<p>&nbsp;21世纪勘查地球化学在经历战术发展时期和战略发展时期后进入全面发展时期。各发展时期都是在特定的历史条</p><p>件下形成的。笔者主要简述全面发展时期的若干特点及需要注意的问题。</p>

"十一五"期间(2006-2010年),国土资源部中国地质调查局 继续推进区域化探与多目标区域地球化学调查计划.在区域化探方面,完成调查面积82.93万km2(累计完成756.62万km2),发现异常4 708处,经验证发现各类矿产411处,其中有色金属矿产273处,占66.4％,取得重大找矿突破.开展矿产资源地球化学评价,通过建立典型矿床地球化 学异常模式,来圈定找矿靶区和进行资源潜力定量预测.在多目标区域地球化学调查方面,完成调查面积26.56万km2(累积完成165.66万km2), 建立生态地球化学评价体系,主要针对重金属元素成因来源、迁移转化、生态效应与变化趋势进行较为全面和深入的研究.土地质量地球化学评价表明,中国土地达 到优质级占53％,优良级占33％,较差等级主要分布在中东部经济社会发达地区.土壤有机碳研究表明,全国表层土壤(0～0.2 m)平均碳密度仅为3 186 t/km2,且各地区碳密度变化幅度较大,说明中国土壤有机碳处于低水平和不稳定状态."十一五"期间勘查地球化学针对重大资源与环境问题,深化和延拓地 质工作内涵,逐步形成矿产资源评价、生态地质科学研究、土地质量与生态评价、全球变化科学研究及基础地学研究等现代地质工作若干重要发展领域.

“十二五”期间(2011～2015年)勘查地球化学以全国区域化探与多目标区域地球化学调查为主导,实行高密度的大数据、大信息综合集成运作,在资源与环境各方面继续取得显著成果,产生广泛影响力和重要经济社会效益,成为地质工作最具活力的领域.已经逐步建立以调查为基础,以理论为指导,融合资源与环境为一体的现代勘查地球化学发展总体框架与科学体系.矿产资源领域以全国区域化探为基础,成矿地球化学理论为指导,建立调查体系、理论体系、评价体系与方法体系.生态环境领域以全国多目标区域地球化学调查为基础,生态地球化学理论为指导,建立调查体系、理论体系、评价体系、预警体系、修复体系及方法体系.这是学科发展成熟的标志.本文简要论述勘查地球化学框架体系的构成、内涵及相互关联等.与此相关,提出若干新思想与新概念,以供讨论.

61Annual fluxes of heavy metals to topsoil in the Yangtze River delta are assessed.61Irrigation water and atmospheric deposition were the important sources.61The leaching amount of heavy metals is larger than the uptake of them by crops.61The average input rates of heavy metals are calculated.61Cadmium had the shortest time from average values to the environmental limits.

61Soil heavy metal input/output fluxes from various pathways were obtained.61Atmospheric deposition is the dominant source of the soil heavy metals.61Soil seepage water is the dominant soil heavy metal output pathway.61Given the present fluxes, the soil may remain uncontaminated in the following decades.61The observed fluxes will not cause accumulation or heavy metal hazards.

<p>运用层次分析法和隶属度函数建立了土地质量地球化学评估模型，以土地利用现状图斑为评价单元，对盘锦地区耕地土地质量进行了地球化学评估。对肥力指标和环境指标综合评价结果显示，盘锦地区耕地环境综合质量状况良好，三级质量以上耕地面积达到了88.04%，是优质的水稻产区，为科学管理土地和发展特色农业提供了可靠的地球化学数据。</p>

基于对浙东沿海某典型固废拆解区重金属元素大气干湿沉降特征的研究,探讨了重金属元素干湿沉降输入对土壤环境的影响。结果表明,研究区露天焚烧等不规范的固废拆解行为造成大气质量恶化,对土地质量造成严重的负面影响。区内干、湿沉降中Cd、Cu、Pb、Zn、Ni等重金属元素的含量均远高于浙江省干、湿沉降平均值和其它相关标准值,并且其年沉降通量在省内居高,尤其是Cu、Zn两种元素每年每平方百米沉降通量分别达7108g、11420g。研究显示,大气沉降能大大增加研究区土壤重金属元素的含量水平,Cu、Zn、Cd、Pb平均年增加量分别达3426ng/g、5819ng/g、6.50ng/g、582ng/g,并且年增加率较大,Pb、Cu、Zn等重金属元素的年增加率达0.5%以上。

Cd属于积蓄性有毒元素,引起慢性中毒的潜伏期可达10～30年之久.中国正在进行的多目标地球化学调查成果显示,长江流域存在全流域的Cd异常.对长江上、中、下游冲洪积物中Cd质量分数的初步研究,发现长江流域Cd异常以自然风化作用为主.针对长江流域Cd异常的特点,在统一技术规范的基础上,采用枯、丰水期悬浮物测量技术、河漫滩/泛滥平原沉积物沉积柱分层采样技术,同位素测年技术来建立长江各支流Cd输入通量的时空变化模型和定量评估方法,估算长江各支流的Cd输入通量,使分散于沿江各省的区域地球化学评价置于同一平台,从而为全面研究长江流域Cd异常的形成机理创造条件.

<p><span id="ChDivSummary" name="ChDivSummary">正在进行的多目标地球化学调查成果显示,长江流域存在全流域的Cd异常。长江流域Cd异常示踪与追源研究的长期目标是查明长江流域沿江各主要支流(汇水面积大于5000km²)Cd等重金属元素的物质来源、迁移形式和输入/输出通量、分辨自然源与人为源各自所占份额,建立沿江各支流Cd时空演化模型,监测它的未来发展趋势,对潜在生态效应进行预警预测;短期目标是针对Cd异常的重点地区,如长江源头、三峡库区、湘江流域、江淮流域、长江三角洲及流域内的4大淡水湖泊,查明Cd异常的来源,重建Cd异常形成的地球化学记录,评估可预见的将来(如10～50年)Cd异常的生态效应。</span></p>

<p>土壤地球化学调查显示，长江沿岸，尤其湖南洞庭湖流域存在以镉为主的重金属高值带。为进一步确定As和Cd等重金属元素在河流中的存在形式、迁移方式和通量等地球化学特征，本研究在洞庭湖水系主要干支流的关键位置布置采样点，分夏季丰水期和冬季枯水期两次，采集了原水、0.45 &mu;m过滤水和0.20 &mu;m过滤水等水样品，以及悬浮物固体样品，分析了水和悬浮物样品中As和Cd、Pb等重金属元素含量。结果发现，As元素在湘江、资水、湘江上游支流西河和耒水中含量最高，耒水、西河及湘江的Pb、Zn含量相对偏高，Cd在湘江、耒水及汨罗江的含量也明显高于其他河流；研究区河水中As、Ni、Cd和Zn等元素在水中离子态比例较大，其溶解态含量受河水pH和温度的控制，湘江、西河、耒水和汨罗江中悬浮物As、Zn、Cu、Cd、Pb和Cu等元素含量远高于其他水系悬浮物，这与这些流域内存在多金属矿区密切相关；不同元素在河水中迁移途径有很大差别，As以溶解态和胶体态为主要迁移形式，Pb、Zn、Cu、Cd和Ni等重金属元素以悬浮物形式迁移的比例最大；主要入湖河流中，湘江输入洞庭湖的As、Zn、Cu和Cd总量最大，年通量分别为961.43 t、478.90 t、101.67 t、59.58 t。</p>

<p>以广西武鸣县典型的碳酸盐岩成土剖面和陆源碎屑岩成土剖面为研究对象，研究了不同成土母质在成土过程中Se元素与其形态在垂向上的迁移变化规律及其影响因素。结果表明：碳酸盐岩和陆源碎屑岩在成土过程中，土壤Se含量均继承了成土母质的特点，且前者在表层明显富集，而后者相对较稳定，算术平均值分别为0.55 mg/kg和1.43 mg/kg。前者的水溶性总硒含量高于后者，平均含量分别为3.48 &mu;g/kg和1.81 &mu;g/kg，但均以硒酸态硒为主，其次是亚硒酸态硒和腐殖酸结合态硒。成土剖面上，土壤Se含量及其形态影响因素研究表明，碳酸盐岩成土剖面上，Se的含量与形态主要受土壤TOC含量和pH值影响；陆源碎屑岩成土剖面上，影响Se的含量及其形态的因素较多，土壤pH值、TOC、Al₂O₃和Fe₂O₃含量以及土壤质地等均对其有不同程度的影响。</p>

<p>土壤重金属污染是珠江三角洲地区主要的生态环境问题之一，直接影响到区域生态系统的稳定和食品安全。通过开展多目标区域地球化学调查、区域生态地球化学评价、局部生态地球化学评价和总体综合评价，系统完成了珠江三角洲经济区47954 km²(包括10 m水深以浅的近岸海域)的生态地球化学调查与评价。按照双层网格化方法系统采集了陆域土壤、近岸海域和珠江水系的主要河流沉积物表层和深层样品，测试了71项元素和指标，建立了珠江三角洲经济区土壤、沉积物地球化学背景值和基准值，首次对珠江三角洲地区区域地球化学特征进行了系统全面的调查，全面查明了珠江三角洲经济区土壤环境质量状况，区内一级和二级土壤分别占总面积的19.9%和57.3%，三级和三级以上土壤占22.8%。定量计算了镉、铅、汞等主要异常元素经河流、成土过程等自然来源和大气干湿沉降、施肥、灌溉、使用农药等人为来源贡献量，阐明了其迁移转化途径及生态安全性。结合研究区特点，系统开展了三角洲形成演化过程的地球化学研究，并在国内首次制定了符合地区特点的珠江三角洲经济区土壤环境质量地方标准。</p>

我国粮食主产区的东北平原一直被认为是严重缺硒或缺硒地方病经常发生的地区,地质大调查以来采用现代分析测试手段进行高精度土壤硒的富集、分布研究,对特色土地资源开发利用具有重要意义。以每4 km2 1个点的表层(0~20 cm)、每16 km21个点的深层(150~180 cm)土壤数据对东北平原土壤硒分布特征及影响因素进行统计分析。结果表明,东北平原表层土壤以足硒为主,足硒面积达51.54%,硒潜在不足面积占25.05%,Se反应不足面积仅为22.63%,富硒土壤面积不足1%;深层土壤则以缺硒为主,硒反应不足面积占80.68%。表层土壤Se含量相对于深层土壤表现出明显的富集特征,仅在西部盐碱化、沙化区及东部土壤发育程度低的基岩区为基本自然状态―弱富集特征,土壤硒继承成土母岩程度较弱,而铁锰氧化物、有机质、土壤类型、质地等理化性质对硒具有明显的富集作用,后期人类活动也是影响硒富集的主要因素,但表生富集作用、人类活动影响不足以使表层土壤达到富硒程度。

The content and the dynamic balance of soil organic carbon directly effect on the soil fertility and crop yield,the Northeast Plain is the largest plain in China,and is located in the Northeast China.With its wide flat terrain and fertile deep tracts became the famous national granary,studying on the soil carbon pool in Northeast Plain of China has great significance.Based on the accurate and high-density soil carbon data collected in the multi-purpose geochemical survey in Liaoning,Jilin and Heilongjiang provinces,the soil carbon pool components and soil properties influence factors on the soil carbon pool components were analyzed.The results showed that the distribution of the organic and inorganic carbon pool has typical characteristics.The soil organic carbon density(SOCD)has a trend of increasing from the west desertificated,saline-alkali plain to the east area of low mountains,and increasing from the south to the north in Northeast Plain of China.However,the soil inorganic carbon has an opposite trend of increasing from the east area of low mountains to the west desertificated,saline-alkali plain.The carbon pool in the Northeast Plain of China is still dominated by the total organic carbon(TOC)with the variation of 56.14% ~94.03% under different soil types.There is an obvious linear relationship between the soil organic carbon and the total nitrogen,the soil inorganic carbon density(SICD)was controlled significantly by the calcium oxide,the SICD and SOCD all have negative correlations with the silicon dioxide.These results showed that the soil composition and soil type are the strongest control factors to the soil carbon pool in the Northeast Plain of China.The soil texture,pH value and other soil properties also have great effect on the soil carbon pool.The scatter plot between the soil total inorganic carbon(TIC)and pH value exhibit the saddle pattern,the scatter plot between the soil TOC and the pH value also exhibit the saddle pattern,but there is difference in shape.The effect of alkaline conditions on soil inorganic carbon content is more obvious.

土壤中不同形态重金属及其转化的影响因素研究对于了解重金属的地球化学行为具有重要意义。本文以山东烟台金矿区及城镇周边土壤为例，探讨了土壤中不同形态重金属与土壤有机质、粘粒、磁化率和pH值的关系及其生态危害性。结果表明：（1）土壤中Pb、Hg等重金属主要以残渣态和铁锰氧化态为主，其他形态所占比例较小，而Cd以离子交换态为主，且随总量的增加，离子交换态含量迅速增加，因此总量可作为表征土壤Cd污染的指标；（2）土壤酸化可使Ni、Zn、Cd、Hg的活动态含量增加；土壤pH对Pb和As活动态的影响符合二次曲线特征，对于Pb污染严重的土壤，使土壤pH维持在中碱性环境，可以降低Pb危害；防止土壤盐碱化，提高有机质含量是消除土壤As污染的有效措施；（3）土壤有机质含量增加可明显降低Pb、Hg、Ni等活动态含量；土壤磁化率与重金属稳定态显著正相关，磁化率升高对生物的危害性不大，但对了解土壤酸化的状况和土壤污染程度有较好的指示作用。

Abstract rade division method for soil geochemical contamination has been established on the basis of the concentration and accumulation grade caused by human exploitation of toxic elements. A preliminary study in the Yangtze River delta and the coastal region of Fijian Province shows that the sediments or parent materials of deep and top soils are of homo-genesis and their element concentrations have good correlation. Geochemical baseline based on deep soil geochemical data can undoubtedly be selected as the reference value to assess soil contamination because deep soil has not been affected by human activity and pollution. Soil geochemical contamination grade standard of the Yangtze River delta was thus set up, and soil contamination of the region was divided according to the standard. The origin and eco-geochemical effect of each contamination grade are discussed in this paper. However, the eco-geochemical effects of soils of different contamination grades need further investigation.

土地利用变化是土壤有机碳库变化的重要原因之一。文中选择中国东北地区,利用多目标区域地球化学调查数据,结合20世纪80年代和2000年土地利用数据,分析了不同土地利用方式下土壤有机碳密度分布特征,以及由于土地利用方式变化形成的土壤碳源汇效应。结果发现:(1)不同土地利用下土壤表层有机碳密度(SOCD)差异较大,沼泽地、有林地等是SOCD相对较高的土地利用类型,而沙地、盐碱地、低覆盖草地等土地利用方式下SOCD较低;(2)按照土地利用方式的构成推算,研究区表层(0～20cm)土壤有机碳储量为482.1×1010 kg,其主要储库为有林地和旱地,分别占土壤总有机碳储量的43.8%和21.4%;(3)东北地区由于土地利用方式变化造成的土壤总碳源值为5.73×1010 kg,总碳汇值为3.56×1010 kg,因此研究区总体上表现为2.17×1010 kg(21.7Tg)的碳源;(4)研究区起到土壤碳汇作用的典型土地利用转化方式有旱地到水田的转化、其他林地和疏林地到有林地的转化等;起到土壤碳源作用的典型土地利用转化方式为有林地到旱地的转化、高覆盖草地到旱地的转化、沼泽到水田和旱地等耕地的转化等。

文章以《江西省鄱阳湖及周边经济区1：25万多目标地球化学调查》资料为基础，详细论述了植 物所需的C、H、O、N、P、K、Ca、Mg、S、Cu、Zn、Fe、Mn、B、Mo、Cl共16种营养元素的分布特征。利用8843件表层土壤样品中 Cd、Hg、As、Pb、Cr等重金属元素含量及其土壤pH值，采用内梅罗指数法对区内元公害水稻产地土壤环境质量、无公害蔬菜产地土壤环境质量以及绿色 食品产地土壤环境质量进行综合评价。在此基础上，对鄱阳湖及周边经济区表层土壤生态地球化学环境质量进行了综合评价。

以2008、2009年所采集的乌裕尔河9个点位水体中的悬浮物为研究对象，对丰、枯水期颗 粒有机碳（POC）含量、碳同位素组成（^13C、^14C）及表观年龄进行了系统测试与分析，以期探讨河流中颗粒有机碳来源与流域土壤侵蚀的关系。研究 结果表明，该河流中颗粒有机碳（POC）主要来源于未受玉米残体及根系输入影响的深层土壤，且土壤中的有机质主要为原始荒草植被残体；扎龙湿地颗粒有机碳 则以自生的现代碳为主。支、干流丰水期颗粒有机碳的^14C表观年龄远远老于枯水期的表现年龄，丰水期颗粒有机质的迁移距离较短，枯水期则刚好相反。与其 他河流颗粒有机碳^14C表观年龄对比结果表明，研究区土壤侵蚀非常严重，且存在显著的季节性差异。综合考虑颗粒有机碳迁移距离及其来源的差异，根据端员 混合模型计算了丰水期各支流对不同干流采样点颗粒有机碳的贡献率。

在银川盆地首次发现大面积富硒区.该富硒区具有富硒土层厚、硒含量适中、宜于开发利用等特点.富硒土地分布区不仅硒含量高,而且污染有害元素的含量特别低,呈"原生态"的自然状态.初步分析认为银川盆地土地富硒主要与成土母质(母岩)有关.

水稻土是我国主要的耕作土壤之一，水稻土有机碳变化与全球气候变化息息相关，因此研究我国主要农耕区水稻土有机碳含量分布特征及影响因素具有重要的现实意义。本文基于全国多目标地球化学调查1：250000土壤数据库，以行政区划分析了水稻土有机碳分布规律，从土壤pH值、年均气温、年均降雨量、耕作方式等角度探讨了其对水稻土有机碳含量的影响，并且采用主成分分析和逐步多元回归模型进行了量化。结果表明：黑龙江松嫩平原水稻土有机碳平均含量最高，为15．1g·kg^-1，海南岛和广东珠三角地区水稻土有机碳含量较低。水稻土pH值对有机碳含量的影响较小，但在弱碱性（7．5〈pH≤8．5）时，pH值与有机碳含量呈显著负相关。黑龙江、吉林等高经纬度区域，受气温变化影响明显，根据线性回归模型推算，若年平均气温每升高0．1℃，水稻土有机碳含量将降低2．51g·kg^-1。耕作方式和农田管理措施变化对土壤有机碳含量有一定影响。年均降雨量、年均气温和土壤pH值是土壤有机碳含量分异的主要驱动因子，其中年均气温的影响最显著。

城市土壤Hg异常/污染是中国 普遍存在的重大生态环境问题。文章对北京市近1000km2范围内的地表土壤、壤中气、大气干湿沉降、大气颗粒物、大气中的Hg含量水平和空间分布模式进 行了系统研究,查明北京地表土壤Hg平均含量为0.41mg/kg,大气干湿沉降物中的Hg平均含量为0.194mg/kg,壤中气Hg的平均含量为 559.65ng/m3,大气颗粒物PM10和PM2.5中的Hg含量分别为0.59和0.67ng/m3,大气中的Hg平均含量为3.13ng/m3。 北京市自2000年起实现了由燃煤转变为燃气的减排措施,导致干湿沉降物中的Hg沉降通量显著减少,2006年大气干湿沉降物中Hg的沉降通量 1.837mg·m-2·a-1,北京市城区(近1000km2)Hg全年沉降为1837kg,空气中总Hg浓度由1998年的 8.3~24.7ng/m3下降到2006年的3.13ng/m3,大气颗粒物中Hg含量由2003年的1.18ng/m3下降到2006年的 0.59ng/m3(PM10)和0.67ng/m3(PM2.5),表明北京市煤改气减排措施的实施显著改善了大气环境质量。通过对土壤中Hg的存在形 式研究,发现土壤中有硫化物(辰砂)及各种Hg盐(HgCl2)的含Hg矿物,Hg也可以各种吸附方式或壤中气方式存在。研究证实北京壤中气Hg与大气 Hg存在显著的相关性(n=131,R=0.267,p0.01),表明壤中气Hg是大气Hg的重要来源之一。利用2005年地表土壤总Hg与Hg释放速 率的线性方程估算,土壤Hg平均释放速率为102.42ng·m-2·h-1,2005年土壤释放进大气的Hg通量为936.70kg。在查明土壤中存在 大量辰砂矿物的同时,还分布有大量具有高温熔融特征的金属微球粒和玻璃质微球粒,证明燃煤和冶金烟尘是地表土壤Hg的主要来源。土壤中Hg、S、pH和辰 砂颗粒浓度在空间上的高度耦合性表明,碱性条件下,土壤中高含量的S和Hg是辰砂形成的重要原因。按国家土壤环境质量标准,北京市I级土壤Hg环境质量的 面积为176km2,Ⅱ级为808km2,Ⅲ级为24km2,超Ⅲ为36km2。Ⅲ级、超Ⅲ级主要分布在二环路以内的中心城区。城南(长安街为界)大气 Hg环境质量明显优于城北,在北四、北五环之间的部分地区,大气颗粒Hg的环境质量为Ⅲ级或超Ⅲ级。在地表土壤Hg含量较高的中心城区,居民每天因呼吸摄 入的Hg高达364ng,对人体健康构成潜在风险。根据我国"十一五"规划中每年实现10%节能减排的目标,对北京市未来50年土壤Hg含量的时空演变趋 势预测,预测2050年北京因干湿沉降带来的Hg输入量为16.03kg,地表土壤释放Hg的输出量为37.36kg,明显大于Hg的输入通量,土壤Hg 的环境质量将得到根本改善。预测到2040年Ⅲ级土壤Hg环境质量的区域将完全消失,到2060年以Ⅰ级土壤为主。

<p>1999～2001年,勘查地球化学取得一系列重要进展和成果,在中国西部以资源调查和评价为主推进区域化探,在中国东部以环境调查和评价为主启动多目标区域地球化学填图,逐步形成新世纪勘查地球化学资源与环境并重的发展格局.与此相适应,提出了资源潜力地球化学评价与生态环境地球化学评价为主导的基本思路和方法.</p>

Abstract: Geochemical distribution data (several tens of millions) of 39 elements were obtained in China's national geochemical mapping program carried out for 24 years over more than 6 million km2 of China's territory. By examining the flood of data, the authors have found much broader geochemical patterns other than dispersion halos and dispersion trains which have been the main subjects of study during the 60 years' development of exploration geochemistry. Such broader geochemical patterns are geochemical anomalies, geochemical provinces, geochemical megaprovinces and geochemical domains. They are surface expressions of the internal structural features of large blocks of rock with higher metal contents. Those large "geochemical blocks" are the net results of the Earth's original heterogeneity and the distribution and redistribution of metals from the initiation and evolution of the Earth up to the present days. The authors got a new idea that the large can provide large metal endowments necessary for the formation of large to superlarge geochemical blocks ore deposits. To explore the internal structure of the geochemical block of a certain element may reveal the trajectory of gradual concentration and formation of ore deposits of that element in the geochemical block. The new geochemical block concept is changing the mineral exploration strategy and methodology in China, providing a powerful tool for global mineral potential assessment and inspiring new ideas for exploration geochemistry, ore-genesis and metallogeny.

Studies on modern oceanic lithosphere and ophiolites have revealed high degrees of chemical and isotopic heterogeneity in the mantle, as well as isotopic contrasts between mantle and crust. These features cannot be explained just by simple extraction of partial melt, but require considerably more complex petrogenetic processes. Here we present an overview of the present knowledge on isotopic heterogeneities of Sr, Nd, Hf and Os in oceanic peridotites (by reviewing data on modern abyssal peridotites and the Alpine–Apennine ophiolites), and discuss their significance in terms of i) length scale and extent of isotopic heterogeneities in the upper mantle and ii) isotopic mantle–crust relations at oceanic settings. Overall results show that mantle peridotites record significant isotopic heterogeneity, detectable on a wide range of length scales, much larger than observed in associated MORB. In addition, abyssal peridotites are on average more depleted than MORB. The high degree of isotopic heterogeneity is clear evidence for the inefficiency of mantle convection in homogenizing mantle rocks. It may be caused by i) variably old depletion events (unrelated to recent MORB production), ii) pyroxenite components in the mantle source, iii) recent pre- and/or post-melting metasomatism. Some abyssal peridotites have extremely depleted isotopic compositions, not seen in MORBs, and these have been interpreted as the evidence for old (1 to 2Ga) refractory domains in the asthenospheric mantle or, alternatively, as evidence for recent incorporation of (also old) subcontinental lithospheric mantle, potentially through delamination during continental breakup. The first hypothesis has been corroborated by finding, in a few ridge segments (e.g. Gakkel Ridge) of correlations between chemical fertility indexes and isotopic (Os, Hf) ratios, indicative of recycling of old residual oceanic lithospheric mantle into the MORB source. However, no general consensus exists yet on the two proposed models. The difference in average isotopic depletion between peridotites and basalts has been also ascribed to the presence of pyroxenites, which have “enriched” isotopic signature relative to the peridotite component. The origin and composition of such small-scale lithological heterogeneities remain however still controversial and poorly constrained, due to the difficulty to link petrologic and geochemical studies with direct field observations, and to the scarcity of chemical and isotopic data on pyroxenites in ophiolitic and abyssal peridotites, i.e. the closest available “proxies” of the MORB mantle. Larger isotopic homogeneity observed in MORB relative to peridotites in single ridge segments clearly reflect their origin as aggregated melts which inevitably “smooth” and average mantle source heterogeneities. Overall, the questions about the origin and spatial distribution of chemical and isotopic heterogeneities are not resolved, and this calls for detailed field-based studies in spatially-controlled settings to shed light on the issue of small-scale mantle heterogeneities and the role of enriched (e.g. pyroxenites) and highly depleted domains in MORB melting.

The average chemical compositions of the continental crust and the oceanic crust (represented by MORB), normalized to primitive mantle values and plotted as functions of the apparent bulk partition coefficient of each element, form surprisingly simple, complementary concentration patterns. In the continental crust, the maximum concentrations are on the order of 50 to 100 times the primitive-mantle values, and these are attained by the most highly incompatible elements Cs, Rb, Ba, and Th. In the average oceanic crust, the maximum concentrations are only about 10 times the primitive mantle values, and they are attained by the moderately incompatible elements Na, Ti, Zr, Hf, Y and the intermediate to heavy REE. This relationship is explained by a simple, two-stage model of extracting first continental and then oceanic crust from the initially primitive mantle. This model reproduces the characteristic concentration maximum in MORB. It yields quantitative constraints about the effective aggregate melt fractions extracted during both stages. These amount to about 1.5% for the continental crust and about 8 10% for the oceanic crust. The comparatively low degrees of melting inferred for average MORB are consistent with the correlation of Na 2O concentration with depth of extrusion [1], and with the normalized concentrations of Ca, Sc, and Al ( 3) in MORB, which are much lower than those of Zr, Hf, and the HREE ( 10). Ca, Al and Sc are compatible with clinopyroxene and are preferentially retained in the residual mantle by this mineral. This is possible only if the aggregate melt fraction is low enough for the clinopyroxene not to be consumed. A sequence of increasing compatibility of lithophile elements may be defined in two independent ways: (1) the order of decreasing normalized concentrations in the continental crust; or (2) by concentration correlations in oceanic basalts. The results are surprisingly similar except for Nb, Ta, and Pb, which yield inconsistent bulk partition coefficients as well as anomalous concentrations and standard deviations. The anomalies can be explained if Nb and Ta have relatively large partition coefficients during continental crust production and smaller coefficients during oceanic crust production. In contrast, Pb has a very small coefficient during continental crust production and a larger coefficient during oceanic crust production. This is the reason why these elements are useful in geochemical discrimination diagrams for distinguishing MORB and OIB on the one hand from island arc and most intracontinental volcanics on the other. The results are consistent with the crust-mantle differentiation model proposed previously [2]. Nb and Ta are preferentially retained and enriched in the residual mantle during formation of continental crust. After separation of the bulk of the continental crust, the residual portion of the mantle was rehomogenized, and the present-day internal heterogeneities between MORB and OIB sources were generated subsequently by processes involving only oceanic crust and mantle. During this second stage, Nb and Ta are highly incompatible, and their abundances are anomalously high in both OIB and MORB. The anomalous behavior of Pb causes the so-called ead paradox , namely the elevated U/Pb and Th/Pb ratios (inferred from Pb isotopes) in the present-day, depleted mantle, even though U and Th are more incompatible than Pb in oceanic basalts. This is explained if Pb is in fact more incompatible than U and Th during formation of the continental crust, and less incompatible than U and Th during formation of oceanic crust.

A mass imbalance exists in Earth for Nb, Ta, and possibly Ti: continental crust and depleted mantle both have subchondritic Nb/Ta, Nb/La, and Ti/Zr, which requires the existence of an additional reservoir with superchondritic ratios, such as refractory eclogite produced by slab melting. Trace element compositions of minerals in xenolithic eclogites derived from cratonic lithospheric mantle show that rutile dominates the budget of Nb and Ta in the eclogites and imparts a superchondritic Nb/Ta, Nb/La, and Ti/Zr to the whole rocks. About 1 to 6 percent by weight of eclogite is required to solve the mass imbalance in the silicate Earth, and this reservoir must have an Nb concentration ≥ 2 parts per million, Nb/La ≥ 1.2, and Nb/Ta between 19 and 37-values that overlap those of the xenolithic eclogites. As the mass of eclogite in the continental lithosphere is significantly lower than this, much of this material may reside in the lower mantle, perhaps as deep as the core-mantle boundary.

本文论述了矿床成矿系列的主要学术思想及研究趋势。文中强调指出，矿床成矿系列概念视成矿是地质历史发展过程中所形成的地质环境中的组成部分，其本身是四维空间中的成矿整体，它们在地史演化过程中从空间的分布、成矿物质的组成都经历着演化，并有一定规律。笔者着重阐明了成矿系列研究领域的重要内容、研究基础、命名及分类系统，以及不同地质作用对成矿系列所占的份额及其相互关系。

在简述地球系统科学的基础上 ,文中提出了由地球系统科学引发的成矿学研究 3个观点 :(1 )成矿系统是一个特色的地质系统 ;(2 )成矿系统与其它系统的关联 ;(3)地质突发事件具有灾害和资源的两重性。针对地球系统科学要求和矿床学学科发展进程 ,提出了 5个亟待加强的研究领域或课题 :(1 )深部过程、浅表环境与成矿系统 ;(2 )重大事件与成矿 ;(3)生命活动与成矿 ;(4 )物理成矿作用和(5 )海洋成矿作用。在结语中 ,作者强调要从地球系统的大背景来研究成矿环境、成矿过程和成矿动力学 ,也即将传统的矿床成因研究提高到地球系统科学的层次 ,为矿床学的发展提供新的广阔的理论基础。

Abstract egional geochemical exploration in China changed greatly from 1999 to 2009. Regional geochemical exploration methods and techniques as well as mineral resources potential assessment have been deliberately studied and remarkable progress has been achieved under the guidance of geochemical theory. The principle of regional geochemical exploration methods and techniques developed aims at demonstrating the primary state of geochemical distribution in the highest degree. Selection of sampling media suitable for landscape and surficial geochemical condition is the key problem for regional geochemical survey. Samples collected should reflect the information of geology and mineralization, and hence weathered material of rocks is usually selected as sampling media. Efforts have also been made to collect the same material over the whole country. The established methods for mineral resources potential assessment and quantitative mineralization prognosis based on the theory of geochemical zoning have promoted the exploration geochemistry from pure methods to a theoretical level for steering mineral prospecting. The main achievements are as follows: systematic methods and techniques of national regional geochemical exploration have been established; analytical process and its quality are strictly controlled; Several geochemical atlases have been published based on accurate geochemical data, which can exactly reveal geological setting and anomalous characteristics; regional geochemical data and its information have been studied profoundly and applied widely; the methodology system and working procedure from regional, reconnaissance to detailed exploration have been established for resource survey, assessment and prognosis. Regional geochemical exploration has been supporting mineral survey in China for a long period, acting as a forerunner of all geological work. It is certain that regional geochemical data will play an important role in new discovery, new understanding and new viewpoints of basic geology, mineralization regularity, and great geological events with the compilation of new geochemical maps covering various regions and the whole country. All this will have great influence on exploration geochemistry and geological work in China.

依据多目标区域地球化学调查数 据对比研究中国中东部地区土壤有机碳分布与变化特征。中东部平原及周边地区河北、河南、湖北、湖南、广东与海南等6省经黄河、长江纵贯南北,由较高纬度带 到较低纬度带,跨越温带、亚热带和热带地区的截然不同的自然景观,调查面积约33.4万km2,表层土壤(0～0.2m)碳储量为906.84Mt,平均 碳密度为2 716.93t/km2。连接更高纬度带的东北平原土壤碳密度,中东部地区由高纬度带至低纬度带碳密度呈现高低高低的规律性变化,即3 327.8t/km2(东北平原)2 207.39、2 421.02t/km2(河北、河南)3 442.15、3 942.92t/km2(湖北、湖南)2 255.90、2 936.72t/km2(广东、海南)。不同生态系统碳密度均值比研究发现,由高纬度带至低纬度带农田与城市系统均值比呈反向变化,农田趋高,城市趋低。 与第二次土壤普查相比,中东部地区20年期间土壤有机碳总计增加115.18Mt,占14.5%,年均增加5.76Mt。但有机碳增加比例极不平衡,由高 纬度带至低纬度带增加比例及变化速率呈显著降低趋势乃至负增长。其中农田、城市系统变化比例呈现增长,呈下降趋势的由大至小为潮间带、河流、湖泊、草原、 森林及沼泽等。

分析了区域地球化学调查样品分 析中原有的质量控制方法的不足,提出了采用实验室内部自我质量控制和实验室外部质量控制相结合的方法。对实验室外部质量控制方法进行了试验,并将测试数据 绘制的元素虚拟地球化学图进行相似性比较,以求改进和完善区域地球化学调查样品分析质量控制方法,促进分析测试质量进一步提高。