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黄金科学技术, 2020, 28(6): 812-824 doi: 10.11872/j.issn.1005-2518.2020.06.088

矿产勘查与资源评价

辽宁二道沟金矿床黄铁矿热电性特征及深部找矿预测

温佳伟,1,2, 史鹏亮1, 刘彦兵1, 张静,2, 屈海浪1, 李元申1, 胡博心1, 缪广1

1.北京金有地质勘查有限责任公司,北京 100011

2.中国地质大学(北京)地球科学与资源学院,北京 100083

Thermoelectric Characteristics of Pyrite and Deep Prospecting Prediction in Erdaogou Gold Deposit, Liaoning Province

WEN Jiawei,1,2, SHI Pengliang1, LIU Yanbing1, ZHANG Jing,2, QU Hailang1, LI Yuanshen1, HU Boxin1, MIAO Guang1

1.Beijing Jinyou Geological Exploration Co. ,Ltd. ,Beijing 100011,China

2.School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China

通讯作者: 张静(1977-),女,河南焦作人,教授,从事矿床学研究工作。zhangjing@cugb.edu.cn

收稿日期: 2020-05-12   修回日期: 2020-06-09   网络出版日期: 2021-01-29

基金资助: 中国黄金集团有限公司地质科研项目“内蒙古金厂沟梁—辽宁二道沟金矿田成矿系统研究及找矿预测”.  WKY201701

Received: 2020-05-12   Revised: 2020-06-09   Online: 2021-01-29

作者简介 About authors

温佳伟(1996-),男,内蒙古乌兰察布人,硕士研究生,从事矿物学、岩石学和矿床学研究工作1938464236@qq.com , E-mail:1938464236@qq.com

摘要

辽宁二道沟金矿为赋存在中生代陆相火山岩中的岩浆热液型矿床,矿脉严格受构造控制。为了预测1号和3号脉深部的延伸规模、成矿环境和矿化情况,通过系统采集分析450~-305 m大部分中段的黄铁矿样品,对成矿温度、剥蚀率、黄铁矿热电性、热电性参数(XNP)均值以及P型黄铁矿不同标高的出现率和离散度进行了研究。结果表明:1号和3号脉成矿温度集中在130~280 ℃之间,属于中低温热液矿床;1号和3号脉剥蚀率等值线向深部分别为低值区和高值区,且均未封闭,热电导型分别以P型、P-N型和P-N型、N-P型为主,在-305 m中段深部XNP均值分别为83.33(矿脉上部)和-8(矿脉中部),在-215 m中段深部P型黄铁矿出现率分别增加和减少,综合说明-305 m中段分别处于1号脉的中上部和3号脉的中部偏下位置,1号脉深部延伸较大,3号脉深部仍有部分延伸;在1号脉-215 m中段深部金的成矿环境逐渐稳定且矿化很好,在3号脉-260 m中段深部金的成矿环境由动荡转为稳定且矿化较好。

关键词: 黄铁矿 ; 热电性特征 ; 剥蚀率 ; 离散度 ; 成矿温度 ; P型黄铁矿出现率

Abstract

Erdaogou gold deposit is a magmatic-hydrothermal deposit hosted in continental volcanic rocks in Liaoning Province,its orebodies are strictly controlled by structures.Predecessors have done a lot of research on the genesis of Erdaogou gold deposit in Liaoning,and carried out a lot of exploration and prospecting work in the mining area, and found some new veins, but the deep prospecting prediction of some mined veins are relatively weak.After years of mining and production, the mine urgently needs to increase resource reserves to maintain development. At present, the control length of No.1 and No.3 veins are about 680 m, while the control length of No. 5-1 vein on the west has reached 1 600 m,and the deep part of No.1 and No.3 veins may still have a certain scale extension.At present,except for the deep prospecting prediction by using the thermoelectricity of pyrite at the middle section of the 250 m to -215 m depth of the No.3 vein, the systematic research on the No.1 and No.3 veins have not been carried out.In order to predict the extension,metallogenic environment and mineralization of No.1 and No.3 veins,this paper systematically studied the thermoelectric characteristics of pyrite,ore-forming temperature,veins denudation rate,XNP mean and the occurrence rate of different elevations of P-type pyrite of the samples at the 450 m to -305 m depth.The results show that the ore-forming temperatures of No.1 and No.3 veins are 130~280 ℃,which belong to medium-low temperature hydrothermal deposits.The average denudation rates of No.1 vein is 45.89%,the contour of denudation rate becomes a low value area to the deep and is not closed,the thermoelectric conductive types is mainly P type, P-N type and mean value of XNP at the -305 m depth is 83.33(upper part of vein),the occurrence rate of P-type pyrite at the middle section of -215 m increases. The average denudation rates of No.3 vein is 50%.The contour of denudation rate becomes a high value area and is not completely closed,the thermoelectric conductive types is mainly P-N type and N-P type,mean value of XNP at the -305 m depth is -8(middle part of vein),the occurrence rate of P-type pyrite in the middle section of -215 m decreases,which show the middle section of -305 m is the middle and upper part of No.1 vein and the lower part of No.3 vein.The deep part of No.1 vein extends greatly,while the No.3 vein still extends partly to the depth.The metallogenic environment of No.1 vein is gradually stable and greatly mine-ralized at the -215 m depth,but the metallogenic environment of No.3 vein changes from turbulent to stable and mineralization is better at the -260 m depth.

Keywords: pyrite ; thermoelectric characteristics ; denudation rate ; dispersion ; ore-forming temperature ; occurrence rate of P-type pyrite

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温佳伟, 史鹏亮, 刘彦兵, 张静, 屈海浪, 李元申, 胡博心, 缪广. 辽宁二道沟金矿床黄铁矿热电性特征及深部找矿预测[J]. 黄金科学技术, 2020, 28(6): 812-824 doi:10.11872/j.issn.1005-2518.2020.06.088

WEN Jiawei, SHI Pengliang, LIU Yanbing, ZHANG Jing, QU Hailang, LI Yuanshen, HU Boxin, MIAO Guang. Thermoelectric Characteristics of Pyrite and Deep Prospecting Prediction in Erdaogou Gold Deposit, Liaoning Province[J]. Gold Science and Technology, 2020, 28(6): 812-824 doi:10.11872/j.issn.1005-2518.2020.06.088

辽宁二道沟金矿位于华北克拉通北缘,北部紧临兴蒙造山带。前人对辽宁二道沟金矿床成因展开了较多研究,基本确定了流体和成矿物质来源于深部壳幔混源岩浆,与对面沟岩体有关1-4,成矿年龄为中生代早白垩世,形成于燕山晚期岩石圈减薄环境35-7,为受构造裂隙控制的岩浆热液型矿床2-3。内蒙古金厂沟梁—辽宁二道沟矿集区属于燕辽成矿带,估测该成矿带内金资源储量有200~500 t,金厂沟梁金矿为大型金矿,而与其相邻5 km的二道沟金矿却为中型矿床8-10。2个金矿床均形成于中生代,Pb同位素显示矿质来源具有一致性和深源性9,成矿均与燕山运动晚期板内岩浆活动及其构造体制转化关系密切79,矿床规模却相差较大,二道沟金矿1号和3号脉目前的开采深度达875 m。

黄铁矿是热液金矿床矿化阶段的主要产物11。高振敏等12统计了102个金矿床,其中85%的金矿床以黄铁矿为主要载金矿物。自20世纪80年代起,我国学者开始将黄铁矿热电性研究应用于金矿床深部找矿预测中并取得了良好效果13-16。前人对二道沟金矿深部找矿预测方面的研究比较薄弱,已有研究主要有:徐万臣等17通过研究二道沟金矿区其他矿脉黄铁矿标型特征,提出了黄铁矿找矿标志;李志国等18通过黄铁矿激光拉曼特征,预测得到3号脉深部存在成矿空间;王鹏等19利用黄铁矿热电性对3号脉500 m以浅部分进行预测。除上述研究之外,对二道沟金矿1号和3号脉的系统性研究工作比较缺乏,在一定程度上制约了二道沟金矿深部找矿工作。

基于此,本文采集了二道沟金矿床1号和3号脉450~-305 m大部分中段的黄铁矿样品,系统测试了黄铁矿热电性,分析了成矿温度、剥蚀率、热电性参数(XNP)、离散度和P型黄铁矿出现率随标高的变化趋势,在此基础上探讨了矿体的延伸、成矿环境及矿化情况,为该区进一步找矿工作提供理论依据。

1 区域地质背景

二道沟金矿位于华北克拉通北缘的努鲁儿虎隆起带上20,被NE向北票—承德断裂和近EW向赤峰—开源深大断裂带所围限(图1)。矿区内还发育有多条NE向次级断裂,将该区划分为多条拗陷带和构造—岩浆隆起带。区域范围内出露的基底地层主要为太古宇建平群变质岩,呈NEE-SWW向分布在努鲁儿虎隆起带花岗岩的两侧2721,中生界侏罗系陆相火山岩主要分布在隆起带东南部、西部和西北部的拗陷盆地中。区域内金矿床分布具有NE向成串的特征,均位于或紧临老变质岩系,虽然成矿时代不同,但主要形成于中生代且集中在140 Ma前后,与燕山期多次构造岩浆活动有关6-79。区域内金矿床的产出环境、成矿条件和赋矿围岩等虽存在明显差异,但均属于同成矿构造期的产物,与进入中生代以后华北克拉通经历构造热液活化及岩石圈破坏有关922

图1

图1   二道沟金矿区域地质简图[图(a)据文献[4]修改;图(b)据文献[20]修改]

1.华力西期或燕山期花岗岩;2.太古宙变质岩;3.震旦系地层;4.晚古生代地层;5.新生代、中生代地层;6.主要断裂;7.主要金矿点;8.研究区

Fig.1   Regional geological map of the Erdaogou gold deposit[Fig.(a) modified after reference[4];Fig.(b) modified after reference[20]]


2 矿区及矿床地质

2.1 矿区地质

矿区内地层主要为太古宇角闪岩相变质岩系和中生界侏罗系流纹岩、火山爆破角砾岩、火山熔结角砾岩和火山碎屑岩等陆相火山岩,变质岩系分布在矿区的北西部。矿区主要侵入岩有娄上岩体、西台子岩体和对面沟岩体(图2)。矿区主要分布有NW、NE和近EW向3组断裂,矿脉整体沿对面沟岩体呈放射状分布,产于岩体侵位时形成的环状、放射状构造裂隙或接触带37923。二道沟金矿矿脉主要呈NW和近EW向展布,NW向矿脉集中分布在矿区中部,典型矿脉有1号、3号、5号和5-1号脉,位于对面沟岩体的东侧,呈左旋分布特征。

图2

图2   二道沟金矿矿区地质简图(据文献[5]修改)

1.太古宙斜长角闪岩;2.中生代火山岩;3.华力西期斑状花岗岩;4.燕山期斑状花岗闪长岩;5.燕山期花岗闪长岩;6.中生代闪长岩;7.主要断裂;8.矿脉;9.辽宁二道沟采矿权范围

Fig.2   Geological map of the Erdaogou gold deposit(modified after reference[5])


2.2 矿床地质特征

二道沟金矿NW向矿脉总体为陡倾斜,倾角为70°~80°,矿脉长度多数大于500 m。1号和3号脉在剖面上常表现为平行脉和分支复合,赋矿围岩主要有流纹岩和火山碎屑岩(图3)。1号脉倾向50°~55°,倾角为78°~80°,矿脉厚度较薄,金品位较好。3号脉倾向55°,倾角为75°~80°,矿脉厚度较薄,往深部金品位变差,矿体厚度变薄。

图3

图3   二道沟金矿4号勘探线剖面简图

1.矿脉;2.流纹岩;3.英安岩;4.凝灰岩;5.火山碎屑岩

Fig.3   Profile of No.4 exploration line in the Erdaogou gold deposit


1号和3号脉为含金石英脉型矿化,矿石矿物主要有黄铁矿、黄铜矿、方铅矿、闪锌矿、黝铜矿和银金矿等;脉石矿物以石英为主,其次为绢云母、方解石和绿泥石等。矿区矿石结构以自形—半自形粒状、碎裂和他形粒状为主,其次为交代残余、交代熔蚀、反应边、固溶体分离和包含结构。矿石构造以块状、角砾状、浸染状、团块状和细脉状为主。

根据矿脉和不同矿化组合的野外穿插关系,将热液成矿期划分为3个阶段,从早到晚依次为石英—黄铁矿阶段(Ⅰ阶段)、金—石英—黄铁矿—多金属硫化物阶段(Ⅱ阶段)和碳酸盐阶段(Ⅲ阶段)。Ⅰ阶段矿石金含量低,形成的黄铁矿颗粒粗大,呈稀疏浸染状分布在矿脉两侧的围岩中,以发育立方体晶型为主[图4(a)];Ⅱ阶段主要形成半自形黄铁矿或黄铜矿、闪锌矿和方铅矿等多金属硫化物,金的富集与该阶段黄铁矿密切相关,本次所测样品均采自该成矿阶段,黄铁矿晶型以五角十二面体及其聚形为主,占所测样品的90%左右,镜下可见呈五边形的切面[图4(b)、4(c)];Ⅲ阶段可见方解石脉切穿含矿石英脉,含金性差[图4(d)]。

图4

图4   二道沟金矿成矿阶段划分

(a)石英脉中分布黄铁矿颗粒;(b)石英硫化物矿石;(c)他形粒状黄铁矿,少数为半自形结构;(d)方解石脉切穿石英多金属硫化物脉Py-黄铁矿;Au-金;Sp-闪锌矿;Gn-方铅矿;Qz-石英;Cal-方解石

Fig.4   Division of metallogenic stages of Erdaogou gold deposit


3 黄铁矿样品采集及测试结果

1号和3号脉目前已从570 m中段开采至-305 m中段,由于矿脉为薄脉状,在各中段沿矿脉每隔40 m进行取样。根据巷道的实际情况,对450~ -305 m大部分中段进行了采样工作,部分中段由于巷道坍塌无法取样或取样数较少。本次采集1号和3号脉黄铁矿样品分别为48件和44件,碎样后在双目镜下从每件样品中挑选出20粒满足测试条件的黄铁矿颗粒进行热电性测试,每件样品测试2次。本次测试工作在北京航空航天大学生产的BHTE-06型热电系数测量仪上完成,主要参数设置:冷端温度(30.0±1)°C,热端温度(60.0±3)℃,控制活化温度在(30.0±0.5)°C 。测试结果见表1表2

表1   1号脉黄铁矿热电系数α值

Table 1  Thermoelectric coefficients of pyrites from No.1 vein

中段/m样品编号N型α/(μV·℃-1P型α/(μV·℃-1
最大值最小值平均值频率/%最大值最小值平均值频率/%
450Y03-01-103.20-549.50-262.7440.00388.7027.00202.0660.00
370Y05-01-36.90-108.60-71.2625.00297.8019.50137.7175.00
Y05-02-14.20-109.20-45.3745.00286.1036.70158.6955.00
Y05-03-237.20-356.60-296.9010.00302.7057.90154.2690.00
Y05-04-33.20-66.30-51.7015.00338.0027.90157.5575.00
330Y06-010.000.000.000.00416.9098.90285.90100.00
Y06-02-85.50-95.70-91.4820.00338.10111.40254.8480.00
Y06-030.000.000.000.00368.70-29.70256.7495.00
250Y08-07-14.40-268.00-101.0825.00422.0049.30213.9175.00
Y08-08-61.40-118.70-86.1135.00370.9011.70169.2965.00
210Y09-01-37.90-177.10-83.2820.00482.0021.80264.1380.00
Y09-02-38.10-266.50-137.2025.00431.7063.00287.1575.00
170Y10-08-53.20-74.70-63.9510.00309.1010.80124.7390.00
130Y11-030.000.000.000.00450.00405.80427.9010.00
90Y12-10-30.00-416.20-143.2830.00300.9039.30159.8470.00
10Y14-060.000.000.000.00366.30177.30267.12100.00
Y14-07-13.70-519.20-263.8230.00424.6092.40298.4170.00
Y14-08-2.80-56.20-21.5315.00268.402.90154.0585.00
Y14-09-71.60-553.30-320.2975265.1032.00129.5425.00
Y14-10-25.40-96.90-60.9230.00324.9014.30114.9270.00
Y14-11-14.60-457.10-130.1845.00329.4040.50143.7455.00
-35Y15-01-26.00-95.70-53.4425.00365.2079.20232.2575.00
Y15-02-14.20-443.80-227.8460.00309.8054.80162.7440.00
Y15-030.000.000.000.00256.20-490.40-330.355.00
Y15-040.000.000.000.00284.9090.20196.07100.00
Y15-05-24.90-81.30-57.2730.00388.6029.60130.0570.00
-80Y16-010.000.000.000.00375.70127.40278.59100.00
Y16-020.000.000.000.00495.8058.70243.56100.00
Y16-03-36.00-137.70-79.0490.00261.80111.40186.6010.00
Y16-040.000.000.000.00312.7033.70137.57100.00
-125Y17-01-25.80-90.90-68.4315.00492.9094.30253.7485.00
-170Y18-01-24.50-43.200.0020.00592.6015.30169.4180.00
Y18-020.000.000.000.00370.00126.10268.24100.00
Y18-03-418.90-418.90-418.905.00416.7045.30251.9195.00
Y18-04-23.50-433.20-196.7425.00508.9023.50186.1475.00
Y18-05-11.80-220.20-75.1625.00367.6023.60134.2575.00
-215Y19-01-101.20-162.90-132.0510.00338.303.80205.4190.00
Y19-02-20.60-434.80-174.8715.00368.3023.10188.0985.00
Y19-030.000.000.000.00336.0069.00251.74100.00
Y19-04-18.70-368.30-156.1070.00266.005.30117.8330.00
-260Y20-01-26.30-36.90-31.6010.00366.8013.20193.1790.00
Y20-02-43.20-59.80-51.5010.00520.1019.10251.5390.00
Y20-03-27.20-130.80-64.6730.00237.702.7082.8970.00
Y20-04-138.10-138.10-138.105.00497.2096.70344.7995.00
Y20-050.000.000.000.00386.6017.90182.26100.00
-305Y21-010.000.000.000.00465.6082.90293.94100.00
Y21-02-108.70-123.70-116.2010.00462.20184.80300.2990.00
Y21-030.000.000.000.00361.90102.40264.24100.00

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表2   3号脉黄铁矿热电系数α值

Table 2  Thermoelectric coefficients of pyrites from No.3 vein

中段/m样品编号N型α/(μV·℃-1P型α/(μV·℃-1
最大值最小值平均值频率/%最大值最小值平均值频率/%
450Y03-02-50.30-50.30-50.305.00370.60111.40218.9595.00
Y03-03-27.20-577.80-467.4685.00222.6021.00142.0715.00
Y03-04-16.00-595.20-344.2485.00253.70252.30253.0015.00
410Y04-01-26.30-175.10-83.8135.00354.8014.70189.8865.00
370Y05-050.000.000.000.00374.6087.30244.06100.00
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330Y06-04-8.50-87.80-47.0465.0099.705.6046.4035.00
Y06-050.000.000.000.00236.2051.60157.67100.00
Y06-06-3.10-519.50-224.2685.00266.106.20148.1715.00
Y06-07-194.10-501.40-423.1040.00324.50167.60243.3960.00
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Y20-070.000.000.000.00324.60103.40221.52100.00
Y20-08-2.50-146.70-54.7075.00246.902.50160.2825.00
Y20-09-133.10-520.90-376.7315.00335.2069.80203.4485.00
Y20-10-24.10-508.10-372.8135.00314.5080.40210.3565.00
Y20-11-42.90-89.40-59.1315.00375.7039.40154.8985.00
Y20-12-5.70-93.20-62.0225.00454.3017.30213.1075.00
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Y21-06-45.60-45.60-45.605.00309.10107.20191.4195.00
Y21-07-49.90-483.60-209.9775.00354.20129.10245.8825.00
Y21-08-59.00-113.80-84.3315.00291.1061.70166.5985.00
Y21-09-46.30-125.70-86.0010.00315.1060.40179.6390.00

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根据表1和表2,号和3号脉黄铁矿热电系数变化范围分别为-418.90~427.90 μV/℃和-467.46~314.52 μV/℃。通过统计每条矿脉黄铁矿不同导型的出现率,得到1号脉N型和P型黄铁矿所占比例分别为22.34%和77.66%,3号脉N型和P型黄铁矿所占比例分别为30.05%和69.95%。将所有黄铁矿颗粒测得的热电系数进行统计分析,可以直观得出1号脉N型和P型黄铁矿热电系数主要集中在 -200~0 μV/℃和100~350 μV/℃(图5),3号脉N型和P型黄铁矿热电系数主要的分布范围为 -400~-300 μV/℃、-100~0 μV/℃和150~350 μV/℃(图6)。

图5

图5   1号脉黄铁矿热电系数直方图

Fig.5   Histograms of thermoelectric coefficients of pyrites from No.1 vein


图6

图6   3号脉黄铁矿热电系数直方图

Fig.6   Histograms of thermoelectric coefficients of pyrites from No.3 vein


4 讨论

黄铁矿热电性通常包括导型和热电系数,黄铁矿是半导体矿物,由于温差的影响引起载流子的扩散从而形成电场,其导电类型划分为N型和P型,P型热电系数通常大于N型,且N型的热电系数为负值,P型为正值。由于高温环境有利于Co、Ni类质同象替代Fe,形成N型黄铁矿;低温环境有利于As、Sb替代S,形成P型黄铁矿,故黄铁矿形成的温度不同,导电类型也不同24。P型黄铁矿的含量通常与金品位成正比25,黄铁矿导型在轴向上通常出现规律性变化,从矿脉的上部到尾部,导型由P型→P-N型→N-P型→N型变化。

根据P型黄铁矿出现率随标高的变化以及计算得到的相应的剥蚀率、热电性参数和离散度可以预测矿脉深部延伸情况,指示成矿环境和矿化程度152426-28

4.1 成矿温度

戈尔巴乔夫29通过大量的数据总结出黄铁矿热电系数与温度之间的关系,其计算方法见式(1)、式(2):

T=(704.51-α)/1.818 (N型) (1)

T=3(122.22+α)/5.0 (P型) (2)

利用上述方程,计算得到1号和3号脉黄铁矿形成的温度范围分别为80~430 ℃和75.07~391.93 ℃。将温度和热电系数数据投点于图7,由图7可知,1号脉N型和P型黄铁矿形成温度主要集中在280~380 ℃和80~330 ℃之间[图7(a)],3号脉N型和P型黄铁矿形成温度主要集中在260~380 ℃和80~340 ℃之间[图7(b)]。

图7

图7   1号脉(a)和3号脉(b)黄铁矿热电系数—温度图

Fig.7   Relationship between thermoelectric coefficients and temperature of pyrites from No.1 vein(a) and No.3 vein (b)


将所有黄铁矿颗粒测试所得的温度进行统计分析,可知1号脉黄铁矿形成温度主要集中在80~300 ℃和320~380 ℃之间[图8(a)],3号脉黄铁矿形成温度主要集中在130~280 ℃和305~380 ℃之间[图8(b)],指示该矿床可能存在2个主矿化阶段。综合分析图7可知,指示1号和3号脉成矿热液早期温度较高,在380 ℃左右,成矿温度主要集中在130~280 ℃之间,属于中低温热液矿床,与王鹏等19利用黄铁矿热电性测得的成矿温度(150~300 ℃)接近。

图8

图8   1号脉(a)和3号脉(b)黄铁矿成矿温度直方图

Fig.8   Histograms of ore-forming temperature of pyrites in No.1 vein (a) and No.3 vein (b)


4.2 矿体延伸情况

(1)剥蚀率及热电性参数均值特征

根据热电系数值可求出黄铁矿的热电性参数(XNP),权志高30将计算方法总结为式(3):

XNP=(2ƒ)-(ƒ+2ƒ

式中:ƒi为样品中相应的补偿热电系数百分比,ƒα>400 μV/℃,ƒα=200~400 μV/℃,ƒα=0~ -200 μV/℃,ƒα<-200 μV/℃。然后,根据热电性参数定量计算出矿脉的剥蚀率(γ),其计算方法见式(4):

γ=50-XNP/4 (4)

由式(4)可知,P型黄铁矿热电系数值越大,矿脉剥蚀率越低,深部找矿前景越好。当遇到剥蚀率由小到大转折时,表明该矿脉以下仍有部分延伸,找矿前景较好。通常,矿脉不同部位对应的XNP值分别为200~100(最上部)、100~50(上部)、50~ -50(中部)、-50~-100(下部)和-100~-200(最下部),由于同一标高不同位置的样品可能由不同成矿阶段形成,所以常用XNPγ的均值来判断矿脉的延伸1631

利用上述方程计算得到1号脉剥蚀率变化范围为22.50%~92.50%,主要集中在20%~55%之间,平均值为45.89%。1号脉剥蚀率在-120 m标高深部由封闭的高值区变为低值区,往深部剥蚀率等值线未封闭且数值呈降低的趋势(图9)。1号脉黄铁矿的XNP均值变化范围为-41.00~83.33,330 m、 -125 m和-305 m中段XNP均值分别为70、55和83.33,指示以上中段处于矿脉的上部,说明1号脉由多期成矿热液叠加形成。由此可知,1号脉深部有很大的延伸。

图9

图9   1号脉剥蚀率等值线图

Fig.9   Contour map of denudation rate from No.1 vein


3号脉剥蚀率变化范围为22.50%~95.00%,主要集中在20%~50%之间,平均值为50%。3号脉剥蚀率在-100 m标高深部由低值区变为高值区,且高值区向深部延伸(图10)。3号脉黄铁矿的XNP均值变化范围为-86.67~90.00,在370 m和250 m中段XNP均值分别为90和72.5,指示以上中段处于矿脉的上部,在-170 m至-305 m中段XNP均值变化范围为 -90→45→11.43→-8,指示-170 m中段处于矿脉的下部,向下又转换为矿脉的中部,说明3号脉由多期成矿热液叠加形成。由此可知,3号脉深部有较大的延伸。

图10

图10   3号脉剥蚀率等值线图

Fig.10   Contour map of denudation rate from No.3 vein


(2)黄铁矿热电性特征

P型黄铁矿主要集中在矿脉的上部,靠近下部N型黄铁矿逐渐增加15-1626。330 m、-125 m和 -305 m中段处于1号脉的上部,由图11可知,P型黄铁矿出现率在250 m、-35 m和-215 m中段由降低转为增加,在-215 m中段深部未见明显降低的趋势,且出现率高达80%~90%,以P型黄铁矿占据绝大多数,说明以上中段为矿脉尾部向新叠加矿脉头部转换的部位,-215 m深部还有很大的延伸。在3号脉-170 m中段深部P型黄铁矿出现率开始增加且该中段处于矿脉的下部,说明该中段深部开始出现新叠加矿脉的头部,符合XNP均值标识结果,在 -215 m中段深部又开始由增加转为降低,N型黄铁矿开始增加,说明深部仍有部分延伸。

图11

图11   不同中段P型黄铁矿出现率

Fig.11   Occurrence rate of P-type pyrite in different middle sections


根据表1表2,统计得到1号脉黄铁矿的热电导型以P型和P-N型为主,其中P型、P-N型和N-P型黄铁矿分别占22.92%、64.58%和12.50%,3号脉黄铁矿的热电导型以P-N型和N-P型为主,其中P型、P-N型和N-P型黄铁矿分别占13.63%、63.64%和22.73%。3号脉N-P型黄铁矿出现率大于1号脉,说明3号脉现开采的位置比1号脉更接近矿体的下部。

综上所述,-215 m中段为1号和3号脉新叠加矿脉的头部位置,-305 m中段分别处于1号和3号脉的中上部和中部偏下位置,1号脉深部有较大距离的延伸,反映出找矿前景很好;3号脉深部仍有一段距离的延伸,反映出找矿前景较好。

4.3 深部成矿环境的稳定性

黄铁矿热电系数离散度(σα´)能够准确反映相差较大的不同样品的热电系数值相对集中与分散的情况1324。离散度的计算方法见式(5):

σα´=σα/α¯*100%

式中:α¯为黄铁矿样品热电系数的平均值;σα为热电系数的标准差(μV/°C)。由式(5)可知,离散度数值越大,指示黄铁矿热电系数的分散程度越大,黄铁矿形成时的环境越不稳定,反之则黄铁矿形成时的环境越稳定。离散度也可以指示不同阶段黄铁矿的叠加程度,早期叠加较强时以N型黄铁矿为主,晚期叠加较强时以P型黄铁矿为主,以上2种情况成矿环境均比较稳定,当2期叠加程度相近时,成矿环境会发生剧烈波动15-16

由离散度与P型黄铁矿出现率关系图可知,图形形态具有类似正态分布的特征[图12(a)、12(b)],图形突峰左侧数值区间对应低离散度和低P型黄铁矿出现率,右侧数值区间对应低离散度和高P型黄铁矿出现率,分别指示矿化较差和矿化好,图形突峰处离散度高且P型黄铁矿出现率较高,指示矿化不连续15-162731。1号脉P型黄铁矿出现率小于30%和大于60%时,以早期和晚期叠加为主,离散度较小,在200%以内,当接近50%左右时,离散度呈指数形态增长[图12(a)]。1号脉离散度在 -215 m中段深部逐渐减小并小于200%[图12(c)],且由表1计算得该标高深部各中段P型黄铁矿出现率均值均大于90%,P型黄铁矿出现率很高且离散度低,说明该中段深部金矿化很好。3号脉P型黄铁矿出现率小于40%和大于60%时离散度较小,在1 000%以内,在两者之间离散度呈指数形态增长[图12(b)]。3号脉在-35 m中段深部,离散度整体小于1 000%,仅在-260 m中段出现个别离散度较大的点[图12(d)],由表2计算得-260 m中段深部P型黄铁矿出现率均值为71%,P型黄铁矿出现率较高且离散度低,说明该中段深部金矿化较好。

图12

图12   成矿环境及矿化标识图

Fig.12   The map of metallogenic environment and mineralization mark


根据离散度在不同标高的变化情况可以反映成矿环境的稳定性,发生离散度急增的中段表明成矿环境稳定性变差,离散度集中分布且数值小指示成矿环境比较稳定16。1号脉离散度小于200%的投点比大于200%的投点多,且分布比较集中,只在450 m和10 m中段出现急增,说明1号脉整体上离散度低,除以上中段外成矿环境很稳定[图12(c)]。3号脉离散度分布比较集中,整体小于1 000%,少部分小于2 000%,说明整体成矿环境稳定,在-260 m中段深部离散度开始由急增转为急降且小于1 000%,说明该中段深部金的成矿环境由动荡转为稳定[图12(d)]。

5 结论

(1)由热电系数计算得到1号和3号脉成矿温度为130~280 ℃,属于中低温热液矿床。

(2)1号和3号脉黄铁矿热电系数变化范围分别为-418.90~427.90 μV/℃和-467.46~314.52 μV/℃,热电导型分别以P型、P-N型和P-N、N-P型为主。

(3)1号脉深部延伸较大,3号脉深部仍有部分延伸。在-215 m中段深部,1号脉成矿环境稳定且矿化很好,在-260 m中段深部,3号脉成矿环境由动荡转为稳定且矿化较好。

http://www.goldsci.ac.cn/article/2020/1005-2518/1005-2518-2020-28-6-812.shtml

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