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| Comprehensive application of borehole log data of the Pulang copper deposit, Yunnan Province |
YANG Chao-Yi1,2( ), ZHU Qian-Kun1,2, JIE Shao-Peng3, KONG Chui-Ai1,2, SHA You-Cai1,2, ZHONG Zhi-Yong1,2, SHEN Qi-Wu1,2, CHEN Zhi-Jun2,4, MA Huo-Lin2,3() |
1. Yunnan Diqing Non-ferrous Metal Co., Ltd., Shangri-La 674400, China
2. Practical Teaching and Innovative Talents Training Base in the Pulang Copper Deposit, Shangri-La 674400, China
3. Institute of Geophysics and Geomatics, China University of Geosciences (Wuhan), Wuhan 430074, China
4. School of Earth Sciences, China University of Geosciences (Wuhan), Wuhan 430074, China |
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Abstract The copper mineralized bodies and orebodies of the Pulang copper deposit in Yunnan Province are mainly distributed in the Pulang complex porphyry body and were formed through complex multi-stage development. This study aims to detail the geophysical response and fractures of copper reservoirs and provide detailed orebody characteristics, fractures, and horizon burial depth to be referenced in the exploration and exploitation of the Pulang copper deposit. First, the borehole-log data in the Pulang copper deposit were sampled for comprehensive evaluation. Then, in combination with the drilling reports and data on partial core samples, this study analyzed the log response characteristics and fractures and identified the lithology of the Pulang copper deposit using mathematical statistics, three-dimensional cross plots, convolutional neural networks (CNNs), and fracture parameter calculation. The log response characteristics of the three major strata of quartz monzonite porphyries, quartz diorite porphyrites, and hornstones in the study area are as follows. The hornstone strata have relatively high resistivity, followed by the quartz diorite porphyrite strata and the quartz monzonite porphyry strata in sequence. The resistivity decreases significantly at the intervals with fractures occurring or at the relatively fractured intervals. The quartz monzonite porphyry strata have a relatively high charge rate (polarization rate) of up to about 10%. The hornstone strata have relatively high radioactive intensity than the quartz diorite porphyrite strata and the quartz monzonite porphyry strata. CNNs were used to identify and analyze the lithology of the three major types of strata based on log data, with an accuracy rate of 97.94%. Finally, this study identified fractures in these strata using dual laterolog data. The resistivity significantly decreases at intervals with fractures occurring and differs greatly between deep and shallow lateral resistivity. The quartz monzonite porphyry strata with a high copper grade have relatively low resistivity and relatively well-developed high-angle fractures. The results of this study are of significance for the identification of ore body characteristics and the exploitation of ore bodies in the Pulang copper deposit.
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Received: 23 March 2022
Published: 24 February 2023
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Corresponding Authors:
MA Huo-Lin
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Tectonic and geological map of the study area(modified from reference[10])
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Comprehensive logging results of well ZK18XX
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The logging curves of quartz diorite porphyrite, quartz monzonite porphyry and hornstone formation
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Three-dimensional cross plot of three logging parameters and copper grade for three lithological formations
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| 岩性 | 自然伽马/API | Ma/% | RD/(Ω·m) | w(Cu)/% | | 分布范围(平均值) | 分布范围(平均值) | 分布范围(平均值) | 分布范围(平均值) | 石英二
长斑岩 | 31~203(135) | 1.9~10.1(4.1) | 204~2931(1223) | 0.3~1.2(0.42) | 石英闪
长玢岩 | 107~219(159) | 0.9~3.9(2.8) | 1302~3901(2015) | 0.33~0.39(0.36) | | 角岩 | 116~238(173) | 2.3~4.7(3.1) | 1537~5972(3180) | 0.32~0.52(0.39) |
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Characteristics of logging response and copper grade parameters for three lithologies
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Convolutional neural network structure schematic
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| 岩性 | CAL/cm | GR/API | RD/(Ω·m) | RS/(Ω·m) | Ma/% | w(40K)/% | w(232Th)/10-6 | w(238U)/10-6 | Label | | 角岩 | 8.4 | 195.3 | 5343.6 | 2122.7 | 4.5 | 2.9 | 12.4 | 5.6 | 0 | | 8.4 | 201.2 | 5343.6 | 2182.5 | 4.7 | 3.1 | 18.8 | 9.1 | 0 | | 8.4 | 170.2 | 5000.0 | 2182.5 | 4.7 | 2.1 | 13.0 | 10.4 | 0 | | 8.3 | 175.3 | 4638.3 | 2302.5 | 4.6 | 4.5 | 0.3 | 8.9 | 0 | | 8.5 | 194.8 | 4638.3 | 2405.9 | 4.3 | 1.8 | 31.3 | 8.5 | 0 | | 8.6 | 198.3 | 4810.1 | 2405.9 | 4.3 | 1.9 | 26.8 | 1.0 | 0 | | 8.4 | 190.6 | 5972.9 | 2270.1 | 4.5 | 5.2 | 9.9 | 11.0 | 0 | | 8.5 | 201.5 | 5972.9 | 2256.6 | 4.3 | 3.0 | 1.3 | 25.9 | 0 | | 8.4 | 187.6 | 4710.3 | 2256.6 | 4.3 | 0.7 | 15.2 | 11.2 | 0 | | 8.4 | 175.9 | 4227.2 | 1883.8 | 4.1 | 8.5 | 9.9 | 1.1 | 0 | | 石英二长斑岩 | 7.7 | 100.5 | 300.1 | 116.7 | 8.2 | 1.7 | 7.5 | 3.4 | 1 | | 7.7 | 98.6 | 300.1 | 116.7 | 9.0 | 1.4 | 8.3 | 2.8 | 1 | | 7.7 | 100.5 | 269.5 | 130.7 | 9.0 | 1.4 | 5.7 | 2.6 | 1 | | 7.7 | 106.2 | 269.5 | 130.7 | 9.0 | 1.4 | 5.1 | 3.3 | 1 | | 7.7 | 106.2 | 256.6 | 112.6 | 7.3 | 1.8 | 4.9 | 6.7 | 1 | | 7.7 | 104.3 | 346.4 | 229.7 | 7.0 | 2.2 | 6.1 | 5.5 | 1 | | 7.7 | 104.3 | 287.6 | 241.9 | 6.2 | 2.5 | 6.8 | 4.7 | 1 | | 7.7 | 108.1 | 287.6 | 241.9 | 6.2 | 2.8 | 10.6 | 4.1 | 1 | | 7.7 | 100.5 | 244.7 | 222.7 | 4.6 | 3.3 | 11.9 | 7.0 | 1 | | 7.7 | 98.6 | 244.7 | 222.7 | 4.6 | 2.2 | 6.1 | 6.4 | 1 | | 石英闪长玢岩 | 9.7 | 147.2 | 2301.8 | 1237.4 | 3.2 | 3.5 | 1.6 | 14.1 | 2 | | 9.9 | 161.8 | 2167.1 | 1348.2 | 3.5 | 3.4 | 4.8 | 3.5 | 2 | | 9.8 | 178.8 | 2117.9 | 1385.7 | 3.6 | 3.2 | 2.8 | 12.7 | 2 | | 9.7 | 140.8 | 1988.1 | 1495.9 | 3.4 | 3.9 | 2.6 | 4.8 | 2 | | 9.9 | 148.5 | 1899.8 | 1514.2 | 3.3 | 3.8 | 14.4 | 0.5 | 2 | | 9.8 | 157.6 | 1783.3 | 1548.3 | 3.2 | 1.5 | 14.7 | 6.4 | 2 | | 9.9 | 161.9 | 1745.4 | 1622.9 | 3.2 | 4.7 | 11.8 | 2.1 | 2 | | 9.8 | 210.4 | 1717.8 | 1686.4 | 3.1 | 1.9 | 3.2 | 15.0 | 2 | | 9.8 | 134.5 | 1699.8 | 1828.1 | 3.1 | 3.9 | 13.1 | 5.7 | 2 | | 9.8 | 171.4 | 1691.3 | 1910.7 | 3.0 | 5.4 | 25.6 | 5.8 | 2 |
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CNN training sample set partial data
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| 真实类别 | 预测类别 | | 角岩 | 石英二长斑岩 | 石英闪长玢岩 | 总计 | | 角岩 | 296 | 2 | 2 | 300 | | 石英二长斑岩 | 0 | 306 | 3 | 309 | | 石英闪长玢岩 | 7 | 5 | 300 | 312 | | 总计 | 303 | 313 | 305 | 921 |
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CNN confusion matrix for lithology prediction
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Cross plot of Y value and fracture dip angle
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| Y值范围 | 裂隙类型 | 倾角范
围/(°) | 判断
点数 | 判断正
确点数 | 判断正
确率/% | | Y≤0.3 | 低角度缝 | 0~30 | 20 | 14 | 70.0 | | 0.3<Y≤0.5 | 倾斜裂缝 | 30~60 | 15 | 13 | 86.7 | | Y>0.5 | 高角度缝 | 60~90 | 22 | 19 | 86.4 |
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Statistical table for judging fracture type by Y value
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| 倾角范围/(°) | 频数/条 | 占比/% | | 0~15 | 3 | 0.76 | | 15~30 | 31 | 7.81 | | 30~45 | 56 | 14.11 | | 45~60 | 65 | 16.37 | | 60~75 | 143 | 36.02 | | 75~90 | 99 | 24.94 | | 总计 | 397 | 100 |
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Dip Angle data of ZK18XX ore-bearing veins
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Cross plot of Wl and fracture dip angle
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Cross plot of Wh and fracture dip angle
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