Research and Application of Micromotional Exploration in the Middle-Lower Yangtze Metallogenic Belt of China

Xiaoqian Sun,Xinfu Li

doi:10.4236/ijg.2021.1210052

Abstract

Micromotion is the daily tiny vibration of the earth’s surface. Micromotional exploration can use the surface wave information of micro motion to study the shallow structure of underground media. In this study, we collected microtremor data at 68 stations in the Middle-Lower Yangtze Metallogenic Belt (MLYMB) and determined the resonant frequency and obtained the distribution of sedimentary thickness in this area by using H/V spectral ratio. According to the results of H/V, the sedimentary layer in the basin is thick, and the predominant frequency of the basin is 0.05 - 0.1 Hz. There are no obvious lateral changes in the impedance interface between bedrock and sedimentary layer in this area. The basement of Tongling, Anqing and Luzhou mining areas and their adjacent areas is Kongling-Dongling type basement, which is composed of a set of metamorphic core complex. The predominant frequency is 0.05 - 0.1 Hz. The sedimentary thickness gradually thinned from 3800 m in the west to 2100 m in the East. Moreover, this article used SPAC (spatial autocorrelation) method to obtain the S-wave velocity structure of the mining area near Luzong. The SPAC method reveals that the depth of the interface between the loose sediments and the volcanic rocks is about 600 m in the study area near the Luzhou mining area in the Middle-Lower Yangtze Metallogenic Belt, and the average depth of the interface between the volcanic rock section and the intrusive complex section is about 1000 m. The thickness of the intrusive rock is more than 2500 m. Tourmaline is developed in the interior of the intrusive rock, which may have better exploration value.

Highlights

The mineralization belt of the Middle-Lower Yangtze area is one of the most important mineral belts in China
The sedimentary thickness of the margin of Jianghan Basin is more than 3000 m, It shows that the thickness of the central sedimentary layer in Jianghan Basin is relatively deep
In the formation with depth greater than 1000 m, the thickness of the intrusive rock is more than 2500 m, according to the results of horizontal component to vertical component method (H/V) spectrum ratio and well logging data. In this formation, tourmaline is developed in the interior of the intrusive rock, which is distributed in black gray clumps and clusters, which may have better exploration value

Summary

Introduction

The mineralization belt of the Middle-Lower Yangtze area is one of the most important mineral belts in China. The existing drilling data in the study area is less [7], and the cost is too high compared with the H/V spectral ratio and spatial autocorrelation method. H/V spectral ratios based on microtremor signals can be used to reliably calculate the resonance frequency and thickness of surficial soft sediments [11]-[17]. Spatial autocorrelation method has been widely used to obtain the S-wave velocity structure underground [26] [27] [28] [29]. We use SPAC method to obtain the S-wave velocity structure of Luzong mining area

Geological Background and Data Collection

Spectral Autocorrelation

Results and Discussion

Conclusions