湘东北幕阜山−梅仙深部电性结构及其对稀有金属成矿的控制作用

Deep electrical structure and its control on rare metal mineralization of Mufu Mountain-Meixian in northeastern of Hunan Province,China

为揭示湘东北幕阜山−梅仙两大岩体之间的深部地质结构,深化岩浆构造的控矿作用认识,实现地球物理深地探测技术在伟晶岩型稀有金属矿床找矿中的应用,对经过湘东北幕阜山−梅仙矿集区的电磁测深剖面进行了处理和解释,结合地质信息推演了深部地质构造格局。频率域大地电磁探测数据阻抗张量和相位张量分解分析表明湘东北仁里矿集区在高频区(大于1 Hz)主要呈现二维构造特征;利用Swift分解和相位张量分解结果对剖面所有测点数据进行电性主轴分析,判断出剖面主要构造走向总体上呈北偏西48°~50°;针对TE、TM两个模式利用Occam反演方法分别进行了单独和联合反演,并对幕阜山−梅仙地区深部电性分布进行了地质解释。本文综合研究结果表明,幕阜山−梅仙两大岩体深部存在走向北西−南东、倾向东北的岩浆构造,此构造控制的岩脉穿插到冷家溪群中,形成一系列走向北西向、倾向南西的含稀有金属伟晶岩群。

In order to reveal the stratigraphic structure between the Mufushan-Meixian pluton in northeastern Hunan,to deepen the understanding of magmatic structure for ore control,and to realize the guidance of geophysical deep exploration technology for pegmatite rare metal deposits,the electromagnetic sounding profile in the area passing through the Mufushan-Meixian ore concentration area in northeastern Hunan was processed and interpreted,and the stratigraphic structure was deduced based on geological information.First,the impedance tensor and phase tensor decomposition analysis of the frequency domain magnetotelluric detection data reveals that the Renli ore cluster in northeastern Hunan mainly presents two-dimensional structural features in the high frequency area(greater than 1 Hz).Second,the Swift decomposition and the phase tensor decomposition result carried out the electrical principal axis analysis on the data of all the survey points of the profile,and it was judged that the main structural trend of the profile was 48°-50°west by north as a whole.Finally,the Occam inversion method was used for the TE and TM modes,respectively.Individual and joint inversions were carried out,and the deep electrical distribution in the Mufushan-Meixian area was obtained and geological interpretation was carried out.The research results show that there is a magmatic structure in the deep part of the Mufushan-Meixian pluton,which strikes the northwest-southeast and tends to the northeast.Under the activity of this structure,the rock veins perpendicular to its azimuth intersect into the Lengjiaxi Group and form a series of rare metal-bearing pegmatite groups trending northwest and leaning southwest.