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1.
鄂尔多斯盆地西缘北部的内蒙古桌子山地区奥陶纪地层出露完整,沉积类型丰富,是研究鄂尔多斯盆地西缘奥陶纪沉积的关键地区。该区在中奥陶世时位于从浅海向深海的转换部位,达瑞威尔期沉积的克里摩里组由深灰色薄层状石灰岩和灰黑色泥岩组成,是研究鄂尔多斯盆地西缘奥陶纪深水氧化-还原条件的一个较为理想的层位。本文在详细的野外观察基础上,测试克里摩里组薄层细粉晶-泥晶石灰岩和灰黑色泥岩的稀土元素（REY）和其他与氧化-还原条件相关的微量元素,主要包括V、Cr、Ni、Co等,着重分析探讨其形成时的氧化-还原条件。结果表明：1）石灰岩和泥岩稀土总量（REE）分别为28.18×10-6和100.37×10-6,轻、重稀土比值分别为9.60和9.69;2）石灰岩和泥岩稀土元素Y/Ho、（La/Yb）N、（La/Sm）N、（La/Nd）N值分别为29.01、1.35、0.92、0.95和25.72、1.21、0.96、1.02;3）石灰岩无Ce负异常或具有微弱的正异常,同时具有明显的Eu正异常,泥岩具有明显的Ce负异常和较弱的Eu正异常;4）石灰岩和泥岩的其他微量元素比值V/Cr、V/（V+Ni）、Ni/Co分别为1.10、0.62、7.75和3.54、0.89、5.15。依据本文研究结果,结合沉积特征和前人研究成果可以推测,克里摩里组沉积于风暴浪基面之下,远离海岸,但同时又受淡水影响,其中石灰岩形成于氧化环境,泥岩形成于还原环境,同一沉积背景下这种氧化与还原环境的交替是由等深暖流造成的,可称为水动力氧化环境。 相似文献
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东北黑土的形成长期备受学者们的关注,然而人类活动不同程度影响着表层黑土的自然特征。地下黑土能较为真实地反映客观属性,但其研究仍然匮乏,由此本文选择松嫩平原黑土区阿荣旗钻孔内的地下黑土为研究对象,进行稀土元素地球化学测试,采用地质统计学分析地下黑土层ΣREE、HREE、LREE的分布特征,结合Ce异常、Eu异常、(La/Yb)N、(La/Sm)N、(Gd/Yb)N、Al2O3/TiO2图解、Ceanom讨论了黑土的物源特征与环境记录。结果显示,阿荣旗地下黑土ΣREE含量较高,平均值为141.45×10-6。球粒陨石标准化曲线表现为向右倾斜,轻稀土富集,δEu微弱负异常,δCe明显负异常。(La/Yb)N平均值7.58,(La/Sm)N平均值为1.14,(Gd/Yb)N平均值为3.54,表明地下黑土重、轻稀土元素分异程度大,轻稀土元素相比重稀土元素分馏... 相似文献
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在研究区域地质背景基础上,分析了金红铅锌矿区赋矿地层及控矿断裂构造岩的稀土元素组成特征.按其特征和配分模式得知：赋矿白云岩属于LREE富集-HREE平坦型,轻重稀土分馏程度都较高,Eu异常差异明显,Ce异常差异较大,（La/Yb）N、（La/Sm）N和（Gd/Yb）N值具有一定的差异;断裂构造岩属于LREE富集-HREE平坦型,轻重稀土分馏程度都较高,Eu异常差异微弱,Ce异常差异明显,（La/Yb）N、（La/Sm）N和（Gd/Yb）N值比较相似.以上特征可作为成矿预测的微观标志. 相似文献
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广西南宁附近从早泥盆世埃姆斯期到晚泥盆世弗拉期发育了一套黑色层状硅质岩,常夹凝灰岩(或凝灰质硅质岩)或与之互层,在弗拉期晚期硅质岩变为浅黄色。本文对该区埃姆斯期、艾菲尔期、吉维特期到弗拉期硅质岩的稀土元素地球化学特征进行了系统研究,其∑REE平均值分别为:18.59×10-6,12.28×10-6,27.44×10-6和43.07×10-6;页岩标准化后Ce含量在这4个阶段均表现为弱-中等的负异常,Ce/Ce*平均值分别为:0.85,0.72,0.85和0.67;Eu/Eu*为弱的正异常,平均值分别为:1.08,1.21,1.46和1.04;(La/Ce)N值中等,平均值分别为:1.42,1.50,1.35和1.73;(La/Yb)N值变化较大,平均值分别为:1.19,1.06,1.24和0.45。这些结果表明该区硅质岩开始形成于陆内裂谷盆地,受陆源影响较大,在晚泥盆世迅速扩张为比较开阔的海盆环境,陆源影响明显减弱。硅质岩的形成虽受到一定热液活动的影响,但热液活动的影响普遍较弱。 相似文献
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对于青藏高原北部羌塘盆地中央隆起带晚古生代的构造演化历史,学术界目前仍存在不同观点。位于盆地中央隆起带角木日地区的羌资5井揭示出的下二叠统展金组细碎屑岩,对于该地区古地理研究和构造背景约束具有重要意义。通过对该井中17个展金组粉砂质泥岩和泥质粉砂岩样品的稀土元素地球化学研究表明:样品 ω(ΣREE) 整体较高,ω(ΣLREE)/ω(ΣHREE)及(La/Yb)N等比值显示其具有较弱的轻、重稀土元素分异;Ceanom,Ce/Ce*,Eu/Eu*等参数反映样品主要形成于具有一定深度的浅海还原环境;(La/Yb)N值自下而上呈降低趋势,表明下部的沉积速率低于上部。稀土元素组合及其比值特征指示展金组物源以玄武岩和沉积岩混合为主。根据La-Th-Sc构造背景判别图解分析,并与不同构造背景下的杂砂岩稀土元素特征比较,认为展金组沉积岩的物源可能来自于具有类似岛弧构造特征的环境。 相似文献
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桦甸盆地始新统油页岩稀土元素地球化学特征及其地质意义 总被引：2，自引：0，他引：2
稀土元素因其稳定的地球化学性质已经成为研究油页岩等细粒湖泊沉积物的物源、古环境、古气候等变化的良好指示剂,具有重要的研究意义。笔者测试并重点分析了桦甸盆地始新统桦甸组油页岩REE地球化学特征。分析结果表明：桦甸含油页岩段稀土元素含量要低于上下段泥岩和炭质页岩样品,油页岩稀土元素总量（∑REE）为（91.51～355.98）×10-6,平均值为162.56×10-6,高于全球平均大陆上地壳成分（UCC）,略低于北美页岩;∑LREE/∑HREE及(La/Yb)N等化学参数表明轻、重稀土元素分异明显,REE分布模式为明显的轻稀土元素富集、重稀土元素亏损呈平坦状、具中等程度的负Eu异常和弱负Ce异常。以Ce异常值反映水介质的氧化还原性,桦甸油页岩形成于缺氧的还原环境;以REE的分异程度来表征油页岩的沉积速率,桦甸组自下而上(La/Yb)N值呈逐渐由增大→降低→增大的变化趋势,含油页岩段的沉积速率普遍比下段和上段低,与根据恢复压实后的桦甸组地层厚度和孢粉年龄估算得出的沉积速率结果相吻合,说明较低的沉积速率更有利于有机质的聚集和保存;以∑REE的纵向变化作为古气候波动的代用指标,高∑REE值指示暖湿的气候环境,低∑REE值指示冷干的气候环境。桦甸油页岩形成于干旱与温湿交替的气候环境,气候通过影响湖泊水体蒸发量与补给量的平衡而控制着湖平面的变化,从而控制了油页岩的层数和厚度。 相似文献
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为探讨下扬子地区二叠系泥页岩的稀土元素特征、物质来源及其地质意义,对研究区昌桥剖面大隆组、龙潭组和孤峰组的泥页岩样品进行了微量和稀土元素地球化学测试.测试结果表明该地区稀土元素（∑REE）含量较高,∑REE平均值为259.15 μg/g,轻稀土元素富集,重稀土元素亏损.稀土元素的配分曲线整体表现为“右倾”,Eu呈明显的负异常,Ce有轻微的负异常.样品的Ceanom值（平均值为-0.07）和δCe值（平均值为0.90）反映了沉积时水体为缺氧的还原环境,有利于形成优质烃源岩,（La/Yb）N值的变化反映研究区在垂向上的沉积速率为:大隆组 < 孤峰组 < 龙潭组.稀土元素数据还表明研究区物源来自上地壳,母岩为长英质岩石,以花岗岩为主.利用La-Th-Sc、Th-Sc-Zr/10、Th-Co-Zr/10三角图版和La/Th-Hf图解,判断得到研究区的构造背景为被动大陆边缘. 相似文献
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为查明吉中地区典型斑岩型矿床矿化特征及成矿规律,对长安堡铜钼矿床地质特征和成矿岩体进行了研究.该矿床成矿岩体为黑云母二长花岗岩.岩石主量、微量及稀土元素组成特征为：高硅,全碱含量不高,富钾,Al2O3含量较高,TiO2含量较低,贫Y和Yb,相对富集大离子亲石元素（LILE）和轻稀土元素（LREE）,而高场强元素（HFSE）、重稀土元素含量（RREE）相对较低,具负Eu异常,（La/Yb）N值较高,2件未蚀变样品具有较低的（Rb/La）N值,与我国东北部地区岛弧钙碱性火成岩地球化学特征基本一致. 相似文献
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云南省昭通市昭阳区锌厂沟位于康滇古陆东缘,在剖面测量及样品系统采集分析基础上,建立了该区下寒武统筇竹寺组泥页岩地球化学剖面,为该区筇竹寺组沉积环境、物源分析提供了定量的地球化学数据。研究结果显示:1）筇竹寺组物源主要来自康滇古陆中元古界东川群、会理群砂泥岩、海相玄武岩,并可能有少许同时代花岗岩,形成于康滇古陆东缘大陆坡或边缘海,自西向东呈康滇古陆—潮坪—浅水陆棚—深水陆棚—水下隆起有序变化,工区位于浅水陆棚相;2）稀土元素δCe值、δEu值及微量元素Mo、V含量、（V）N/（V+Ni）N比值、（Cu）N/（Zn）N比值反映筇竹寺组底部为深水陆棚环境,上部总体为浅水陆棚沉积环境,局部水体加深为深水陆棚沉积环境。总体上该区以浅水陆棚为优势相,并具酸性还原环境特点;3）微量元素Rb、Ba、Ga、V、Zn、Mo、Cd、Sn、Zr有明显的富集。主量元素（SiO2）N/（Al2O3）N比值及微量元素Ba、U含量、Zn-Ni-Co三角图、U/Th比值、Co/Zn比值表明有生物或热水作用的参与。 相似文献
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四川宣汉地区二叠系茅口组和吴家坪组的硅岩,主要以结核状、条带状和团块状产出。根据硅岩的岩石学及地球化学特征,对其成因进行了系统研究。野外观察硅岩形态多样,与围岩呈缝合线状接触,在剖面上受一定层位控制,团块状硅岩中含石灰岩斑块等。显微镜下观察,硅岩中见方解石残余结构及白云石菱形假晶等。野外观察和显微镜下观察表明这些硅岩应为交代作用形成。常量元素分析表明硅岩以SiO2为主（69.61％～99.21％）,其他化学成分含量较低（0.01％～16.07％）,Fe/Ti、（Fe+Mn）/Ti及Al/（Al+Fe+Mn）值反映了硅岩的形成与热水活动有关,样品点在Al-Fe-Mn三角图中的投影位于富铁端;微量元素Co/Ni、V、Ti/V、Th/U和Rb/Sr值都较低,样品点在（Cu+Co+Ni）-Fe-Mn三角图中的投影也位于富铁端;硅岩中稀土元素总量低（低于10×10-6）,Ce明显负异常,Eu弱负异常,LREE/HREE值低,Eu/Eu*值相对较高。上述特征表明研究区硅岩在形成过程中有热水物质参与沉积,在成岩过程中通过SiO2交代作用形成。 相似文献
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There is significance to study high-frequency cyclicity thin-bedded limestone which deposited in carbonate ramp and deep-water basin for its well record of astronomic cycles. And there is an ideal section for these studies in the lower part of Kelimoli Formation, in Darriwilian Stage, Middle Ordovician of western Ordos Basin(Zhuozishan area in Inner Mongolia) for its well rhythmic alternations of thin-bedded limestones and mudstones. This work focused on detailed vertical sedimentary successions analysis of these thin-bedded limestones based on detailed field work, as well as the data of rare earth elements and other related trace elements in limestones. The results show as follows: ① there are four types of sedimentary successions(bundles) in thin-bedded limestones, including thinning-upward succession, thickening-upward succession, bidirectional succession(thickening- and thinning-upward) and waving-upward succession; ② the section consists of 145 limestone-mudstone rhythmics, 33 bundles and 7 superbundles; ③ the variation in(La/Nd)N and Mn/Fe molar ratios of limestones along with depth have a similar trend which decreases from bottom to top in general, but have some anomalies distribution; ④ the variation in REE concentrations and Eu anomalies along with depth have a perfect enantiomorphous relationship as well as coupling with the molar ratios of(La/Nd)N; ⑤ the variation of crystal size, V/Cr and V/(V+Ni) molar ratios also have a similar trend which is increasing and then decreasing from bottom to top, and have some local enantiomorphous relationship with the molar ratios of(La/Nd)N in the overall similar distribution patterns. Some conclusion can be drawn according to the types of sedimentary successions and its distribution in profile as well as the ratios of some geochemical parameter along depth based on previous works. These include: ① thickening-upward and bidirectional successions maybe reflect the intensity of tectonism and contour current which is controlled by Milankovitch cycle respectively, and the rising of sea level may be was responsible both for the thinning-upward and waving-upward successions; ② the intensity of contour current which is controlled by Milankovitch cycle was acted throughout the depositions, and the range of deposition time is not less than 2.9 Ma; ③ the vertical sedimentary evolution is perhaps controlled by the alternating of tectonism and rising sea levels, and the section suggests two tectonic stages. 相似文献
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Measurement of the major and trace elements were carried out on the Lower Cretaceous limestones interbedded in the volcano-sedimentary Alisitos Formation, northwestern México to understand the source of rare earth elements (REEs) and paleo-redox conditions. The five limestone beds (from the base up, Unit 5 to Unit 9) of the Alisitos Formation show large variations in SiO2 content (0.9–27.9%). A low concentration of CaO is observed in Unit 6 and Unit 8, and high content of CaO is observed in Unit 5, Unit 7 and Unit 9. The limestones are depleted in many trace elements with respect to Post-Archaean Australian Shale (PAAS), whereas Sr shows slight enrichment when compared to PAAS. The concentrations of ΣREE are higher in Unit 6 and Unit 8 (37.4 ± 7.5; 46.6 ± 19.4; respectively) than Unit5, Unit7, and Unit 9 (9.1 ± 3.2; 11.3 ± 9.4; 4.2 ± 2.5; respectively). The limestones of the Alisitos Formation show a non-seawater-like REE + Y pattern with positive Eu anomalies relative to PAAS (0.95–2.47). Variations in ΣREE, Al2O3, Zr, Sc, REE + Y patterns, and Y/Ho ratios are influenced mainly by the amount of terrigenous materials. The variations in the Eu/Eu*, La/Sc and La/Co suggest that the terrigenous materials included in the lower four limestone beds (from Unit 5, Unit 6, Unit 7 and Unit 8) were likely contributed by intermediate to felsic rocks whereas terrigenous materials from Unit 9 were derived from mafic to intermediate source rocks. The slightly negative to slightly positive Ce anomalies in the studied limestones resulted from variations in the bottom water oxygenation. This was also corroborated by V/Cr and Ni/Co ratios suggesting that the depositional environments experienced large fluctuations in oxygenation conditions ranging from oxic to anoxic conditions during the deposition of limestones of the Alisitos Formation. 相似文献
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采用电感耦合等离子体质谱(ICP-MS)及X射线荧光光谱(XRF)等方法,分析山西西铭煤矿2号、3号、8 号和9号煤中稀土元素的含量特征和赋存状态,并根据稀土元素Ce、Eu、Gd、Y和常量元素Al2O3/TiO2的异常揭示其成煤环境及物质来源。研究结果显示:(1)西铭煤矿煤中稀土元素含量与世界煤值和美国煤值基本相等,但低于中国煤中稀土元素含量的平均值;稀土元素以中-重稀土富集型为主,其次是轻稀土富集型和轻-中稀土富集型。(2)西铭煤矿成煤环境总体上以弱还原性为主,且受酸性沼泽水环境影响。(3)煤中稀土元素的物质来源主要为陆源碎屑物质,判断其沉积源岩为酸性或中-酸性岩浆岩。 相似文献
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S. O. Idakwo 《Journal of the Geological Society of India》2017,90(4):495-502
Major, trace and rare earth elements (REE) concentrations in limestone beds of the Asu River Group within the Middle Benue Trough were measured to understand the depositional conditions, characteristics and source of REE. The limestone has high content of CaO (Average of 46.55%), followed by SiO2 (Average of 7.90 %), Fe2O3(t), MgO and Al2O3. The limestones are depleted in most of the trace elements (Co, V, Rb, Ba, Zr, Y, Nb, Hf and Th) when compared with the Post-Archean Australian Shale (PAAS). The observed large variations in ΣREE contents among various limestones of the present study (12.22 to 142.53ppm) are mainly due to the amount of terrigenous matter present in them. The characteristics of non-seawater-like REE patterns, elevated REE concentrations, high LaN/YbN ratios and low Y/Ho ratios, suggest that the observed variations in ΣREE contents are mainly controlled by the amount of detrital sediments in the limestones of the Asu River Group in the middle Benue trough. The observed variations in Ce contents and Ce anomalies in the studied samples resulted from detrital input. The limestones show positive Mn* values (0.30 to 0.78) and low contents of U (～0.60–3.20 ppm) suggesting that they were deposited under oxygen-rich environment. 相似文献
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松辽盆地中二叠统哲斯组发育一套暗色泥岩、灰色砂砾岩与灰岩沉积组合,灰岩中产海相腕足类和双壳类化石。由于受钻井进尺和取心资料限制,前人对盆地覆盖区晚古生代地层及其沉积环境研究较少。对采自松辽盆地杜101井、杜103井剖面哲斯组的白云质灰岩进行了系统的稳定同位素和微量元素、稀土元素分析,首次获取了盆地覆盖区中二叠统灰岩元素地球化学资料。测试结果显示碳同位素δ13CPDB值一般>0(均值为1.68‰),氧同位素δ18OPDB值全部<-15‰(均值为-19.98‰),碳、氧稳定同位素关系图解显示二者呈正相关关系,表明白云岩化作用对灰岩同位素改造作用明显。稀土元素(REE+Y)总量为56.88×10-6~143.72×10-6,均值为108.92×10-6,PAAS标准化后显示具有轻稀土相对于中稀土和重稀土亏损、δEu(均值0.94,最大值1.57)负异常、δCe(均值0.87,最大值1.06)普遍负异常和相对高的Y/Ho均值(均值34.59)等特点,与正常海相具有大体相同的稀土元素配分模式;而微量元素Ba(均值281.55×10-6)、Zn(均值71.91×10-6)、Y(均值17.44×10-6)、Zr(均值117.75×10-6)和Rb(均值66.84×10-6)等元素含量整体较高,Sr/Ba(均值2.91)、Th/U(均值2.75)、V/Cr(均值1.45)和V/(V+Ni)(均值0.66)等比值适中,指示研究区哲斯组沉积时期主体为一种频繁受陆源碎屑混染作用影响的碳酸盐台地或滨海岸环境。 相似文献