Exploration Indicators of Altered Minerals of Gold Deposits in the Sanshandao Fault Zone,Jiaodong Peninsula
The Jiaodong Peninsula represents the largest gold orefield in China and ranks as the third largest globally,with orebodies predominantly controlled by fault structures.The mineralization of gold deposits within the Sanshandao fault zone exhibits variability attributable to alterations in the controlling fault structures,leading to disparities in ore body continuity and ambiguous exploration indicators.This study systematically cataloged and sampled multiple drill holes and underground tunnels along exploration line 30 in the Beibuhaiyu and Sanshandao gold deposits.Based on the paragenetic associations of minerals and the cross-cutting relationships among ore veins,the gold deposits in the northern sea area can be categorized into four distinct metallogenic stages:quartz-pyrite-potassium feldspar(stage Ⅰ),quartz-pyrite-chalcopyrite-native gold(stage Ⅱ),quartz-pyrite-galena-sphalerite-native gold(stage Ⅲ),and barren siderite-calcite(stage Ⅳ).Notably,stage Ⅱand stage Ⅲ represent the primary metallogenic phases for native gold.The analysis of ore-bearing and barren sections of controlling faults through shortwave infrared spectroscopy has demonstrated substantial differences in alteration mineral composition,Al-OH absorption peak positions,and crystallinity index(IC).Notably,elevated Pos2200 and IC values exhibit a strong positive correlation with gold mineralization.Furthermore,statistical evaluation of grade data from multiple drill holes,augmented by machine learning algorithms,underscores the significant influence of IC values.The analysis of trace elements in pyrite revealed substantial positive correlations among elements including arsenic(As),lead(Pb),bismuth(Bi),tellurium(Te),antimony(Sb),and,gold(Au).Consequently,this study has established a novel exploration indicator grounded in variations in fault attitude,shortwave infrared spectroscopy markers,and pyrite elemental,commposition.This indicator holds considerable significance for informing practical prospecting efforts.
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