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1.
贵州碳酸盐岩风化壳主元素、微量元素及稀土元素的地球化学特征 总被引：5，自引：0，他引：5
《地球化学》2015,(4)
选取贵州高原喀斯特地区的典型碳酸盐岩原生风化剖面为研究对象,研究主元素、微量元素及稀土元素在风化壳的迁移转化及其分布规律特征,为解释碳酸盐岩风化壳元素的地球化学变化提供依据。结果显示,从上陆壳标准化蛛网图可知,Pb、Co在剖面富集,而Na、K、Cr、Rb、Sr和Ba则亏损。风化壳∑REE的变化范围为167.4~1814.2μg/g,稀土元素从剖面下部往上逐渐减少,剖面中上部LREE比HREE淋滤程度大。稀土元素球粒陨石标准化后Ce正负异常,Eu轻微负异常。以风化前缘为分界,在风化前缘以下的土层,Ce负异常,风化前缘以上的土层,Ce正异常。此外,在风化壳岩土界面附近存在一个明显且突变的碱性障,岩土界面土样的元素含量较岩粉平均增加了21倍。我们的研究显示,风化剖面主元素和微量元素的变化波动特征较为一致,说明主元素和微量元素在风化过程中的地球化学行为较为一致。铁壳层中稀土元素的含量最低,与上陆壳稀土元素十分相近,为研究上陆壳与碳酸盐岩铁壳层之间的相互联系起到了一定的借鉴作用。 相似文献
2.
碳酸盐岩风化形成的红土保存着喀斯特发展演化历史证据,同时也是喀斯特地区土壤研究的重要对象。文章选取云
南石林地区的两处典型碳酸盐岩剖面为研究对象,对主量元素,微量元素及稀土元素在风化层的迁移特征及分布规律进行
研究,为探究风化层的成因提供依据。结果显示：（1） 以Ti为参比元素的剖面迁移特征表明,两剖面的主量元素在成土过
程中有相似的迁移规律,多数表现为淋失;微量元素略有差异,富集淋失程度不一。（2） UCC 标准化蜘蛛图显示,相对于
基岩,风化层中的Ca和Sr均出现亏损;与UCC相比,Fe、Ti等元素轻微富集,Mg、Ca、Na、K、P等元素显示了强烈的亏
损特征。（3） 基岩与风化层的REE分布模式相似,但风化层的稀土相对富集,轻稀土元素间的分异较大而重稀土元素间的
分异较小,且SJC剖面的轻、重稀土元素比值大于QST剖面;稀土元素球粒陨石标准化后,SJC剖面的Eu为负异常,剖面
上部和下部出现Ce负异常;QST剖面Ce负异常,Eu明显负异常。（4） 元素含量变化和元素对Al-Ti、Al-Fe及Zr-Hf相关性
说明剖面上覆红土是下伏基岩风化的结果。研究结果显示,两个剖面的元素地球化学特征与基岩存在很好的继承性,风化
层是基岩原位风化的产物。 相似文献
3.
利用岩性及地层厚度推测喀斯特地区的风化成土量——以贵阳金阳地区为例探讨二叠系以上地层的成土能力 总被引：1，自引：0，他引：1
碳酸盐岩成土是喀斯特地貌发展及演化历史研究的关键问题。研究了贵阳市金阳地区碳酸盐岩风化成土剖面和红粘土层下基岩分布情况,结合该地区地层发育、厚度、岩性等特征,以及碳酸盐岩风化成土的经验数值,推算了研究区成土厚度。同时,根据理论成土厚度与实际保存红粘土厚度对比分析,确认目前保存下来的红粘土层是早更新世以来的第三个夷平期的产物,形成时间可能为4～13万年。现代碳酸盐岩上的红粘土层不仅由碳酸盐岩风化成土形成,而且很大一部分是由碳酸盐岩岩系中的碎屑岩夹层风化成土而来,同时侏罗系碎屑岩成土也占较大比例。因此,喀斯特环境中红粘土的形成及物质来源比较复杂,并非单一的碳酸盐岩风化成土。 相似文献
4.
新疆霍什布拉克铅锌矿床地质、地球化学特征研究 总被引：6，自引：3，他引：3
新疆霍什布拉克铅锌矿床的矿体和含矿地层的产状一致,主矿体的矿石具有条带状、纹层状构造,矿石中大量发育霉球状、管状和环带状生物结构,显示出层控、热水沉积成因的特点。含矿地层和矿石样品的主量元素PER图解显示含矿碳酸盐岩以含石膏的灰岩为主,围岩的白云岩化微弱,矿化与硅化关系密切。矿石、含矿碳酸盐岩和页岩、粉砂质灰岩和泥质粉砂岩等碎屑岩具有各自鲜明的微量元素分布特征,上层矿体矿石中较强的富集过渡族元素Ti、V、Cr、Mn、Co、Ni、非活动性元素Zr、Hf及大离子亲石元素Sr和Pb,亏损活动性元素Na、K、Rb、Ba和非活动性元素Nb、Th。其围岩重结晶泥晶灰岩富集Ti、Mn、Ni、Sr和Pb,亏损Na、K、V、Fe、Rb、Ba、Zr、Hf、Nb和Th。下层矿体的围岩页岩和泥质、粉砂质灰岩样品的微量元素分布在平均上地壳线附近,部分样品较明显的富集Ti、V、Cr、Mn、Co、Ni、Rb、Y、Zr和Hf,亏损Na、Fe、Sr、Nb。上层矿体矿石和下层矿体围岩中的部分碎屑岩富集强亲岩浆元素Cr、Co、Ni,且上层矿体矿石的稀土元素分布模式具有强的正Eu异常,部分下层矿体围岩具有较明显的正Eu异常。地质和地球化学特征显示该矿床属于热水沉积矿床中的SEDEX型矿床。 相似文献
5.
江苏东海芝麻房预先导孔(CCSD-PP1)橄榄岩及其反映的上地幔亏损和交代事件 总被引：1，自引：0，他引：1
芝麻房预先导孔橄榄岩岩石类型有二辉橄榄岩、方辉橄榄岩、单辉橄榄岩和纯橄榄岩,其中前3种多数含有石榴子石.这些岩石在垂向上显示成层性,没有某种方向的韵律变化,它们之间呈渐变过渡关系.对样品进行主量元素、微量元素、稀土元素和Sr、Nd、O同位素分析表明,随着样品MgO含量的增高,Al2O3、CaO逐渐降低,呈良好的相关关系,并且大致上从石榴橄榄岩类到不含石榴子石的橄榄岩类主量元素的亏损程度增高,两者一般均比原始地幔主量元素亏损.稀土元素配分型式表现为右倾的轻稀土富集型,在微量元素蛛网图上,也表现为强不相容元素和微量元素到适度不相容元素的总体右倾型,与原始地幔相比,均富集强不相容元素.富集程度的不同与主量元素的亏损无对应关系,说明主量元素和微量元素各自的特点不是同一种事件造成的,而是先前地幔部分熔融作用之后又发生了富含不相容元素流体的交代作用.Sr、Nd同位素具有富集特点,变化范围较大,而且主量元素较亏损的岩石更富集Sr同位素,显示了交代富集的特点.稀土元素(Ce/Yb)N比值和εNd之间的负相关关系和Rb丰度与Sr同位素之间的正相关关系表明,富集Sr、Nd同位素的流体和富集不相容微量元素的流体均来自地幔. 相似文献
6.
江苏东海芝麻房预先导孔（CCSD-PPl）橄榄岩及其反映的上地幔亏损和交代事件 总被引：10，自引：2，他引：10
芝麻房预先导孔橄榄岩岩石类型有二辉橄榄岩、方辉橄榄岩、单辉橄榄岩和纯橄榄岩，其中前3种多数含有石榴子石。这些岩石在垂向上显示成层性，没有某种方向的韵律变化，它们之间呈渐变过渡关系。对样品进行主量元素、微量元素、稀土元素和Sr、Nd、O同位素分析表明，随着样品MgO含量的增高，Al2O3、CaO逐渐降低，呈良好的相关关系，并且大致上从石榴橄榄岩类到不含石榴子石的橄榄岩类主量元素的亏损程度增高，两者一般均比原始地幔主量元素亏损。稀土元素配分型式表现为右倾的轻稀土富集型，在微量元素蛛网图上，也表现为强不相容元素和微量元素到适度不相容元素的总体右倾型，与原始地幔相比，均富集强不相容元素。富集程度的不同与主量元素的亏损无对应关系，说明主量元素和微量元素各自的特点不是同一种事件造成的，而是先前地幔部分熔融作用之后又发生了富含不相容元素流体的交代作用。Sr、Nd同位素具有富集特点，变化范围较大，而且主量元素较亏损的岩石更富集Sr同位素，显示了交代富集的特点。稀土元素(Ce／Yb)x比值和εNd之间的负相关关系和Rb丰度与Sr同位素之间的正相关关系表明，富集Sr、Nd同位素的流体和富集不相容微量元素的流体均来自地幔。 相似文献
7.
本文以偃龙铝土矿为对象,研究了铝土矿的地球化学特征,讨论了其成矿物质来源。铝土矿含矿岩系中不同矿产的SiO_2、Al_2O_3、Fe_2O_3、FeO的元素含量变化较大,且总量较高,说明铝土矿在形成过程中,其源岩风化程度较高。Al_2O_3与SiO_2、Fe_2O_3、K_2O含量呈负相关关系,与TiO_2、A/S呈正相关关系。含矿岩系明显具有富集轻稀土、亏损HREE的特征,在垂向上,其稀土元素含量较高的是Ce、La、Nd(均为轻稀土),低含量的是Tm、Ho、Eu、Lu。微量元素方面,偃龙铝土矿比山西铝土矿富集的元素有Li、Be、Sc、Ni、Cu、Zn、Zr等稀有金属元素和亲铜元素,而这些元素在贵州大竹园铝土矿中的含量比偃龙铝土矿更富集。偃龙铝土矿的成矿物质来源于基底碳酸盐岩风化残余,在广泛海侵时,残余物质经搬运沉积成矿。 相似文献
8.
9.
风化粘土层-半风化岩石型不整合的矿物学、地球化学特征 总被引：2，自引：0，他引：2
不整合是构造运动和海(湖) 平面升降的产物, 其风化粘土层可作为油藏的良好封盖层, 半风化岩石孔缝系统可作为油气运移通道, 也可为油气聚集提供良好储层.深入分析不整合结构在矿物含量变化、元素及其氧化物含量变化方面的微观特征是划分不整合结构的基础, 对不整合油气藏的勘探实践具有重要意义.不整合结构可划分为风化粘土层-半风化岩石型、半风化岩石型和沉积间断型.通过济阳坳陷义和庄凸起前第三系风化粘土层-半风化岩石型不整合结构矿物与元素变化的实测数据, 结合典型地区风化壳的矿物、元素分析结果, 分析了风化粘土层-半风化岩石型不整合结构的矿物学、常量元素地球化学特征: 其矿物学特征主要表现为长石、云母等原生矿物的蚀变和高岭石、伊利石及蒙脱石等次生粘土矿物的明显增多, 粘土矿物在风化粘土层中部或风化粘土层下部-半风化岩石上部较为富集; 其常量元素地球化学特征表现为Ca、Na元素含量迅速减少, 在风化粘土层下部与半风化岩石上部通常具有Fe、Al元素的富集带, K、Mg元素的变化由于交代作用等因素而变得复杂. 相似文献
10.
白云岩风化剖面元素地球化学特征:对黔中九架炉组“三稀金属”富集机制的启示 总被引：2，自引：1，他引：1
黔中早石炭世九架炉组铝土矿含矿岩系富集Ti、Li、Sc、V、Ga、Nb、Ta、Zr、Hf、Th和稀土(REEs)等"三稀金属",具有成为独立矿床或伴生资源的潜力。这些元素大部分与九架炉组共有同一母岩,且富集程度受母岩的成分和风化作用控制。本研究选取九架炉组母岩乌当娄山关群白云岩和纳雍牛蹄塘组泥质白云岩的现代风化剖面为研究对象,研究元素在风化作用过程中的迁移特征及分布规律,进而为九架炉组微量元素的富集机制提供启示。研究获得以下认识:1)依据剖面结构、ZrHf、Nb-Ta、Y-Ho二元图特征及REE配分曲线和Eu/Eu*值的相似性表明研究区土层主要来源于基底或母岩的风化; 2)白云岩风化成土过程中Si、Fe、Cr、As、Sb、Ti、Nb、Ta、Zr、Hf、Th、REEs等元素化学性质相对稳定,富集程度较高,而Ca、Mg、Na、K、Sr、P、Mo、Cd等元素化学性质活泼,容易淋失亏损; 3)纳雍剖面REEs~(3+)和Ca~(2+)半径差与REEs富集系数相关性良好,表明碳酸盐岩风化过程中,含钙矿物磷灰石是稀土元素分配的重要控制因素; 4)九架炉组的母岩也是Ti、Li、Sc、V、Ga、Nb、Ta、Zr、Hf、Th等微量元素的主要物质来源,母岩风化过程中,这些微量元素首先在副矿物、黏土矿物、铝矿物及磷灰石等矿物相中初步富集,之后随风化碎屑物一起沉积形成微量元素超常富集地层; 5)纳雍剖面地表和地下水提供了部分P、Be、Zn、Sb、Pb、Y及REEs来源,指示水体迁入作用也是九架炉组REEs富集的重要原因。研究表明黔中九架炉组微量元素的来源较复杂,风化-沉积过程中,化学性质稳定的元素残留在风化碎屑物中并被搬运-沉积在负地形中,而化学性质活泼的元素首先被带入水体,在沉积-成岩过程中特定条件下发生二次富集作用(例如次生矿物的形成及吸附)形成微量元素富集的地层。 相似文献
11.
In this paper we report the results of the analysis of rare earth (REE), large-ion lithophile (LILE), and high field strength (HFSE) elements in minerals from the alkaline lamprophyre dikes of the Kola region and the Kaiserstuhl province by the local method of laser ablation inductively coupled plasma mass spectrometry. The contents of Y, Li, Rb, Ba, Th, U, Ta, Nb, Sr, Hf, Zr, Pb, Be, Sc, V, Cr, Ni, Co, Cu, Zn, Ga, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu were measured in olivine, melilite, clinopyroxene, amphibole, phlogopite, nepheline, apatite, perovskite, and the host fine-grained groundmass. The obtained data on trace element partitioning among the mineral phases of the alkaline ultrabasic rocks of the dike series indicate that the main mineral hosts for the HFSEs and REEs in alkaline picrites, olivine melanephelinites, and melilitites are perovskite and apatite comprising more than 90% of these elements. Among major rock-forming minerals, melilite, clinopyroxene, and highly magnesian amphibole make a significant contribution to the balance of REEs during the evolution of melanephelinite melts. The partition coefficients of Ni, Co, Cu, Zn, Sc, V, Cr, Ga, Y, Li, Rb, Ba, Th, U, Ta, Nb, Sr, Hf, Zr, Pb, Be, and all of the REEs were calculated for olivine, clinopyroxene, amphibole, phlogopite, nepheline, perovskite, and apatite on the basis of mineral/groundmass ratios. Variations in the composition of complex zoned clinopyroxene phenocrysts reflect the conditions of polybaric crystallization of melanephelinite melt, which began when the magmas arrived at the base of the lower crust and continued during the whole period of their ascent to the surface. The formation of green cores in clinopyroxene is an indicator of mixing between primary melanephelinite melts and phonolite magmas under upper mantle conditions. The estimation of the composition of primary melts for the rocks of the alkaline ultrabasic series of the Kola province indicated a single primary magma for the whole series. This magma produced pyroxene cumulates and complementary melilitolites, foidolites, and nepheline syenites. 相似文献
12.
高分辨电感耦合等离子体质谱法测定地质样品中稀土元素的氧化物干扰研究 总被引：3，自引：3，他引：0
电感耦合等离子体质谱(ICP-MS)用于测定稀土元素经常会引起M+、MO+、MOH+离子的质谱重叠干扰,其中制约分析准确度和精密度的主要因素是多原子离子干扰,尤其是轻稀土元素的氧化物和氢氧化物对重稀土元素的干扰,以及钡的7个天然同位素形成的氧化物和氢氧化物对轻稀土元素的干扰.本文采用高温高压密闭消解地质样品,高分辨电感耦合等离子体质谱法(ICP-MS)测定其中的痕量稀土元素,研究了低、中、高三种分辨率模式下氧化物的干扰情况,确定了最佳的测定同位素和合适的分辨率.分析结果表明,在低、中分辨率模式下,轻稀土元素Ce、Pr、Nd、Sm的氧化物和Ba的氧化物干扰明显,Gd元素的测定值严重偏离;在高分辨模式下,Ba氧化物对Eu的干扰以及大部分轻稀土元素氧化物对重稀土元素的干扰基本可以消除,无需进行校正,而只有157Gd受到141pr16O的干扰突出,当样品中Pr/Gd的浓度比值大于100时,Gd的测量值必须进行数学校正. 相似文献
13.
以新疆库拜煤田塔里奇克组煤层为研究对象,对其煤化学及地球化学特征进行分析。认为研究区煤层属低水分、低灰分、特低硫分、高挥发分的长焰煤-气肥煤;煤中的常量元素Al、Ca、Fe、Mg和K平均含量低于中国煤常量元素的平均含量,并有较大的变化范围,仅Na平均含量高于中国煤的平均含量;煤中的微量元素Cu和Co含量高于中国煤的平均含量,Ni和Zn含量接近中国煤的平均含量．其它微量元素含量均明显低于中国煤的平均含量。阐明了Al、Li、Cr、Ti、Zr、Ga、Nb以及轻稀土元素（La、Ce和Nd）具有较强的亲无机性,在煤中主要以无机态存在;Li、Sc、Ti、V、Cr、Ga、Rb、Zr、Nb及重稀土元素中的La、Ce、Pr、Nd、Sm、Gd元素主要与硅铝酸盐矿物及微量的重矿物组合有较好的亲和性：As、Sr元素主要以碳酸盐矿物的形式存在。 相似文献
14.
Khadija Semhi Osman A. E. Abdalla Salah Al Khirbash Tabisam Khan Salim Asaidi Sardar Farooq 《Arabian Journal of Geosciences》2009,2(2):143-150
Groundwater samples from six wells and various species of plants from soils developed on ophiolites were collected from an arid area (AlKhod area, Oman) and analyzed for trace elements including rare earth elements (REEs). The distribution patterns of REEs in plants indicated an enrichment in middle REEs (MREEs?=?Sm to Dy) and heavy REEs (HREEs?=?Ho to Lu), when they are normalized to the REE composition of the Post Archean Australian Shale (PAAS), with a significant negative anomaly in Ce and a positive anomaly in Eu. Compared to Oman ophiolites, the REEs in different species of plants are depleted in Ce and enriched in MREEs and slightly enriched in light REE (LREE?=?from La to Nd). Relative to PAAS, the distribution of REEs in groundwaters revealed similar patterns to the REE distribution in plants. The distribution patterns of REEs in plants relative to those in waters are nearly flat. These patterns suggest that the transfer of REEs from soil solutions to the groundwaters in Oman occurs without any significant fractionation. 相似文献
15.
高分辨电感耦合等离子体质谱法测定地球化学样品中钪钇和稀土元素 总被引：4，自引：2，他引：2
建立了高分辨电感耦合等离子体质谱法(HR-ICP-MS)测定地球化学样品中钪、钇、镧、铈、镨、钕、钐、铕、钆、铽、镝、钬、铒、铥、镱和镥的分析方法。样品经氢氟酸-硝酸-硫酸-王水消解,试液直接用HR-ICP-MS测定钪、钇和14种稀土元素。用高分辨模式有效地避免了多原子离子及难熔氧化物离子对待测元素测定的干扰,为钪、钇和14种稀土元素选择了最佳的测定同位素和合适的分辨率;用地球化学标准物质制备的溶液优化仪器工作参数,确定了最佳的仪器测定条件。方法检出限(6σ)为0.003～0.013μg/g(稀释因子为1000),相对标准偏差(RSD,n=12)小于6%。方法经国家一级地球化学标准物质验证,测定值与标准值吻合。 相似文献
16.
滇西南那邦变质基性岩地球化学与俯冲板片裂离 总被引：4，自引：1，他引：3
中缅边界那邦麻粒岩相变质基性岩地球化学特征表明其原岩是岩浆岩,并具有ＭＯＲＢ的特性,其岩石化学具有以下特征：岩石的ＴＦｅ／ＭｇＯ值低（１．１０～２．１７）,ＡＦＭ图解上显示拉斑玄武岩演化趋势;ＴｉＯ２含量（１．１４％～１．８１％）高稀土亏损、重稀土较有富集的配分形式,稀土元素和总量（∑ＲＥＥ）值十倍于球粒陨石（２４～５０μｇ／ｇ）,（Ｌａ／Ｓｍ）Ｎ＝０．４３～０．７５（Ｌａ／Ｙｂ）Ｎ＝０．４５～０ 相似文献
17.
Experimental cpx/melt partitioning of 24 trace elements 总被引：46，自引：13，他引：46
Cpx/melt partition coefficients have been determined by ion probe for 24 trace elements at natural levels in an alkali basalt experimentally equilibrated at 1,380°C and 3 GPa. One goal was to intercompare Ds for both high-field-strength elements and rare earth elements (REE) in a single experiment. Relative to the REE spidergram, Hf and Ti show virtually no anomaly, whereas Zr exhibits a major negative anomaly. Other incompatible elements (Ba, K, Nb) fall in the range of published values, as do elements such as Sr, Y, Sc, Cr and V. Pb shows a value intermediate between La and Ce. Values for Be, Li and Ga are reported for the first time, and show that Be is as incompatible as the light REEs whereas Li and Ga are somewhat more compatible than the heavy REE. 相似文献
18.
《Applied Geochemistry》2001,16(3):351-361
Neodymium and Sr isotopic compositions and the rare earth elements (REE) distribution patterns have been determined in salts adjacent to a basaltic dyke along 2 parallel horizontal profiles. The salts, originally consisting of carnallite (KMgCl3 · 6H2O), have been transformed during basalt intrusion mainly into halite (NaCl) and sylvite (KCl) by fluids saturated in NaCl. The Sr isotope data suggests that much more fluid penetrated the upper than the lower horizon. The Nd isotope data shows that in the upper horizon, where fluid flow was stronger, Nd is essentially derived from the basalt. In contrast, in the lower horizon a strong salt Nd component is present.The REE data document in both horizons is a strong depletion of Ce, Pr, Nd, Sm and Eu with increasing distance from the basalt. This depletion of the light rare earths (LREE) is stronger in the upper horizon where fluid flow was stronger. The authors suggest that this REE fractionation is more likely due to precipitation of LREE-enriched accessory minerals such as apatite, than to differential REE solubility caused by selective REE complexation. This finding is of interest for REE behaviour in brines in general, and for the behaviour of radioactive REE and actinides in a salt repository for high-level nuclear waste in particular. 相似文献
19.
《Chemie der Erde / Geochemistry》2021,81(2):125761
Trace elements distribution, including rare earth elements (REEs), in stream sediments of an abandoned U mining site in the Eastern Carpathians, Romania, were of high concern of interest in the present work. A total number of 40 riverbed sediments samples collected from the Bistricioara River and local tributaries (Primatar, Bradul, Prisacani, Barasau, Grintiesul Mare and Valea Seaca) were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) and energy dispersive X-ray fluorescence spectrometry (XRF). All REEs including La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu were identified and quantified in the present work using ICP-MS technique. For other 24 elements (Ti, V, Cr, Co, Zn, Li, Be, Rb, Sr, Y, Sc, Zr, Nb, Sb, Ba, Ta, W, Pb, U, Ni, Cu, Mo, As, Th) similar information was obtained either by ICP-MS or XRF techniques. The impact and the relevance of the obtained data base might be significant at a local scale of about 50 km2.Enrichments of some trace elements of interest in comparison to the upper continental crust allowed discrimination between various mineralization processes specific for the investigated areas. Uranium mineralization and Paltin-type (Pb, Zn) mineralization seems to be specific for the NW area of the investigated region. Negative anomaly characteristic for the upper crustal rocks was identified for Eu and Ce elements. Evidences were obtained also for the existence of ultramafic rocks (Ni, Cr, Co and V) in the investigated riverbed sediments. The observation was also confirmed by the binary plots analysis of Th/Cr vs. Th/Co and Cr/V vs. Y/Ni pairs. From the investigated tributaries to Bistricioara River, Barasau seems to exert the highest influence on the abundances of REEss in the entire area. Most probably some chemical parameters such as the pH of the water streams influence leaching and depletions of some chemical constituents in various minerals specific for the region.The existence of magnetite, garnets, pyrite and sillimanite minerals was confirmed by SEM-EDAX and XRF analysis, as well by optical microscopy. Principal Component Analysis runs confirmed the association of some chemical elements in the riverbed sediments in close connection with the minerals from which they originate.The present work reports for the first time upon the authors knowledge clear scientific evidence and chemical information concerning the geology and geochemistry, i.e. transition metals, high field strength elements, alkali and alkaline earth elements, rare earth elements (REEs) and others, in stream sediments crossing the Tulghes-Grinties mining area (Eastern Carpathians, Romania). For the analysed REEs this is the first study reporting consistent information on the concentrations of the entire array of both light REEs (six elements) and heavy REEs (ten elements) in Bistricioara Basin stream sediments. Relevant scientific data related to geochemical characteristics of ultramafic rocks existent in the investigated area were also generated. Moreover, data reported in the present work might be considered as a reference geochemical database relevant for the investigated area, which can be used as a trustworthy input for a systematic national geochemical atlas. 相似文献
20.
《地学前缘(英文版)》2023,14(2):101517
We present in situ trace element and Nd isotopic data of apatites from metamorphosed and metasomatized (i.e., altered) and unaltered granitoids in the Songnen and Jiamusi massifs in the eastern Central Asian Orogenic Belt, with the aim of fingerprinting granitoid petrogenesis, including both the magmatic and post-magmatic evolution processes. Apatites from altered granitoids (AG) and unaltered granitoids (UG) are characterized by distinct textures and geochemical compositions. Apatites from AG have irregular rim overgrowths and complex internal textures, along with low contents of rare earth elements (REEs), suggesting the re-precipitation of apatite during epidote crystallization and/or leaching of REEs from apatite by metasomatic fluids. εNd(t) values of the these apatites are decoupled from zircon εHf(t) values for most samples, which can be attributed to the higher mobility of Nd as compared to Sm in certain fluids. Apatites from UG are of igneous origin based on their homogeneous or concentric zoned textures and coupled Nd-Hf isotopic compositions. Trace element variations in igneous apatite are controlled primarily by the geochemical composition of the parental melt, fractional crystallization of other REE-bearing minerals, and changes in partition coefficients. Sr contents and Eu/Eu* values of apatites from UG correlate with whole-rock Sr and SiO2 contents, highlighting the effects of plagioclase fractionation during magma evolution. Apatites from UG can be subdivided into four groups based on REE contents. Group 1 apatites have REE patterns similar to the host granitoids, but are slightly enriched in middle REEs, reflecting the influence of the parental melt composition and REE partitioning. Group 2 apatites exhibit strong light REE depletions, whereas Group 3 apatites are depleted in middle and heavy REEs, indicative of the crystallization of epidote-group minerals and hornblende before and/or during apatite crystallization, respectively. Group 4 apatites are depleted in heavy REEs, but enriched in Sr, which are features of adakites. Some unusual geochemical features of the apatites, including the REE patterns, Sr contents, Eu anomalies, and Nd isotopic compositions, indicate that inherited apatites are likely to retain the geochemical features of their parental magmas, and thus provide a record of small-scale crustal assimilation during magma evolution that is not evident from the whole-rock geochemistry. 相似文献