【作者】 张善明；

【导师】 吕新彪；

【作者基本信息】 中国地质大学 ， 矿产普查与勘探， 2010， 硕士

【摘要】 广西大瑶山西侧多金属一重晶石成矿带位于桂中腹地,地处大瑶山西侧,是广西“十五”矿产勘查规划的重点找矿区域之一,但对该区成矿作用的研究及新技术运用于找矿预测方面相对滞后,导致自盘龙铅锌矿后,该区的找矿勘探一直未取得突破。基于此,本论文以生产和科研工作为基础,重点分析区域成矿作用,建立切合实际的多金属成矿模型,归纳控矿因素,总结成矿规律,并运用GIS技术对区域矿产做出预测评价。已有的研究对该区矿床的成因众说纷纭,通过归纳,认为目前的争议主要集中在两方面：(一)一类认为该区矿床属受一定层位控制的,中低温热水沉积—后期热卤水再作用的铅锌重晶石矿床；(二)另一类则认为该区矿床为受深大断裂控制的,热液充填型铅锌铜重晶石矿床。为此,本文在分析区域成矿地质背景的基础上,对地层岩性、构造、热水沉积岩及成岩后生作用等方面与成矿的关系进行了深入的论述,最后还引用典型矿床作了实例说明。大量的论述表明,研究区多金属矿床具备“生、储、盖”三位一体的控矿条件组合和“层、相、位”三位一体的成矿规律。简言之,从成矿条件的角度来讲,矿源层+白云岩、含生物屑炭质灰岩及层间破碎带+泥岩或泥质岩构成了生、储、盖三位一体的控矿条件组合。从成矿作用来讲,成矿物质来源以泥盆系地层和寒武系地层为主,部分来自深源岩浆作用；含矿流体主要为沿深大断裂下渗的海水和雨水在深部被加热而形成,但也有深源流体的掺入；热源主要为地热增温和岩浆作用释放的热量；对于成矿温度,不同地区、不同类型矿床略有差异,整体上来看,北段铜、铅、锌、金矿床(点)成矿温度为181—230℃,南段铅锌、黄铁矿矿床(点)成矿温度为135—197℃。从成矿规律的角度来看,赋矿层位+沉积相+构造位置构成了“层、相、位”三位一体的矿床时空分布规律组合。研究区的热水沉积岩主要有重晶石岩、硅质岩、铁白云石、次生层状硅质岩、燧石结核灰岩等,大量有关它们分布、产状、形成环境及岩石地球化学方面的研究证明,它们是在一次大规模的热水沉积事件中形成的,并因此形成象州断陷盆地内由重晶石岩—硅质岩—铁白云石岩一次生层状硅质岩—燧石结核灰岩组成的热水沉积建造,该建造与矿体在空间分布、产状及成因机理上密切相关,显示出热水沉积岩的成矿效应。我们在研究区多个区段做过系统的1：2.5万沟系次生晕化探扫面工作,同时,还比较系统地收集了区域1：5万、1：10万化探资料,并将1：2.5万的实测数据进行尺度放大后对1：10万、1：5万数据进行局部修正融合,然后再一次圈定化探异常,本文选取主要成矿元素(Cu、Pb、Zn、Ba、Au)进行了异常说明。整体上发现化探异常具以下特征：①硅化岩区Au、Cu、Ba、Zn、Pb异常显著。灰岩区Zn、Pb异常显著。硅质岩区Au、Ag、Cu异常显著；②Ba异常普遍,尤其在硅化岩区,而灰岩区的官桥组地层Ba异常亦明显,Zn次之；③异常总体上呈现出两类组合,即Ba-Zn-Pb组合和Ba-Cu-Au组合；④自北向南的异常元素组合呈现出Cu-Au-Zn-Pb-Ba-Ag系列→Ba-Zn-Pb-Cu系列→Pb-Zn-Ba系列的分带特征。同时,对研究区不同尺度的物探特征也做了简要说明。基于这些认识,总结了区域多金属矿成矿规律。从成矿时间上来看,大瑶山西侧地区自下泥盆系地层形成时就有铅锌黄铁矿等同生矿床的形成,随后至下泥盆世官桥期时,就开始发生了盆地热卤水的成矿作用,自此进入区内铅锌的主要成矿时期。随后自印支期至燕山期,伴随着构造运动和岩浆活动,已形成矿床遭受改造,并形成以铜、铅锌及金矿为主的脉状矿化。在空间分布上,区域构造格架决定了矿带的位置及展布,矿源层及层序边界面决定了赋矿层位。而局部构造、热水沉积作用、蚀变作用及对应的成矿作用又决定了矿体的位置、矿种的空间分布及组合等。而在矿物共生组合规律上,由于成矿专属性的作用,不同的大地构造位置及成矿地质条件决定了不同的矿床类型,并因此产出不同的矿种,形成不同的矿物共生组合。最后,在研究区建立了两套预测模型,模型Ⅰ：针对具有层控特征的铅锌黄铁矿及重晶石矿体,模型Ⅱ：另一套针对热液成因的铜,铅锌,金及重晶石矿。按照建立的两个预测模型,对提取的地质变量进行控矿权重赋值,并用专家打分法进行修正,再对成矿信息量按成矿有利度大小进行重分类,随后对每个预测单元格内的成矿有利度进行计算,生成区域找矿有利地段预测图。通过计算,在大瑶山西侧确定了4个成矿远景区,分别是东乡—通挽铅锌黄铁矿远景区,水村—东乡铅锌铜远景区,头排—寺村重晶石、铜铅锌远景区,古尝—龙江铜、金、重晶石成矿远景区,本次预测共圈定铅锌铜多金属—重晶石找矿有利地段13个,A级找矿有利地段4个,B级找矿有利地段4个,C级找矿有利地段5个。通过本文研究,形成以下结论：(1)在大瑶山西侧的多金属矿床主要是多期成矿作用叠加而成的复成因类型矿床,分别为海底热水沉积作用形成的同生铅锌多金属含矿层、断陷盆地内由热卤水作用形成的层控型铅锌多金属矿化叠加和受构造控制的深部热液充填交代型铜金多金属—重晶石矿化。但以第二类占主要,是大瑶山西侧寻找大规模矿体的主攻类型。(2)热水沉积岩具有重要的控矿作用,空间上相关,成因上相联,特征明显且稳定。而在以往针对该区的找矿及研究工作中,热水沉积岩往往被忽略,所以加强对热水沉积岩的成矿研究,对找矿预测及矿体的定位勘探至关重要,也是打破该区的传统找矿思路,用新理论取得找矿突破的最关键一步。(3)研究区的成矿作用具有典型的“生、储、盖”三位一体的控矿条件组合和“层、相、位”三位一体的成矿规律。(4)预测有利区内各种示矿信息及找矿标志明显,成矿地质条件充分,大量已知矿床(点)在有利区内产出,大部分地区勘探程度较低,并且已有的工作也都是以“就矿找矿”的思路对断裂破碎带控制的矿体作了一些地表评价和部分深部验证,说明通过调整找矿思路和方法,该区第二轮找矿有取得突破的良好前景。更多还原

【Abstract】 The Pb、Zn、Cu multi-metal—barite ore deposit of western Dayaoshan, Guangxi is locating in Guizhong basin, western of the Dayaoshan mountain, which is one of the most important exploration area of "The Tenth Five Years Plan"of Guangxi. Eventhough, the study of metallogenetic mechanism and new technology for ore prospecting and forecasting in this area is fall behind, as a result, the ore exploration in this aera have got little achievement since the finding of Panlong Pb-Zn deposit in 2003. So, based on field work and room study, this paper analyzed the minerogenetic mechanism, and then built the mineralization model for this area, generalized the major ore constraints, summarized the metallogenetic law, at the last, we have also did some mineral resource prediction and assessment (MRPA) for this area in GIS.There are many wording for the metallogenetic mechanism in this area, after studied many literatures, we found all these wording are focusing on two respects:①Someone thout the ore in this area was mainly controlled by stratum, and the ore was forming in mid-low temperature water sedimentary and then reformed by later hydrothermal,the main mineral resources are galena,sphalerite,barite;②While the others hold the point that the ore was mainly controlled by deep faults, and the ore was forming in hydrothermal silting these fault and cranny,so the main mineral resources are galena,sphalerite,chalcopyrite,barite and so on. In these, based on the ore forming setting analysis,this article have discussed the stratum,lithology,structure,hot water sedimentary rock and the epigenesis after deposition,at the end,we have cited a typical ore deposit to explain the analysis. A great many exposition have made known that the ore in this area have the three ore controlling factors "source,fill,cover" to an organic whole and three ore forming laws" stratum,face,position"to an organic whole character.To the mineralization, source bed +dolostone,biological fossil bearing carbon limestone and crush belt between layers+mudfish or mud-bearing stone have beening constituted to form the three ore controlling factors "source,fill,cover" to an organic whole. While to the mineralization laws,ore contained stratum+ sedimentary face+ constructive position have beening constituted to form the three ore forming laws"stratum, face, position" to an organic whole.There are five kinds of hot water sedimentary rock,they are barite, silicolite, ferrodolomite, secondary layer silicolite, nodular chert limestone,the study about their distributed,occurrence,forming environment and the rock geochemical character have prove that they have formed in a wide ranging hot water sediment event,and therefore formed the hot water sedimentary buildups barite-silicolite-ferrodolomite-secondary layer silicolite-nodular chert limestone in the Xiangzhou fault basin,there are strong relation between the hot water sedimentary buildups and the ore deposits,the hot water sediment event have played a important role in the ore forming course.As a result,this paper hold the opinion that there are three types of ore deposit in the study are,the first type is the syngenetic Pb-Zn-multi-metal—Barite ore deposit formed in the sea floor hot water sedimentent, the second type is the stratabound Pb-Zn-multi-metal ore deposit formed as the hot brine evolution in the fault basin, while the third type is the structure-constrainted Cu-multi-metal—Barite ore deposit formed as the hydrothermal silting these fault-cranny and reactived with country rock. The ore-forming matters mainly came from Devonian and Cambrian stratum, some portion came from deep magmatism; The ore-bearing fluid came from the seawater and rainwater, which infiltrated follow the deep faults and been heated in the deep, but there was still deep fluid mixed into the ore-bearing fluid.The heat mainly came from the terrestrial heat and magmatism.At different region or different type of ore deposits have different ore forming temperature, overall, the Pb、Zn、Au deposit in the northern part has the ore forming temperature 181—230℃, while the Pb、Zn、pyrite in the southern part has the temperature 135—197℃.We have did the valley’s secondary soil geochemical prospecting at the scale 1:25000 in some parts of this area systemly, meanwhile, we have collected 1:50000,1:100000 soil geochemical data this area systemly, then we larged the 1:25000 soil geochemical data’s scale to 1:50000 or 1:100000, and then did some revise to the data we collected using these data, at last draught the anomaly map again. This article would select the main ore-forming element to state the soil geochemical character. On the whole, we found the soil geochemical has some characters as the following:①The Au、Cu、Ba、Zn、Pb anomaly is very obvious in silicification area, while the Zn、Pb anomaly is very obvious in limestone area, and the Au、Ag、Cu is very obvious in silicolite area;②The Ba anomaly is very widespread, especially in silicification area, while in the "Guanqiao formation" in limestone area, the Ba anomaly is also very widespread, and the Zn takes second place;③There are mainly two types of elements group in anomaly, one group is the Ba-Zn-Pb while the other group is the Ba-Cu-Au;④From north to south, there are some laws in the elements grouping, that is they have such grouping from Cu-Au-Zn-Pb-Ba-Ag to Ba-Zn-Pb-Cu to Pb-Zn-Ba as from north to south。Beside, we have stated the geophysics character in our study area simply.Based on these knowledge, we summarized the mineralization law in our study area. At the time of mineralization, the minerogenetic began as the low Devonian forming, and then in the "Guanqiao sedimentary"of low Devonian, there came the hot brine minerogenetic as the Xiangzhou fault basin had already formed, most of the deposit in our study area had formed in this time.And at the Yinzhi-Yanshan period, this area had undergone great tectonic movement and magmatism, the ore deposit had been reformed, and the nervation of Cu、Pb、Zn had arised. In the space distribution, the tectonic setting determined the ore deposits distributed, the source bed and the interface of layers determined the ore-bearing stratum, while the mini-structure、hot water deposit、alteration and minerogenetion had determined the ore body’s location mineral’s grouping and zoning.In the mineral grouping, metallogenic specialization and heritage, as well as the tectonic setting and metallogenic geology condition determined the ore types and mineral grouping.At the last, we have built two kinds of mineral resource prediction and assessment model, No.1:to the strata-bound Pb、Zn、pyrite and barite deposit; No.2:to the hydrothermal Cu、Pb、Zn、Au and barite deposit. According to the two MRPA model, we abstracted geology variances and evaluated each of them, revised them by expert commentary, and then sorted them according the benefit to mineralization each geology variances did, at last we calculated the weight of each geology variances in every forecast grid and generated the map for the preferable ore-finding area.After that work, we have defined four probable ore-forming area, they are Dongxiang-Tongwan Pb、Zn、pyrite probable forming area, Shuicun-Dongxiang Pb、Zn、Cu probable forming area, Toupai-Sicun barite、Cu、Pb、Zn probable forming area and Guchang-Longjiang Cu、Au、barite probable forming area, Meanwhile, we have also defined thirteen preferable ore-finding area, among them, the A grade is four,B grade is four,and C grade is five.After this study, we got the conclusion as following:①There are three types ore deposit in western Dayaoshan, the first type is the syngenetic Pb-Zn-multi-metal—Barite ore deposit formed in the sea floor hot water sedimentent, the second type is the stratabound Pb-Zn-multi-metal ore deposit formed as the hot brine evolution in the fault basin, while the third type is the structure-constraints Cu-multim-metal—Barite ore deposit formed as the hydrothermal silting these fault-cranny and reactived with country rock. Among them,the second type is very widespread in our study area,and so it is the main type we should pay great attention to in our exploration.②The hot water sedimentary had played a important role in the metallogenic, they have strong relation between the ore deposit in space distribution and genesis, and the characters is very obvious and stable.While in the past ore exploration and study in this area, we payed little attention to the hot water sedimentary, so we should realize the importance of the hot water sedimentary and do some stud, we may make great progress in our exploration unexpected, it is also one of the most important step to go away from the traditional exploration thinking in this area.③There is a very typical character that the ore in this area have the three ore controlling factors "source, fill, cover" to an organic whole and three ore forming laws"stratum, face, position"to an organic whole character.④The ore indication and ore-finding sign is very clearly in the preferable ore-finding area, the ore-forming condition is good, there are many ore deposits and mineralization outcrops in the preferable ore-finding area too, meanwhile, most of this area have skin-deep exploration, so if we have the right theory and better technology, there is no doubt that our exploration will make great progress in this area.更多还原