个级别的砷浓度图(百万分之 20、百万分之 20 至 100 和百万分之 100)。潜在的高砷浓度区可能与金矿化有关。该地区的地质与土壤暴露相关,这在某些地方被分类捕获,从而提高了准确性,但也使分类分析具有挑战性。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Inferring arsenic anomalies indirectly using airborne hyperspectral imaging – Implication for gold prospecting along the Rise and Shine Shear Zone in New Zealand

Well-exposed mineral deposits are scarce at a global level and presently potential mineral-rich sites are underlying vegetation cover and topsoil, which are suboptimal for direct remote sensing based exploration techniques. This study aims to implement an indirect approach to arsenic (As) distribution mapping using the surface manifestations of the subsurface geology and link it to the known gold mineralisation in the study area. Rise and Shine Shear Zone (RSSZ) in New Zealand is broadly a part of the Otago schist hosting lower to upper green-schist facies rocks manifesting mesothermal gold mineralisation. The area has several surficial geological imprints separating mineralised and non-mineralised zones, but these are dominated by topographic ruggedness, soil moisture and vegetation (mainly grass/tussock) spectra in the hyperspectral data. Initially, a band selection using Recursive Feature Elimination (RFE) was executed. The bands generated were tallied with the field and geological understanding of the area. The resultant 85 bands were then further put through Orthogonal Total Variation Component Analysis (OTVCA) to concise the information in 10 bands. OTVCA output was then classified using Random Forest classifier to map three levels of As concentration (<20 ppm, between 20 and 100 ppm and >100 ppm). The potentially high As concentration zones are likely to be related to the gold mineralisation. The geology of the area correlates with soil exposure which is captured by the classification in some parts, this increases the accuracy but also makes the classification analysis challenging.

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来源期刊
Journal of Geochemical Exploration
Journal of Geochemical Exploration 地学-地球化学与地球物理
CiteScore
7.40
自引率
7.70%
发文量
148
审稿时长
8.1 months
期刊介绍: Journal of Geochemical Exploration is mostly dedicated to publication of original studies in exploration and environmental geochemistry and related topics. Contributions considered of prevalent interest for the journal include researches based on the application of innovative methods to: define the genesis and the evolution of mineral deposits including transfer of elements in large-scale mineralized areas. analyze complex systems at the boundaries between bio-geochemistry, metal transport and mineral accumulation. evaluate effects of historical mining activities on the surface environment. trace pollutant sources and define their fate and transport models in the near-surface and surface environments involving solid, fluid and aerial matrices. assess and quantify natural and technogenic radioactivity in the environment. determine geochemical anomalies and set baseline reference values using compositional data analysis, multivariate statistics and geo-spatial analysis. assess the impacts of anthropogenic contamination on ecosystems and human health at local and regional scale to prioritize and classify risks through deterministic and stochastic approaches. Papers dedicated to the presentation of newly developed methods in analytical geochemistry to be applied in the field or in laboratory are also within the topics of interest for the journal.
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