Combined Magnetic and Transient Electromagnetic Methods to Locate and Predict the Dislocated Concealed Orebody at the Deep Edge of Yanqianshan Iron Deposit in Anshan-Benxi Area

doi:10.19657/j.geoscience.1000-8527.2024.006

Abstract

Abstract:

It’s becoming more and more challenging to find iron ores with economic values since all iron mines on the surface have been explored. The main directions of iron prospecting turn to the concealed orebodies. In particular, locating and identification of the concealed orebodies in deep (or periphery) parts of the existing mines have become the focus and main challenges of current geophysical exploration projects. With this view, we focus our study on locating and identifying the concealed orebodies in deep (or periphery) structural faults of the existing mines by taking the concealed iron orebodies in Yanqianshan, Anshan-Benxi area as a study case. Based on the previous geology and geophysical studies, we conducted the joint detection application studies by using the ground-based high-precision magnetic method and the transient electromagnetic method, which is based on large fixed source central loop devices and multi-turn overlapping loop devices.The research findings indicate that high-precision ground magnetic methods can delineate the planar boundaries of concealed iron ore bodies, thereby narrowing down prospective mining areas. In the eastern and southwestern sectors of the Yanqianshan Mountain iron ore deposit, two mineralization prediction zones have been identified. In the eastern anomaly zone, transient electromagnetic methods were employed to locate and identify the depth and morphology of concealed iron ore bodies. Through drilling verification, a substantial concealed magnetic iron ore body with a depth of 320 to 410 meters was discovered, exhibiting a stable eastward extension and a gradual thickening trend. Based on these findings, it is inferred that the southwestern anomaly zone, exhibiting similar anomalous characteristics, holds significant exploration potential. The multi-turn overlapping loop device of the transient electromagnetic method has higher resolution than the center loop device and is more suitable for detecting and locating concealed metal ore bodies under the cap layer.

Key words: concealed ore bodies, Yanqianshan Iron Mine, construction error, high-precision magnetic me-thod, transient electromagnetism

CLC Number:

YAN Di, FU Jianfei, JIA Sanshi, CHENG Hao, WANG Zhimeng. Combined Magnetic and Transient Electromagnetic Methods to Locate and Predict the Dislocated Concealed Orebody at the Deep Edge of Yanqianshan Iron Deposit in Anshan-Benxi Area[J]. Geoscience, 2024, 38(01): 35-45.

Figures/Tables 10

Fig.1 Regional geological maps of the study area

Fig.2 Schematic geologic map showing the structures in the study area[22]

Table 1 Geophysical properties of rock ores in Yanqian-shan iron ore deposit

岩(矿) 石名称	块数	磁化率K(10^-5SI)		电阻率ρ(Ω·m)
岩(矿) 石名称	块数	范围	均值	范围	均值
磁铁矿	12	9614~25960	17747	448~3411		1722
假象赤铁矿	8	761~9529	4571	1036~7654		3277
闪长玢岩	8	6~930	229	2188~4971		3934
花岗岩	7	0.05~2	0.4	2256~6178		3500
千枚岩	10	1~17.7	5.3	796~3269		2583
石英片岩	5	0.5~0.7	0.6	1816~42908		13250

Fig.3 Schematic diagram of magnetic survey line layout for Yanqianshan iron deposit

Fig.4 Results of high-precision magnetic survey data polarity processing for Yanqianshan iron deposit

Fig.5 High precision magnetic survey data processing for Yanqianshan iron deposit

Fig.6 Magnetic anomaly field and spatial location map of ore bodies stacked at an elevation of -300 meters

Fig.7 Processing results of line g1 detection data for GDP-32

Fig.8 TerraTEM line t1 detection data processing results

Fig.9 Diagrammatic cross-section from the validation by drilling YZK1

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