新疆博格达山北麓白杨河剖面页岩地球化学特征及其地质意义

通过博格达山北麓白杨河剖面芦草沟组页岩的地球化学特征的综合研究,讨论了芦草沟组页岩的元素富集特征和沉积环境以及源区物源特征和构造背景。结果表明:1研究区页岩P元素极为富集,这受控于页岩中凝灰质火山灰夹层的广泛发育;2对比于世界页岩微量元素分布,白杨河页岩相对富集Li、B、Pr、Tb、Dy、Ho、Er、Tm和Lu元素,其他元素相对亏损;3白杨河剖面页岩地化参数揭示芦草沟组自下而上气候由温湿向干热转变,进而引起水体由淡水向咸水的转变和还原程度的进一步加强;4物源区遭受低级-中等风化程度,物源类型主要为长英质火成岩,其次为铁镁质火成岩;5物源区大地构造背景以大陆岛弧-活动大陆边缘构造背景为主。     

ASD地面光谱仪在新疆白杨河铀矿床蚀变信息研究中的应用

新疆白杨河铀矿床是我国目前已探明的中型矿床,矿床蚀变特征的研究有助于对白杨河矿床外围及深部找矿提出更好的找矿认识。使用ASD可见光-短波红外地面光谱仪对白杨河矿床地表以及钻孔岩心进行光谱测量,发现了矿床中蚀变矿物主要有高铝绢云母、中铝绢云母、低铝绢云母、绿泥石、蒙脱石、赤铁矿、褐铁矿等。矿床地表铀矿化异常地段主要发育高铝绢云母蚀变;钻孔岩心中铀矿化富集部位蚀变矿物组合为高铝绢云母、绿泥石、赤铁矿。研究结果可为矿床外围及深部铀矿勘探提供参考与借鉴。     

遥感技术在内蒙古东乌珠穆沁旗萨麦地区的找矿应用

本文以内蒙古东乌珠穆沁旗萨麦地区1:5万巴彦塔拉等4幅区域地质调查范围为研究区,以ETM+影像数据为信息源,以波谱理论为基础,从遥感图像中提取蚀变信息继而进行遥感找矿实践。针对区内铁染、羟基蚀变类型使用主成分分析等方法,将研究区划分为10个异常区,结合区域构造特征情况,对异常区域开展了1:1万路线调查,综合判定后,选择了4个找矿靶区进行了化探剖面探测并进行了成果分析,结果显示遥感蚀变信息与野外调查和化探异常吻合较好。     

Geochemical Constraints on the Origin of Banded Iron Formation‐Hosted Iron Ore from the Archaean Ntem Complex (Congo Craton) in the Meyomessi Area,Southern Cameroon

Banded iron formations (BIFs) are the most significant source of iron in the world. In this study, we report petrographic and geochemical data of the BIF from the Meyomessi area in the Ntem Complex, southern Cameroon, and discuss their genesis and the iron enrichment process. Field investigations and petrography have revealed that the studied BIF samples are hard; compact; weakly weathered; and composed of magnetite, subordinate quartz, and geothite. The geochemical composition of the whole rock reveals that iron and silica represent more than 98 wt% of the average composition, whereas Al₂O₃, TiO₂, and high‐field strength elements (HFSE) contents are very low, similar to detritus‐free marine chemical precipitates. The total iron (TFe) contents range from 48.71 to 65.32 wt % (average of 53.29 wt %) and, together with the low concentrations of deleterious elements (0.19 wt % P on average), are consistent with medium‐grade iron ores by global standards. This interpretation is confirmed by the SiO₂/Fe₂O_3total versus (MgO + CaO + MnO)/Fe₂O_3total discrimination plot in which most of the Meyomessi BIF samples fall in the field of medium‐grade siliceous ore. Only one sample (MGT94) plots in the high‐grade magnetite–geothite ore domain. The high Fe/Ti (376.36), Fe/Al (99.90), and Si/Al (29.26) ratios of the sample are consistent with significant hydrothermal components. The rare earth elements (REE) contents of the studied BIF samples are very low (∑REE: 0.81–1.47 ppm), and the Post‐Archaean Australian Shale (PAAS)‐normalized patterns display weak positive Eu anomalies (Eu/Eu*: 1.15–1.33), suggesting a syngenetic low‐temperature hydrothermal solutions, similar to other BIF worldwide. However, the Meyomessi BIFs show high Fe contents when compared to the other BIFs. This indicates an epigenetic mineralization process affected the Meyomessi BIF. From the above results and based on the field and analytical data, we propose that the genetic model of iron ores at the Meyomessi area involves two stages of the enrichment process, hypogene enrichment of BIF protore by metamorphic and magmatic fluids followed by supergene alteration as indicated by the presence of goethite in the rocks.     

Porphyry Copper Deposit Prognosis in the Middle Region of the Bangonghu–Nujiang Metallogenic Belt,Tibet, Using ASTER Remote Sensing Data

The B angonghu–N ujiang metallogenic belt is considered to be T ibet’s third copper belt after the Y ulong and G angdese copper belts. The D uolong gold‐rich porphyry copper deposit, located in the western part of the B angonghu–N ujiang belt was recently recognized as a superlarge prospect. The A dvanced S paceborne T hermal E mission and R eflection R adiometer (ASTER ) was used to characterize the D uolong porphyry deposit alteration area, and three methods, color enhancement, band ratio transformation, and spectral angle mapping, were utilized to extract the phyllic and argillic alteration zones, which are typically considered the most important predictors of porphyry copper. Seven prospecting areas, which match mapped alteration zones, were delineated in the D uolong deposit. In addition, an ASTER image of the eastern region of the B angonghu–N ujiang belt in the X iongmei area was used to extract alteration information, and an area with image characteristics similar to the D uobuza and B olong ore deposits was identified as a prospecting area. Numerous malachite outcrops were identified in the field, and both laboratory analysis and isotopic dating confirmed that the deposit had formed concurrently with the D uobuza deposit (119 M a). Geologic mapping at the 1:5000 scale was conducted in the area, and three types of ore‐bearing rocks were identified, indicating that this area has significant potential to host ore deposits. The discovery of the X iongmei copper mining area is significant for the B angonghu–N ujiang belt.     

陕西凤太矿集区多金属成矿作用的构造控制

陕西凤县-太白(简称凤太)矿集区铅、锌、金、银、铜多金属资源丰富,已发现二十余个大中小型矿床。在大地构造位置上,凤太矿集区位于南秦岭造山带北缘,紧邻商丹缝合带。以往的工作缺乏对矿集区整体的构造研究,本次工作通过比较系统的构造测量和解析,提出在南秦岭晚三叠世碰撞造山过程中,凤太矿集区南北两条边界断裂带的左行走滑运动导致在区内衍生了NNE向主压应力场,从而形成了NWW向复式褶皱、脆韧性剪切带、断裂和节理(纵向破裂)、B型线理,以及NNE向断裂和节理(横向破裂)、劈理、张裂隙等一系列构造组合,所有构造形迹都是在统一构造应力场下随着构造层次不断抬升,脆韧性和脆性递进变形叠加的产物,共同构成了一个大型压扭性走滑双重构造变形系统。在构造几何学上,凤太矿集区整体上表现为一个隔档式复式褶皱,由一组NWW向紧闭复背斜和一组相对宽缓复向斜组成。区内的多金属成矿作用、岩浆活动、动力变质变形作用的同位素年龄数据集中于230~190Ma。综合地质演化和成矿作用的研究成果,提出在南秦岭碰撞造山过程中引发的动力变质变形作用和岩浆活动提供了成矿元素和成矿流体,在温压梯度以及浮力效应的驱动下向上运移至走滑双重构造变形系统中的有利扩容空间中发生充填型和交代型矿化,即凤太矿集区多金属矿床是区域大规模变形变质-岩浆活动-流体作用的产物,是在构造作用这一主导因素控制下形成的一个多金属后生热液成矿系统。     

贵州泥堡金矿床构造蚀变体岩相学及地球化学特征

贵州泥堡金矿构造蚀变体(SBT)为产出于茅口组(P_2m)和龙潭组(P_3l)或峨眉山玄武岩(P_3β)之间沉积间断面-不整合界面附近的一套硅质蚀变岩石组合。采用光学显微镜及ICP-MS研究SBT样品岩相学及元素地球化学特征,结果显示,SBT矿石样品中主要矿物有石英、黄铁矿、褐铁矿、萤石、白云石和辉锑矿等,蚀变类型主要为黄铁矿化、白云石化和硅化,微观结构主要为砂状、岩屑-凝灰碎屑结构、交代结构等,构造主要有浸染状、块状、角砾状、条带状和脉状构造。SBT微量元素标准化曲线以Au、As、Sb、Hg、Te的强烈富集,Li、Sc、Cr的亏损和Cd、Ta的富集为特征。稀土元素CI球粒陨石标准化配分模式图表现为轻稀土富集的右倾型,LREE/HREE为6. 98～19. 91,"四分组"效应明显,重稀土分馏不明显,解释为受热液作用强烈; SBT微量元素标准化图及稀土元素配分曲线均表现出与围岩相似,表明继承了原岩的元素组成;δEu为0. 80～1. 84,显示Eu从明显负异常到明显的正异常;δCe为0. 72～1. 25,显示Ce从明显负异常到弱正异常,认为流体来源于深部或至少经历过对富含斜长石源区的水-岩反应,而不是含矿地层的改造热液。     

甘肃省明舒井地区高光谱蚀变异常及找矿分析

正明舒井地区位于甘肃省北西侧,敦煌市北侧、瓜州县北西侧。前人在该区及周边区域开展了区调、矿调及相关多金属矿的勘查工作(王瑞军等,2014,2017),在遥感地质方面,仅开展了多光谱遥感的应用工作,而针对高光谱遥感的研究工作还未开展。明舒井地区基岩出露好、地形起伏小、切割弱,地表蚀变发育,矿床、矿点分布较多,具备开展高光谱遥感技术的地质和自然地理条件,有利于发挥高光谱的技术优势。     

青海茫崖石棉矿区变质超基性岩的蚀变演化序列：岩石化学及矿物学证据

青海茫崖石棉矿区超基性岩体是由原岩以纯橄岩、辉橄岩和橄辉岩为主体组成的富镁质超基性岩体,经历自变质和后期多期热液的叠加变质蚀变作用,经蛇纹石化后形成蚀变完全的蛇纹岩岩体,其中部分蛇纹岩又进一步发生滑石化及碳酸盐化蚀变为滑石菱镁片岩、菱镁滑石片岩、滑石片岩和菱镁岩等。本文在野外地质调查基础上,在室内通过镜下岩矿综合鉴定、全岩化学成分分析以及电子探针成分分析等手段进行了岩石化学特征、矿物学特征及其蚀变演化过程研究。结果表明,该变质超基性岩体蛇纹岩主要特征组合矿物为蛇纹石(利蛇纹石、叶蛇纹石、纤蛇纹石)、磁铁矿、菱镁矿、滑石、水镁石、铬铁矿,变余矿物有斜方辉石、单斜辉石和铬铁矿,滑石菱镁片岩类主要组成矿物为菱镁矿、滑石、蛇纹石及磁铁矿,局部可见石英脉。该地区变质超基性岩体较完整地记录了橄榄岩水化、滑石化及碳酸盐化作用过程的各个阶段,超基性岩蚀变演化过程主要有两个作用阶段:(Ⅰ)橄榄石、辉石类矿物的蛇纹石化作用及蛇纹石绿泥石化作用;(Ⅱ)富Ca、CO2流体交代蛇纹石、滑石及水镁石的碳酸盐化作用。蛇纹石化等变质蚀变作用促进了Si、Mg及Fe元素化学活动性,使元素发生富集与迁移,对于次生矿物的形成与演化起到了一定的催化作用。多期不同组成流体热液的交代作用过程,清晰地展示了利蛇纹石、纤蛇纹石和叶蛇纹石的演化序列,以及滑石、水镁石、铬铁矿和磁铁矿的形成过程及标形特征。     

基于ASTER与Sentinel-2A融合数据的云南普朗铜矿化蚀变信息提取

云南普朗铜矿区是我国提高战略性金属矿产铜矿资源的主要潜力地段,该矿区位于多云多雨山地高原区,采用传统地面调查方法开展找矿勘查工作受限较大,而遥感技术可在其中发挥重要作用。鉴于此,本研究选取ASTER和Sentinel-2A多光谱遥感数据,在光谱协同统一两种数据源的地表反射率基础上,采用高通滤波(High-Pass Filtering,HPF)的融合方法兼顾两种数据在短波红外波段和可见光近红外波段的优势,获取了具有高空间分辨率和高光谱保真度的ASTER-Sentinel-2A融合数据集;进而利用"比值+主成分分析法"与"主成分分析+能谱-面积法",开展了普朗铜矿区矿化遥感蚀变信息识别,并通过深入分析及野外验证,提出了对普朗铜矿蚀变信息分布特征及找矿潜力地带的新认识:(1)在原蚀变填图工作中判定为青磐岩化带的东部区域,重新进行了蚀变带的划分;(2)东部区域中新划分的钾化硅化带和绢英岩化带,具有较大找矿潜力。本研究可为普朗铜矿找矿勘查提供参考。