Journal of Earth Science

CONTENTS

2017, 28(3): .

[Abstract](205) [PDF 152KB](3)

Abstract:

High Water Content in Primitive Mid-Ocean Ridge Basalt from Southwest Indian Ridge (51.56° E): Implications for Recycled Hydrous Component in the Mantle

Wei Li, Zhenmin Jin, Haiming Li, Chunhui Tao

2017, 28(3): 411-421. doi: 10.1007/s12583-017-0731-y

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The Southwest Indian Ridge (SWIR) is an ultraslow spreading end-member of mid-ocean ridge system and is characterized by weak or even an absence of magmatism. The segment between Indomed (ITF) and Gallieni (GTF) transform faults in the SWIR, however, displays extremely magmatic accretion with an unusual thick crust (up to 9.5 km). Although H₂O is present in trace amounts in the mantle, it has a strong influence on mantle melting and magmatism in the shallow crust. The mid-ocean ridge basalts (MORB) worldwide show strong variation in H₂O contents, but with a nearly uniform H₂O/Ce ratio. Regionally distinctive H₂O contents and H₂O/Ce ratios are inferred to be related to the H₂O variation in the source and can be used to constrain the mantle heterogenity. In this study, we measured the H₂O and trace elements of clinopyroxene phenocrysts from one basalt dredged from the ITF-GTF segment, SWIR (51.56^oE). The estimated H₂O content (1.3 wt.%±0.3 wt.%) in the primitive ITF-GTF basaltic melt is much higher than that in typical MORB samples, but similar to oceanic island basalts (OIB) and back-arc basalts (BABB). In addition, the calculated H₂O/Ce ratio (1 672–4 990) are extremely high, bearing "arc-like" signature. This study provides evidence that arc-related hydrous components are involved in the mantle source beneath the ITF-GTF ridge segment. It further lends support to the hypothesis that the mantle beneath the central SWIR may have experienced an ancient hydrous melting event in an arc terrain prior to or during the closure of the Mozambique Ocean in the Neoproterozoic.

Zircon U-Pb Age, Geochemical Data: Constraints on the Origin and Tectonic Evolution of the Metamafic Rocks from Longmuco-Shuanghu-Lancang Suture Zone, Tibet

Yanwang Wu, Cai Li, Mengjing Xu, Chaoming Xie, Ming Wang

2017, 28(3): 422-432. doi: 10.1007/s12583-017-0730-z

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Bulk-rock major and trace elements and zircon U-Pb data are reported for Permian metamafic rocks from Guoganjianan, in the western part of Longmuco-Shuanghu-Lancang suture zone. These results offer new insights into mantle source characteristics and geodynamic setting of Permian ophiolitic fragments. U-Pb isotopic dating using SHRIMP Ⅱ method reveals that the metamafic rocks were formed at 274.7±3.9 and 279.8±3.6 Ma. The metamafic rocks mostly show N-MORB-typed rare earth element patterns and are enrichment in large-ion lithophile elements, indicating that they are probably derived from partial melting of a depleted mantle in a back-arc basin. Our new data, together with recent studied results on Paleozoic ophiolitic fragments suggest the Paleo-Tethys Ocean in Central Qiangtang opened at Cambrian and widened between Ordovician and Devonian. Northward subduction started in the Late Devonian–Early Carboniferous and a back-arc basin developed during Permian.

Age, Genesis, and Tectonic Setting of the Mo-W Mineralized Dongshanwan Granite Porphyry from the Xilamulun Metallogenic Belt, NE China

Xuebing Zhang, Keyong Wang, Chengyang Wang, Wen Li, Qi Yu, Yicun Wang, Jianfeng Li, Duo Wan, Guanghuan Huang

2017, 28(3): 433-446. doi: 10.1007/s12583-016-0934-1

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The Xilamulun molybdenum polymetallic metallogenic belt in eastern Inner Mongolia forms one of the most important Mo metallogenic belts in northeastern China. The Dongshanwan porphyry Mo-W polymetallic deposit, in the northeastern part of the Xilamulun metallogenic belt, occurs along the periphery of a granite porphyry and consists of Mo-W-Ag sulfide and oxide disseminations and veinlets in hydrothermal assemblages. LA-ICP-MS zircon U-Pb dating of the Dongshanwan granite porphyry yields a crystallization age of 142.15±0.91 Ma, whereas molybdenite Re-Os isotopic dating model ages are of 139.9-141.5 Ma and an isochron age is of 140.5±3.2 Ma (MSWD=1.2). The age consistency indicates that the Dongshanwan deposit was a product of Early Cretaceous magmatism. The Dongshanwan granite porphyry is a high-alkali high-potassium intrusion and has high SiO₂ (75.39 wt.%-76.15 wt.%), low Al₂O₃ (12 wt.%-13 wt.%), Ba, Ti, P, and Sr contents, with negative Eu anomalies. The Y/Nb ratios are comparable to those of average continental crust and island arc basalts, corresponding to type-A2 granites. Our geochemical data indicate that the granite porphyry emplaced in an Early Cretaceous post-orogenic extensional environment following Mongol-Okhotsk oceanic subduction and subsequent continental collision.

Nitrate Removal by a Permeable Reactive Barrier of Fe⁰: A Model-Based Evaluation

Qinghua Wu, Chunmiao Zheng, Jiafa Zhang, Fawang Zhang

2017, 28(3): 447-456. doi: 10.1007/s12583-016-0924-2

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Permeable reactive barrier (PRB) filled with zero valent iron (ZVI, Fe⁰) can be an effective option to remove nitrate from contaminated groundwater. The long-term performance of such PRBs, however, might be compromised by the problem of declining reactivity and permeability, which could cause a decrease in the nitrate removal efficiency. In this study we explored suitable model formulations that allow for a process-based quantification of the passivation effect on denitrification rates and tested the model for a 40 years long operation scenario. The conceptual model underlying our selected formulation assumes the declining reactivity of the ZVI material through the progressing passivation caused by the precipitation of secondary minerals and the successive depletion of the ZVI material. Two model scenarios, i.e., the base model scenario which neglects the explicit consideration of the passivation effect and one performed with the model in which the impact of the passivation effect on denitrification was considered, were compared. The modeling results illustrate that nitrate removal in the model of considered passivation started to be incomplete after 10 years, and the effluent nitrate concentration of PRB rose up to 86% of the injected water concentration after 40 years, in contrast to the base scenario, corresponding well with the field observations of successively declining nitrate removal efficiencies. The model results also showed that the porosity of the PRB increased in both models. In order to improve and recover the reactivity of ZVI, pyrite was added to the PRB, resulting in completely nitrate removal and lower consumption of ZVI.

Reactive Transport Modeling of Long-Term CO₂ Sequestration Mechanisms at the Shenhua CCS Demonstration Project, China

Guodong Yang, Yilian Li, Aleks Atrens, Danqing Liu, Yongsheng Wang, Li Jia, Yu Lu

2017, 28(3): 457-472. doi: 10.1007/s12583-016-0919-6

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Carbon dioxide injection into deep saline aquifers results in a variety of strongly coupled physical and chemical processes. In this study, reactive transport simulations using a 2-D radial model were performed to investigate the fate of the injected CO₂, the effect of CO₂-water-rock interactions on mineral alteration, and the long-term CO₂ sequestration mechanisms of the Liujiagou Formation sandstone at the Shenhua CCS (carbon capture and storage) pilot site of China. Carbon dioxide was injected at a constant rate of 0.1 Mt/year for 30 years, and the fluid flow and geochemical transport simulation was run for a period of 10 000 years by the TOUGHREACT code according to the underground conditions of the Liujiagou Formation. The results show that different trapping phases of CO₂ vary with time. Sensitivity analyses indicate that plagioclase composition and chlorite presence are the most significant determinants of stable carbonate minerals and CO₂ mineral trapping capacity. For arkosic arenite in the Liujiagou Formation, CO₂ can be immobilized by precipitation of ankerite, magnesite, siderite, dawsonite, and calcite for different mineral compositions, with Ca²⁺, Mg²⁺, Fe²⁺ and Na⁺ provided by dissolution of calcite, albite (or oligoclase) and chlorite. This study can provide useful insights into the geochemistry of CO₂ storage in other arkosic arenite (feldspar rich sandstone) formations at other pilots or target sites.

Arsenic, Iron and Organic Matter in Quaternary Aquifer Sediments from Western Hetao Basin, Inner Mongolia

Naijing Liu, Yamin Deng, Ya Wu

2017, 28(3): 473-483. doi: 10.1007/s12583-017-0727-7

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To investigate geochemical and mineralogical features of sediments from aquifers containing high levels of dissolved arsenic (As) in western Hetao Basin, Inner Mongolia, sediment samples were collected for XRD (X-ray diffraction), amorphous Fe/Mn oxides, and humic/fulvic acid analyses, in addition to As determination. In the study area, the total As contents in the sediments were in the range 5.3–28.8 mg/kg; while that associated with humic substances in the range 4–9 mg/kg, accounting for 26%–47% of the total As. The results of XRD analysis suggest that clay and silt contain certain small amounts of iron oxides minerals, such as ferrihydrite, hematite and goethite, whereas have higher As and Fe₂O₃ contents. Up to one third of As in the sediments could be extracted by ammonium oxalate, and high As contents were generally found in organic-rich clay or silty clay samples with high FA/HA ratio. As is strongly associated with humic substances and Fe oxyhydroxides, which may be the major sink and source of As in the aquifer sediments.

Aquatic Species Dominate Organic Matter in Qinghai Lake during the Holocene: Evidence from Eolian Deposits around the Lake

Fangming Zeng, Xiangjun Liu, Xiangzhong Li, Chongyi E

2017, 28(3): 484-491. doi: 10.1007/s12583-016-0926-X

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Total organic carbon (TOC) in lake sediments and its stable carbon isotope (δ¹³C_org) are widely applied to investigate paleoenvironmental changes even though their implications are complicated and multi-explanatory. Organic geochemistry studies of lake sediments from Qinghai Lake have been investigated, but some interpretations are controversial. In this study, TOC of one Holocene eolian section and δ¹³C_org of three eolian sections were studied around Qinghai Lake. Results indicate that the TOC content in eolian deposits was low during the Early Holocene, and gradually increased to high values during the Middle and Late Holocene. The variation in TOC content of eolian deposits is different from that in the lacustrine sequence from Qinghai Lake during the Holocene. The δ¹³C_org values in the eolian sections were relatively stable, with oscillation amplitudes of ~4‰ (ranging from -25.8‰ to -22.1‰), in contrast to ~10‰ variations in δ¹³C_org values (varying from -30‰ to -20‰) in lacustrine sediments. Through comparison of TOC and δ¹³C_org values between eolian deposits and lacustrine sediments, we can confirm indications that the organic matter in Qinghai Lake sediments during the Holocene was primarily a contribution of the aquatic species in the lake. This is significant for understanding the origin of organic matter in lake sediments on the northeastern Qinghai-Tibetan Plateau and for paleoenvironmental inferences using such proxies.

Atacamite and Nantokite in Kaerqueka Copper Deposit of Qimantag Area: Evidence for Cenozoic Climate Evolution of the Qaidam Basin

Liwen Yi, Xiangping Gu, Anhuai Lu, Xiangyu Li, Dexian Zhang, Zhiling Wang, Jianping Liu, Shuai Li, Zhengxiang Shu, Cui Yu, Hongyan Zuo, Can Shen

2017, 28(3): 492-499. doi: 10.1007/s12583-017-0548-8

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Using a mineralogy method to reflect climate evolution is a new approach to research Cenozoic environmental progression of the Qaidam Basin. In this paper, we present the chemical composition and crystallographic parameter of atacamite, nantokite, and tenorite in cryptocrystalline aggregates from the Kaerqueka copper deposit of Qimantag metallogenic belt by means of electron microprobe and in-situ X-ray diffraction analyses. Atacamite and nantokite occur in an intimate intergrowth as the secondary precipitation of chalcopyrite and bornite filling in the interstitial space of andradite in the Kaerqueka copper deposit, with an average composition of Cl: 12.38 wt.%, Cu: 63.76 wt.%, O: 21.46 wt.%. X-ray microdiffraction shows that the intergrowth contains nantokite with a cubic unit cell a=5.403(2) Å and atacamite with an orthorhombic unit cell a=6.030(3), b=6.883(2), c=9.114(1) Å. XRD quantitative calculation shows that the nanometric aggregate contains 36.07 wt.% tenorite, 18.41 wt.% atacamite, and 45.52 wt.% nantokite. The presence of nantokite and atacamite requires saline solutions for their formation and hyper-arid climate conditions for their preservation. Combined with the data of salt lakes and the pollen sequence of western China, we suggest that during the uplift of the Tibetan Plateau and the retreat of the Paratethys, saline water was forced to the surface through a basal fracture zone. In the hyper-arid climate of the Qaidam Basin, the recharge of groundwater by direct precipitation is negligible, and groundwater is derived from inflow from the salt lakes. Thus, atacamite is preserved. In addition, spertiniite in the edge and fractures of atacamite and nantokite may represent wetter climate after the formation of atacamite and nantokite.

Distinguishing Oil and Water Layers in a Porous Cracked Medium by Interpreting Acoustic Logging Data on the Basis of Hudson Theory

Xue'ang Zhang, Zhuwen Wang, Zhichao Yang

2017, 28(3): 500-506. doi: 10.1007/s12583-017-0620-4

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During surveys, water layers may interfere with the detection of oil layers. In order to distinguish between oil and water layers in a porous cracked medium, research on the properties of cracks and oil and water layers and their relation to acoustic logging rules is essential. On the basis of Hudson's crack theory, we simulated oil and water layers in crack-porous medium with different crack parameters corresponding to the well-field response. We found that in a cracked medium with high crack angle or low number density of cracks, compressional and shear wave velocities are sensitive to crack characteristics; further, these velocities are more sensitive to crack characteristics when the waves propagate through the water layer than when they propagate through the oil layer. Compressional and shear wave velocities increase with an increase in crack angle: in the water layer, the increase is approximately linear. On comparing the full waveforms observed in the oil and water layers, we find that the amplitudes of most waves are higher in the water layer. Among the considered waves, the Stoneley wave suffers maximum amplitude attenuation in the oil layer. The maximum excitation intensity for oil layer is greater than that for the water layer. These results can guide further cracked media logging field exploration work.

Mapping Spatial Distribution Characteristics of Lineaments Extracted from Remote Sensing Image Using Fractal and Multifractal Models

Cheng Lyu, Qiuming Cheng, Renguang Zuo, Xueping Wang

2017, 28(3): 507-515. doi: 10.1007/s12583-016-0914-x

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Mapping mineral prospectivity in vegetated areas is a challenge. For this reason, we aimed to map spatial distribution characteristics of linear structures detected in remote sensing images using fractal and multifractal models. The selected study area was the Pinghe District of the Fujian Province (China), located in the Shanghang-Yunxiao polymetallic and alunite ore belt (within the Wuyishan polymetallic belt), where mineral resources such as copper, molybdenum, gold, silver, iron, lead, zinc, alunite and pyrophyllite have been discovered. The results of our study showed that: (1) the values of fractal dimension for all lineaments, NW-trending lineaments, and NE-trending lineaments, are 1.36, 1.32, and 1.23, respectively, indicating that these lineaments are statistically self-similar; (2) the fractal dimensions of the spatial distribution of the linear structures in the four selected hydrothermal-type ore deposits of the Pinghe District, named Zhongteng, Panchi, Xiaofanshan and Fanshan, are 1.43, 1.52, 1.37 and 1.37, respectively, which are higher than the mean value in South China; (3) the spatial distribution of the linear structures extracted from the remote sensing image and displayed by the contour map of fractal dimensions, correlates well with the known hydrothermal ore deposits; and (4) the results of the anomaly map decomposed by the spectrum-area (S-A) multifractal model is much better than the original fractal dimension contour map, which showed most of the known hydrothermal-type deposits occur in the high anomalous area. It is suggested that a high step tendency possibly matches with the boundary of the volcanic edifice and the deep fault controlling the development of the rock mass and the volcanic edifice. The complexity of the spatial distribution of mapped lineations (faults) in the Pinghe District, characterized by high values in the anomaly map, may be associated with the hydrothermal polymetallic ore mineralization in the study area.

A New Empirical Method for Constructing Capillary Pressure Curves from Conventional Logs in Low-Permeability Sandstones

Cheng Feng, Yujiang Shi, Jiahong Li, Liang Chang, Gaoren Li, Zhiqiang Mao

2017, 28(3): 516-522. doi: 10.1007/s12583-016-0913-6

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Pore structure reflected from capillary pressure curves plays an important role in low-permeability formation evaluation. It is a common way to construct capillary pressure curves by Nuclear Magnetic Resonance (NMR) log. However, the method's efficiency will be severely affected if there is no NMR log data or it cannot reflect pore structure well. Therefore, on the basis of J function and diagenetic facies classification, a new empirical model for constructing capillary pressure curves from conventional logs is proposed here as a solution to the problem. This model includes porosity and the relative value of natural gamma rays as independent variables and the saturation of mercury injection as a dependent variable. According to the 51 core experimental data sets of three diagenetic facies from the bottom of the Upper Triassic in the western Ordos Basin, China, the model's parameters in each diagenetic facies are calibrated. Both self-checking and extrapolation tests show a positive effect, which demonstrates the high reliability of the proposed capillary pressure curve construction model. Based on the constructed capillary pressure curves, NMR T₂ spectra under fully brine-saturated conditions are mapped by a piecewise power function. A field study is then presented. Agreement can be seen between the mapped NMR T₂ spectra and the MRIL-P log data in the location of the major peak, right boundary, distribution characteristics and T₂ logarithmic mean value. In addition, the capillary pressure curve construction model proposed in this paper is not affected by special log data or formation condition. It is of great importance in evaluating pore structure, predicting oil production and identifying oil layers through NMR log data in low-permeability sandstones.

Chemical and Isotopic Responses to Intensive Groundwater Abstraction and Its Implications on Aquifer Sustainability in Shijiazhuang, China

Zhongshuang Cheng, Yongbo Zhang, Chen Su, Zongyu Chen

2017, 28(3): 523-534. doi: 10.1007/s12583-017-0729-5

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The stress imposed on groundwater resources due to intensively exploited aquifer has resulted in groundwater depletion in the North China Plain (NCP). Management of groundwater resources needs to understand the changes or dynamic responses due to the exploitation. The response of groundwater systems to intensive exploitation and groundwater availability were assessed by the combined use of conventional hydrochemical data and environmental isotopes in Shijiazhuang, NCP. The generally increased concentration of total dissolved solids (TDS), major cation and anion of groundwater in the past 40 years indicated high vulnerability of aquifer system but a short turn over time by intensive groundwater exploitation, which also was proved by changes of groundwater renewal rate estimated by tritium. The vertical distribution of tritium in aquifers showed that the active groundwater recharge zone has been extended from the depth of 100 to ~150 m since 1985, indicating an enhancement of active groundwater flushing of local groundwater system due to intensive groundwater abstraction. The enrichment trend of δ¹⁸O and δ²H value with groundwater abstraction, suggested the impacts of local recharge from irrigation return. The increase concentrations of nitrate with time indicated high aquifer vulnerability. A comprehensive effort should be developed for effective management strategies that ensure long-term, stable, and flexible water supplies to meet water demands in the NCP.

Heavy Metal-Polluted Aerosols Collected at a Rural Site, Northwest China

Xiaoyu Zhang, Zhongqin Li, Nozomu Takeuchi, Feiteng Wang, Shengjie Wang, Xiaoni You, Ping Zhou

2017, 28(3): 535-544.

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Daily samples of aerosol (n=27) were collected from September 21st to October 4th, 2013 in Fukang (44.17oN, 88.45oE, 475 m a.s.l.), Xinjiang, Northwest China. The enrichment factors (EFc) of selected 49 elements showed that the aerosols had extremely high concentrations of heavy metals, probably indicating their anthropogenic origins. Morphology of individual aerosol particles was determined by scanning electron microscopy and energy-dispersive X-ray microanalysis. Based on morphology and elemental composition, the particles were clustered into three dominant types: (Ⅰ) crustal originated particles: Si/Al-rich particles (36%) and Si/Fe-rich particles (24%); (Ⅱ) mixed source particles; and (Ⅲ) pollution derived particles: Pb-rich particles (10%). The backward trajectories were calculated using the HYSPLIT model, and the results indicated the different anthropogenic sources for heavy metals in Fukang aerosols. Air mass from north was identified as the most polluted source when compared to south and west.

Relationship between Landslides and Active Normal Faulting in the Epicentral Area of the AD 1556 M~8.5 Huaxian Earthquake, SE Weihe Graben (Central China)

Gang Rao, Yali Cheng, Aiming Lin, Bing Yan

2017, 28(3): 545-554. doi: 10.1007/s12583-017-0900-z

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In this paper, we focus on the characteristics of the landslides developed in the epicentral area of AD 1556 M~8.5 Huaxian Earthquake, and discuss their relations to the active normal faults in the SE Weihe Graben, Central China. The results from analyzing high-resolution remote-sensing imagery and digital elevation models (DEMs), in combination with field survey, demonstrate that: (ⅰ) the landslides observed in the study area range from small-scale debris/rock falls to large-scale rock avalanches; (ⅱ) the landslides are mostly developed upon steep slopes of ≥30°; and (ⅲ) the step-like normal-fault scarps along the range-fronts of the Huashan Mountains as well as the thick loess sediments in the Weinan area may facilitate the occurrence of large landslides. The results presented in this study would be helpful to assess the potential landslide hazards in densely-populated areas affected by active normal faulting.

Cretaceous Carbonate Deposits of Neotethys Ocean in the Northwest of Iran

Rahim Mahari, Somaieh Sadigh Janbehan

2017, 28(3): 555-562. doi: 10.1007/s12583-017-0685-0

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Cretaceous carbonate deposits are considerably extensively distributed in the northwest of Iran and form most of the paleohighs of the region and different Cenozoic sedimentary units have deposited over these units with angular unconformity. Cretaceous stratigraphic units of northwestern Iran can be divided into three main categories: clastic, shallow carbonate and pelagic. Clastic facies include conglomerate, breccia and fine-grained clastic groups and carbonate facies are composed of series of microfacies of open sea (A), bar (B), lagoon (C), and tidal flat. Relatively deep carbonate deposits with different trace fossils are also indications of deeper parts of the Cretaceous sedimentary environments in the northwest of Iran. With reference to the expansion of narrow Neotethys Ocean (Khoy-Zanjan), shelf margin sedimentary environments of Neotethys Ocean can be assumed for the Azarshahr-Tabriz region, where flysch and clastics facies in the coasts of Varaghan deposited towards the northern parts with increase of depth. Investigation on the expansion of narrow Neotethys Ocean by using different sedimentary facies during the present study is considered as an important step to complete paleogeographic data of Cretaceous time in the northwestern region of Iran and Middle East.

2017 Vol. 28, No. 3

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