国际地球化学填图样品分析方法和数据对比

以中国和世界发达国家或地区(欧洲、北美、澳大利亚与日本)过去10年内完成的或目前正在开展的全球性或国家性地球化学填图项目为例,总结了国际地球化学样品分析技术的新进展,并以中国实验室与欧洲实验室的分析数据的对比结果,剖析国际地球化学填图样品分析技术面临的挑战。研究表明:分析组成地壳所有元素的构想已被越来越多国家性、全球性地球化学填图项目所采纳;中国是世界上唯一具有填图样品76元素分析能力的国家;高水平的分析实验室(欧洲与中国)取得的数据大部分可以实现对比,但仍有10余个元素的分析数据存在明显偏差。实现所有分析元素数据的全球可对比,应是今后国际地球化学填图样品分析技术的主要发展方向。     

国际地球化学填图样品分析方法和数据对比

以中国和世界发达国家或地区(欧洲、北美、澳大利亚与日本)过去10年内完成的或目前正在开展的全球性或国家性地球化学填图项目为例,总结了国际地球化学样品分析技术的新进展,并以中国实验室与欧洲实验室的分析数据的对比结果,剖析国际地球化学填图样品分析技术面临的挑战。研究表明:分析组成地壳所有元素的构想已被越来越多国家性、全球性地球化学填图项目所采纳;中国是世界上唯一具有填图样品76元素分析能力的国家;高水平的分析实验室(欧洲与中国)取得的数据大部分可以实现对比,但仍有10余个元素的分析数据存在明显偏差。实现所有分析元素数据的全球可对比,应是今后国际地球化学填图样品分析技术的主要发展方向。     

A regional soil and sediment geochemical study in northern California

Regional-scale variations in soil geochemistry were investigated in a 20,000-km² study area in northern California that includes the western slope of the Sierra Nevada, the southern Sacramento Valley and the northern Coast Ranges. Over 1300 archival soil samples collected from the late 1970s to 1980 in El Dorado, Placer, Sutter, Sacramento, Yolo and Solano counties were analyzed for 42 elements by inductively coupled plasma-atomic emission spectrometry and inductively coupled plasma-mass spectrometry following a near-total dissolution. These data were supplemented by analysis of more than 500 stream-sediment samples from higher elevations in the Sierra Nevada from the same study site. The relatively high-density data (1 sample per 15 km² for much of the study area) allows the delineation of regional geochemical patterns and the identification of processes that produced these patterns. The geochemical results segregate broadly into distinct element groupings whose distribution reflects the interplay of geologic, hydrologic, geomorphic and anthropogenic factors. One such group includes elements associated with mafic and ultramafic rocks including Cr, Ni, V, Co, Cu and Mg. Using Cr as an example, elevated concentrations occur in soils overlying ultramafic rocks in the foothills of the Sierra Nevada (median Cr = 160 mg/kg) as well as in the northern Coast Ranges. Low concentrations of these elements occur in soils located further upslope in the Sierra Nevada overlying Tertiary volcanic, metasedimentary and plutonic rocks (granodiorite and diorite). Eastern Sacramento Valley soil samples, defined as those located east of the Sacramento River, are lower in Cr (median Cr = 84 mg/kg), and are systematically lower in this suite compared to soils from the west side of the Sacramento Valley (median Cr = 130 mg/kg). A second group of elements showing a coherent pattern, including Ca, K, Sr and REE, is derived from relatively silicic rocks types. This group occurs at elevated concentrations in soils overlying volcanic and plutonic rocks at higher elevations in the Sierras (e.g. median La = 28 mg/kg) and the east side of the Sacramento Valley (median 20 mg/kg) compared to soils overlying ultramafic rocks in the Sierra Nevada foothills (median 15 mg/kg) and the western Sacramento Valley (median 14 mg/kg). The segregation of soil geochemistry into distinctive groupings across the Sacramento River arises from the former presence of a natural levee (now replaced by an artificial one) along the banks of the river. This levee has been a barrier to sediment transport. Sediment transport to the Valley by glacial outwash from higher elevations in the Sierra Nevada and, more recently, debris from placer Au mining has dominated sediment transport to the eastern Valley. High content of mafic elements (and low content of silicic elements) in surface soil in the west side of the valley is due to a combination of lack of silicic source rocks, transport of ultramafic rock material from the Coast Ranges, and input of sediment from the late Mesozoic Great Valley Group, which is itself enriched in mafic elements. A third group of elements (Zn, Cd, As and Cu) reflect the impact of mining activity. Soil with elevated content of these elements occurs along the Sacramento River in both levee and adjacent flood basin settings. It is interpreted that transport of sediment down the Sacramento River from massive sulfide mines in the Klamath Mountains to the north has caused this pattern. The Pb, and to some extent Zn, distribution patterns are strongly impacted by anthropogenic inputs. Elevated Pb content is localized in major cites and along major highways due to inputs from leaded gasoline. Zinc has a similar distribution pattern but the source is tire wear.     

区域化探数据在浅覆盖区地质填图中的应用方法研究

区域化探数据包含丰富的地质信息,可用于浅覆盖区区域地质填图。笔者系统研究了浅覆盖区水系沉积物化学成分与基岩化学成分的关系,利用水系沉积物氧化物成分,以区域岩石化学成分为约束,提出了基岩化学成分推断方法;根据水系沉积物与其矿物化学成分间质量平衡关系,提出了基岩矿物组成推断方法。在此基础上提出了地球化学推断地质图的编制方法,并在典型森林-沼泽浅覆盖区进行了试验,地质调查和钻探工程验证了该方法的有效性。充分利用区域化探资料,提取地质填图信息,是提高浅覆盖区地质填图质量的有效途径。     

Application of multi-element statistical analysis for regional geochemical mapping in Central Japan

Some 434 stream sediment samples were collected in Central Japan for a nationwide geochemical mapping project. The resulting geochemical maps are compared with geological, mineral resource and land use maps. Spatial distribution patterns of elemental concentrations in stream sediments are determined mainly by surface geology. Elevated elemental concentrations of alkali elements, Be, Ga, Y, Cs, Ba, lanthanide (Ln), Tl, Th, and U are consistent with outcrop areas of granite, felsic volcanic rock, and accretionary complexes. High concentrations of MgO, Al₂O₃, P₂O₅, CaO, 3d transition metals, Zn, and Sr are present in sediments supplied from mafic volcanic rock, high pressure metamorphic rocks, and mafic-ultramafic rocks in accretionary complexes.A procedure is established and guidelines are set for a statistical test suite for geochemical mapping. Analysis of variance (ANOVA) and multiple comparison tests are effective for comparing means among the data subsets that are classified by parent lithological materials. Among the many procedures that have been proposed for multiple comparison tests, the Holm procedure was selected for this study. Multiple comparison statistically confirmed the correspondence of elemental abundance in stream sediments with surface geologies. However, visual interpretation of some elements is inconsistent with results of multiple comparison. According to the Holm procedure, the U content in stream sediments is affected not by granite, but by felsic volcanic rock. The Holm procedure clarifies that As, Sb, and Bi, that are not explained by the presence of mineral deposits, are enriched significantly in samples derived from accretionary complexes. Hydrothermal activity on the ocean floor might affect their levels of enrichment. Significant enrichment of Cu, Zn, Cd, Sn, Sb, Hg, and Pb observed in urban areas are also supported by the Holm procedure. The authors inferred that these sediment samples had been contaminated.     

化探资料在地质填图中的应用

根据多年工作实践,总结了应用土壤地球化学资料解决基础地质问题的实例,其中包括判断下覆岩性、圈定构造、地层对比划分等问题,阐述了在解决地质问题中的地球化学原理和应用条件,介绍了如何利用残积晕在浅覆盖区、干旱草原区、热带雨林区扩大地质填图的基岩出露面积,识别推断下覆地层岩性;通过残积晕和上置晕推断隐伏构造;通过地球化学建造晕进行地层划分和对比。认为在矿产地质调查中充分利用地质调查区的化探资料,是可以提高地质填图质量的,并有助于解决常规地质工作中遇到的问题。地质与化探的结合也可以提高化探异常的地质解释能力。     

Application of geochemical mapping techniques to a complex Precambrian shield area in Labrador, Canada

Lake sediment and water geochemical data from a complex area of the Canadian shield in Labrador, Canada, display spatial variation patterns that can be linked to bedrock geology. Composite variables derived by R-mode factor analysis are effective in discriminating large-scale lithotectonic divisions, but single-element raw or residual data (corrected for effects of lake depth, Fe, Mn and LOI) provide better resolution of smaller-scale features and major tectonic boundaries.Archean high-grade gneiss regions are typified by high pH and Ni, coupled with depletion of U and F. This signature is developed most strongly over mafic igneous rocks, but is present also over Archean granitoid orthogneisses. Archean crust affected by Proterozoic structural and thermal reworking retains a high Ni signature, but is not depleted in U and F. An Early Proterozoic belt of felsic intrusive and extrusive rocks is defined by enrichment in F, U, Mo, Pb and Zn. Single-element variations suggest large-scale zonation of the belt, with the strongest enrichment over blocks interpreted to represent high crustal levels. Prominent geochemical boundaries coincide with major faults within this belt. High-grade metamorphic terranes comprising Early to Middle Proterozoic crust affected by the 1.0-Ga Grenville Orogeny show low geochemical relief, and are characterized by strong depletion in incompatible elements.In addition to reflecting the dominant rock types in each domain, some of these patterns may be related to the age, erosion level and orogenic history of the crust. For example, the Archean signature may reflect fundamental contrasts in the compositions of Archean and Proterozoic crust, suggested also by lithogeochemical and petrogenetic studies. Geochemical zonation over Early Proterozoic igneous rocks may be a function of crustal level, with the most differentiated granites, volcanic rocks and hydrothermal mineralization present in the uppermost levels of the belt. Depletion of incompatible elements over both Archean and Proterozoic high-grade metamorphic rocks may reflect expulsion of these elements by dehydration and anatexis.     

Tectonic terranes, metallogeny and regional geochemical surveys: an example from northern British Columbia

This study utilizes three major data sources: distribution of geological units; density, type, age and distribution of mineral deposits; and elemental analyses from regional geochemical stream sediment surveys to define parameters that ‘characterize’ tectonic terranes in northern British Columbia. A similar approach could be applied anywhere in the Canadian Cordillera.This area, NTS map sheets 104N, 104O and 104P along the British Columbia-Yukon border, forms a transect through allochthonous terranes into North American rocks. These are: the allochthonous island-arc Stikine, oceanic Cache Creek, cataclastic Yukon/Tanana, and island-arc Quensel terranes, the pericratonic Dorsey terrane; the parautochthonous oceanic Sylvester allochthon; and the autochthonous miogeoclinal North American Cassiar terrane. Plutonic rocks of Jurassic-Cretaceous to Tertiary age intrude all terranes.Data sources used in the study are geological base maps and reports, the Ministry of Energy Mines and Petroleum Resources' mineral deposit database (MINFILE) and analytical data from the National Regional Geochemical Survey stream sediment and water sampling program.Geological maps were compiled from various sources and plotted to act as bases for geochemical and mineral deposit overlays for analysis and interpretation.Geochemical samples were separated into background and anomalous populations and compared according to their source terranes. We found that mean concentrations from background sample populations for some elements are statistically distinctive for different terranes. Unfortunately, elemental correlation coefficients for the terranes are similar so cannot be used to characterize each terrane.Data on mineral deposits and occurrences were compiled from minfile and other sources. Particular attention was paid to deposits with histories of production or significant reported reserves. Deposits were sorted by type and commodity to produce synoptic metallogenic maps.The combined data from geological, geochemical and mineral deposit databases form a strong tool for interpreting and predicting patterns of mineralization.     

Anomalous geochemical patterns from northern Sumatra: their assessment in terms of mineral exploration and regional geology

A regional stream sediment survey has been conducted in Sumatra north of 4°N. The survey area is approximately 38,000 km² of mountainous terrain mostly covered by dense tropical rainforest. The overall sample density achieved by the survey was one per ten km². However, the difficult terrain and thick vegetation blanket have meant that a uniform sample density was not obtained. The uneven sample density has presented problems with interpretation of the geochemical patterns and identification of anomalous areas for mineral exploration purposes.Two methods have been designed for identifying mineral exploration targets from the geochemical results found by the survey. The first method uses computerised probability calculations and the second a simple empirical formula. Both methods appear to give similar results.Northern Sumatra has very distinct geochemical patterns. Copper shows a linear zone of high values along the axial Barisan Mountain Range, which are derived from two main sources: the Sumatran ophiolites and copper-rich calc-alkaline intrusives. High chromium values also occur not only over the ophiolites, but also over placers derived from them. High lead values are grouped to the east of the linear copper zone and they border the oil and gas basins of the eastern coastal strip. High tin values occur west of the copper rich intrusives, but east of the present-day subduction zone off the west coast of Sumatra. The overall pattern fails to conform to the classic zonation of mineral deposits across a simple subduction system, perhaps because large transcurrent faults have sliced northern Sumatra into blocks and so brought blocks of different provenance into contact. This explanation is confirmed by the lithium distribution, which reveals two wholly distinct provinces astride the Sumatran Fault System.     

桂北豆乍山岩体放射性地球化学特征及其干热岩资源潜力研究

对桂北豆乍山岩体钻孔样品进行了放射性生热元素含量、岩石密度和岩石热导率测试.结果 显示该岩体花岗岩U平均含量为17.49×10-6,Th平均含量为27.54×10-6,K2O平均含量为4.64％,放射性生热率平均值6.46 μW/m3,高于地壳平均值及大部分华南其他岩体的放射性生热率值;岩石密度平均在2.57 g/cm...     

Geochemical and metallogenic provinces: a discussion initiated by results from geochemical mapping across northern Fennoscandia

The concept of metallogenic province has won general acceptance in economic geology. It is agreed that metallogenic provinces offer good opportunities for exploration of new ore deposits. The concept of geochemical province is also established, but its exact meaning is disputable. In this paper, geochemical province is used as an abnormal spatial distribution of an element or element combination in a particular sample type as measured by a particular analytical technique. The practical consequences of this concept of geochemical provinces in mineral exploration seem not to have been fully utilized, although geochemical and metallogenic provinces could only be different manifestations of the same regional features. The location of geochemical provinces should be of greater importance in exploration than the location of metallogenic provinces, simply because a geochemical province can be identified early in an exploration program, while a metallogenic province cannot be defined until a number of ore discoveries has already been made. We have compared metallogenic provinces with geochemical provinces obtained by regional geochemical mapping in Fennoscandia (mainly data from the Nordkalott Project) and other places such as England, Wales, Germany and Alaska in order to study to what degree large-scale geochemical dispersion patterns can be associated with clusters of economically interesting mineral deposits.It is concluded that metallogenic provinces lie within or coincide with a number of geochemical provinces, some of which may have causal relationships with the ore deposits. It can be assumed that an enormous hierarchy of large and small geochemical provinces exist at the earth's surface. The main features of this system would be detectable by worldwide low-density geochemical mapping. Such mapping should be performed in order to shorten the time lapse between possible rises in the demand of certain raw materials and their supply. Worldwide geochemical mapping would also contribute to a better understanding of major geochemical processes of the Earth and provide baselines for environmental research.     

黔北下志留统龙马溪组烃源岩有机地球化学特征及其古环境意义

通过对黔北地区下志留统龙马溪组烃源岩的有机碳、类异戊间二烯烃、萜烷及甾烷等有机地球化学的研究,发现具有以下特征:①正构烷烃分布以单峰分布为主,主峰碳为nC₁₈~nC₂₀;②Pr/Ph比值在0.16~1.24之间,普遍具有植烷优势;③伽马蜡烷指数>0.10;④Ts/(Tm+Ts)比值较高,在0.42~0.61之间,且分布十分稳定;⑤C₂₇/C₂₉甾烷比值在0.65~1.53之间,多数样品具C₂₉甾烷分布优势;⑥有机碳含量普遍大于0.5%,且自下向上呈规律性递减;⑦δ¹³C_org<-28‰,普遍偏轻。这些特征均指示研究区龙马溪组的有机物产率较高,同时具有良好的有机质保存环境。通过对比岩性及有机地球化学剖面,将龙马溪组烃源岩划分为3个发育阶段。     

Factors controlling regional spatial distribution of 53 elements in coastal sea sediments in northern Japan: Comparison of geochemical data derived from stream and marine sediments

In all, 53 elements were analyzed in 1406 coastal sea sediment samples collected from an area off Hokkaido and the Tohoku region of Japan during a nationwide marine geochemical mapping project. The spatial distribution patterns of the elemental concentrations in coastal seas along with the existing geochemical maps in terrestrial areas were used to define natural geochemical background variation and mass transport processes. The terrestrial area is covered by mafic volcanic rocks and accretionary complexes associated with ophiolite, which has small amounts of felsic volcanic rocks and granite. The spatial distribution patterns of elements enriched in mafic lithologies such as Fe (Total Fe₂O₃) and Sc in marine environments are influenced by adjoining terrestrial materials. The spatial distribution patterns of Cr and Ni concentrations, which are highly abundant in ultramafic rocks on land, are used to evaluate the mass transport from land to the sea and the dispersive processes caused by oceanic currents. The scale of mass transport by oceanic currents occurs up to a distance of 100–200 km from the coast along the coastal areas. The regional differences of elements rich in felsic lithologies such as K (K₂O), Nb and La in marine sediments are determined mainly by the relative proportion of minerals and lithic fragments enriching felsic materials to those associated with mafic materials. The spatial distribution of elemental concentration is not always continuous between the land areas and coastal sea areas. That difference is interpreted as resulting from (1) transportation of marine sediments by oceanic currents and storm waves, (2) contribution of volcanic materials such as tephra, (3) occurrence of shell fragments and foraminifera tests and (4) distribution of relict sediments of the last glacial age and early transgression age. Contamination with Cu, Zn, Cd, As, Mo, Sn, Sb, Hg, Pb and Bi was not observed in marine environments because the study area has little anthropogenic activity. Terrestrial materials are the dominant source for these metals. The Mo, Cd, Sn, Sb, Hg, Pb and Bi are abundant in silty and clayey sediments locally because of early diagenetic processes, authigenic precipitation and organic substances associated with these elements. The spatial distribution of As concentration shows exceptions: it is concentrated in some coarse and fine sands on the shelf. The enrichment is explained by adsorption of As, sourced from a coal field, to Fe hydroxide.     

Identification and mapping of geochemical patterns and their significance for regional metallogeny in the southern Sanjiang,China

The southern Sanjiang region, southwestern China, comprises various continental blocks, tectonic sutures and arcs. This complex structural area is a proper place for the recognition of geochemical patterns and understanding of regional metallogenesis. Considering each individual tectonic unit (i.e., western South China block, Ailaoshan suture, Simao block, Changning–Menglian suture, Baoshan block and Tengchong block) as a statistical unit, this study identifies the distribution patterns of geochemical elements, distinguishes elemental associations for different geological backgrounds (controlled by the regional lithology) and diverse mineralizations, and thereby delineates the mineralized anomalies. To achieve the goals, the kriging interpolation, staged factor analysis and local singularity technology were utilized after the centered logratio (clr) transformation of stream sediment geochemical data. The spatial distributions of metallogenic elements (Au, Ag, Cu, Pb, Zn and Sn) show that not all the areas with high concentrations of elements contain ore deposits. It means that the formation of ore deposits is an independent anomalous geological event, not necessarily related to the original regional abundance of geochemical elements. The different element associations obtained by staged factor analysis of 28 elements are able to reveal the geological backgrounds and metallogenic signatures for different tectonic units. For example, the element associations for the first, second and third factors (Fs) in the western South China block are groups of Ti–Co–V, Sb–Ag–As and Th–U–Be (see text for the detailed element associations), which represent the Emeishan flood basalts, Ag–Pb mineralization and felsic rocks, respectively. Similarly, the element associations Co–V–Cu, Be–U–Th and Sb–Ag–Au for F1, F2 and F3 in the Ailaoshan suture respectively represent the ophiolite complex and mafic rocks, felsic rocks and Au mineralization. The associations from F1 to F4 in the Simao block are Th–U–Sn, V–Co–Cr, Cd–Ag–Pb and Au–Sb, which represent the Linchang batholith, mafic rocks, Ag–Pb–Zn mineralization and Au mineralization, respectively. The distribution patterns of their factor scores can roughly distinguish the anomalies caused by regional backgrounds and mineralizations. The local singularity of factor scores for mineralization can further identify mineralized areas in most of the tectonic units. Nevertheless, an exception occurs in the western South China block where the background element association, Ti–Co–V–Cu–Ni–Cr–P–Mn–Nb–Zn (F1), obscures the Au signature. Therefore, we substituted the single element Au for mineralized element association (F1) to perform singularity mapping, and obtained better result. It was concluded that the combination of staged factor analysis, local singularity and tectonic setting is effective in regional metallogenic potential analysis.     

A Triassic large igneous province in the Pontides, northern Turkey: geochemical data for its tectonic setting

A strongly deformed and metamorphosed Triassic oceanic seamount(s) and plateau succession extends as an east–west belt for 1100 km along the Pontides of northern Turkey. This succession, known widely as the Nilüfer unit, consists mainly of metabasic lava and tuff–marble–phyllite association including tectonic slices of ultramafic rock and gabbro. According to the conodont findings the unit formed during the Early to Mid-Triassic, and the isotopic age data indicate that it underwent high-pressure greenschist facies metamorphism during the latest Triassic period. The metavolcanic rocks form over 80% of the sequence. The Nilüfer unit covers an area of 120,000 km², with the volume of mafic lava estimated as 2×10⁵ km³. Such a huge volcanic pile has erupted rapidly in a relatively short period during the Early to Mid-Triassic (approx. 10 Ma). Hypotheses for the origin of the Nilüfer unit include a ‘seamount’, ‘intra-arc and/or fore-arc basin’, ‘oceanic plateau’, and ‘Early Triassic rift’. The geochemistry of metabasites and that of relict magmatic clinopyroxenes indicate that there are two main mafic rock groups in the Nilüfer unit displaying tholeiitic and alkaline affinities. No metabasite and clinopyroxene sample display typical orogenic basalt affinity or a subduction signature. Geochemical data obtained in this study are consistent with the derivation of the metabasites from the topmost extrusive layers of an oceanic plateau (LIP) together with the volcanic rocks of seamount(s).     

“三江”地区北段区域地球化学元素组合异常提取及其找矿意义

由于地球化学元素携带了某种矿化信息,因此元素地球化学异常往往是指示矿床存在的一种直接标志。随着勘查地球化学的深入发展,有关矿致地球化学异常圈定方法已成为人们关注的焦点。利用"三江"北段1∶20万地球化学数据,运用R型因子分析,查明该区不同矿化类型的指示元素组合,以因子得分为综合指标,采用泛克里格剩余值圈定地球化学异常。结果得到2种元素组合:Ag-Zn-Pb-Sb-Bi组合(与热液型铅锌银矿床有关)和Mo-Cu组合(与斑岩型钼矿床有关)。圈定的组合异常与已知的矿床点在空间上具有很好的对应关系,说明利用R型因子分析与泛克里格法相结合圈定元素组合异常的方法能够较好地确认地球化学元素组合异常,并提示异常与矿化类型之间密切相关的规律性,为"三江"北段地区找矿提供信息。     

利用自组织特征映射神经网络和K-means聚类算法挖掘区域化探数据中的地质信息

区域化探数据包含丰富的地质信息,从区域化探数据中挖掘出这些信息,对于区域地质研究具有重要意义.笔者提出了一种利用自组织特征映射网络和K-means聚类算法挖掘区域化探数据中地质信息的方法,将标准化之后的元素含量数据作为模型输入值,通过自组织神经网络进行聚类,再通过K-means算法进行二次聚类,从聚类结果中分析其中包含的地质信息.以英格兰西南部某区水系沉积物区域化探数据为例,进行实例研究以检验该方法的实际效果.实例结果表明:①利用该方法得出的聚类结果图很好地响应了地质体的空间分布,可用于推断地质体的分布特征;②地质信息隐藏在每个聚类类型的地球化学特征之中,通过对这些特征进行分析和解释,可以挖掘出其中所包含的信息;③基于SOM网络和K-means聚类的区域化探数据挖掘方法是一种有效的地质信息获取方法,对于传统区域地质研究可以起到补充和增强的作用.     

峨眉山大火成岩省和西伯利亚大火成岩省地球化学特征的比较及其成因启示

峨眉山大火成岩省和西伯利亚大火成岩省是发生于二叠 -三叠纪之交的重要岩浆事件。它们在主要元素、微量元素和Sr、Nd、Pb同位素特征上具有相似姓 ,但是峨眉山大火成岩省的不相容元素比值和同位素比值的变化范围相对要小一些。相对而言 ,峨眉山玄武岩具有高的Fe8和Sm/Yb值 ,暗示了其熔融深度较西伯利亚大火成岩省深 ,而熔融程度较低 ,两者的源区均为石榴石二辉橄榄岩。根据Nd同位素特征估算峨眉山和西伯利亚地幔柱的 Nd≈ 2 ,接近于原始地幔特征。综合其他地球化学特征 ,认为两个大火成岩省可能起源于同一个来自于核 -幔边界的超级地幔柱     

“三江”地区北段区域地球化学元素组合异常提取及其找矿意义

由于地球化学元素携带了某种矿化信息,因此元素地球化学异常往往是指示矿床存在的一种直接标志。随着勘查地球化学的深入发展,有关矿致地球化学异常圈定方法已成为人们关注的焦点。利用“三江”北段1∶20万地球化学数据, 运用R型因子分析,查明该区不同矿化类型的指示元素组合,以因子得分为综合指标,采用泛克里格剩余值圈定地球化学异常。结果得到2种元素组合：Ag-Zn-Pb-Sb-Bi组合(与热液型铅锌银矿床有关)和Mo-Cu组合(与斑岩型钼矿床有关)。圈定的组合异常与已知的矿床点在空间上具有很好的对应关系,说明利用R型因子分析与泛克里格法相结合圈定元素组合异常的方法能够较好地确认地球化学元素组合异常,并提示异常与矿化类型之间密切相关的规律性,为“三江”北段地区找矿提供信息。     

Organic geochemical characteristics of time-series settling particles in northern South China Sea and their implications

Organic carbon, total nitrogen, amino acids, sugars, and chlorophyll were determined in < 1 mm fractions of the samples collected by successive large aperture time-series sediment traps (Honjo-Mark M) in northern South China Sea during September 1987 to October 1988. The ratio of C/N and the relative abundance of amino acids and sugars show that organic matter in the settling particles from northern South China Sea is derived mainly from marine plantkon (especially phytoplankton). The organic carbon fluxes in our sediment traps are lower than those in other sediment traps. But the relative contents of C_org/total particulate matter are generally similar to those in the Panama Basin, Arabian Sea and Subarctic Pacific. It is suggested that monsoon-caused changes of physical and chemical conditions in the upper euphotic layer would control the fluxes of organic matter as well as its composition and transport in northern South China Sea. This project was financially supported by both Sino-German Scientific Cooperation Program and National Natural Science Foundation of China (No. 49070269, 49776297).