戈壁覆盖区准平原化过程中成矿元素的分散与迁移——以金窝子金矿为例

我国的干旱戈壁大部分地区都经历了准平原化过程,在这一过程中伴随着元素的迁移和再分配,使得地球化学勘查变得十分困难.本文以新疆金窝子矿区为例,针对戈壁覆盖区化探采样工作中出现的地球化学异常,从自然景观和地质演化人手,利用空气动力反循环钻连续实时取样,研究元素在戈壁覆盖层中的地球化学空间分布特征,分析得出戈壁覆盖区准平原化过程中元素的分散及迁移情况,进而让我们更深入地去研究荒漠戈壁区地球化学异常的形成机理问题.     

干旱戈壁区金属元素的垂向变化与分散——以新疆金窝子金矿为例

本文选择被风化物覆盖(4米至几十米厚)的金窝子金矿作为研究对象。分析矿体上方风化层和非矿上方的垂直剖面中的各种金属元素的总量及活动态含量,以获得金属元素在风化层中的活动规律,为化探找矿提供方法依据。结果发现金等的某种活动态的分布模式在矿体上方呈现双层分布,即他们趋向于在垂直剖面的底部与顶部富集,而在中部降低。可以解释为元素在剖面底部风化层中的富集是由于金继承了矿体的风化产物,而在地表或近地表的富集是由于从矿体迁移至地表的元素被粘土物质和铁锰氧化物膜所吸附。     

金矿立体地球化学探测模型与深部钻探验证

深部资源地球化学探测科学问题的的焦点是元素大深度垂向迁移机理和立体地球化学探测模型的建立。本文以胶东蚀变岩型金矿和贵州水银洞卡林型金矿钻孔岩芯和地表联合取样获得的数据, 建立千米深度立体地球化学探测模型。蚀变岩型金矿立体地球化学模型显示, Au、S和Hg与金矿密切相关, 分布模式既有相似性又有差异性, Au的立体几何分布模式兼具矿化剂元素S和远程指示元素Hg的双重特征, 金异常和矿化剂元素硫与矿体倾斜方向一致, 反映了成矿过程中流体沿控矿构造的轴向运移; 金异常与类气体元素汞在垂向上一致, 而且出现从矿体到地表的连续贯通式异常, 反映了流体沿微裂隙和纳米孔的垂向迁移。卡林型金矿立体地球化学模型显示, Au、As、Sb、Hg、Tl和S在不整合面都显示高含量特征, 与深部层状主矿体分布一致; 在矿体上覆地层中都存在弱异常, 显示了明显的成矿流体沿隐伏微小断裂垂向迁移特点; 所不同的是Sb和Tl元素在不整合面附近显示了最高的元素含量, 而Sb和Hg在近地表均显示了明显高的异常特征。立体几何模型清晰地显示了矿体的展布特征和范围, 而且金及其伴生元素垂向迁移在地表形成清晰异常, 为利用金及伴生元素和矿化剂元素进行深部矿体三维预测提供了重要依据, 对指导深部金矿勘查发挥了重要作用。针对胶东蚀变岩型金矿地表完全被土壤覆盖区的穿透性地球化学微细粒级土壤采样, 金属活动态提取分析圈定的异常, 经深部钻探验证, 胶东焦家成矿带五一村3200 m钻探, 在2428.00~3234.16 m深度发现6层矿化体, 其中高品位矿体位于2854 m深度; 上宫金矿地表基岩出露, 采集断层泥或裂隙岩石样品, 可以清晰探测深部异常, 经2000 m钻探, 在1312 m处发现高品位金铅锌银矿体; 贵州水银洞采集地表细粒级土壤, 能够直接有效地揭示深部金矿体, 经500~1500 m钻探验证, 在300~1500 m深度新增金资源量203 t。     

干旱荒漠区隐伏金矿覆盖层中金的分布与迁移：以新疆金窝子金矿田210金矿带为例

以新疆金窝子金矿田210金矿带为例,实验研究了该区地气和土壤活动态测量等深穿透地球化学方法的效果。实验表明地气测量和土壤活动态测量可以有效地反映覆盖层下隐伏矿体。揭露矿体覆盖层的钻孔研究表明,金活动态形式具有“C”型分布特征。采集矿体上方地表异常位置土壤孔隙中地气、土壤样品,使用透射电子显微镜(TEM)实测样品中微粒物质的粒径、形貌和成分,在地气和土壤中观测到了Au-Cu、Au-Bi成矿元素纳米微粒,此微粒是形成地表深穿透地球化学异常的物质,来源于覆盖层下隐伏矿体。微粒到达地表,可以形成地气和土壤活动态异常。纳米微粒具有可从土壤颗粒表面分离的性质,在其向上迁移过程中,可以从吸附固定状态解吸,此性质可以用于解释活动态异常在钻孔垂直剖面上的“C”型分布。     

甘肃省合作市早子沟金矿原生晕三维特征及深部找矿预测

为了评价早子沟金矿深部找矿潜力和找矿方向,以早子沟金矿61个钻孔为研究对象,对矿体出露较厚大的70勘查线原生晕数据进行多元统计分析和三维空间分布特征研究。研究表明:(1)相关分析和聚类分析结果反映,与主成矿元素Au相关性最密切的元素为As、Ag;(2)原生晕的形态特征和空间分布特征显示,矿体原生晕发育,且分带明显,矿床的前缘晕元素为As、Sb、Hg,近矿晕元素为Au、Ag、Cu、Pb、Zn,尾晕元素为W、Mo、Bi;(3)对原生晕数据进行三维插值分析,构建了早子沟金矿各元素原生晕三维模型。Au、As、Sb、Ag等指示元素和As+Sb/Au+Ag元素异常累加比值的异常模型显示,在2500 m以浅,异常规模较小;在2500 m以深,异常规模呈现出向深部越来越大,且延伸稳定。结合异常元素的空间分布特征,提出早子沟金矿78～85勘查线2000 m以深仍有较大的找矿潜力。     

地壳元素分布及其生态环境效应

地球演化引起物质分异加上人类活动使元素在地表的分布很不均匀.从局部到全球,地球化学异常分布具有谱系模式.元素不仅是生物的基本组成物质,而且在生命活动中起着复杂而重要的作用.生物与其生存环境的协调平衡是生物演化和发展的基本准则,因此,元素地球化学异常的谱系分布模式对应着相应的生物作用和生态效应.本文初步探讨了不同级次地球化学异常的生态环境效应特征.     

东北太平洋东部CCB53孔沉积物Mn元素活化、迁移和沉淀与沉积环境演化的统一

本文引用地质矿产部“七五”东北太平洋CCB53孔柱状沉积物（＜63μm）的元素地球化学分析数据,采用“标准元素对比值法”定量分离Mn元素在不同物源（陆源、生物源、热液源和自生源）中的绝对含量,确定Mn元素地球化学本底,提取CCB53柱状沉积物中Mn元素的正、负异常。据此讨论了Mn元素发生活化、迁移和再沉淀的时间演化规律,即从沉积物的底部到顶部（22．42～0Ma）,Mn元素经历了四个活化、迁移和沉淀旋回,分别为840～320、320～170、170～120和120～0。Mn元素的正、负异常分布与自生源组分和氧化还原环境的变化对比分析表明,Mn元素正、负异常分布与自生源组分的高→低变化规律和氧化还原条件的周期振荡紧密相关。早期成岩过程中发生的氧化还原环境的振荡是元素发生活化、迁移和沉淀的动因。     

黑色页岩风化过程中元素的活动性及参照系的选取初探--以湖南省麻田、桃花江剖面为例

系统考察了湖南省麻田和桃花江两个不同发育程度的下寒武统黑色页岩风化剖面,并提出了元素在理想剖面中的分布模式(概念模型);通过对比分析这两个剖面中元素的分布特征与理想分布模式的关系,并结合元素相关性研究、等质量图解的判别分析、微量元素的赋存状态及地球化学性质的探讨,认为在黑色页岩风化过程中,Ti为不活动元素,可作为参照系来计算其它元素的相对迁移性,Nb、Ta的活动性较小,Zr与Hf之间存在着共迁移现象;研究表明化学风化程度是影响元素活动性的重要因素.     

浙江省诸暨地区元素地球化学分布与标度律

以浙江省诸暨地区为例, 从3个不同尺度上(从区域到局部) 研究了元素的地球化学分布模式, 提出元素服从多重分形分布的观点, 并将这种分布模式解释为地球化学背景与异常之间的关系.在矿床上方通常存在多重分形嵌套的地球化学模式.最后, 指出了标度不变性原理在地球化学研究中的应用前景.      

大冶铜绿山铜铁矿床尾矿砂中重金属与微量元素环境地球化学特征研究

为了解铜绿山铜铁矿床尾矿砂中重金属元素的释放迁移地球化学过程及其扩散范围,运用ICP.MS对大冶铜绿山铜铁矿床尾砂库的尾矿砂及其相关的水系沉积物和土壤中重金属元素、稀土元素进行了测试分析.环境地球化学研究发现,研究区重金属元素在尾矿砂垂向剖面和水系沉积物中具有较明显的垂向和横向空间分布规律;尾砂库西北边水稻田土壤明显受到Cu、Zn、Cd等重金属元素的污染,稀土元素分布模式及微量元素比值研究揭示了污染原因可能是水稻田土壤继承了附近废弃的选矿厂和矿体的特征;尾矿砂和水系沉积物稀土元素分布模式及微量元素比值的变化规律,在一定程度上可以解释重金属元素在垂向和横向空间上的分布特征.     

Geochemistry of red residua underlying dolomites in karst terrains of Yunnan-Guizhou Plateau: II. The mobility of rare earth elements during weathering

The aim of this study is to characterize the evolution of the rare earth elements (REE) in the Pingba red residua on karst terrain of Yunnan-Guizhou Plateau. The in-situ weathering and the two-stage development of the profile had been inferred from REE criterions. The REE were significantly fractionated, and Ce was less mobilized and separated from the other REEs at the highly enriched top of the profile. This is consistent with the increase of oxidation degree in the regolith. And it is also suggested that the wet/dry climate change during chemical weathering caused Ce alternative change between enrichment and invariance in the upper regolith. Chondrite-normalized REE distribution patterns for samples from dolomites and the lower regolith are characteristic of MREE enrichment and remarkable negative Ce-anomalies patterns (similar to the convex-up REE patterns). The following processes are interpreted for the patterns in this study: (1) the accumulation of MRRE-rich minerals in dolomite dissolution, (2) water–rock interaction in the weathering front, and (3) more leaching MREE from the upper part of the profile. The latter two explanations are considered as the dominant process for the formation of the REE patterns. Samples from the soil horizon exhibit typical REE distribution patterns of the upper crust, i.e., La_N/Yb_N=10 and Eu/Eu*=0.65. All data indicate that the leaching process is very important for pedogenesis in this region. The experiments demonstrating that abnormal enrichment of REE at the upper regolith–bedrock interface is caused by a combination of volume change, accumulation of REE-bearing minerals, leaching of REE from the upper regolith, and water–rock interaction during rock–soil alteration processes. Our results support the conclusion that the weathering profile represents a large, continental elemental storage reservoir, whereas REE enrichment occurs under favorable conditions in terms of stable tectonics, low erosion and rapid weathering over sufficiently long time.     

Gold dispersion in a tropical rainforest weathering profile at Dondo Mobi, Gabon

At Dondo Mobi in the gold district of Eteke, south Gabon, gold mineralization was studied in a tropical forest setting. The mineralization occurs in quartz veins within amphibolites of an Archaean gneiss-amphibolite series. Gold distribution patterns were studied in the different horizons of the weathering profile and in the different grain-size fractions of the materials sampled from three pits sunk in the weathered zone: upslope (pit P1), directly overlying (pit P2) and downslope (pit P3) of the mineralization.The weathering profile consists of an upper, thick, loose sandy argillaceous horizon (H1), an irregular nodular horizon with laterite nodules or blocks (H2) and a saprolite layer (H3) up to 70 m thick. In each pit, the specific geochemical signature of the bedrock is recognized in the three horizons of the weathering profile. Some groups of elements, e.g., Cr-Ni or Ba-V-P₂O₃, characterize amphibolite or black shale, respectively. Signal attenuations in the upper horizon can be explained by a homogenization effect. That can be related to a mushroom supergene dispersion, simultaneously inducing vertical decrease and lateral enrichment in element contents. Gold also mushrooms extensively in the different horizons of the weathering profile. The dispersion pattern is somewhat anisotropic, a strong enlargement being observed in the upper (H1) and intermediate nodular (H2) horizons alike. However, the evolution of Au distribution is not the same for all grain-size fractions: (a) in the finest fraction, Au is regularly distributed in the weathering profile at the anomalous top and tends to preserve an equivalent level of concentration laterally; (b) in the coarsest fraction, the maximum Au content is found in the upper horizon just above the mineralized structure; it is rapidly decreases laterally, in the surface halo.The Au geochemical dispersion halo consists mainly of fine-grained gold developed from rather coarse-grained mineralization. Its characteristics suggest that Au dispersion was produced as a result of Au dissolution together with collapse of the weathering profile causing gold migration over short distances.The minimal volumetric reduction of saprolite in the upper horizon can be estimated to be in the range of 60%, on the basis of the content of the different grain-size fractions and the density variations in the various horizons.In exploration, geochemical techniques, even using wide sample spacing, are proving quite adequate to prospect for Au in tropical rainforest weathering environment. Indeed, significant, well-contrasted dispersion haloes facilitate detection of rather confined mineralization.     

申家窑金矿床地气测量异常特征

河南申家窑金矿床属典型的蚀变破碎带型金矿,矿区大部分被第四系沉积物所覆盖。文章通过偏光显微镜与扫描电子显微镜观察、电子探针微区分析、矿石成分化学分析等方法,认为申家窑金矿床的主要金矿物为自然金和银金矿,主要载体矿物为石英、黄铁矿和方铅矿。作者在总结矿床矿物学特征的基础上,实验研究了地气测量在该隐伏矿床上方黄土覆盖层的勘查效果。地气测量使用泡塑为捕集介质,利用surfer软件绘制元素空间分布图。元素空间分布图表明Au具有明显的地球化学异常,同时Cu、Pb、Zn等成矿伴生元素也存在异常。综合矿床矿物学的研究结果和元素空间分布特征,认为地气测量异常为矿致异常,地气异常结果能够指示深部隐伏矿体的产状。地气测量方法作为深穿透地球化学找矿方法之一,在研究区能够反映深部矿化,可以应用于黄土覆盖区寻找隐伏矿床。     

Geochemical dispersion of gold related to copper-gold mineralization in northeastern Thailand

The nature of gold dispersion in soils and stream sediments associated with a copper-gold-mineralized system in northeastern Thailand has been investigated as a basis for identifying appropriate geochemical exploration techniques for the search for comparable deposits in similar environments.Soils were collected with varying relationships to mineralization as a basis for determining sample representativity, size distribution of gold, variation with soil horizon and possible pathfinder elements. Similarly, stream sediments were collected to estimate sample representativity, size distribution of gold, variation of gold with depth in the stream sediment profile and to compare the relative recoveries of gold in field-panned and laboratory-prepared heavy-mineral concentrates. Samples were analyzed for Au and potential indicator elements by a variety of methods but mostly by instrumental neutron activation analysis.Results indicate the consistent distribution of fine-grained gold in soils which allows Au analysis of relatively small samples from B-horizon soils to be used effectively and reliably to identify the surficial patterns of gold mineralization in the study area. Anomalous patterns of other indicator elements, Co, As, Cu, Sb, W, Pb, Zn, Ag, Fe and Mn, may contribute additional information regarding type of mineralization. This finding indicates the effectiveness of soil surveys in gold exploration, particularly in areas of deep weathering where fresh bedrock exposures are infrequent.Unlike soils, size distributions of gold in stream sediments, as a result of the local flow regime, vary both between sampling sites and at depths within a sampling site. Exploration requires Au analysis of the fine fraction (minus 63 μm) of active stream sediments to reduce the problem of sampling representativity. The presence of coarse-grained gold in the stream channel has drawn attention to the possible benefit of using the conventional field-panning method as a semiquantitative technique for providing immediate results. However, highly erratic distribution of pannable gold on a very local scale together with variable proportions of the total gold recovered in field-panned or heavy-mineral concentrates highlights a potentially serious drawback of the method. Combination of analysis of the minus 63 μm fraction and field panning appears warranted to cover the possible existence of gold of a wide size range in stream sediments.The overall results indicate the utility of geochemical exploration techniques in the search for gold mineralization. However, particular care is necessary in the design and implementation of geochemical techniques to ensure maximum reliability of exploration.     

荒漠戈壁区超低密度地球化学调查与评价——以东天山为例

中国的干旱荒漠戈壁区,约占国土面积的1/4.自然特点是极其干旱,沙漠和戈壁广布,土壤呈碱性.大部分面积尚未进行区域化探扫面工作,即使进行工作的地区,由于风成沙和土壤碱性的影响,结果并不理想,难以了解整个地区资源潜力.超低密度地球化学方法经过近10年发展,已经显示它不受地表覆盖物影响,能够快速有效地圈定战略靶区.因此,超低密度地球化学方法被用于东天山1.5×105km2的调查试点研究,发现弱胶结层是干旱荒漠区超低密度调查的有效采样介质,并且深部含矿信息主要赋存在细粒级部分和氧化地球化学障中,使用细粒级部分与提取氧化物膜中的金属元素相互补充可以有效地识别含矿信息.使用超低密度地球化学方法可以达到迅速、有效圈定有利于大型矿床或矿集区战略靶区的目的.通过1.5×105km2地球化学调查,制作了30余种元素地球化学图,填补了东天山部分地区地球化学空白.新发现远景Cu、Au、U和W异常10余处,并发现东天山存在3条Cu异常带东天山北带、中带和南带,其中土屋铜矿和黄山铜镍矿都位于中带,新发现的维权铜矿位于南带,北带还有待于进一步证实.相信这些异常的发现,对今后整个东天山矿产勘查的战略部署具有重要意义.     

戈壁覆盖区景观演化与AU的分散迁移

我国西北部一些戈壁荒漠区经历长期的风化侵蚀作用而形成准平原,景观演化过程改变了元素的分散模式,对地球化学勘查是很大的难题.为了研究戈壁覆盖区元素在准平原化过程中的分散与迁移情况,选择新疆金窝子金矿,并运用空气动力反循环钻开展了采样研究工作.结果表明:金倾向于在矿体上方垂向剖面的顶层和底层土壤中富集;地表或近地表富粘土层...     

川西北下二叠统栖霞组微生物丘的发现及地质意义*

通过野外露头与钻井剖面的室内外分析,确认在四川盆地西北部(川西北)下二叠统栖霞组中发育有微生物丘,它们主要由凝块灰(云)岩、叠层灰(云)岩和微生物粘结颗粒灰(云)岩等组成。这些微生物碳酸盐岩发育较为典型的凝块、叠层、窗格、粘结等组构。微生物丘大小不一,实测高度一般为几十厘米至几米,宽度通常变化于几米至几十米之间,具有底平顶凸的典型丘形外貌,以发育向上变浅的沉积序列为特征,一般由丘基、丘核、丘盖3个微相组成,也可与颗粒滩共同构成微生物丘滩复合体。基于区域古地理背景和微生物丘特征的剖析,认为川西北地区栖霞期沉积环境总体受限,推测为半局限—局限台地环境,水深较浅,能量普遍不高;海平面频繁的相对升降变化和微生物丘的侧向迁移叠置,导致发育于缓坡背景下的碳酸盐岩台地极易受限,引起早期沉积物发生与丘滩发育密切相关的准同生期白云石化作用。因此,微生物丘滩复合体是栖霞组白云岩储集层发育的物质基础,台缘坡折带、台内缓坡折带和高地是栖霞组白云岩储集层发育的有利区带,这对寻找规模性层位不稳定的带状白云岩储集层具有重要的指导作用,并将大大拓展栖霞组白云岩储集层的勘探领域。     

Concentration of gold in in situ laterites from Mato Grosso

The gold concentration studied is located in lateritic soils overlying Precambrian schists of the Cuiaba Group in Mato Grosso, Brazil. The following five horizons may be recognized from bottom to top: (1) a gray-blue altered schist horizon, (2) a red argillaceous alterite, (3) a horizon characterized by iron oxihydroxide-rich pebbles and quartz fragments in an iron oxihydroxide-rich matrix and clays, (4) an iron crust, and (5) the present soil. The most significant gold content is found in the third horizon just below the iron crust. According to geological study and morphological observations of the gold particles, the gold ore mined today is the result of two combined processes, i.e., the ferrallitic alteration of quartz lodes enclosed in schists and the effect of the red argillaceous alterite which acts as an impervious structure preventing the largest gold grains from migrating downward during their mechanical concentration.     

叠合型不整合结构与油气分布样式：以塔中石炭系东河砂岩为例

探讨了东河砂岩三级层序界面处发育的不整合结构在空间上有序分布所造成油气的差异运聚。将东河砂岩划分为底部不整合上覆层、原状输导层、风化残余层、风化黏土层、顶部不整合上覆层和区域盖层6类成藏结构单元。成藏结构单元在塔中西北地区和塔中东南地区组成不同,构成两类7种不整合成藏结构样式。两类成藏结构样式分别对应两类的油气藏组合:(1)在塔中地区西北部成藏结构单元被分隔,油气沿东河砂岩段顶部风化黏土层及盖层底部发生运移,形成不整合遮挡型油气藏组合,包括不整合上覆层背斜油气藏、不整合上覆层岩性油气藏和风化残余层低幅背斜油气藏3种油气藏;(2)在东南地区成藏结构单元之间发生连通,油气底部不整合上覆层和盖层底部向隆起部位侧向输导,形成不整合连通型油气藏组合,包括连通型背斜油气藏和连通型地层超覆油气藏2种油气藏。这为东河砂岩的进一步勘探开发提供了指导。