鄂东南矿集区典型矽卡岩-斑岩矿床蚀变矿物短波红外(SWIR)光谱研究与勘查应用

鄂东南矿集区是我国著名的矽卡岩-斑岩型铜铁金矿床产区,研究程度较高,近年来矿产勘查进入了深部找矿的新阶段,需要较新的勘查方法与思路。本文介绍了利用短红外光谱(SWIR)技术,对鄂东南典型的铜绿山矽卡岩型Fe-Cu-Au矿床、鸡冠嘴矽卡岩型Cu-Au矿床、铜山口矽卡岩-斑岩型Cu-Mo-W矿床进行的蚀变矿物综合研究最新成果。在确定蚀变矿物组合类型、形成期次、蚀变分带的基础上,揭示了主要蚀变矿物SWIR特征值的指示规律,并进一步提取各个矿床的蚀变矿物SWIR勘查标志,如铜绿山矿床富Fe绿泥石(Pos2250 2253nm)、高结晶度高岭石族(Pos2170 2170nm,Dep2170 0. 18)、白云母族-蒙脱石异常Pos2200值( 2212nm或2202nm)、高岭石、迪开石及皂石的大量出现,可以作为铜绿山铜铁金矿床有效的蚀变矿物勘查标志;鸡冠嘴矿床白云母族-蒙脱石Pos2200特征值的高值( 2209nm)区域对矿体位置具有较好的指示性;铜山口矿床绿泥石的高Fe-OH吸收峰位值(Pos2250 2249nm)和高Mg-OH吸收峰位值(Pos2335 2333nm)的高频出现,可以作为铜山口铜钼钨矿床的有效勘查标志。这些研究成果表明蚀变矿物可以为鄂东南矿集区提供有效的勘查标志体系,同时,这些最新的勘查标志也在铜绿山铜铁金矿床得到了初步的应用和验证。

The short wave infrared (SWIR) spectral characteristics of alteration minerals and applications for ore exploration in the typical skarn-porphyry deposits, Edong ore district, eastern China

The Edong ore district in southeastern Hubei Province is a famous skarn-porphyry ore deposits region in China. In recent years, mineral exploration in the deep area has been paid attention, which requires new exploration methods and approaches. In this study, the latest comprehensive research results for the alteration minerals in the Tonglvshan Cu-Fe-Au skarn deposit, Jiguanzui Cu-Au skarn deposit and Tongshankou Cu-Mo-W skarn-porphyry deposit were presented, especially based on the application of the short wave infrared spectrum (SWIR). On the basis of the assemblages of alteration minerals, paragenesis and alteration zoning, trends of the main alteration mineral SWIR features were identified, and criteria for exploration were further extracted for each skarn (-porphyry) deposit. For instance, high Pos2250 values (> 2253nm) of Fe-rich chlorite, high crystallinity (Pos2170 > 2170nm, Dep2170 > 0.18) of kaolinite group, anomalous high and low Pos2200 (< 2202nm, or > 2212nm) values of white mica-montmorillonite, emerging of kaolinite, dickite and saponite, can be used as vectors towards mineralization center in the Tonglvshan Cu-Fe-Au deposit; the high Pos2200 (> 2209nm) values of white mica-montmorillonite can be used as vectors for the Jiguanzui Cu-Au deposit; and the high frequency of chlorite Pos2250 (> 2249nm) and Pos2335 (> 2333nm) can be used as vectors for the Tongshankou Cu-Mo-W deposit. The variations of SWIR spectral features of these phyllosilicate minerals are mainly related to the chemical compositions and temperature of hydrothermal fluid and surrounding rocks. The occurrences of dickite and kaolinite in the deep area at Tonglvshan indicate that the hydrothermal fluid may have experienced the evolution from high-temperature, alkaline to medium-low-temperature, intermediate-acid conditions. These research findings show that the alteration minerals can provide effective exploration indicators for the skarn-porphyry deposits in the Edong ore district, and these results have been preliminarily applied and verified in the Tonglvshan Cu-Fe-Au deposit.