鄂尔多斯盆地砂岩型铀矿深穿透地球化学勘查方法实验

鄂尔多斯盆地尚未开展区域化探扫面工作。文中以东胜砂岩型铀矿区为例,开展深穿透地球化学勘查方法实验。东胜铀矿床产于侏罗系直罗组下段,为隐伏矿床。研究发现,富含细粒级地表结层是半干旱盆地砂岩型铀矿区域地球化学勘查的有效采样介质。在东胜砂岩型铀矿区及周边2 000 km2的方法实验中,每4 km2采集一个样品,过筛后取-200目进行全量分析,在矿化出露区及隐伏矿区圈出了铀及相关元素的地球化学异常。对元素比值R=lnU/(lnCe+lnY+lnZr+lnNb)在不同区域分布特征的研究表明,样品中活动态铀是形成铀异常的主要原因,提取细粒级土壤组分进行全量分析,可作为区域深穿透地球化学的砂岩型铀矿找矿指标。在矿床尺度深化穿透地球化学勘查方法中,因实验区地形特点使得富含细粒级地表结层样品不易普遍取得,地表土壤的全量分析不能满足勘查要求,需要采用铀专属性强的提取试剂进行元素活动态分析。文中采用作者研制的MML-U活动态提取剂,在东胜铀矿区孙家梁矿段剖面实验中,成功探测到矿体上方土壤中的U、Mo、V等元素的活动态异常。     

Geochemical challenges of diverse regolith-covered terrains for mineral exploration in China

In recent years mineral exploration has concentrated on concealed deposits in regolith-covered terrains. In China, the regolith-covered landscapes mainly include desert windblown sand basins, desert peneplains, semi-arid grassland, loess plateaus, forestry land, alluvial plains and laterite terrains. These diverse regolith-covered areas represent geochemical challenges for mineral exploration in China. This paper provides an overview of recent progress on mechanisms of metal dispersion from the buried ore deposits through the transported cover to the surface and penetrating geochemical methods to detect the anomalies. Case studies show that, in arid and semi-arid desert sand-covered terrains, sampling of fine-fraction (− 120 mesh, < 0.125 mm) clay-rich horizon soil is cost-effective for regional geochemical surveys for sandstone-type uranium, gold, and base metal deposits. Fine-fraction sampling, selective-leaching and overburden drilling geochemical methods can effectively indicate the 210 gold ore body at Jinwozi goldfield. In alluvium-covered terrains, fine-grained soil sampling (− 200 mesh, < 0.074 mm) combined with selective leaching geochemistry shows clear ring-shaped anomalies of Cu and Ni over the Zhouan concealed Cu–Ni deposit. In laterite-covered terrains, the anomalies determined by the fine-fraction soils and selective leaching of absorbed metals on coatings of Fe–Mn oxides coincide well with the concealed deposit over the Yueyang ore deposits at the Zijin Au–Cu–Ag field. Nanoparticles of hexagonal crystals mainly native copper, gold and alloys of Cu–Fe, Cu–Fe–Mn, Cu–Ti, and Cu–Au were observed in gases, soils and ores using a transmission electron microscope (TEM). The findings imply that nanoparticles of gold and copper may migrate through the transported cover to the surface. Uranium is converted to uranyl ions [UO₂^2 +] under oxidizing conditions when migrating from ore bodies to the surface. The uranyl ions are absorbed on clay minerals, because clay layers have a net negative charge, which needs to be balanced by interlayer cations. Nanoparticles of Au and Cu and ion complexes of U are more readily absorbed onto fine fractions of soils containing clays, colloids, oxides and organic matters. Thus, fine-grained soils enriched with clays, oxides and colloids are useful media for regional geochemical surveys in regolith-covered terrains and in sedimentary basins. Fine-fraction soil sampling combined with selective leaching geochemistry is effective for finding concealed ore bodies in detailed surveys. Penetrating geochemistry at surface sampling provides cost-effective mineral exploration methods for delineation of regional and local targets in transported cover terrains.     

盆地金属矿穿透性地球化学勘查模型与案例

近20年来,越来越多的大型金属矿床在盆地内部及其边缘被发现。传统的勘查地球化学方法对盆地及盆山边缘覆盖区无能为力,深穿透地球化学探测技术为解决盆地及其边缘覆盖区找矿难题提供了一种行之有效的手段。文章通过对沉积砂岩盆地铀矿、火山岩盆地银多金属矿、变质岩盖层铜镍矿和沉积盖层金矿开展探测试验,得出:(1)砂岩型铀矿中活动性铀主要以铀酰络阳离子的形式存在,铀酰络阳离子很容易受地下水运动及蒸发蒸腾作用而发生迁移,迁移通道包括砂岩的孔隙、构造裂隙等,到达地表后,铀酰络阳离子易与土壤中带负电的黏土矿物结合而赋存其中,使用微细粒分离和活动态提取两种方法均能圈定矿致异常;(2)火山岩盆地中,与火山岩近乎同期形成的矿床,矿床形成过程中含矿流体携带成矿元素银、金、铜等沿构造裂隙运移,迁移到地表后被土壤中的黏土矿物所吸附,使用土壤活动态测量和微细粒分离测量均能有效圈定已知矿体,异常直接位于矿体上方;(3)变质岩盆地超基性岩体在侵位过程中,岩体与变质岩接触带将产生大量的构造裂隙,因此当流体通过岩体与围岩接触带时,将携带矿体中铜、镍向上迁移至地表,形成环状异常;(4)洛宁盆地金矿成矿过程中,成矿元素金、银等以络合物、纳米级单质或合金等形式通过流体携带顺着构造破碎带向上迁移,地表岩石风化发生成矿元素解离,后期被黄土覆盖,矿体或岩石解离的化合物或纳米颗粒可以穿过黄土孔隙向上迁移至地表,并赋存于表层黄土的细粒级黏土中,因此采用土壤微细粒分离测量可圈出矿致异常。本文根据深穿透地球化学方法应用效果,异常的形态,并结合盖层的特点,成矿元素的存在形式、迁移方式以及在地表的赋存状态,初步建立了盆地金属矿深穿透地球化学勘查模型,为盆地盖层区地球化学勘查提供了理论与技术支撑。     

陕西秦岭巴山地区化探异常查证找矿实例分析

在陕西秦岭巴山地区9万km²内,通过1:20万区域化探扫面,发现了一批多元素综合异常,并根据地质构造背景分析划分出五个异常带(区)。其中新发现的北秦岭Au、Ag、Pb、Zn异常带,规模大、元素组合复杂且含量高,为一重要的金、多金属成矿带。1986年开始,在该区大力开展区域化探异常查证工作。通过1:5万水系沉积物测量,圈定了以金元素为主的化探异常。在主体异常部位系统地开展了1:1万土壤测量和槽探工程,于当年就在周至县马鞍桥发现了金矿体。随后又根据化探异常特征,布置了钻探和坑探工程验证。经进一步检查和详查,确认马鞍桥金矿为一大型金矿床。     

土壤氡气测量在鄂尔多斯盆地西缘砂岩型铀矿勘查中的应用

在鄂尔多斯盆地某矿床进行土壤Rn测量条件试验的基础上,对鄂尔多斯盆地西缘研究区进行了区域测量工作。通过对数据处理,划分出5片具有成矿远景的异常区,并对异常进行评价解释,为钻探施工提供了重要的参考依据。研究结果表明,土壤Rn测量方法能够在盆地区域范围内划分出异常区,是一种快速评价砂岩型铀矿化的重要地球化学勘查方法。     

覆盖区勘查地球化学理论研究进展与案例

覆盖区勘查地球化学近年在迁移机理研究上最显著的进展是在矿体上方覆盖层土壤中直接观测到Cu、Au等纳米金属微粒和植物细胞中的成矿元素,从纳米尺度和分子水平直接观测到的微观迁移证据使得覆盖区勘查地球化学迁移机理研究从描述性模型向实证性模型实现了质的飞跃.通过对北方干旱沙漠覆盖区金矿、中部湿润农田覆盖区铜镍矿、南方植被红土覆盖区的铜金银矿研究表明,Cu、Au元素主要以纳米微粒形式穿透火山岩、变质岩和土壤覆盖层,用深穿透地球化学的微粒分离和铁锰氧化物提取技术可以有效指示隐伏矿体.干旱盆地砂岩型铀矿的研究表明,铀在氧化条件下以铀酰络阳离子(UO₂2+) 形式迁移到地表,并被土壤中粘土所吸附,吸附相中的铀占全部的铀比例最高(17%~40%),使用物理分离粘土或化学提取粘土吸附相铀可以有效地指示深部铀矿体.      

河南省南召县银洞岭银矿床地球化学特征

银洞岭银矿床位于豫西南铅锌银多金属成矿区.通过对区域成矿地质背景研究,选择找矿靶区,采用土壤地球化学、植物地球化学、壤中气汞量测量等方法,确定矿化有利地段并实施钻探验证,最终发现隐伏银矿床.银洞岭银矿床的发现,是深穿透地球化学方法寻找隐伏矿床的成功范例.     

Surface geochemical and biogeochemical expression of base‐metal mineralization at Woodlawn,New South Wales,Australia

The presence of base‐metal mineralization at Woodlawn was first recognised early in 1968 when a roadside reconnaissance geochemical sampling survey, conducted over felsic volcanic rocks in the Goulburn‐Tarago area, encountered anomalous B horizon soils containing up to 200 ppm Cu, 800 ppm Pb and 300 ppm Zn. Regional soil thresholds have been determined at 50 ppm Cu, 90 ppm Pb and 50 ppm Zn. Chip samples from the subsequently located gossan revealed up to 2000 ppm Cu, 8000 ppm Pb and 2000 ppm Zn, 500 ppm Sn, 25 ppm Ag and 3000 ppm As.

The first grid B horizon soil geochemical survey was conducted in 1968 over the gossan and surrounding area, and repeated with closer spaced sampling in the first half of 1970. The first survey delineated strong Cu (to 1000 ppm) and Pb (to 2500 ppm) anomalies coincident with the gossan zone, and intense hydromorphic zinc anomalies (to 3000 ppm) located down slope from the gossan in residual clay‐soils derived from dolerite bedrock. Threshold values have been determined at 140 ppm Cu, 700 ppm Pb and 580 ppm Zn. Ag and Sn in B horizon soils show pronounced anomalies coincident with the gossan and are suitable metals for geochemical target definition. Of fourteen trace elements determined in 1974 from B and C horizon soils on two lines across the ore zone Cu, Pb, Zn, Se, Ba, Sn and Ag show direct correlation with the mineralization, whereas Cd and Mn show moderate hydromorphic dispersion, having accumulated principally in clay soils derived from dolerite weathering. As, Sb and Bi, whilst responding over the ore zone, show elevated values in soils over hanging‐wall units; Ni and Co show maximum levels in soils over dolerite bedrock.

Bark and leaves of Acacia mearnsii, collected from a line across the gossan, contain anomalous levels of Cu, Pb, Zn, Sn and Ti near the ore zone, and weaker, but clearly anomalous Mn and Ni levels over dolerite bedrock. Both bark and leaves of Acacia mearnsii reflect the presence of concealed mineralization. The shrub Solanum linearifolium grows preferentially over and close to the Woodlawn ore zone, where it contains up to 840 ppm Cu, 250 ppm Pb, 7300 ppm Zn, 6 ppm Sn and 250 ppm Ti in leaf ash compared with levels of 200 ppm Cu, 2 ppm Pb, 400 ppm Zn, 0.8 ppm Sn and 60 ppm Ti in plants growing 1.5 km from the ore zone. This shrub has potential as an indicator of base‐metal mineralization.     

A regional-scale geochemical survey of soil O and C horizon samples in Nord-Trøndelag,Central Norway: Geology and mineral potential

A highly efficient, low-density sampling strategy was employed to study the geochemical expression of geological bodies and the mineral potential on the county scale in Central Norway. Soil O and C horizon samples (N = 752) were collected in Nord-Trøndelag and parts of Sør-Trøndelag, and analysed for 53 chemical elements (Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Ge, Hf, Hg, In, K, La, Li, Mg, Mn, Mo, Na, Nb, Ni, P, Pb, Pd, Pt, Rb, Re, S, Sb, Sc, Se, Sn, Sr, Ta, Te, Th, Ti, Tl, U, V, W, Y, Zn, and Zr) and Pb isotopes in an aqua regia extraction. At the sample density of one site/36 km² the four metal deposits, which have been mined in the area within the last 50 years were all detected as geochemical anomalies. In addition, a number of new anomalies that may warrant follow-up surveys were found. In terms of geology the Grong–Olden Culmination is marked by a distinct ²⁰⁶Pb/²⁰⁷Pb isotope anomaly. Geochemical differences distinguish the most important belts of mafic metavolcanic lithologies in the area. Though the Fosdalen iron ore deposit is only marked in the soil O horizon, the C horizon outlines the more prominent anomalies of possibly economic interest. Climatic factors like the input of marine aerosols along the coast are clearly visible in the soil O horizon. Low-density geochemical mapping of two sample materials provides important complementing information for the interpretation of the geochemical variation in Nord-Trøndelag county.     

冲积平原区隐伏金属矿地气法试验研究

文章通过冲积平原区(山东王家庄铜矿区)的地气试验研究及其与常规土壤测量结果的对比,总结了冲积平原区隐伏金属矿矿床上方地气元素的分布特征.研究结果认为:①在不同覆盖条件、常规土壤测量无效的情况下,地气测量均可发现清晰的金属元素异常,异常强度高,且与矿体空间位置相吻合;显示出地气法在厚覆盖条件下对隐伏金属矿的独特作用;②液...     

Bio-climatic imprints on a Holocene loess palaeosol from China

Micromorphology, heavy minerals, pollen and soil properties were examined in a typical Holocene loess profile in the north of the Loess Plateau, consisting of a palaeosol (locally known as the Ansai palaeosol) underlain by the Malan loess and overlain by modern loess. The palaeosol consists of an upper humus-rich (AB) horizon over a clay-rich (Bt) horizon. The humus-rich horizon is intensely weathered, contains precipitated calcitic material derived from the overlying modern loess, and has both high pollen content and diversity. Clay coatings in the clay-rich horizon indicate formation by eluviation–illuviation of clay. Pedogenetic characteristics and pollen analysis imply that the vegetation during the time of most intensive soil development is likely to have been a warm-temperate forest. A complex interpretation of the loess–palaeosol sequence recognizes several development stages. The phase of soil development, maximum and minimum limiting ages for which are ca. 8800 and 4400 ¹⁴C years BP, involved continuing but reduced loess deposition, and successive Holocene bio-climatic environment overprinted new features on the palaeosol.     

二连盆地哈达图铀矿床综合物化探特征及找矿意义

二连盆地哈达图铀矿床是我国大型可地浸砂岩型铀矿床,矿体埋深大、品位富,研究其地电化学等综合物化探特征,可为建立覆盖区航放异常有效查证技术方法提供依据.基于矿床地质及航磁航放特征的分析,开展组合物化探方法测量及特征分析.研究表明:哈达图铀矿床位于受断裂构造控制的北东向、北北东向中等磁场区及中等-弱磁场的梯度带;航空及地面...     

隐伏铜矿区土壤微细粒测量有效性实验——以江西通江岭铜矿为例

土壤微细粒分离测量是一种可应用于隐伏矿勘查的地球化学技术, 亟需开展多景观、多矿种有效性实验。本文以位于湿润低山丘陵区的江西通江岭铜矿为研究区, 开展土壤微细粒分离测量试验, 并讨论其异常形成机理。结果显示, 主成矿元素Cu与Zn、Pb、Ag、Au等有较强的相关性, 该组元素富集系数大、空间变异强, 在研究区内趋于强烈富集。面积性试验结果显示Cu-Pb-Zn-Au多元素组合异常与已知矿体有良好对应关系。剖面试验表明断层和地层接触界面土壤成矿元素含量较高, Cu、Pb、Zn等异常可以指示隐伏矿体。根据元素组合及空间分布特征, 预测研究区东部第四系覆盖区存在隐伏铜金矿体以及19线南段深部有隐伏多金属矿体, 其中19号线南段在2019年详查工作中钻获铜铅锌多金属矿体。以上结果证实了低山丘陵景观区土壤微细粒测量探测隐伏矿床的有效性。断裂带、地层接触带既是容矿空间, 也是深部成矿物质向地表迁移的主要通道, 灰岩地层中的溶蚀缝与构造缝是次要迁移通道。深部成矿物质在多营力作用下迁移至地表, 并被土壤微细粒中的铁锰氧化物、黏土矿物和无定型硅铝氧化物所捕获, 在地表形成地球化学异常。     

综合物化探方法在朱拉扎嘎金矿的应用

朱拉扎嘎金矿,经综合物化探普查,在大面积覆盖区发现0.5km²高视极化率、中低视电阻率激电异常和低缓磁异常。已施工的8个钻孔均见矿,估算黄金储量大于30t。沿走向,激电异常在北东、南西两端有大幅度向外延伸趋势,可能是深部硫化物矿层向外延伸的反映。     

会昌岩背锡矿田地球化学特征及隐伏矿床预测异常指标探讨

在岩背锡矿田,运用土壤地球化学异常寻找锡矿床,取得了显著效果,尤其是岩背锡矿床的发现和扩大,以及上湾隐伏锡矿床预测,为应用土壤地球化学异常找矿积累了经验。本文在阐述矿田土壤地球化学异常分布的基础上,着重对与矿床有关的土壤地球化学异常特征,以及隐伏锡矿床预测的异常指标进行了探讨。     

土壤地球化学测量在三道湾子金矿床的应用

三道湾子金矿位于大兴安岭燕山期成矿带东南部, 是近年来新发现的典型的石英脉型金矿床。通过在该矿床土壤中进行的金元素富集层位及粒度试验, 确定B2层为土壤测量的取样层位和-40目为样品加工粒级, 圈定Au、Ag、As、Sb异常多处, 各元素异常浓集中心与已知金矿体吻合较好。经过对异常验证, 发现了新矿体, 扩大了矿床规模, 土壤测量在该区找矿效果显著。     

隐伏矿床上方纳米铜颗粒存在形式与成因

在铜镍矿床覆盖层土壤颗粒中和其下伏原生矿石中同时采集到金属纳米颗粒,颗粒在其粒径大小、形貌、连接和簇聚形式、微粒元素组合等性质上相似,表明两者为同成因物质,是内生成矿作用元素存在形式,土壤颗粒中金属纳米颗粒来自深部矿体。在金矿上方土壤颗粒中采集的纳米金属颗粒,与在铜镍矿床覆盖层土壤颗粒中采集观测到的微粒,在微粒性质可以对比,表明元素的纳米微粒是稳定形式,在其源区形成后可借助多种营力,穿越后期地质作用覆盖层,在近地表被土壤地球化学障捕获滞留,是深部矿化的有效传递物质。深穿透地球化学技术可从土壤中分离富集采集到此纳米微粒,并通过其微粒性质,追踪其源区性质。此研究结果在实用意义上,可为以土壤作为采样介质的深穿透地球化学勘查探测覆盖区隐伏矿方法提供理论依据。     

河南千鹅冲钼矿地球化学异常特征及找矿模型

河南省光山县千鹅冲钼矿是近年在大别山北麓发现的特大型隐伏斑岩钼矿床。通过梳理该矿床从发现到突破近30年的找矿历程,研究矿床成矿地质特征及与矿床相关的元素区域异常、局部异常和原生异常特征,总结了该钼矿地球化学找矿标志及找矿模型。该矿床的找矿实践又一次证明了斑岩型钼矿化探具有较好的找矿效果,无论是1∶20万、1∶5万水系沉积物测量,还是1∶1万土壤测量或钻孔岩石测量等方法,均能揭示斑岩型钼矿的指示元素,并具有良好的找矿指示作用。     

地球化学勘查快速圈定找矿靶区——以黑龙江省黑河市大新屯锑-金矿床的发现为例

黑河市大新屯锑-金矿床位于大兴安岭成矿带东北部,区内构造、岩浆活动频繁.1∶5万水系沉积物Sb、Au、Hg异常强度较高,规模较大,是金及多金属成矿有利部位.为了对区内1∶5万水系沉积物异常进行评价,选定了规模最大的新07Hs-35异常,利用土壤地球化学测量工作方法对异常进一步查证.经土壤地球化学测量工作后圈定Sb、Au、Hg、Ag、As、W土壤地球化学异常多处,以Sb、Hg、Au异常为主,各元素异常浓集中心吻合较好.因此利用槽探工程对圈定的土壤地球化学异常进行了验证,发现了锑-金矿体,从而确定了大新屯锑-金矿找矿靶区,说明地球化学勘查快速确定找矿靶区是成功的.     

Geochemical patterns from local to global

The historical development of geochemical exploration is, in a sense, a process of progressive enlargement of areal coverage by exploration projects and progressive widening of sampling space. Along with this process, a hierarchy of geochemical patterns from small to large is gradually discovered and understood. In this paper, we try to summarize systematically the whole hierarchy of geochemical patterns from local, regional, provincial, megaprovincial to global, using examples obtained in China.Local anomalies (various types of dispersion halos, trains and fans) within areas not exceeding a few km², can be delineated when sampling is done with very close intervals in limited areas. Regional anomalies within areas of tens to hundreds km² and threshold values lower than local anomalies can be identified only when large areas of more than thousands of km² are mapped with wider space sampling. Geochemical provinces with areas of thousands or tens of thousands of km² can be discovered if even larger areas, of more than tens or hundreds of thousands of km², are covered with very low density sampling. More than millions of km² should be covered in order to discover geochemical megaprovinces somewhere in the world. Such megaprovinces are often associated with extraordinarily large mineral resources. If ultra-low density geochemical mapping can be carried out across national boundaries on a continental or global scale, we could find even broader geochemical patterns which will reflect the global tectonic features.The classification of geochemical patterns according to their sizes is necessary because it will be extremely useful in planning sampling layout in order to hit targets of certain size ranges. This in turn is arranged in different geochemical projects for achieving specific aims.