Genesis, metallogenic model, and prospecting prediction of the Nibao gold deposit in the Guizhou Province, China

Southwestern Guizhou province is one of China’s most important distribution areas of Carlin-type gold deposits. The Nibao deposit is a typical gold deposit in southwestern Guizhou. To elucidate the genesis of the Nibao gold deposit, establish a metallogenic model, and guide prospecting prediction, we systematically collected previously reported geological, geochemical, and dating data and discussed the genesis of the Nibao gold deposit,based on which we proposed the metallogenic model.Earlier works show that the Nibao anticline, F1 fault, and its hanging wall dragged anticline(Erlongqiangbao anticline) were formed before or simultaneously with gold mineralization, while F2, F3, and F4 faults postdate gold mineralization. Regional geophysical data showed extensive low resistivity anomaly areas near the SBT(the product of tectonic slippage and hydrothermal alteration)between the P2/P3 and the strata of the Longtan Formation in the SSE direction of Nibao anticline in the lower plate of F1 and hanging wall dragged anticline(Erlongqiangbao anticline), and the anomaly areas are distributed within the influence range of anticlines. Simultaneously, soil and structural geochemistry show that F1, Nibao anticline,Erlongqiangbao anticline, and their transition areas all show good metallogenic elements(Au, As, and S) assemblage anomalies, with good metallogenic space and prospecting possibilities. There are five main hypotheses about the source of ore-forming fluids and Au in the Nibao gold deposit:(1) related to the Emeishan mantle plume activity;(2) source from the Emeishan basalt;(3) metamorphic fluid mineralization;(4) basin fluid mineralization;(5) related to deep concealed magmatic rocks;of these, the mainstream understanding is the fifth speculation. It is acknowledged that the ore-forming fluids are hydrothermal fluids with medium–low temperature, high pressure, medium–low salinity, low density, low oxygen fugacity, weak acidity, weak reduction, and rich in CO_(2)and CH_(4). The fluid pressure is 2–96.54 MPa, corresponding to depths of 0.23–3.64 km. The dating results show that the metallogenic age is ~141 Ma, the extensional tectonic environment related to the westward subduction of the Pacific Plate. Based on the above explanation, the genetic model related to deep concealed magmatic rocks of the Nibao gold deposit is established, and favorable prospecting areas are outlined;this is of great significance for regional mineral exploration and studying the genesis of gold deposits.

Ore-forming and Exploration Models of the Baguamiao Gold Deposit,Shaanxi Province

The Baguamiao superlarge gold deposit in Shaanxi Province is one of the typical cases in China that are hosted by sedimentary rocks. Explorers and researchers have discussed the gold mineralization enrichment conditions by studying sulphur, oxygen, carbon, silicon stable isotopes and mineralizing fluid features of the Baguamiao gold deposit and proposed a hydrothermal sedimentation-magmatic reconstructing gold mineralization model featuring multi-sources of ore-forming materials and multistage mineralizations. In addition, prospecting for “Baguamiao-type” gold deposits was started in the Fengtai Basin and a great number of important prospecting targets such as Tonglinggou, Simaoling, Guoansi and Dachaigou were discovered.

An integrated ore prospecting model for the Nyasirori gold deposit in Tanzania

The Nyasirori gold deposit,located in the middle-western end of the Musoma-Mara Archean greenstone belt in Tanzania,is a tectonic altered rock type gold deposit controlled by shear tectonic zone.This work conducted high-precision ground magnetic measurements to delineate fault structures and favorable prospecting targets,utilized induced polarization(IP)intermediate gradient to roughly determine the distribution and extension of the tectonic altered zone and gold ore(mineralized)bodies,and further carried out IP sounding and magnetotelluric sounding to locate the tectonic altered zone and gold ore(mineralized)bodies.The anomalous gradient belt of the combination of positive and negative micromagnetic measurements reflects the detail of shallow surface tectonic alteration zone and gold mineralization body.Micromagnetic profile anomalies indicate the spatial location and occurrence of concealed tectonic alteration zone and gold(mineralized)ore bodies.Soil geochemical measurements indicate that the ore-forming element Au correlates well with As and Sb,and As and Sb anomalies have a good indication to gold orebodies.Based on the multi-source geological-geophysical-geochemical information of the Nyasirori gold deposit,this work established an integrated prospecting model and proposed a set of geophysical and geochemical methods for optimizing prospecting targets.

Geological Characteristics and Regional Prospecting Model of Wulanchongji Gold Orebody, Alxa Youqi, Inner Mongolia, China

Five gold deposits (mineralization) were found in the study area by means of geological mapping, soil geochemical survey and trough exploration engineering. The ore-bearing lithology is mainly metamorphic feldspar sandstone of the Upper Carboniferous Benbatu Formation, and the gold (mineralization) body is controlled by both structural factors and stratigraphic factors of the Upper Carboniferous Benbatu Formation. The genetic type is preliminary concluded to be volcanic hydrothermal type, and the metallogenic age is late Variscan. In this paper, by studying the geological characteristics and metallogenic geological conditions of the gold orebody in the area, a regional prospecting model has been established, which is of great significance to better guide the prospecting work of similar gold deposits in the area and the region.

METALLOGENIC REGULARITIES OF LARGE CONCEALED AND BLIND URANIUM DEPOSITS AND METALLOGENIC PROGNOSIS BY SYNTHETIC INFORMATION IN GRANITIC EXOCONTACT ZONES──Taking Eastern Hunan and Adjacent Areas as Examples

Under the guide of advanced theories of geosciences, new technology and methods of prospecting, integrating sedimentation, magmatic emplacement, metamorphism and deformation with mineralization by means of intersectional subjects, the author has revealed that the geodynamic setting of formation of uranium deposits of granitic exocontact zone type in eastern Hunan and neighbouring areas has a specia1 stretching strike-slip structure, a special thermal rock series,a special texture and composition of the crust and mantle, elaborated the macroscopic and microscopic features of stretching decollement faults in the Mingyuefeng area, and summed up the metallogenic regularities of typical uranium deposits, factors for a genetic mode1 and the criteria for prospecting by synthetic information, on the basis of which he has made prognosis of concealed and blind uranium deposits.

Geology and mineralization of the Sanshandao supergiant gold deposit(1200 t)in the Jiaodong Peninsula,China:A review

The Jiaodong Peninsula in Shandong Province,China is the world’s third-largest gold metallogenic area,with cumulative proven gold resources exceeding 5000 t.Over the past few years,breakthroughs have been made in deep prospecting at a depth of 500‒2000 m,particularly in the Sanshandao area where a huge deep gold orebody was identified.Based on previous studies and the latest prospecting progress achieved by the project team of this study,the following results are summarized.(1)3D geological modeling results based on deep drilling core data reveal that the Sanshandao gold orefield,which was previously considered to consist of several independent deposits,is a supergiant deposit with gold resources of more than 1200 t(including 470 t under the sea area).The length of the major orebody is nearly 8 km,with a greatest depth of 2312 m below sea level and a maximum length of more than 3 km along their dip direction.(2)Thick gold orebodies in the Sanshandao gold deposit mainly occur in the specific sections of the ore-controlling fault where the fault plane changes from steeply to gently inclined,forming a stepped metallogenic model from shallow to deep level.The reason for this strong structural control on mineralization forms is that when ore-forming fluids migrated along faults,the pressure of fluids greatly fluctuated in fault sections where the fault dip angle changed.Since the solubility of gold in the ore-forming fluid is sensitive to fluid pressure,these sections along the fault plane serve as the target areas for deep prospecting.(3)Thermal uplifting-extensional structures provide thermodynamic conditions,migration pathways,and deposition spaces for gold mineralization.Meanwhile,the changes in mantle properties induced the transformation of the geochemical properties of the lower crust and magmatic rocks.This further led to the reactivation of ore-forming elements,which provided rich materials for gold mineralization.(4)It can be concluded from previous research results that the gold mineralization in the Jiaodong gold deposits occurred at about 120 Ma,which was superimposed by nonferrous metals mineralization at 118‒111 Ma.The fluids were dominated by primary mantle water or magmatic water.Metamorphic water occurred in the early stage of the gold mineralization,while the fluid composition was dominated by meteoric water in the late stage.The S,Pb,and Sr isotopic compositions of the ores are similar to those of ore-hosting rocks,indicating that the ore-forming materials mainly derive from crustal materials,with the minor addition of mantle-derived materials.The gold deposits in the Jiaodong Peninsula were formed in an extensional tectonic environment during the transformation of the physical and chemical properties of the lithospheric mantle,which is different from typical orogenic gold deposits.Thus,it is proposed that they are named“Jiaodong-type”gold deposits.

Soil geochemical prospecting prediction method based on deep convolutional neural networks-Taking Daqiao Gold Deposit in Gansu Province, China as an example

A method is proposed for the prospecting prediction of subsurface mineral deposits based on soil geochemistry data and a deep convolutional neural network model.This method uses three techniques(window offset,scaling,and rotation)to enhance the number of training data for the model.A window area is used to extract the spatial distribution characteristics of soil geochemistry and measure their correspondence with the occurrence of known subsurface deposits.Prospecting prediction is achieved by matching the characteristics of the window area of an unknown area with the relationships established in the known area.This method can efficiently predict mineral prospective areas where there are few ore deposits used for generating the training dataset,meaning that the deep-learning method can be effectively used for deposit prospecting prediction.Using soil active geochemical measurement data,this method was applied in the Daqiao area,Gansu Province,for which seven favorable gold prospecting target areas were predicted.The Daqiao orogenic gold deposit of latest Jurassic and Early Jurassic age in the southern domain has more than 105 t of gold resources at an average grade of 3-4 g/t.In 2020,the project team drilled and verified the K prediction area,and found 66 m gold mineralized bodies.The new method should be applicable to prospecting prediction using conventional geochemical data in other areas.

贵州水银洞金矿床成矿规律与找矿预测模型

水银洞金矿床是黔西南地区超大型金矿床之一,由于多年的开采和生产规模的扩大,保有资源量越来越少,亟须综合研究成矿规律和分析成矿潜力。在综合分析以往资料基础上,结合野外调查,认为水银洞金矿床成矿地质体为深部隐伏岩浆岩体,成矿构造为灰家堡背斜与其两侧的逆冲断裂,成矿结构面为浅部三叠系地层裂隙面、龙潭组地层层间裂隙面和切层裂隙面、龙潭组地层与茅口组地层不整合接触面,成矿具有明显垂向分带特征。结合地球物理和地球化学信息构建找矿预测模型,圈定5处找矿潜力区,即控制边界区(包括已知矿体或矿权边界的北部和南部)、新矿化样式/新矿种找矿区(簸箕田矿段以东地区)、新类型/新空间找矿区(水银洞矿权范围隆起区的深部)、新找矿方向区(矿区西南部背斜,如矮煤洞背斜)和探索找矿区(灰家堡背斜水银洞矿权边界以西至回龙断裂之间的区域),为进一步找矿预测提供了参考。

甘肃文县阳山金矿床高楼山矿段构造叠加晕地球化学特征及岩浆—构造—成矿耦合关系简析

甘肃文县阳山金矿是产于勉县—略阳弧形缝合带中段内的超大造山型金矿床。在26年的勘探工作中,安坝和葛条湾矿段一直是阳山金矿勘查的核心矿段。高楼山矿段于2021年正式进入普查阶段。本文旨在更好地了解矿区的深部隐伏盲矿,并对其未来的发展前景进行预测。结果表明,高楼山矿段69号勘探线剖面的成矿及伴生元素构造叠加晕的轴(垂)向分带序列从上而下依次为:Cu-As-Pb-Zn-Mn-Co-Ag-Au-Sb-Mo-Bi;共圈定两处深部找矿靶区,在1850 m标高处,213号矿脉的前缘晕仍然存在,而且随着深度的增加,前缘晕的强度也在不断加强,这表明矿体正在向更深处延伸;而在1750 m标高处,前缘晕的增强更加显著,这暗示着深部可能存在隐伏的矿体。此外,在分析69号勘探线3个钻孔构造叠加晕的基础上,提出新的阳山金矿构造控矿模式——推覆体复式褶皱构造控矿,并对ZK4901岩心的千枚理、断层、岩体、矿(化)体产状特征,利用统计分析方法进一步佐证了该模式。本文研究认为阳山金矿主体受逆冲断裂构造作用控制,含矿构造以北倾为主,局部受到褶皱的制约,岩浆岩主要沿断裂带产出,可形成矿(化)体,并根据岩浆岩有无矿化,将矿(化)体产出类型分为“2大类、5小类”,同时指出岩浆热液与成矿关系密切,但高品位的矿体主要分布在千枚岩中。这将为今后的勘探和开采提供重要的参考。

河南嵩县九仗沟金矿床地球化学特征与勘查模式

九仗沟金矿位于熊耳山—外方山矿集区内的蛮峪—店房金矿带北段,是典型的大型构造蚀变岩型金矿床。采用1/5万水系沉积物测量圈定了找矿靶区,1/1万土壤地球化学测量确定了矿化富集部位,岩石地球化学(原生晕)测量识别出构造破碎带和矿化强度,并预测矿体相对剥蚀程度。研究表明:不同尺度地球化学测量为该金矿勘查提供了不同阶段的找矿信息,找矿效果显著。其中,利用水系沉积物测量在九仗沟矿区范围内圈定了11-丙-Au异常,利用土壤地球化学测量发现了九仗沟1-甲_(1)-Au-Ag-Pb-Cu-Hg-As-Bi-Ni异常,利用原生晕剖面微量元素峰值部位确定了F_(1)构造矿化蚀变带。通过总结该矿床地球化学异常特征和找矿标志,建立了勘查地球化学模式,为区域及矿区周边相同类型的金矿勘查提供理论指导。

冀东矿集区金厂峪金矿床“三位一体”成矿预测模型及找矿预测

金厂峪金矿床作为冀东矿集区规模最大、开采历史最悠久的矿床之一,为中国的金资源量提供了保障。目前,该矿床找矿工作遇到瓶颈,为解决深边部增储的关键问题,根据“三位一体”勘查区找矿预测理论与方法对其进行了立典式研究,建立矿床“三位一体”成矿预测模型对深边部找矿工作进行指导。通过对金厂峪金矿床的典型剖面、巷道进行大比例尺构造、矿化蚀变填图,查明了成矿构造和成矿结构面,刻画了矿区成矿构造空间展布形态。在确定金厂峪金矿床成矿地质体基础上,进一步梳理其与成矿构造和成矿结构面、成矿作用特征标志间的关系,初步构建了“三位一体”成矿预测模型,推测深部找矿目标应集中在Ⅴ号矿脉0勘探线—55勘探线-1000~-600 m标高,外围找矿靶区则应在Ⅰ号、Ⅲ号、Ⅳ号矿脉的西侧。经工程初步验证,“三位一体”成矿预测模型预测效果良好,对金厂峪金矿床的接续性找矿生产工作具有良好的现实指导意义。

雪峰弧形构造带中段天明金矿地质特征及找矿标志

湖南省安化县天明金矿地处江南造山带雪峰弧形构造带中段,金矿成矿地质条件优越。在综合研究区域资料和勘查成果的基础上,根据地球物理、地球化学、遥感等地质资料,对比分析了天明金矿与邻区典型金矿的成矿地质环境、矿体展布、矿石特征及矿床成因特征,探讨了天明地区的成矿地质条件和找矿标志,并初步建立了天明地区金矿的成矿模式和综合找矿模型。天明金矿目前已揭露3条近EW向的破碎蚀变带,其成因类型为造山与重熔岩浆热液混合型金矿,且在垂向分带上显示出石英脉型—构造蚀变岩型的分带特征。研究成果可以为天明金矿及同类型金矿的找矿工作提供参考。

物化遥综合找矿方法在西藏隆子县拉九地区的应用

西藏隆子县拉九地区成矿地质条件优越,寻找金多金属矿的潜力较大。在综合分析区域地质背景的前提下,通过遥感地质解译研判成矿有利部位,确定拉九地区为成矿预测Ⅳ区,利用1/5万水系沉积物测量进行扫面,圈定了多处化探综合异常。选择在拉九异常(HS-13-B2)内,开展1/1万土壤地球化学剖面测量、壤中1/1万汞气测量及激电中梯测量等大比例尺化探物探工作,初步圈定了2处化探综合异常,发现3个极化体和2处视极化率异常,优选其中有利的成矿靶区,经异常查证和槽探工程揭露,发现3条金矿矿化蚀变带,实现了找矿新发现。基于物化遥综合找矿信息初步建立了以矿床地质—地球化学—地球物理—遥感特征为标志的综合信息找矿模型。实践证明,运用物化遥综合找矿方法可极大地提高找矿效率,该工作为今后在高原山区开展多金属找矿勘查提供了参考。

甘肃北山老君庙北金矿土壤地球化学特征及找矿前景

甘肃北山老君庙北金矿位于甘肃北山南带,属于塔里木陆块东北缘,为窑洞梁—小西弓古元古代裂谷盆地构造环境。本次找矿通过1∶10000土壤地球化学测量工作,圈定了综合异常区5个,综合异常经槽探工程验证,新发现金矿体3条、金银矿体1条、低品位金矿体2条,取得了较好的找矿成果。同时,结合矿区地质、地球化学综合异常特征,建立了以HT1综合异常区为主体的地质—地球化学综合找矿模型,并提出了下一步找矿方向,为矿区深部和外围找矿工作提供了重要的参考依据。

粤东北差干钼金多金属矿成矿特征及模式探讨

对差干钼金多金属矿床成矿地质条件、矿体特征、围岩蚀变特征等进行初步调查与统计,对矿区的控矿构造、岩浆及成矿作用等进行分析研究,探讨了矿区成矿物质来源、控矿因素、矿体赋存特征以及成矿模式。差干钼金多金属矿床矿体主要产于晚白垩世酸性火山岩地层中,尤其是晚白垩世气孔流纹岩、球粒流纹岩地层,矿石类型为钼金矿脉型,蚀变种类主要为硅化、钾(钠)长石化、胶状黄铁矿化、赤铁矿化、绿泥石化、萤石化和碳酸盐化等。矿区成矿物质主要来源于火山岩本身已有成矿物质以及火山喷气阶段深部岩浆源,矿体受北北东向鹿子坑断裂和北西西向2组不同级别、不同方向构造的联合控制,构造分支复合变异部位、侵入体接触界面、裂隙发育部位以及层间破碎带是矿化富集的有利部位,多期多阶段蚀变和成矿作用有利于形成厚大的钼金多金属矿体。

东昆仑百吨沟金矿床地质特征及找矿模型

百吨沟金矿床位于东昆仑成矿带中段,近年来在该矿床内发现了多处金矿点,显示良好的找矿前景。据调查和分析,该矿床严格受NNW向断裂构造控制,其赋矿地层为新元古界丘吉东沟组、长城系小庙组。该矿床中矿石金属矿物有自然金、富含金银辰砂、螺状硫银矿、黄铁矿、毒砂、磁黄铁矿等,有黄铁矿化、硅化和绢云母化与金矿密切相关的围岩蚀变。晚三叠世中酸性侵入岩为金矿的形成提供热源该矿床受益于含碳质和黄铁矿地层所提供的吸附障效应和还原障效应,是脆韧性剪切带、岩浆热液及特殊地层岩性耦合的结果。

陕西太白金矿床“三位一体”找矿预测模型及深部找矿预测

为了解决制约矿山找矿突破的关键问题,运用勘查区找矿预测理论与方法,通过开展矿区三位空间构造-蚀变专项地质填图,对典型矿床进行了解剖,重点研究了太白金矿床(角砾岩型金矿床)的成矿构造和成矿结构面,查明了矿区成矿构造系统,构建了成矿构造的空间格架基础。通过对太白金矿床成矿地质体、成矿构造和成矿结构面、成矿作用特征标志的梳理和总结,初步构建了“三位一体”找矿预测模型,并结合构造原生晕测量成果,圈定了5处找矿靶区和3处远景区,其中一处找矿靶区经工程验证探获了工业矿体,初步证明“三位一体”找矿预测模型预测效果良好,对矿区找矿工作具有较好的现实指导意义。

坦桑尼亚恩泽加绿岩带隐伏金矿床综合找矿模型

恩泽加绿岩带是坦桑尼亚重要的成矿带之一,产出了高登普莱德(Golden Pride)等多个大型金矿。通过对坦桑尼亚恩泽加绿岩带已发现的隐伏金矿床进行分析研究,结果显示恩泽加绿岩带隐伏金矿床构造控矿作用明显;高精度磁法和激电中梯测量结果显示含矿构造蚀变带具有高磁、低阻、相对高极化的特征;土壤地球化学测量结果显示成矿元素Au异常在空间分布上大于相应的含矿构造蚀变带的分布范围,其浓集方向与含矿构造蚀变带展布一致,并与指示元素As、Sb的套合性较好。根据该区域隐伏金矿床的地质、地球物理及地球化学特征,对该区隐伏金矿床的找矿标志进行了总结,明确了各找矿标志与隐伏金矿床之间的关系,并在此基础上构建了恩泽加绿岩带隐伏金矿床的综合找矿模型,该模型的应用显示了多种技术手段联合实施在寻找绿岩带型隐伏金矿床的有效性。

皖南外桐坑金矿床地质、地球化学特征及找矿模型

外桐坑金矿位于江南造山带东北缘太平断裂褶皱带,是受断裂控制的热液蚀变型金矿床。为进一步分析该矿床的成矿规律,明确找矿方向,提高找矿效果,在开展野外地质调查的基础上,采用土壤地球化学测量、岩石地球化学剖面测量等技术手段开展了地质、地球化学特征及找矿模型研究。土壤地球化学测量结果显示,Au、As异常显著,主要沿NE向次级断裂分布;岩石地球化学剖面测量结果显示,矿区NE向张性次级断裂显著富集Au、As、Ag、Sb,可有效指示金矿化的分布特征。金矿体赋存于志留纪霞乡组中,成矿物质及热源主要来自于燕山期花岗岩岩浆热液,成矿构造为NE向榔桥—里东坑张性断裂,含矿构造为主断裂上盘NE向硅化、毒砂矿化、黄铁矿化、绢云母化蚀变破碎带。依据成矿规律,构建了外桐坑金矿“构造-岩浆岩”成矿体系地质-地球化学找矿预测模型,明确次级断裂破碎带、金砷地球化学异常、绢英岩化蚀变等可作为外桐坑外围金矿找矿标志,指出矿区内破碎蚀变带、矿区深部以及外围沿榔桥—里东坑断裂分布的水系沉积物Au异常区具有较好的找矿前景。

顾及构造改造的胶西北大尹格庄金矿床三维成矿预测

矿床在形成后常被构造改造,但现有三维成矿预测中对其关注较少。笔者选择胶东半岛大尹格庄构造蚀变岩型金矿为研究对象,采用基于不规则三角网(TIN)的构造复原方法还原被断裂错断的矿体与控矿断裂的三维结构,开展复原前后的矿化空间/控矿因素对比分析并实现深边部三维成矿预测。结果表明,构造复原方法消除了断裂和矿体被错断产生的空间距离及倾角变化;复原后的矿化分布具有更强的空间自相关性,被错断区域的矿化分布由分散变为连续。此外,相同参数下,复原后的预测模型比复原前模型具有更高的性能,说明对复原后的矿化分布和控矿指标之间的关联关系表达更加显著。因此,顾及构造改造的三维成矿预测有利于预测结果的准确性,可为大尹格庄矿床深部找矿工作提供可靠参考。