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1.
湘西寒武纪早期黑色岩系中富含源于上层海水生物体的有机质, 其稀土元素(REE)特征不被碎屑物质干扰, 能有效地反映海洋上层水体的古环境特征.样品中作为有机质主体的干酪根的重稀土富集、Ce负异常、Y正异常和Eu无明显异常等特点与现代海水一致, 其特征可能反映古海洋上层水体的氧化还原信息.扬子地台各相区沉积剖面底部可能出现滞流(或硫化)环境, 随后沉积环境逐渐氧化.全岩样品中Ce的负异常可能由有机质提供, Ce/Ce*值由剖面底部的较低值向上逐渐升高可能意味着海洋上层水体含氧量的逐渐上升, 而海水含氧量逐渐升高或许是由寒武纪早期海洋底部硫化环境的减弱所导致. 相似文献
2.
碳酸盐岩是地球表层岩石圈的重要组成部分,其化学组成可提供沉积环境与海洋水体演化等信息,然而,前人对碳酸盐岩中稀土等元素的分布与变化特征关注不足。本文选择穿越中国东部6个一级大地构造单元的3条地球化学走廊带,系统采集了582件碳酸盐岩地层样品,并准确分析了包括稀土元素(REE)在内的81项指标的含量。结果表明,中国东部地球化学走廊带碳酸盐岩稀土元素(REE＋Y)总量为(0.59～183)×10-6,均值为24.0×10-6,纯净碳酸盐岩(CMC含量≥99％)均值为4.80×10-6。PAAS标准化后其显示具有轻稀土相对于中稀土和重稀土略亏损、δEu轻微正异常、δCe中度负异常等特征。白云岩中稀土含量、LREE/HREE值一般低于石灰岩;砂泥质含量相近时,前中生代各时代碳酸盐岩稀土分布模式相差不大,各构造单元稀土分布特征基本相似;与其他时代相比,中生代及中新元古代碳酸盐岩具有相对较平坦的稀土分布模式。研究表明,碳酸盐岩中稀土分布受碎屑物质影响明显,表现为稀土元素含量与碳酸根负相关,与碎屑物质相关元素(Si、Ti、Rb、Cs、Th、Zr等)、黏土相关元素(Al、Fe、K等)等正相关。成岩过程及白云化过程对较纯净碳酸盐岩中稀土分布特征影响不明显。我国古生代纯净碳酸盐岩分布模式受控于海相环境,其分布模式与现今海水相近;中生代纯净石灰岩受到陆相或海陆交互相的影响,具有较平坦的稀土分布模式。氧化还原条件对δCe的影响较δEu更为明显,δCe值受海相环境控制,极端正异常值(δCe＞1.3)受到还原环境或/和热液影响。若假定海水中REE自中元古代至今无太大变化,各时代稀土元素分配系数均值介于103.55～102.39,分配系数差异是造成碳酸盐岩中轻稀土亏损、Ce负异常及Y正异常的主要原因。微生物(席)可富集稀土等金属元素并改变沉积环境,这可能是造成中新元古界碳酸盐岩较平坦的稀土分布模式的主要原因。 相似文献
3.
《新疆地质》2019,(4)
为研究北羌塘三叠系康南组灰岩地球化学特征及沉积环境,对研究区灰岩进行全岩分析,探讨古气候条件及海水特征,反演灰岩形成的海水稀土分布模式。结果表明:样品主量元素含量变化较大;具富集Rb,K,Ba,Sr,U,Zr,Th、亏损Ni,Cs,V,Sc,Hf,Nb,Pb的特征;稀土元素总量较低,重稀土元素相对富集,δEu弱负异常,δCe呈明显负异常。主量元素特征反映样品受到陆源物质的混入且混入作用抑制了灰岩的形成;微量元素比值特征反映样品形成于氧化环境。微量元素特征图解反映样品为正常的海水沉积,δEu及δCe异常反映样品受到后期热液活动的影响;康南组灰岩反演海水稀土元素与正常海水稀土组成一致。 相似文献
4.
对大同盆地典型高砷地下水开展了稀土元素地球化学研究.研究表明: 高砷地下水具有低∑REE含量及富集重稀土(HREEs)特征.地下水中低含量∑REE与含水层沉积物中Fe-Mn氧化物/氢氧化物对REEs的吸附有关.地下水中重稀土元素相对于轻稀土元素的富集可能是吸附作用和碳酸根离子同REEs发生络合作用的共同结果.采用平均大陆上地壳标准化的地下水稀土元素分布表现出显著的Ce及Eu正异常.地下水Ce/Ce*值及Eu含量与Fe+Mn具有显著相关性, 表明铁锰氧化物还原性溶解是控制Ce/Ce*值及Eu含量特征的主要因素.Ce/Ce*值及Eu含量与As浓度的关系表明, Ce异常及Eu含量特征能对地下水中As的富集进行有效指示. 相似文献
5.
《矿物学报》2016,(1)
本研究选择中国东部主要的花岗岩分布区中位于中温带、暖温带和热带的8个花岗岩风化壳作为研究对象,对比研究了不同气候环境下花岗岩风化过程中稀土元素(REE)的分布规律及其演化特征。结果表明,各气候带的花岗岩风化壳的REE分布具有一定的共性规律,风化产物的REE总量相对基岩都有不同程度的富集,且都表现出轻稀土(LREE)相对重稀土(HREE)富集以及一定程度的Eu负异常。由于REE的迁移和淋滤,导致其在风化壳内的再分配。通常REE在半风化层富集,p H值和粘土矿物含量等内因变化是导致这一现象的主要因素。对于少数表层REE富集的现象,如SD-DG、HN-3剖面,气候环境与地质条件等外因则是这一现象的主导因素。受海洋性气候影响显著的风化壳(QHD-1,HN-3),以基岩为标准,容易发生HREE富集的轻、重稀土分异的现象。大部分花岗岩风化壳中,Ce通常在剖面上部出现正异常,而在下部出现与之互补的Ce负异常。 相似文献
6.
为研究采矿对土壤-植被REE生物地球化学特征的影响,采集大宝山多金属矿区及背景区土壤及优势植物芒萁、马尾松叶片,测量REE含量.对比分析样品中REE分布模式、∑REE、δEu、δCe及四重效应等地球化学特征.结果表明:受采矿活动影响,矿区土壤REE含量均值达284.99 mg/kg,显著高于背景区,且表土层REE含量明显高于心土层;相对于背景区,矿区土壤和植被轻重稀土分馏更弱;研究区土壤和植被都为Eu亏损,大都为Ce富集,马尾松与土壤REE含量呈正相关,REE富集植物芒萁在背景区富集系数反而更高;矿区环境抑制植物对REE正常的迁移和分异,对植被生长不利,植被REE分布分异特征是其对生长环境的反映和适应. 相似文献
7.
本文系统地研究了鄂尔多斯盆地南部延长组凝灰岩元素和同位素地球化学特征。结果表明:凝灰岩主量元素具有高K、高Al、Si中等至高、低Na的特征;REE总体特征为轻稀土富集、重稀土亏损,∑REE在48.57～402.12μg/g之间变化,Eu呈现出负异常,在0.34～0.82内变化,δCe范围在0.80～2.08之间;微量元素中U含量在3.12～144μg/g之间,Ba、U、Th、Hf和Ce呈明显正异常,Nb、P、Ti和Rb呈现负异常。详细的分析表明:U的富集和一些微量元素如Ta、Dy、Lu等相关,Th与∑REE存在明显的正相关性,这些变化可能和盆地中铀矿的富集有关;凝灰岩的硫同位素总体呈现深源特征。根据以上的研究对凝灰岩的形成原因及形成环境进行了探讨。鄂尔多斯盆地南部延长组凝灰岩来源于秦岭造山带火山作用,其中的铀元素富集是由于砂岩型铀矿中铀向凝灰岩迁移而被还原所致。本研究对盆地砂岩型铀矿的铀运移和富集机理认识具有一定指导意义。 相似文献
8.
中国西北地区石炭系泥岩稀土元素地球化学特征及其地质意义 总被引：19，自引：3，他引：19
详细研究了中国西北地区石炭系泥岩的稀土元素地球化学特征。各样品稀土总量为18 86× 10 -6～ 6 2 0 4× 10 -6,变化较大 ,其中祁连地区REE总量为 76 49× 10 -6～ 6 2 0 4×10 -6,甘肃永昌煤山子剖面的稀土总量最高 ,新疆北部地区泥岩和灰岩 (泥灰岩 )的稀土总量均较低。各泥岩样品的轻稀土富集 ,Eu负异常 ,δEu介于 0 44～ 0 90之间 ,δCe部分为正异常 (>1) ,部分为负异常 (<1)。研究区样品的Sm含量与北美页岩样品相比为正异常 ,Dy出现负异常的样品较多。根据稀土元素δCe和Ceanow的变化 ,反映当时新疆北部地区水介质环境大部分为缺氧的还原条件 ;祁连地区为海陆过渡环境 ,部分为氧化条件 ,另一部分为缺氧的还原条件 ,这与其他相标志所显示的结果是一致的。根据稀土元素组合及比值的变化 ,显示物源区母岩为花岗岩和玄武岩的混合来源 ,稀土分布模式均为轻稀土富集、重稀土亏损型 ,重稀土配分曲线较为平坦 ,显示源岩为粘土岩、花岗岩和中性岩的混合来源。 相似文献
9.
本文以赣南小流域水体为研究对象,利用VG Axiom高分辨多接受双聚焦等离子体质谱仪测定了水体中溶解态稀土元素(DREE)的含量,分析了水体中DREE的分布分异机制,并探讨了稀土元素(REE)产生分异的原因.结果表明,赣南所有的采样区水体中Ce都表现为负异常,说明其在风化壳中少活化.受自然风化作用控制为主的水体相对于页岩除Ce亏损、Eu富集外产生的分异很小,其中Eu的正异常源于Eu富集矿物的优先溶解;蒸发盐矿影响下的水体相对于自然作用为主的水体DREE没有发生明显分异;受稀土矿影响的水体中重稀土元素(HREE)富集、Eu负异常的分布模式继承了稀土矿区风化壳的特征;赣州市下游干流水体中中稀土元素(MREE)富集、Eu负异常的分布模式主要是人为影响的结果. 相似文献
10.
淮北花沟西井田煤中微量元素及其环境意义分析 总被引：1，自引：0，他引：1
通过对30件煤样微量元素含量的测定,分煤层、分类型(稀土元素、环境意义微量元素)讨论了煤中微量元素的分布特征。研究发现各样品的稀土元素主要赋存于矿物质中,稀土元素含量均呈正常质量分数水平分布,各煤层的稀土元素分布表现为轻稀土富集、重稀土亏损。受陆源影响的煤,ΣREE含量高,稀土元素主要由陆源物质继承而来。受海水影响的煤,ΣREE含量低,分布模式具有海水性质。形成后受河流冲刷的煤,灰分增加,煤中稀土元素含量增加。该研究成果为煤炭资源的合理开发和利用提供基础资料。 相似文献
11.
在香港国家地质公园西贡火山岩园区,核心地质景观是白垩纪粮船湾组(Kkh)火山岩优美的六方形石柱(柱状节理),它们的岩石类型长期存在熔岩和火山碎屑岩之争。笔者等经野外调查和薄片岩石学研究,确认粮船湾组火山岩实属一种特殊的熔岩——流纹质碎斑熔岩,以普遍的柱状节理、斑晶具有碎斑结构和珠边结构、基质发育霏细结构和流动构造为特征;它们不仅代表了香港地区中生代最晚期火山喷发的产物,而且构成了西贡破火山机构的中央侵出相岩穹。推断粮船湾组火山岩石柱是地球上已知面积最大的流纹质碎斑熔岩石柱群(～150 km2),目前所见的火山岩石柱仅是长期剥蚀后的残余部分。 相似文献
12.
Rare earth elements (REE) of dissolved and suspended loads in the Xijiang River, South China 总被引：4，自引：0，他引：4
The Xijiang River is the main channel of the Zhujiang (Pearl River), the second largest river in China in terms of water discharge, and flows through one of the largest carbonate provinces in the world. The rare earth element (REE) concentrations of the dissolved load and the suspended particulate matter (SPM) load were measured in the Xijiang River system during the high-flow season. The low dissolved REE concentration in the Xijiang River is attributed to the interaction of high pH and low DOC concentration. The PAAS-normalized REE patterns for the dissolved load show some common features: negative Ce anomaly, progressively heavy REE (HREE) enrichment relative to light REE (LREE). Similar to the world’s major rivers the absolute concentration of the dissolved REE in the Xijiang River are mainly pH controlled. The degree of REE partitioning between the dissolved load and SPM load is also strongly pH dependent. The negative Ce anomaly is progressively developed with increasing pH, being consistent with the oxidation of Ce (III) to Ce (IV) in the alkaline river waters, and the lack of Ce anomalies in several DOC-rich waters is presumably due to both Ce (III) and Ce (IV) being strongly bound by organic matter. The PAAS-normalized REE patterns for the dissolved load and the SPM load in rivers draining the carbonate rock area exhibit middle REE (MREE) enrichment and a distinct maximum at Eu, indicating the preferential dissolution of phosphatic minerals during weathering of host lithologies. Compared to the Xijiang River waters, the MREE enrichment with a maximum at Eu disappeared and light REE were more depleted in the South China Sea (SCS) waters, suggesting that the REE sourced from the Xijiang River must be further fractionated and modified on entering the SCS. The river fluxes of individual dissolved REE introduced by the Xijiang River into the SCS vary from 0.04 to 4.36 × 104 mol a−1. 相似文献
13.
通过1：50 000区域地质调查,发现云南省会泽县一带灯影组中普遍发育硅质岩。本文通过硅质岩岩石学特征和地球化学特征分析,重点探讨了灯影组各段硅质岩的成因机制和沉积环境。结果表明：震旦系-寒武系灯影组下段硅质岩中相对富集Al和Ti,总稀土（ΣREE）相对较高,Ce呈负异常,Eu呈正异常;中段硅质岩中相对富集Ca和Mg,总稀土较低,LREE>HREE,Ce呈负异常,Eu呈正异常;上段硅质岩总稀土较低,LREE>HREE,Ce大部分呈负异常,Eu呈正负异常。综合硅质岩岩石学、地球化学特征,并结合震旦纪区域地质构造演化,认为研究区内下段硅质岩表现为正常海水沉积、中段硅质岩表现为典型热水沉积、上段表现出正常海水沉积受热水沉积影响的特征。硅质岩形成于复杂大陆边缘的浅海陆棚环境。 相似文献
14.
Timothy Wyndham Malcolm McCulloch Chantal Alibert 《Geochimica et cosmochimica acta》2004,68(9):2067-2080
In this study we have used laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), to produce a high resolution coral record of rare earth elements (REE), Mn and Ba from coastal Porites corals from the Great Barrier Reef of Australia. Validation of the LA-ICP-MS technique indicated that the method provides accurate and reproducible (RSD = 13-18%) analysis of low concentration REE in corals (∼1 to 100 ppb). The REE composition in coral samples was found to closely reflect that of the surrounding seawater and distribution coefficients of ∼1-2 indicated minimal fractionation of the series during incorporation into coral carbonate. To explore the idea that coral records of REE can be used to investigate dissolved seawater composition, we analyzed two coastal corals representing a total of ∼30 yr of growth, including a 10-yr overlapping period. Comparable results were obtained from the two samples, particularly in terms of elemental ratios (Nd/Yb) and the Ce anomaly. Based on this evidence and results from the determination of distribution coefficients, we suggest that useful records of seawater REE composition can be obtained from coral carbonates. When compared to the REE composition of a mid shelf coral, coastal corals showed a significant terrestrial influence, characterized by higher REE concentrations (greater than 10 times) and light REE enrichment. The REE composition of coastal seawater inferred from the coral record was dependent on seasonal factors and the influence of flood waters. REE fractionation displayed a strong seasonal cycle that correlated closely with Mn concentration. We suggest that higher Nd/Yb ratios and higher Mn concentrations in summer result from scavenging of heavy REE by particulate organic ligands and Mn reductive dissolution respectively, both processes displaying higher rates during periods of high primary productivity. The Ce anomaly also displayed a strong seasonal cycle showing an enhanced anomaly during summer and during flood events. This is consistent with the Ce anomaly being primarily controlled by the abundance of Ce oxidizing bacteria. Based on these arguments, we suggest that the coral record of dissolved REE and Mn may be regarded as a useful proxy for biological activity in coastal seawater. 相似文献
15.
珠江三角洲地区上更新统与全新统之间广泛发育1层杂色黏土,其成因多认为主要是由上更新统沉积物在末次冰盛期暴露于地表风化而成。对取自珠江三角洲3条钻孔（PRD09、PRD16和PRD17）的岩心样品分析表明,受风化作用的影响,其稀土元素含量和分异特征发生了较明显的变化。杂色黏土层的稀土总量大大低于下伏沉积物,而在邻近风化层的下伏沉积物中稀土元素却表现为明显富集,尤其是重稀土元素的富集。风化作用强度较大的PRD09孔和PRD17孔下伏沉积物中的稀土富集程度高于风化作用强度相对较小的PRD16孔。珠江三角洲在末次冰盛期时普遍发育的酸性介质条件,促进了风化层的稀土元素发生溶解和迁移。在风化过程中,由于轻、重稀土元素具有不同的溶解迁移能力和吸附能力,导致杂色黏土层的REE指标值（LREE/HREE、(La/Gd)N和(La/Yb)N）高于下伏沉积物。风化过程对Ce、Eu异常有一定的影响,但不十分明显,杂色黏土层的Ce、Eu异常值仅略低于下伏沉积物。 相似文献
16.
贵州大竹园大型铝土矿是中国近年来取得重要找矿进展的大型铝土矿之一。以采自大竹园矿区栗园向斜不同部位铝土矿、铝土岩和黏土岩的样品为研究对象,分析了这些样品的稀土元素含量（质量分数）特征及空间分布特征,研究了稀土元素含量与铝土矿质量及成矿过程的关系,最后就稀土元素对于成因和环境的指示意义进行了讨论。结果表明：铝土矿、铝土岩和黏土岩稀土元素总含量（不包括Y）分别为107.07×10-6、185.00×10-6和246.28×10-6,依次增高,说明铝土矿的成矿过程是一个稀土元素贫化的过程,也是Eu异常和Ce异常趋于增大的过程,即相对于黏土岩来说,铝土矿具有高Eu异常、Ce异常的特征;相对于重稀土元素来说,无论是栗园向斜西翼还是东翼,铝土矿轻稀土元素相对富集,且轻稀土元素含量以及La与Yb含量之比均随深度变浅而增加;单纯利用稀土元素图解不能有效反映成矿物质的来源,但可以大体反映含矿岩系形成于海相或海陆过渡相环境;大竹园大型铝土矿与黔北其他铝土矿一样,总体上属于沉积型,可能与古喀斯特化过程、古风化过程有关。 相似文献
17.
The rare earth elements(REE) composition of the polymetallic crusts and nodules obtained from the South China Sea(SCS) were analyzed through inductively coupled plasma mass spectrometry.Results revealed great differences in the REE abundances(∑REE) of the SCS polymetallic crusts and nodules; the crusts show the highest ∑REE, whereas the nodules exhibit the lowest ∑REE. The similarity in their NASC-normalized patterns, the enriched light REE(LREE), the markedly positive Ce anomaly(δCe), and the non-or weakly positive Eu anomaly(δEu), suggest that the polymetallic crusts and nodules are of hydrogenetic origin. Moreover, the REE contents and their relevant parameters are quite different among the various layers of the crusts and nodules, which probably results from the different marginal sea environments and mineral assemblages of the samples. The growth profiles of the SCS polymetallic crusts and nodules reveal the tendency ∑REE and δCe to slightly increase from the outer to the inner layers, suggesting that the growth environments of these samples changed smoothly from an oxidizing to a relatively reducing environment; in addition, the crust ST1 may have experienced a regressive event(sea-level change) during its growth, although the REE composition of the seawater remained relatively stable. On the basis of the regional ∑REE distribution in the SCS crusts and nodules,the samples collected near the northern margin were influenced by terrigenous material more strongly compared with the other samples, and the REE contents are relatively low. Therefore, the special geotectonic environment is a significant factor influencing the abundance of elements, including REE and other trace elements. Compared with the oceanic seamount crusts and deep-sea nodules from other oceans,the SCS polymetallic crusts and nodules exhibit special REE compositions and shale-normalized patterns, implying that the samples are of marginal sea-type Fe-Mn sedimentary deposits, which are strongly affected by the epicontinental environment, and that they grew in a more oxidative seawater environment. This analysis indicates that the oxidized seawater environment and the special nano property of their Fe-Mn minerals enrich the REE adsorption. 相似文献
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19.
Ahmed Saif Al-Mikhlafi 《Environmental Geology》2008,54(6):1145-1153
The concentration rare earth elements and Yttrium (REE + Y) were determined in coral sands from Kavaratti Island, Arabian
Sea, India. Chondrite-normalized REE + Y patterns show: (1) high REE concentration particularly light REE (LREE) enrichment;
(2) consistent negative Ce anomaly; (3) nearly chondritic Y/Ho ratios. All these features are consistent with the geochemistry
of well oxygenated seawater with significant terrestrial contribution. The seawater composition of Nd/Yb ratio inferred from
the coral record point to the dominance of LREE more than the heavy REE (HREE). The high terrestrial input rich in LREE and
property of adsorption/scavenging processes of LREE than that of HREE may be the cause. Terrigenous contributions were detected
on the basis of co-occurring trace element concentrations (Sc, Hf and Th) and Y/Ho ratio. Except for La, the REE distribution
coefficients, KD(REE)s, are between 100 and 300. KDs are high comparing to the other elements in biogenic calcite which is
attributed to detrital contamination during elemental incorporation. This study may not reflect original seawater chemistry
but it can be a good proxy to indicate proximity of corals to terrigenous input sources. 相似文献
20.
柞水银洞子银铅多金属矿床地球化学特征、成矿模式及找矿预测 总被引：2，自引：0，他引：2
柞水银洞子银铅多金属矿床岩、矿石稀土总量变化较大,稀土分配模式总体均为右倾型,富集轻稀土,重稀土分异不明显,重晶石脉、矿石皆呈负铈异常,铈亏损这一特征反映了成矿过程中的海底热水溶液作用。该矿床硫同位素组成变化范围大,且以重硫为主,主矿体含矿溶液总硫值与泥盆纪海水基本一致,反映硫源来自半封闭还原条件的泥盆纪海水。铅同位素分析表明矿床铅来源主要为深源,与海底火山活动存在一定关系。已有的同位素年龄数据和研究分析表明该矿床形成于中泥盆世,成矿作用与热水沉积成岩作用同时发生,相关证据也证明热水沉积作用是主要的成矿方式。研究认为,该矿床属热水喷流沉积成因,银洞子银铅多金属矿床的形成可以分为海底喷气沉积成矿和改造成矿期两个成矿期,前者是本矿床最主要的成矿期,形成了热水沉积岩(重晶石岩、硅质岩等)以及细粒金属矿物,建立了成矿模式。结合区内地质勘查工作,提出了5条找矿标志,并通过资料研究分析,从矿区外围找矿和新区找矿两个方面进行找矿预测,指出了8片预测靶区。这为深化认识柞水-山阳沉积盆地内成矿机理和指导找矿指明了方向。 相似文献