Iron isotopic systematics of UHP eclogites respond to oxidizing fluid during exhumation   总被引：1，自引：0，他引：1       下载免费PDF全文

D.‐Y. Li  Y. L. Xiao  W.‐Y. Li  X. Zhu  H. M. Williams  Y.‐L. Li 《Journal of Metamorphic Geology》2016,34(9):987-997

The iron stable isotope compositions (δ⁵⁶Fe) and iron valence states of ultrahigh‐pressure eclogites from Bixiling in the Dabie orogen belt, China, were measured to trace the changes of geochemical conditions during vertical transportation of earth materials, for example, oxygen fugacity. The bulk Fe³⁺/ΣFe ratios of retrograde eclogites, determined by Mössbauer spectroscopy, are consistently higher than those of fresh eclogites, suggesting oxidation during retrograde metamorphism and fluid infiltration. The studied eclogites (five samples) display limited mid‐ocean ridge basalts (MORB)‐like (~0.10‰) δ⁵⁶Fe values, which are indistinguishable from their protoliths, that is, gabbro cumulates formed through differentiation of mantle‐derived basaltic magma. This suggests that Fe isotope fractionation during continental subduction is limited. Garnet separates display limited δ⁵⁶Fe variation ranging from ?0.08 ± 0.07 ‰ to 0.02 ± 0.07‰, whereas coexisting omphacite displays a large variation of δ⁵⁶Fe values from 0.15 ± 0.07‰ to 0.47 ± 0.07‰. Omphacite also has highly variable Fe³⁺/ΣFe ratios from 0.367 ± 0.025 to 0.598 ± 0.024, indicating modification after peak metamorphism. Omphacite from retrograde eclogites has elevated Fe³⁺/ΣFe ratios (0.54–0.60) compared to that from fresh eclogites (~0.37), whereas garnet displays a narrow range of ferric iron content with Fe³⁺/ΣFe ratios from 0.039 ± 0.013 to 0.065 ± 0.022. The homogenous δ⁵⁶Fe values and Fe³⁺/ΣFe ratios of garnet suggest that it survived the retrograde metamorphism and preserved its Fe‐isotopic features and ferric contents of peak metamorphism. Because of similar diffusion rates of Fe and Mg in garnet and omphacite, and constant Δ²⁶Mg_{omphacite‐garnet} values (1.14 ± 0.04‰), equilibrium iron isotope fractionation between garnet and omphacite was probably achieved during peak metamorphism. Elevated Fe³⁺/ΣFe ratios of omphacite from retrograde eclogites and variant Δ⁵⁶Fe_{omphacite‐garnet} values of the studied eclogites (0.13 ± 0.10‰ to 0.48 ± 0.10‰) indicate that oxidized geofluid infiltration resulted in the elevation of δ⁵⁶Fe values of omphacite during retrograde metamorphism.  相似文献   

广西栗木钨锡铌钽矿区流体包裹体及氢氧同位素研究   总被引：2，自引：0，他引：2  

刘翔 《地质与勘探》2016,52(6):1016-1028

本文通过对广西栗木矿区金竹源矿床和水溪庙矿床的流体包裹体研究,得出该矿区流体包裹体主要有两相H_2O-NaCl和H_2O-NaCl-CO_2两种类型。显微测温结果表明:两相H_2O-NaCl型流体包裹体均一温度主要集中于181.9~258.8℃,盐度w(Na Cleq)主要集中于4.01%~6.87%,密度0.690~0.988 g/cm3;H_2O-NaCl-CO_2型流体包裹体均一温度为178.5~331.1℃,主要集中在两个温度段,分别为高-中温段(265.3~315.5℃)和中-低温段(202.3~264.1℃),盐度w(NaCleq)主要集中在0.21%~5.05%,密度为0.678~0.886 g/cm3。栗木矿区成矿流体有两个温度集中段,且具有低盐度、低密度的特征。氢氧同位素研究结果表明:金竹源矿床钨锡铌钽矿化花岗岩石英δD值为-73.6‰~-62.8‰,δ~(18)OV-SMOW值为7.5‰~8.9‰,计算得δ~(18)OH2O值为6.00‰~7.40‰;水溪庙矿床钨锡铌钽矿化花岗岩石英δD值为-73.8‰~-58.3‰,δ~(18)OV-SMOW值为11.0‰~13.2‰,计算得δ~(18)OH2O值为9.50‰~11.70‰,水溪庙矿床含钨锡石英脉石英δD值为-75.3‰~-56.6‰,δ~(18)OV-SMOW值为11.8‰~14.1‰,计算得δ~(18)OH2O值为2.20‰~4.50‰。栗木矿区钨锡铌钽矿化花岗岩成矿流体来源于岩浆水,含钨锡石英脉成矿流体来源于岩浆水和大气降水的混合流体。  相似文献   

History of faulting in the Northern Hastings Block,southern New England Orogen     

J. Yan  R. Offler 《Australian Journal of Earth Sciences》2016,63(7):821-841

Brittle failure is common in the Devonian to Permian rocks in the Northern Hastings Block (NHB) and is manifested by faults of different orientation and kinematic histories, but the timing of fault movement is not well defined. In this study, faults in the NHB were analysed with the map pattern of cross-cutting faults used to estimate the relative time of movement and relationship to other faults. We defined five episodes of faulting or fault reactivation that affected the NHB. The Yarras Fault System on the southwestern side of the NHB and the Parrabel Fault and related faults on the eastern side of the NHB are the two major fault systems responsible for transporting and rotating the NHB in the late Carboniferous. Faults on the eastern, northeastern and northern part of Parrabel Dome started and stopped moving after emplacement of the Hastings Block and before the intrusion of the Werrikimbe Triassic granitoids. We suggested that the movement on the major bounding faults is related to the accommodation of the NHB to the folding and cleavage development in the adjoining Nambucca Block, and is associated with the earliest part of the Hunter–Bowen Orogeny. Limited dextral movement on the extensions of the Taylors Arm Fault System caused minor displacements in the northeastern part of the NHB during the Late Triassic. Some small faults cut the Triassic granitoids or Triassic Lorne Basin sediments indicating tectonic activity continued post-Triassic.  相似文献   

从平衡-封闭-静态转向非平衡-开放-动力学研究-热液矿床成因的若干新概念概述     

张荣华  胡书敏  张雪彤 《地质学报》2016,90(9):2437-2453

热液金属矿床成因研究过程中,观测与实验始终是密切结合的。上世纪70年代,平衡热力学的实验数据的快速积累,使人们用热力学理论计算可以预测和反演矿石和岩石的成因。但是,没有矿物-水溶液的反应速率数据,又没有与流体力学的结合,搞清楚矿石成因是困难的。七、八十年代,开始研究矿物与水溶液的反应动力学实验。科学家们开始瞄准了从平衡-封闭-静态转向非平衡-开放-动力学研究的这个大方向。1992年我们建立地球化学动力学开放研究实验室。研究高温高压矿物与水反应速率,发现固液的开放体系的自组织现象。实验发现温度影响矿物的各个元素反应速率改变,发现在跨越水临界态时矿物与水反应速率涨落、在近临界的气-液两相不混溶区一些金属进入气相、超临界流体的氧化作用及特别的溶剂性能影响矿物溶解性质。实验证实:临界态区流体与矿石成因有关。水岩相互作用的反应动力学实验温度从低温到550度,揭示矿石的金属来源、迁移、金属与蚀变分带机制。一大批大于300度的矿物与水反应动力学实验在国际界是少有报道的。九十年代,超高压的科学发展,与同步辐射光源的技术进步的结合,使固体地球科学又迈向了地球深内部。我们发展了高温高压流体性质的原位直测(测量850℃水溶液)红外谱,发现深部流体的新性质:气液两相流体的新结构,在临界温度区(300~400℃),水分子氢键网络的破坏受压力影响不大(23MPa~3GPa),同时,出现水的高电导率。研发新仪器为开放-流动-非平衡的反应动力学实验与极端条件下物质性质的直接观测结合,在科学前沿领域开辟了创新道路。  相似文献   

硫酸参与的长江流域岩石化学风化速率与大气CO2消耗   总被引：4，自引：0，他引：4  

张连凯  覃小群  刘朋雨  黄奇波 《地质学报》2016,90(8):1933-1943

流域的岩石化学风化过程是全球碳循环中的重要环节。以往的流域水化学碳汇通量估算大多是基于碳酸的风化作用。而实际上,硫酸和碳酸一样,也参与了流域碳元素的地球化学循环,从而对全球碳循环过程产生影响。长江流域水体近几年出现酸化现象,大部分河段SO42-和Ca2+含量增高,其对应的岩石风化过程和大气CO2消耗速率也发生变化。文章对长江干流及主要支流2013年不同季节的离子组成进行监测,利用水化学平衡法和Galy估算模型,对长江流域岩石化学风化速率和CO2消耗通量进行了估算,对硫酸参与下的长江流域岩石风化和碳循环过程进行了分析。结果表明,长江流域水体离子主要来源于硅酸盐岩风化和碳酸盐岩风化。其中碳酸盐岩风化对河水离子贡献率为92%。在硅酸盐岩广泛分布的赣江流域,碳酸盐岩风化离子贡献也达85%。分析表明,硫酸参与了长江流域的岩石风化过程,对水体中离子产生一定影响。硫酸的参与加快了碳酸盐岩的化学风化速率,平均提高约30%,但是使流域大气CO2消耗速率降低。在不考虑蒸发岩溶蚀作用下,平均从516×103 mol/km2·a降至356×103 mol/km2·a,降低约31%。在各支流中,硫酸对乌江流域碳酸盐岩的风化和碳循环的影响最大,而对雅砻江的影响最小,这与乌江流域的含煤地层、矿床硫化物及大气酸沉降有关。  相似文献   

滇黔北坳陷寒武系碳酸盐岩古海洋环境特征及地质意义   总被引：1，自引：1，他引：0  

王鹏万  斯春松  张润合  李娴静  马立桥  黄羚  徐云俊  鲁慧丽 《沉积学报》2016,34(5):811-818

为厘定滇黔北坳陷寒武系碳酸盐岩古海洋环境,揭示成岩流体与岩溶作用的潜在联系,并预测有利储层发育层段,基于镇雄羊场碳酸盐岩剖面实测及系统取样基础上,采用微量元素、碳氧锶同位素及铸体薄片等分析手段,地球化学与岩石学方法相结合,探讨碳酸盐岩古海洋环境及地质意义。研究结果表明:滇黔北坳陷寒武系清虚洞组-娄山关组整体为海相环境,古海洋温度处于12.82℃~32.84℃之间,主体为温暖或炎热的亚热带气候。海平面具有主体震荡下降的趋势,存在8期海平面变化旋回,发育对应的岩相组合,其同位素演化曲线可作为地层划分依据。微量元素、同位素地球化学及岩石学特征证实娄山关组岩溶作用相对发育,成岩流体混入强氧化性低温大气水,有利储层纵向上主要分布在海平面下降旋回的高部位。  相似文献   

Comparative Study of the Carbon Emission Situation and Goals between China and India     

Yang Zhanhong  Luo Hong  Xue Jie  Zhang Baoliu 《地球科学进展》2016,31(7):764-773

As the two large developing and populous countries, China and India face the dual challenges of economic development and climate change. Both of them are active in carbon emissions reduction, while India also bears the pressure of being “benchmarked” against China. With taking China and India as the sample of a comparative analysis, and the statistical value of a long sequence as the basic analysis data, based on the detailed analysis and comparison of carbon emissions history, the carbon emissions situation of the two countries from various dimensions including economic development, energy reserves and consumption, etc. were comparatively analyzed. The carbon intensity and energy structure after achieving the objectives were measured and compared by focusing on the carbon emissions reduction targets in China and India. The comparative results show that: China’s total carbon emissions are greater than India’s, but the growth rate of emissions, per capita emissions are significantly lower than India’s, while the carbon intensity decreases significantly faster than that of India. China has taken more efforts to make commitments to carbon reduction than India. With India’s energy structure adjustment, the situation will be gradually better than that in China.  相似文献   

Comparative Analysis of International Energy Consumption Characteristics and China's Countermeasures     

Yang Zhanhong  Lü  Lianhong  Cao Bao  Wang Xiao  Luo Hong 《地球科学进展》2016,31(1):94-102

With the rise of low carbon economy and the deterioration of the international energy situation, most countries in the world pay more attention to energy issues. In this paper, based on a comparison with several countries of large energy consumption, we used long sequence statistics to analyze the energy consumption characteristics from the world and the history, including energy consumption, energy consumption structure and energy efficiency, and then summed up the characteristics of energy consumption in developed countries, analyzed China's energy consumption process and the current stage, and found out the main problems of energy consumption in China. At last, countermeasures for the healthy development of China's energy were proposed, including actively promoting scientific and technological progress, upgrading energy structure, developing low carbon economy, rationalizing energy prices, improving the proportion of clean energy consumption and emphasizing synergistic effect on environment protection.  相似文献   

滇东南安那金矿床成矿流体地球化学研究   总被引：1，自引：1，他引：0  

董文斗  沈能平  苏文超  蔡佳丽 《岩石学报》2016,32(11):3321-3330

云南安那金矿床位于右江盆地南缘,产于二叠纪辉绿岩侵入体之中,广泛发育乳白色石英网脉,蚀变辉绿岩体即为金矿体。与右江盆地以沉积岩为容矿岩石的卡林型金矿床类似,具有硅化、粘土化、碳酸盐化和硫化物化等热液蚀变特征。本文对安那金矿床石英中的流体包裹体岩相学、显微测温学、激光拉曼光谱以及氢氧同位素组成进行了分析,发现成矿期石英中的流体包裹体主要为富含CO_2气-液两相或三相流体包裹体,其均一温度范围为208~312℃(平均254℃),盐度很低,变化范围为0~2%Na Cleqv,成矿溶液的密度为0.88~0.98g/cm~3,表明形成安那金矿床的成矿流体属于中温、低盐度、中-低密度的流体。激光拉曼光谱分析显示,石英中包裹体的气相成分富含CO_2、N_2以及微量CH_4等挥发分。成矿流体的氢氧同位素组成显示变质流体成因,结合矿石显微岩相学结构,认为流体溶蚀交代辉绿岩中的含Ti-Fe辉石或者钛铁矿,溶解Fe的硫化作用过程是含Au黄铁矿和毒砂沉淀富集的重要机制。成矿作用可能与右江盆地南缘印支期造山事件有关。  相似文献   

CMIP5地球系统模式溶解氧模拟结果分析     

鲍颖  李阳春 《海洋学报(英文版)》2016,35(12):28-37

本文基于常用的统计方法,通过与WOA09观测的海洋溶解氧浓度数据进行比较,定量地评估了9个CMIP5地球系统模式在历史排放试验中海洋溶解氧气候态特征的模拟能力。在海表,由于地球系统模式均能很好地模拟海表温度（SST）,模式模拟的海表溶解氧浓度分布与观测一致,模拟结果无论是全球平均浓度偏差还是均方根误差均接近0,空间相关系数与标准偏差接近1。在海洋中层以及深层这些重要水团所在的区域,各模式的模拟能力则差异较大,尤其在溶解氧低值区（OMZs）所在的500m到1000m,各模式均出现全球平均偏差、均方根误差的极大值以及空间相关系数的极小值。在海洋内部,模式偏差的原因比较复杂。经向翻转环流和颗粒有机碳通量均对模式的偏差有贡献。分析结果表明物理场偏差对溶解氧偏差的贡献较大。一些重要水团,比如北大西洋深水,南极底层水以及北太平洋中层水在极大程度上影响了溶解氧在这些海区的分布。需要指出的是,虽然在海洋内部各模式模拟的溶解氧浓度偏差较大,但是多模式平均结果却能表现出与观测较好的一致性。  相似文献