西藏尼木岗讲斑岩铜钼矿床地质特征及成矿预测

发布时间：2018-07-10 12:55

  本文选题：成岩-成矿年代学 + 岩浆岩地球化学　； 参考：《中国地质大学》2017年博士论文

【摘要】：西藏尼木岗讲铜钼矿床大地构造位于冈底斯陆缘火山-岩浆弧,成矿带上位于冈底斯带中段。矿床是由一系列产于二长花岗斑岩中的板状次级铜钼矿体组成。将岗讲Cu-I矿体作为主要研究对象,对矿体形态变化特征、成岩成矿年代学、矿化富集规律及成矿机理等进行重点研究,采用EH-4、高精度磁测技术,结合已有遥感、土壤地球化学测量、激电测量数据的再处理,在岗讲矿区及外围开展找矿预测评价工作。通过研究,所获得的主要成果及认识如下:(1)岗讲Cu-I矿体总体上由一系列近南北向、向西陡倾的板状次级矿体组成,矿体品位、厚度定量分析表明,品位数值为单峰分布,北段矿体厚度大于南段矿体,品位略低于南段矿体,矿体垂向上具有“上铜下钼”的分带特点。(2)在充分分析岗讲矿区主要侵入岩体的矿物组成、主量及微量元素基础上,探讨了区内岩体的岩浆来源、形成的地质背景,对岩体的含矿性进行了评价。岗讲侵入岩体属于高钾钙碱性准铝质-弱过铝质I-S过渡型花岗岩,相对偏向S型。各岩体微量元素普遍富集Rb、Th、U、Sr等大离子亲石元素,相对亏损Nb、Ta、Zr等高场强元素,强烈亏损HREE、Y和Yb元素,稀土元素分配模式均表现为弱负铕异常的右倾斜轻稀土富集型,反映岩体之间相似的岩浆源区,形成于印度-亚洲大陆碰撞后的应力松弛伸展阶段;从元素富集角度对各岩体与成矿关系进行评价,认为二长花岗斑岩是主要的成矿母岩;岗讲矿区矿化斑岩与无矿化岩石微量元素对比研究表明,两者具有相似的稀土、微量元素分配模式,矿化斑岩∑REE、LREE/HREE、(La/Yb)N随着矿化强度的增强而表现为连续下降的趋势,暗示原岩与矿化斑岩的内在联系,微量元素在热液活动中呈比例迁出。(3)系统的成岩成矿年代学研究表明,岗讲矿床二长花岗斑岩、花岗闪长斑岩和英云闪长玢岩LA-ICP-MS锆石U-Pb加权平均年龄分别为16.6±0.3Ma(MSWD=0.94),16.1±0.2Ma(MSWD=1.07),14.4±0.4Ma(MSWD=1.12),结合野外地质调查,厘定出岗讲复式岩体侵入序列为含巨斑黑云二长花岗岩→二长花岗斑岩→流纹斑岩(深部定名为英云闪长玢岩)→安山玢岩;12件辉钼矿样品获得的Re-Os同位素模式年龄加权平均值为13.4±0.1Ma(MSWD=0.65),等时线年龄为13.6±1.6Ma(MSWD=1.2),成矿时代为中新世,成岩成矿是一个连续的岩浆-热液演化过程,形成于印度-亚洲大陆碰撞造山后的伸展阶段。(4)构建岗讲Cu-I矿体原生晕分带模式,垂向上表现为上部Mn、Co、Sb、Cu,中部Cu、Mo、Ni、Bi、W,下部为Zn、Ag、Pb,选取分带指数值(Cu×Mo×Sb)D/(Pb×Zn×Ag)D作为构建深部找矿预测模型的指标,建立了岗讲矿床原生晕定量评价模型;围岩蚀变分带由内而外依次为钾-硅化带、黄铁绢英岩化带、泥化带和桻磐岩化带,铜钼矿化主要发生于钾-硅化阶段,黄铁矿绢英岩化次之,多种蚀变带叠加是成矿的有利部位;划分矿床的形成阶段,包括岩浆期、热液期和表生期,岩浆期矿化规模大,但强度普遍偏低,热液期和表生期对铜钼矿化起到了明显的改造富集、次生氧化淋滤作用;关于矿床的形成机理,认为岗讲矿床的形成是印度-亚洲大陆碰撞后伸展阶段的构造-岩浆-成矿事件之一,铜钼矿化与中新世两期含矿热液活动息息相关,含矿热液沿岩体裂隙叠加贯入,多期次结晶分异最终形成品位较高的细脉-浸染状铜钼矿体;控矿构造、剥蚀深度、盖层性质最终导致岗讲与厅宫、白容、驱龙矿床在矿体品位、规模方面的差异。(5)在总结岗讲矿区及外围找矿标志和找矿预测准则基础上,针对不同勘查区的研究程度、地质特征选取不同的勘查技术手段进行找矿预测,提出预测依据并对找矿远景区进行圈定和评价,认为岗讲EH-4剖面西侧的D1低阻异常空间上连续性好,为矿致异常的可能性较大;白容南部具有成为白容“第二条”东西向矿(化)带的潜力;绒岗蒙西北部遥感蚀变异常明显,野外踏勘发现规模较大的褐铁矿化带,显示巨大的找矿前景;提出了白容北部寻找类似于汤巴拉矽卡岩型铜多金属矿的新思路,试验性EH-4剖面和高精度磁测剖面反映的深部异常位置与构建的白容-汤巴拉地质推测模型计算的理论深度基本一致。圈定的找矿远景区有待更进一步的勘查与研究工作,以期实现提质增储目的。
[Abstract]:In this paper , the major achievements and understandings are as follows : ( 1 ) The Cu - I ore body is composed of a series of plate - shaped secondary copper - molybdenum ore bodies , which are formed in two - length granodiorite porphyry . The main achievements and the recognition are as follows : ( 1 ) The Cu - I orebodies are mainly composed of a series of plate - shaped secondary ore bodies which are located in the south - to - north direction and the west - steep dip , and the ore grade and thickness quantitative analysis indicate that the grade values are single - peak distribution , and the ore body thickness of the north segment is larger than that of the south segment orebodies , and the ore body is slightly lower than that of the south segment orebodies . ( 2 ) Based on the analysis of the mineral composition , main quantity and trace elements of the main intrusive rock mass in the mining area , the ore - bearing properties of the rock mass are evaluated . The results show that the intrusive rock mass belongs to the high - field strength elements such as Rb , Th , U , Sr and so on , and the REE distribution patterns show that the two feldspar granite porphyry is the main ore - forming mother rock . The age - weighted average age of the two - long granite porphyry and the REE distribution pattern is 13.6 卤 1.6Ma ( MSWD = 1.2 ) . ( 4 ) The primary halo zoning pattern of Cu - I orebodies is constructed . The vertical upward trend is the upper Mn , Co , Sb , Cu , Cu , Mo , Ni , Bi , W , the lower part is Zn , Ag and Pb . ( 5 ) On the basis of summarizing the geological prospecting and prospecting indicators and the prospecting prediction criterion , the authors put forward the basis for the prediction of prospecting for different exploration areas and the geological characteristics , and put forward the prediction basis and the potential for prospecting the remote areas . The southern part of Bairong has the potential to be the second " east - west mineral " zone of the EH - 4 section , and the experimental EH - 4 section and the high - precision magnetic survey section reflect the large scale of the brown iron ore belt . The exploration and research work is still to be further explored in the area of prospecting and exploration , with a view to achieving the purpose of upgrading the quality and storage .
【学位授予单位】：中国地质大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P618.41;P618.65
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本文编号：2113455