流体包裹体爆裂法在山东焦家金矿深部找矿中的潜在应用

流体包裹体爆裂法作为一种辅助找矿手段,于20世纪70—80年代曾被前苏联和中国的地质工作者用于找矿勘探实践中,并取得了一定成效。以往许多爆裂法研究表明,矿体所在部位的爆裂强度(频次)较高,而随着远离矿体进入围岩,爆裂频次逐渐降低。一般认为这是由于围绕矿体热液活动强烈和流体包裹体丰度较高所致,因而在矿床(体)及其周围形成蒸发晕正异常。通过对胶西北地区焦家蚀变岩型金矿112线和144线8个钻孔的系统采样和爆裂法测试分析发现,焦家金矿床的花岗岩围岩爆裂曲线具有高的爆裂频次、明显的爆裂峰和高的相变峰,随着围岩蚀变增强,爆裂频次、爆裂峰和相变峰从钾化带经过黄铁绢英岩化带、硅化带到金矿石呈有规律降低,在矿体(化)中心,爆裂频次很低,不显示爆裂峰和相变峰,从而围绕矿体构成蒸发晕负异常。这些爆裂特征,特别是围绕矿体的蒸发晕负异常,对于胶北地区深部金矿找矿勘探具有潜在的应用价值。

The potential application of the decrepitation method of fluid inclusions to the exploration of deep-seated gold deposits in the Jiaojia gold belt, Shandong Province

The decrepitation method of fluid inclusions was used in former Soviet Union and China in the 1970’s and 1980’s to help mineral exploration.This method can be used in combination with other measurements in mineral exploration.Previous studies of the decrepitation method have shown that the decrepitation intensity(frequency) near the ore body is high and will decrease gradually with the increasing distance from the ore body,which is believed to be caused by strong hydrothermal activity and relatively high abundance of fluid inclusions around the ore body.Hence,positive anomalies are likely to occur in/around the ore body.Samples were collected from 8 drill holes along No.112 and 144 exploratory lines in the Jiaojia gold deposit in northwestern Shandong Peninsula,and quartz separates from the samples were analyzed by DT-4 acoustic decrepitometer developed by Prof.Xie Yihan of the Institute of Geology and Geophysics,Chinese Academy of Sciences in Beijing.The results show that the unaltered granites in the Jiaojia gold deposit exhibit high decrepitation frequencies and their decrepigrams(decrepitation curves) have a pronounced peak with normal distribution in the temperature interval of ca.360～450℃ and a sharp peak at 573℃ which is the phase transition temperature of α/β-quartz.With the increase in alteration intensity,the decrepitation frequencies decrease from the K-feldspathization zone through the pyrite-phyllic alteration zone to the gold ore.The decrepigrams of gold ores in the mineralization center become weak-waved curves or nearly horizontal lines with very low decrepitation frequencies,and negative steam aureoles occur around the gold ore body.Hence the unique decrepigrams and negative steam anomalies can be applied to gold exploration in northwestern Shandong peninsula.