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1.
马莲河流域地处鄂尔多斯盆地南部黄土高原区,按储水介质和埋藏条件可将地下水分为黄土潜水、基岩潜水和基岩承压水三类,利用2015—2018年流域的295组地下水水化学数据,分析了地下水中锶(Sr2+)的质量浓度水平、垂向分布及沿流向分布的特征,并采用因子相关性研究地下水中Sr2+的来源和富集成因。结果表明:马莲河流域地下水富锶现象显著,黄土潜水、基岩潜水和基岩承压水中锶的平均质量浓度分别为1.14 mg/l、1.39 mg/l和5.24 mg/l;地下水中锶富集成因主要是含锶矿物天然状态下的水-岩作用,黄土潜水、基岩潜水和基岩承压水三类地下水中Sr2+的主要来源分别为碳酸盐岩与铝硅酸盐岩、碳酸盐岩与硫酸盐和碳酸盐矿物的溶滤作用;地下水中Sr2+的质量浓度沿流向呈逐渐增大的趋势,在不同区域中随深度变化的趋势不一致。 相似文献
2.
为探讨复合维生素B(叶酸、B_6和B_(12))能否抑制PM_(2.5)对大鼠的急性肺损伤作用,本研究将56只SD大鼠随机分成对照组、不同剂量(0. 4、2. 0、10. 0 mg/m L) PM_(2.5)染毒组和相应的复合维生素B干预组(0. 02 mg/m L叶酸、1 mg/m L维生素B6、0. 002 5 mg/m L维生素B12),取肺组织进行HE染色观察组织病理学形态变化并进行病理学评分;收集支气管肺泡灌洗液(BALF)测定总蛋白(TP)、乳酸脱氢酶(LDH)、碱性磷酸酶(AKP)、酸性磷酸酶(ACP)、丙二醛(MDA)、超氧化物歧化酶(SOD)和过氧化氢酶(CAT)的含量。结果显示,PM_(2.5)染毒能对大鼠肺组织造成不同程度的病理性损伤,复合维生素B能减缓此损伤;与对照组相比,低、中、高剂量的PM_(2.5)染毒大鼠可引起BALF中LDH、AKP、ACP、TP和MDA含量显著升高(P 0. 05),而SOD和CAT活性显著降低(P 0. 05),且TP和MDA含量随染毒剂量的增加而升高(P 0. 05),CAT活性随染毒剂量的增加而降低; 3个染毒剂量的复合维生素B干预组LDH、TP和MDA含量显著降低(P 0. 05),而SOD和CAT活性显著升高(P 0. 05); PM_(2.5)低、高剂量+复合维生素B组BALF中ACP含量显著降低(P 0. 05); PM_(2.5)中剂量+复合维生素B组BALF中ACP含量无显著改变;仅有PM_(2.5)低剂量+复合维生素B组AKP含量降低(P 0. 05),其余干预组AKP含量无显著变化。因此认为,PM_(2.5)降尘能打破机体的氧化-抗氧化平衡,造成大鼠急性肺损伤,而复合维生素B能减缓此损伤,对机体起到保护作用。 相似文献
3.
地氟病属于"钙矛盾疾病" 总被引：14，自引：0，他引：14
膳食低钙是地氟病病区居民中的普遍现象，是地氟病(氟骨症)的主要促发和加重因素。低钙的作用不仅在于增如肠道氟的吸收，更在于它和过量氟同样都可引起甲状旁腺激素分泌增多，都可促进成骨、破骨功能活跃。过量氟可进一步加重机体缺钙。我们最近的研究证明，氟中毒大鼠肝、肾、脑组织Ca^2 ]i升高，培养的成骨细胞样细胞染氟后细胞内钙亦增加；即氟中毒存在着全身缺钙继而细胞内钙增多的钙矛盾现象，属于钙矛盾疾病。为控制和消除地氟病危害，应把减少氟的摄入和改善居民钙营养两结合起来。 相似文献
4.
东南极拉斯曼丘陵硼硅酸盐矿物组合硅硼镁铝矿-硼柱晶石-电气石的形成过程及其岩石学意义 总被引：1，自引：0，他引：1
东南极拉斯曼丘陵长英质片麻岩中产出大量的电气石-硼柱晶石-硅硼镁铝矿之硼硅酸盐矿物组合,这些矿物(电气石除外)的形成晚于变质峰期一般的硅酸盐矿物。电气石可多次出现,硅硼镁铝矿之后形成硼柱晶石,很少见两种以上的硼硅酸盐矿物能够同时结晶,各种硼硅酸盐矿物在同一期、甚至同一阶段内呈递进关系。在硼硅酸盐矿物的结晶过程中,B2O3和Al2O3较为活动从而SiO2的活度相对受到抑制,即存在组分的分异和活性波动,表明络阴离子SiO44-、PO43-、BO33-活动高峰并非同步因而,挥发分组分对深熔作用的影响可能是有限的;同时,结晶的金属阳离子组分不断发生分异。不同的硼硅酸盐矿物形成的介质条件有所差异:电气石形成于富钙的弱酸性溶液,硅硼镁铝矿应为近中-碱性溶液介质,而硼柱晶石形成于含少量氟的偏碱性介质环境。除温压因素外,流体挥发分种类和介质条件也影响到硼硅酸矿物的多期次、多阶段的变化,从而造成矿物组合的复杂性。本区长英质岩石中硼(B)及其他挥发分组分的较高含量可由原岩成分决定,亦可经由变质-深熔作用引起,即深熔作用时熔体的整体优先吸收硼(硼的第一次富集)及随后熔体结晶阶段的局部残留和富集硼(硼的第二次富集)。Gdd-Prs-Trn硼硅酸盐矿物组合的存在,表明发生了以脱水为主的高级变质作用,同时伴随强烈的深熔作用。挥发分组分在露头尺度体系中可能属于开放性质,而在更大尺度和范围内则基本封闭;在深熔作用中,硼等挥发分的存在影响了熔体的组成使得岩浆熔点降低、熔融成分调整粘度有所降低,更容易运移;而且,熔体可以携带这些挥发分,当熔体结晶时挥发分析出、结晶局部富集而形成硼硅酸盐矿物,尤其是沿着一些构造有利部位发生显著的聚集。 相似文献
5.
重庆市主城区降雨酸度的影响因子分析 总被引：4，自引：0，他引：4
重庆市是我国酸雨较严重的地区之一，其酸沉降状况具有代表意义。本分析了重庆市2000年和200l年的降雨指标(离子组分、pH、电导率)和空气质量指标(SO2和NO2)，降雨指标采用离子色谱法和电极法，空气质量指标采用紫外脉冲荧光法和化学发光法分析。结果表明，大气颗粒物、SO2及NO2对降水的酸度有不同影响。大气颗粒物中的碱式钙盐可明显降低雨水酸度，其可能来源为建筑施工；含有SO4^2-、NO3^-和NH4^ 的酸式盐可有效增加雨水酸度。大气中的SO2对降雨酸度增高贡献较大，而NO2贡献不明显。较小的[NO3^-]/[SO4^2-]值(0．125)显示重庆市的固定源的污染比流动污染源更强。 相似文献
6.
内蒙古东乌旗碱性侵入岩的时代、成因及地质意义 总被引：3，自引：0，他引：3
内蒙古东乌旗西部的碱性侵入岩为碱性花岗岩和石英正长岩组合,含钠铁闪石.采用LA-MC-ICP-MS锆石U-Pb法对2件碱性花岗岩样品进行年代学研究.定年结果分别为272.3±0.7 Ma和271.7±0.7 Ma,属早二叠世晚期.13件样品的地球化学数据显示:碱性花岗岩具高SiO2(72.62％～78.46％),富碱(K2O+Na2O=7.54％～9.80％),贫CaO(0.66％～0.91％)、MgO(0.07％～0.31％)的特征,铝饱和指数A/CNK为0.87～0.99,碱性指数NK/A为0.91～1.04,属准铝质-过碱质碱性岩系列;稀土总量中等(∑REE=146.4×10-6～389.0×10-6),轻重稀土分馏均较弱-(La/Yb)N 3.74～6.83],强烈的负Eu异常(δEu为0.12～0.36);贫Ba、Sr、P、Ti,富Rb、Th、U、Hf等元素,显示“A1”型花岗岩的特征.石英正长岩与碱性花岗岩相比较,Ba的含量(554×10-6～1230×10-6)显著高于后者(Ba=74×10-6～207×10-6),Eu负异常缺失(δEu=0.94～1.24),可能由岩浆源区深度的差异造成的.二者均具非常低Sr(27.20×10-6～157.00×10-6,2个样品大于100×10-6)和高Yb(2.08×10-6～7.26×10-6,除P24-11-1为1.36×10-6)的特征,与板内花岗岩特征一致.综上,我们认为东乌旗碱性侵入岩可能为造山后-非造山伸展体制岩浆作用的产物,标志着大约在272Ma兴蒙造山带部分造山演化可能处于造山后向非造山构造转换阶段. 相似文献
7.
天山北部上石炭统前峡组火山岩地球化学特征及构造意义 总被引：1，自引：0，他引：1
上石炭统前峡组火山岩位于早石炭世巴音沟蛇绿岩北侧,为一套以火山碎屑岩为主夹熔岩和陆源碎屑岩建造。岩石及地球化学特征显示,该组火山岩是以安山岩为主的玄武岩+玄武安山岩+安山岩+英安岩组合,里特曼指数介于1.20～3.43,属钙碱性系列。稀土总量(ΣREE)为69.53×10-6～111.32×10-6,(Ce/Y)N=1.12～2.25,(La/Yb)N=1.86～5.39,δEu=0.79～1.21,为轻稀土略富集、Eu亏损不明显的火山岩类型。岩石显著富集大离子亲石元素K、Rb、Ba、Th,亏损高场强元素Nb、Ta、Hf、Ti、Y,其中Nb含量绝大多数介于1.89×10-6～2.65×10-6,与大洋地壳Nb含量平均值2.2×10-6接近。锶初始比值为0.70425～0.70428,与岛弧区玄武岩的0.70437接近,这些特征均与俯冲带大陆岛弧火山岩一致。与之伴生的滨浅海-半深海相沉积地层和南部早石炭世巴音沟蛇绿岩的存在,表明前峡组火山岩是巴音沟蛇绿岩所代表的早石炭世洋壳在晚石炭世时期向北俯冲消减的产物。 相似文献
8.
《地质科技情报》2021,(3)
在内陆干旱区,作为重要饮用水源的地下水常面临氟含量超标问题。查明内陆干旱区高氟地下水的分布规律,了解氟在地下水中的富集过程及其影响因素,既可丰富高氟地下水的研究体系,也是保证内陆干旱区饮水安全的重要基础。以新疆阿克苏地区典型山前洪积扇——依格齐艾肯河-喀拉玉尔滚河河间地带为研究区,基于水文地球化学调查结果,刻画了高氟地下水的分布区;结合氟离子含量与特征性水化学指标间的关系,揭示了高氟地下水的成因机制。结果表明:(1)地下水中氟含量的变化范围为0.8～6.1 mg/L,83%的水样氟含量超过《生活饮用水卫生标准》(GB 5749-2006)规定的上限(1.0 mg/L);(2)总体上,氟含量沿地下水流动路径逐渐增大,低氟地下水(ρ(F~-)≤1.0 mg/L)分布在国道314以北的补给区,高氟地下水(ρ(F~-)1.0 mg/L)分布在国道314以南的径流区和排泄区;(3)高氟地下水的水化学类型以Cl·HCO_3-Na型为主,而低氟地下水则以Cl·SO_4-Na型为主,高氟地下水相比于低氟地下水优势阴离子偏向于HCO~-_3;(4)地下水的pH值范围为7.9～8.9(均值为8.4),表明其处于弱碱环境中。地下水中ρ(F~-)与pH值呈正相关,此外构成浅层含水层的上更新统沉积物中含有黑云母、氟磷灰石等矿物,其表面存在一定数量的可交换F~-,这表明水中OH~-与矿物表面F~-间的阴离子交换可能对氟的富集有一定贡献;(5)地下水的F~-含量与Ca~(2+)含量呈负相关,即高氟地下水中ρ(Ca~(2+))小于低氟地下水。考虑到氟化钙(CaF_2)是自然界中的主要含氟矿物,也是地下水中氟的主要来源,ρ(F~-)与ρ(Ca~(2+))间的这种负相关指示着高氟地下水中可能存在去Ca~(2+)、Mg~(2+)作用,如阳离子交替吸附或碳酸盐岩沉淀等。研究区地下水样中ρ(F~-)与ρ(Mg~(2+))间也呈负相关关系,且和ρ(F~-)与ρ(Ca~(2+))间的关系高度相似,也佐证了高氟地下水中去Ca~(2+)、Mg~(2+)作用的存在;(6)绝大部分地下水样品都位于氯碱性指数图的负值区域,且ρ(F~-)与CAI-1和CAI-2均呈较好负相关,CAI-1和CAI-2都随ρ(F~-)的增大而减小,这表明高氟地下水中存在Ca~(2+)、Mg~(2+)与Na~+间更强的交换作用,对氟富集起着重要作用。地下水中ρ(F~-)与SAR间呈较好正相关关系,且高氟地下水样的SAR均值(5.71)远大于低氟地下水SAR均值(1.67),这也进一步证明高氟地下水中的Ca~(2+)、Mg~(2+)与含水介质的Na~+间存在强烈的交替作用,对氟的富集起着重要作用;(7)所有地下水样中的萤石均处于未饱和状态,且萤石的饱和指数(SI)与F~-含量间呈现较好的正相关,这表明地下水对含氟矿物(主要是萤石)的持续溶解应是导致研究区地下水中氟富集的主要原因。与之相反,研究区所有地下水样中的方解石均处于过饱和状态(SI0)。这表明CaCO_3的沉淀可能促进了CaF_2的溶解,导致地下水中氟离子质量浓度增高;(8)研究区低氟地下水的δ~(18)O值介于-11.20‰～-10.67‰间,平均值为-10.94‰,而高氟地下水的δ~(18)O值介于-11.65‰～-11.21‰间,平均值为-11.49‰,即低氟地下水较高氟地下水富集δ~(18)O。此外,F~-质量浓度较低(ρ(F~-)≤3.0 mg/L)的地下水样中δ~(18)O值与F~-质量浓度呈负相关,即低氟地下水具有更正的δ~(18)O值;F~-质量浓度较高(ρ(F~-)≥4.8 mg/L)的地下水样中δ~(18)O值与F~-质量浓度的相关性不显著,随F~-质量浓度的增高,δ~(18)O值基本维持不变。以上表明蒸发浓缩作用对地下水中氟的富集贡献较小;(9)研究区地下水中ρ(F~-)/ρ(Cl~-)比值与ρ(F~-)间呈现正相关,即ρ(F~-)/ρ(Cl~-)比值随ρ(F~-)增高呈增大趋势,这也说明地下水中氟富集的主要原因是含氟矿物的溶解,而不是蒸发浓缩作用。此外,Gibbs图也提供了证据:研究区地下水样基本处于水岩作用主导区域,表明地下水化学特征(包括氟的富集)主要受水岩作用控制,蒸发浓缩影响很小。总之,地下水中氟的富集主要由溶解作用引起,OH~-与矿物表面F~-间的交换也有贡献,但蒸发浓缩作用影响微弱。含氟矿物持续溶解的驱动机制是阳离子交替吸附(地下水中Ca~(2+)与岩土颗粒表面Na~+之间)及方解石沉淀所引起的地下水中Ca~(2+)的衰减。 相似文献
9.
由于缺乏系统的同位素分析研究工作，过去对东蒙地区燕山期岩浆岩的成因探讨，主要集中在大量岩石地球化学方面的分析研究，因此，其成因观点和岩浆起源的认识也各持己见，主要有3种认识：1)本区中生代壳源和幔源共生的“双模式”观点，认为锡多金属成矿与这种“双模式”的岩浆岩有成因联系；2)中生代花岗岩属于引张环境下，地幔上隆所引发的亚碱性一碱性非造山岩浆作用的产物；3)中生代岩浆岩是中生代大陆内部伸展造山环境下底侵作用形成的一套壳幔混熔岩浆的产物。总之，研究者多认为燕山期岩浆岩具有壳幔混合起源的特征。笔者对燕山期花岗质岩石的钕、锶、铅同位素进行了分析研究。其εNd(t)全为正值，变化范围为 0．75～ 8．12，平均值为 3．07，说明该区燕山期花岗岩的物质来源与亏损地幔有成因联系。其初始锶比值比较集中，变化于0．7028～0.7096，平均为0．7063，介于现代大洋玄武岩(0．702～0．706)和大陆地壳(0．706～0．718)之间，更接近大洋玄武岩。该区燕山期花岗岩的初始铅同位素的3个比值^206Pb/^204Pb、^207Pb／^204Pb、^308b／^204Pb都较高，平均值分别为18．3742，15．5500，38．1810。由钾长石的铅同位素比值计算出来的μ值介于9．51～8．91之间，低于μ=9．74的陆壳演化线。结合邻区兴蒙—北疆一带的岩浆岩同位素研究成果，笔者认为东蒙地区的燕山期花岗岩岩浆起源于亏损地幔的部分熔融作用和亏损地幔起源的晚华力西期古蒙古洋壳的部分熔融作用，即燕山期花岗岩浆最终起源于亏损地幔。并且提出了亏损地幔—古蒙古洋壳—边缘陆块活化的演化模式。 相似文献
10.
塔里木盆地西北缘早二叠世后碰撞花岗质岩浆活动及其构造意义 总被引：1，自引：0，他引：1
塔里木地块西北缘的阔什布拉克钾长花岗岩富碱(Na_2O+K_2O平均8.36%8%),富钾(K_2O/Na_2O=1.27～1.47),准铝质(A/CNK=0.82～0.88),属于高钾钙碱性系列岩浆岩。岩石的稀土含量较高(∑REE=263.90×10~(-6)～445.75×10~(-6)),富集Th、U、Ta、Nb、Hf和Y等高场强元素和大离子亲石元素Rb,具有强的负Eu异常(δEu=0.003～0.019),富集高不相容元素(Zr+Nb+Ce+Y=368×10~(-6)～531×10~(-6)350×10~(-6)),高Ga(Ga/Al×10 000=4.17～4.722.6),显示出A型花岗岩的地球化学特征。岩石Th/U比值(平均为3.86)、Nb/Ta比值(平均为12.75)和Rb-Th富集、Ti亏损指示其壳源成因。对花岗岩进行的LA-ICP-MS微区原位锆石U-Pb定年结果表明,花岗岩的结晶侵位年龄为275.4±2.8 Ma。综合西南天山与塔里木盆地早二叠世花岗质岩浆活动的特点,认为早二叠世西南天山的后碰撞岩浆活动不仅在西南天山内部引起了强烈的花岗质岩浆活动,而且对塔里木地块西北边缘的花岗质岩浆活动也有显著的影响。阔什布拉克A型花岗岩也说明西南天山地区的碰撞造山作用在275.4±2.8 Ma之前已经趋于结束,以南天山洋盆为代表的古亚洲洋已基本结束了其演化历史。 相似文献
11.
The stable isotopic composition (13C and 18O) and elemental (Sr and Mg) of marine molluscs are presented for Carditacea and Solenacea shells collected off the Mediterranean coast of Egypt. Based on shell microstructures and mineralogy, the bivalve shells are preserved in their original mineralogy and chemistry.The Sr and Mg concentrations of the bivalve shells have mean values of 1960 ppm and 226 ppm respectively. The stable isotopic composition generally show high values of 18O and 13C. The 18O values range from +0.1 to –1.8 PDB and most shells are highly enriched in13C; averaging +2.5 PDB. These elemental and isotopic signatures are analogous to modern marine bivalves from other localities.The oxygen and carbon isotopes, together with the calculated temperatures, suggest that the aragonitic bivalve shells were precipitated in isotopic equilibrium from warm marine waters. 相似文献
12.
河北平原地下水锶同位素形成机理 总被引：5，自引：0，他引：5
为了研究河北平原地下水锶同位素的来源与形成机理, 对所采水样进行了分析.研究了87Sr/86Sr比值“时间积累效应”: 随着地下水年龄和埋深的增大而增大; 与地下水中过剩4Heexc呈正相关关系, 与δ18O和δD呈负相关关系.探讨了Sr2+与87Sr/86Sr比值的关系, 将地下水分为3类: (1) 中等Sr2+含量与高87Sr/86Sr比值水(Ⅰ类水); (2) 低Sr2+含量与高87Sr/86Sr比值水(Ⅱ类水); (3) 高Sr2+含量与低87Sr/86Sr比值水(Ⅲ类水), 即热水.通过综合分析认为: (1) 河北平原第四系地下水中的放射成因Sr是由富含Na和Rb的硅酸盐矿物风化作用提供的, 主要矿物为斜长石; (2) 黄骅港热水中的放射成因Sr是由碳酸盐溶解形成的, 87Sr/86Sr比值低, Sr/Na比值大; (3) 补给区地下水是由流经火成岩和变质岩区地下水的侧向补给的, 87Sr/86Sr比值中等.第三系地下水放射成因Sr的来源及形成机理尚须进一步研究. 相似文献
13.
Strontium concentrations of 253 natural water samples from Skagafjördur, a Tertiary tholeiitic flood basalt region in northern Iceland range between 0.10 and 28 ppb. Surface environments (rivers, lakes, and peat soil waters) include the whole range of observed Sr concentrations whereas the Sr concentrations of ground waters are, in most cases, <3.5 ppb. Concentrations of Sr derived from basalt dissolution (i.e., rock-derived Sr) in waters of rivers and lakes exhibit a near linear correlation with the concentration of rock-derived Ca with a median molar Ca/Sr ratio of 1350. This systematic correlation suggests that Ca and Sr concentrations are controlled by weathering processes, i.e., the extent of dissolution of the basalt. The relative mobility of Sr during weathering in Skagafjördur is approximately half that of Ca, which is consistent with observed relative mobilities of these elements elsewhere in Iceland and in other basaltic regions. Peat soil waters commonly have lower concentrations of Sr and higher Ca concentrations than rivers and lakes, and molar ratios of rock-derived Ca to Sr in peat soil waters exhibit no systematic pattern. In several cases calculated concentrations of rock-derived Sr in peat soil waters yield negative values, suggesting a mineralogic sink for Sr in these waters.The low Sr concentrations in cold and thermal ground waters (<3.5 ppb) suggest mineralogic control over Sr in the ground water systems. Precipitation of secondary Sr minerals such as strontianite and celestite is ruled out as the ground waters are understaturated with respect to these minerals. Ground waters are characterized by high Ca/Sr molar ratios (∼5000 compared to bedrock Ca/Sr ratio of 730) suggesting that Sr is being preferentially incorporated (relative to Ca) into secondary minerals. The secondary minerals present in the bedrock in Skagafjördur that can preferentially incorporate Sr include zeolites, such as heulandite, chabazite, and thomsonite, and smectite. Ion-exchange calculations demonstrate that activities of Sr2+ and Ca2+ in ground water solutions in Skagafjördur are consistent with ion-exchange equilibria between these waters and heulandite from other Tertiary basalts in Iceland suggesting that this mineral may play an important role in controlling the concentration of Sr in the Skagafjördur ground waters. Incorporation of Sr into calcite cannot explain the observed high Ca/Sr ratios of the Skagafjördur ground waters because calcite, when precipitating, only admits limited amounts of Sr. Aragonite is not considered a likely candidate either because it has only very slight preference for Sr over Ca and ground waters above 40 °C are undersaturated with respect to this phase. However, predicted Sr content of calcite in equilibrium with the Skagafjördur ground waters (0.5-83 ppm Sr) is in good agreement with measured Sr content of this mineral in Tertiary basalts elsewhere in Iceland (<0.1-63 ppm), suggesting that the Skagafjördur ground waters can be used as analogues for Tertiary crustal solutions involved in the zeolite facies metamorphism of the Icelandic crust. 相似文献
14.
Mustafa Kuscu Oya Cengiz Asuman Kahya 《Journal of the Geological Society of India》2018,91(4):496-504
The sediment-hosted huntite-magnesite deposits are located in the Egirdir-Hoyran lake basin in the Isparta Angle (southern Turkey). The deposits occur at two different localities in the region: (1) Kemersirti huntite deposit, (2) Köytepe huntite-magnesite deposit. The huntite-magnesite occurrences are found in shallow lacustrine rocks of the Miocene-Pliocene Kizilcik Formation and formed as a result of Neogene tectonic activity. Based on X-ray diffraction and scanning electron microscopic studies, the mineral assemblage of huntite deposits contains mostly huntite, less magnesite, dolomite, very little calcite, illite, simectite, brucite, and quartz in the Kemersirti area but contain huntite, magnesite, dolomite, and calcite in the Köytepe area.In the huntite and magnesite-bearing huntite samples, MgO varies from 32.70 to 37.95 wt. %, CaO from 7.83 to 15.10 w.t. %, and SiO2 from 0.99 to 10.60 w.t. %. Ba and Sr are dominant minor elements in the deposits. Ba and Sr for huntite and magnesite bearing huntite in the study area vary from 11 to 233 ppm and from 325 to 765 ppm, respectively. As, U, Zr, V and Ce contents ranged from 11.5-146 ppm, 0.5-3.7 ppm, 1.4-13.2 ppm, 7-34 ppm, and 0.9-2.7 ppm respectively. The huntite-magnesite is characterized by relatively lower Ni (0.5-2.4 ppm) and Co (0.5-1.1 ppm) contents. The huntite and magnesite-bearing huntite occurrences have higher Ba, Sr, As, Zr, V, and U contents than those of the other elements. The d13C isotope values vary between 7.8‰ to 8.8‰ PDB for huntite+magnesite, 8.2‰ PDB for huntite, 1.4‰ PDB for magnesite+dolomite, and 4.0‰ PDB for limestone from deposits in the study area. The δ18O isotope values of the huntite deposits ranged from 30.4 to 35.5‰ SMOW for huntite+magnesite, 32.4‰ SMOW for huntite, 29.8‰ SMOW for magnesite+ dolomite, and 26.9‰ SMOW for limestone.The presence of nodular huntite and the abundance of gastropod, ostracoda and Chura shells in the carbonate units indicate that the huntite occurrences are precipitated at shallow, alkaline (8.5-9.5 pH) and lower temperature (approximately 25°C) lake conditions. The Mg++, Ca++ and Si++ ions for the huntite formation were derived from the surrounding rocks such as ultrabasic rocks, dolomite, dolomitic limestone, and limestone in the Egirdir-Hoyran lake basin. Also, the C isotope ratios indicate that the CO2 source for the huntite formations results to sedimentary basin from metamorphic CO2, carbonate rocks, fresh water carbonates, and ground water. The source of oxygen for the huntite formation may come from marine limestone, fresh water carbonates and meteoric water. 相似文献
15.
The clinopyroxenes and garnets from garnet lherzolite nodules in kimberlites were analyzed for the major and trace elements (Sc, Ti, V, Cr, Mn, Co, Sr, and Zr) with the secondary ion mass spectrometry (SIMS) techniques using an ion-microprobe. The concentration ranges for clinopyroxenes are: 12–90 ppm Sc, 60–2540 ppm Ti, 110–350 ppm V, 2400 ppm-1.68% Cr, 470–1100 ppm Mn, 18–70 ppm Co, 85–710 ppm Sr, and 6.3–120 ppm Zr. Those for garnets are: 71–180 ppm Sc, 140–6200 ppm Ti, 220–450 ppm V, 1.05–6.24% Cr, 1600–5220 ppm Mn, 33–92 ppm Co, and 66–250 ppm Zr.These data were used to assess a possible use of distribution of transition elements between clinopyroxene and garnet for geothermometry/geobarometry. The distribution coefficients of V and Mn show good correlations with (Ca/Ca+Mg+Fe)CPX, suggesting their potential usefulness.The abundances of these elements in minerals (and estimated whole-rocks) suggest that garnet lherzolite nodules in kimberlites can be classified into three groups. It is suggested that one of the groups (Group I) could be close to the pristine mantle on the basis of Ti and Zr abundances as well as REE systematics. Arguments on Ti/Zr ratios among different nodule types suggest that abundant granular garnet lherzolites could be cumulates crystallized from a residual liquid after ilmenite was extracted.IPG Contribution No. 281 相似文献
16.
塔里木盆地北部丘里塔格群(寒武系至奥陶系)白云岩的成因 总被引：17，自引：2，他引：17
本文通过详细岩石学及地球化学研究,探讨了塔里木盆地丘里塔格群(寒武至奥陶系)白云岩的成因。研究表明藻纹层白云岩、微晶白云岩及颗粒白云岩中的颗粒为近地表准同生白云化的产物。结晶白云岩(细晶以上)及颗粒白云岩中的中粗晶白云岩胶结物是深埋藏成岩环境的产物。并对埋藏白云化的镁离子来源及搬运机理进行了探讨。 相似文献
17.
Guo Feng; Nakamuru Eizo; Fan Weiming; Kobayoshi Katsura; Li Chaowen 《Journal of Petrology》2007,48(4):661-692
Palaeocene (c. 55–58 Ma) adakitic andesites from the Yanjiarea, NE China, are typically clinopyroxene-bearing sodic andesitescontaining 60· 9–62· 2% SiO2 and 4·02–4· 36% MgO, with high Mg-number [100 Mg/(Mg+ Fe) atomic ratio] from 65· 5 to 70· 1. Whole-rockgeochemical features include high Cr (128–161 ppm) andNi (86–117 ppm) concentrations, extremely high Sr (2013–2282ppm), low Y (10–11 ppm) and heavy rare earth elements(HREE; e.g. Yb = 0· 79–1· 01 ppm), and mid-oceanridge basalt (MORB)-like Sr–Nd–Pb isotopic compositions[e.g. 87Sr/ 86Sr(i) = 0· 70298–0· 70316,Nd(t) = +3· 8 to +6· 3 and 206Pb/ 204Pb = 17·98 – 18· 06], analogous to high-Mg adakites occurringin modern subduction zones. However, mineralogical evidencefrom clinopyroxene phenocrysts and microcrystalline plagioclaseclearly points to magma mixing during magma evolution. Iron-richclinopyroxene (augite) cores with low Sr, high Y and heavy REEcontents, slightly fractionated REE patterns and large negativeEu anomalies probably crystallized along with low-Ca plagioclasefrom a lower crustal felsic magma. In contrast, high Mg-numberclinopyroxene (diopside and endiopside) mantles and rims havehigher Sr and lower HREE and Y concentrations, highly fractionatedREE patterns (high La/Yb) and negligible Eu anomalies, similarto those found in adakites from subduction zones. The Yanjiadakitic andesites can be interpreted as a mixture between acrust-derived magma having low Mg-number and Sr, and high Yand HREE, and a mantle-derived high Mg-number adakite havinghigh Sr and low Y and HREE concentrations. During storage and/orascent, the mixed magma experienced further crustal contaminationto capture zircons, of a range of ages, from the wall rocks.The absence of coeval arc magmatism and an extensional tectonicregime in the Yanji area and surrounding regions suggest thatthese Palaeocene adakitic andesites were formed during post-subductionextension that followed the late Cretaceous Izanagi–Farallonridge subduction. Generation of these adakitic andesites doesnot require contemporaneous subduction of a young, hot oceanicridge or delamination of eclogitic lower crust as suggestedby previous models. KEY WORDS: magma mixing; adakitic andesites; Palaeocene; NE China 相似文献
18.
Volcan Popocatepetl, Mexico. Petrology, Magma Mixing, and Immediate Sources of Volatiles for the 1994-Present Eruption 总被引：1，自引：0，他引：1
Volcán Popocatépetl has been the site of voluminousdegassing accompanied by minor eruptive activity from late 1994until the time of writing (August 2002). This contribution presentspetrological investigations of magma erupted in 1997 and 1998,including major-element and volatile (S, Cl, F, and H2O) datafrom glass inclusions and matrix glasses. Magma erupted fromPopocatépetl is a mixture of dacite (65 wt % SiO2, two-pyroxenes+ plagioclase + Fe–Ti oxides + apatite, 3 wt % H2O, P= 1·5 kbar, fO2 = NNO + 0·5 log units) and basalticandesite (53 wt % SiO2, olivine + two-pyroxenes, 3 wt % H2O,P = 1–4 kbar). Magma mixed at 4–6 km depth in proportionsbetween 45:55 and 85:15 wt % silicic:mafic magma. The pre-eruptivevolatile content of the basaltic andesite is 1980 ppm S, 1060ppm Cl, 950 ppm F, and 3·3 wt % H2O. The pre-eruptivevolatile content of the dacite is 130 ± 50 ppm S, 880± 70 ppm Cl, 570 ± 100 ppm F, and 2·9 ±0·2 wt % H2O. Degassing from 0·031 km3 of eruptedmagma accounts for only 0·7 wt % of the observed SO2emission. Circulation of magma in the volcanic conduit in thepresence of a modest bubble phase is a possible mechanism toexplain the high rates of degassing and limited magma productionat Popocatépetl. KEY WORDS: glass inclusions; igneous petrology; Mexico; Popocatépetl; volatiles 相似文献
19.
中国金伯利岩地球化学 总被引：4，自引：0，他引：4
本文利用了100多个金伯利岩的主要元素及微量元素分析结果,用Si/Mg、C.l——(SiO_2+Al_2O_3+Na_2O)/(MgO+2K_2O)、Mg/(Mg+Fe)比值及SiO_2、Al_2O_3及Na_2O含量研究了金伯利岩的混染程度。结果表明,绝大部分金伯利岩受到了混染作用的影响,它们的成分实际上不能代表形成这些岩石的岩浆的成分。金伯利岩的Al_2O_3和Na_2O的含量比其他碱性超基性及基性岩石的Al_2O_3和Na_2O含量低得多。含金刚石的金伯利岩比不含金刚石的金伯利岩的MgO、(Cr_2O_3+NiO)高,而TiO_2+Al_2O_3+Na_2O+K_2O+P_2O_5低。 我国金伯利岩中Cr-Al,Ni-Co,Ni-Cr,Ni-V,Sc-Ti,Zn-Ti,Ba-Sr,Zr-Hf,Nb-Ta,U-Th,K-Rb呈正相关关系。 相似文献
20.
Highly evolved rhyolite glass plus near-solidus mineral assemblages in voluminous, dacitic, crystal-rich ignimbrites provide an opportunity to evaluate the late magmatic evolution of granodiorite batholiths. This study reports laser-ablation ICP-MS analyses of trace element concentrations in feldspars, hornblende, biotite, titanite, zircon, magnetite, and interstitial glass of the crystal-rich Fish Canyon Tuff. The high-silica rhyolite glass is characterized by relatively high concentrations of feldspar-compatible elements (e.g., 100 ppm Sr and 500 ppm Ba) and low concentrations of Y (<7 ppm) and HREE (~1 ppm Yb), hence high LREE/HREE (Ce/Yb >40) compared to many well-studied high-silica rhyolite glasses and whole-rock compositions. Most minerals record some trace element heterogeneities, with, in particular, one large hornblende phenocryst showing four- to six-fold core-to-rim increases in Sr and Ba coupled with a decrease in Sc. The depletions of Y and HREE in the Fish Canyon glass relative to the whole-rock composition (concentrations in glass ~30% of those in whole rocks) reflect late crystallization of phases wherein these elements were compatible. As garnet is not stable at the low-P conditions at which the Fish Canyon magma crystallized, we show that a combination of modally abundant hornblende (~4%) + titanite (~0.5–1%) and the highly polymerized nature of the rhyolitic liquid led to Y and HREE depletions in melt. Relatively high Sr and Ba contents in glass and rimward Sr and Ba increases in euhedral, concentrically zoned hornblende suggest partial feldspar dissolution and a late release of these elements to the melt as hornblende was crystallizing, in agreement with textural evidence for feldspar (and quartz) resorption. Both observations are consistent with thermal rejuvenation of the magma body prior to eruption, during which the proportion of melt increased via feldspar and quartz dissolution, even as hydrous and accessory phases were crystallizing. Sr/Y in Fish Canyon glass (13–18) is lower than the typical adakitic value (>40), confirming that high Sr/Y is a reliable indicator of high-pressure magma generation and/or differentiation wherein garnet is implicated. 相似文献