Coincident negative shifts in sulfur and carbon isotope compositions prior to the end-Permian mass extinction at Shangsi Section of Guangyuan, South China     

Pengwei Li  Junhua Huang  Min Chen  Xiao Bai 《Frontiers of Earth Science》2009,3(1):51-56

Sulfur isotope composition of carbonate-associated sulfate (δ³⁴S_CAS) and carbon isotope composition of carbonate (δ¹³C_carb) were jointly investigated on the Late Permian rocks at Shangsi Section, Guanyuan, Northeast Sichuan, South China. Both δ³⁴S_CAS and δ¹³C_carb show gradual decline trends in Late Permian strata, inferring the occurrence of the long-term variation of marine environmental conditions. Associated with the long-term variation are the two coincident negative shifts in δ³⁴S_CAS and δ¹³C_carb, with one occurring at the boundary between Middle Permian Maokou Formation and Late Permian Wujiaping Formation and another at Middle Dalong Formation. Of significance is the second shift which clearly predates the regression and the biotic crisis at the end of Permian at Shangsi Section, providing evidence that a catastrophic event occurred prior to the biotic crisis. The frequent volcanisms indicated by the volcanic rocks or fragments, and the upwelling are proposed to cause the second negative excursion. An abrupt extreme negative δ³⁴S_CAS (ca. −20‰) associated with a low relative concentration of CAS and total organic carbon without large change in δ¹³C_carb is found at the end of the second shift, which might arise from the short-term oxygenation of bottom waters and sediments that resulted from the abrupt sea level drop.  相似文献   

Platinum-group element geochemistry of mafic rocks from the Dongchuan area,southwestern China     

Siqi Yang  Hong Zhong  Weiguang Zhu  Wenjun Hu  Zhongjie Bai 《中国地球化学学报》2017,36(1):52-65

Mafic intrusions and dykes are well preserved in the Yinmin and Lanniping districts, located within the western margin of the Yangtze Block, SW China. Although these mafic rocks from the two areas formed during different periods, they share similar ranges of PGE concentration. Most of the Yinmin gabbroic dykes contain relatively high PGE concentrations (PGEs = 13.9–87.0 ppb) and low S contents (0.003 %–0.020 %), higher than the maximum PGE concentrations of mafic magmas melting from the mantle. Two exceptional Yinmin samples are characterized by relatively low PGE (PGEs = 0.31–0.37 ppb) and high S (0.114 %–0.257 %) contents. In contrast, most samples from the Lanniping gabbroic intrusion have low PGE concentrations (PGEs = 0.12–1.02 ppb) and high S contents (0.130 %–0.360 %), except that the three samples exhibit relatively high PGE (PGEs = 16.3–34.8 ppb) and low S concentrations (0.014 %–0.070 %). All the Yinmin and Lanniping samples are characterized by the enrichment of PPGE relative to IPGE in the primitive-mantle normalized diagrams, and the high-PGE samples exhibit obvious Ru anomalies. This study suggests that during the ascent of the parental magma, removal of Os–Ir–Ru alloys and/or chromite/spinel leads to high Pd/Ir ratios and Ru anomalies for the Yinmin high-PGE samples and relatively lower Pd/Ir ratios and Ru anomalies for the Lanniping low-PGE samples. We propose that the magmas parental to the Yinmin gabbroic dykes are initially S-unsaturated, and subsequently, minor evolved magma reached sulfur saturation and led to sulfide segregation. Although the Lanniping parental magmas are originally not saturated in S, the high Cu/Pd ratios (3.8 × 10⁴ to 3.2 × 10⁶) for most of the Lanniping samples indicate the S-saturated state and sulfide segregation. A calculation shows that the PGE-poor magmas might have experienced 0.01 %–0.1 % sulfide segregation in the magma chamber. Therefore, our study provides a possible opportunity to discover PGE-enriched sulfide mineralization somewhere near or within the Lanniping mafic intrusion.  相似文献   

Spatial-temporal heterogeneity of industrial structure transformation and carbon emission effect in Xuzhou Metropolitan Area     

Fangdao Qiu  He Yuan  Liangyu Bai  Fei Li 《中国地理科学(英文版)》2017,27(6):904-917

Employing decoupling index and industrial structure characteristic bias index methods, this study analyzed the spatial-temporal characteristics of industrial structure transformations and their resulting carbon emissions in the Xuzhou Metropolitan Area from 2000 to 2014, with a focus on their relationships and driving factors. Our research indicates that carbon emission intensity from industrial structures in the Xuzhou Metropolitan Area at first showed an increasing trend, which then decreased. Furthermore, the relationship between emissions and industrial economic growth has been trending toward absolute decoupling. From the perspective of the center-periphery, the Xuzhou Metropolitan Area formed a concentric pattern, where both progress towards low emissions and the level of technological advancement gradually diminished from the center to the periphery. In terms of variation across provinces, the ISCB index in the eastern Henan has decreased the slowest, followed by the southern Shandong and the northern Anhui, with the northern Jiangsu ranking last. During this period, resource- and labor- intensive industries were the primary growth industries in the northern Anhui and the eastern Henan, while labor-intensive industries dominated the southern Shandong and capital-intensive industries dominated the northern Jiangsu. In terms of city types, the spatial pattern for industrial structure indicates that recession resource-based cities had higher carbon emission intensities than mature resource-based cities, followed by non-resource-based cities and regenerative resource-based cities. Generally, the industrial structure in the Xuzhou Metropolitan Area has transformed from being resource-intensive to capital-intensive, and has been trending toward technology-intensive as resource availability has been exploited to exhaustion and then been regenerated. Industrial structure has been the leading factor causing heterogeneity of carbon emission intensities between metropolitan cities. Therefore, the key to optimizing the industrial structure and layout of metropolitan areas is to promote industrial structure transformation and improve the system controlling collaborative industrial development between cities.  相似文献   

Petrogenesis of Ore‐Related Granodiorite Porphyry in the Jiande Copper Deposit,SE China: Implications for the Tectonic Setting and Mineralization          下载免费PDF全文

Hui Chen  Pei Ni  Guo‐Guang Wang  Ren‐Yi Chen  Zhi‐Cheng Lü  Zhen‐Shan Pang  Lin Geng  Bai‐Sheng Zhang  Hui‐Xiang Yuan 《Resource Geology》2017,67(2):117-138

Adakitic rocks and related Cu–Au mineralization are widespread along eastern Jiangnan Orogen in South China. Previous studies have mainly concentrated on those in the Dexing area in northeastern Jiangxi Province, but information is lacking on the genesis and setting of those in northwestern Zhejiang Province. The Jiande copper deposit is located in the suture zone between the Yangtze and Cathaysia blocks of South China. This paper presents systematic LA–ICP–MS zircon U–Pb dating and element and Sr–Nd–Hf isotopic data of the Jiande granodiorite porphyry. Zircon dating showed that the Jiande granodiorite porphyry was produced during the Middle Jurassic (ca. 161 Ma). The Jiande granodiorite porphyry is characterized by adakitic geochemical affinities with high Sr/Y and La_N/Yb_N ratios but low Y and Yb contents. The absence of a negative Eu anomaly, extreme depletion in Y and Yb, relatively low MgO contents, and relatively high ²⁰⁷Pb/²⁰⁴Pb ratios, indicated that the Jiande granodiorite porphyry was likely derived from partial melting of the thickened lower continental crust. In addition, the Jiande granodiorite porphyry shows arc magma geochemical features (e.g., Nb, Ta and Ti depletion), with bulk Earth‐like ε_Nd (t) values (?2.89 to ?1.92), ε_Hf (t) values (?0.6 to +2.8), and initial ⁸⁷Sr/⁸⁶Sr (0.7078 to 0.7105). However, a non‐arc setting in the Middle Jurassic is indicated by the absence of arc rocks and the presence of rifting‐related igneous rock associations in the interior of South China. Combined with the regional Neoproterozoic Jiangnan Orogeny, it indicates that these arc magma geochemical features are possibly inherited from the Neoproterozoic juvenile continental crust formed by the ancient oceanic crust subduction along the Jiangnan Orogen. The geodynamic environment that is responsible for the development of the Middle Jurassic Jiande granodiorite porphyry is likely a localized intra‐continental extensional environment along the NE‐trending Jiangshan‐Shaoxing Deep Fault as a tectonic response to far‐field stress at the margins of the rigid South China Plate during the early stage of the paleo‐Pacific plate subduction. In terms of Cu mineralization, we suggest that the metal Cu was released from the subducted oceanic slab and reserved in the juvenile crust during Neoproterozoic subduction along the eastern Jiangnan Orogen region. Partial melting of the Cu rich Neoproterozoic juvenile crust during the Middle Jurassic time in the Jiande area caused the formation of adakitic rocks and the Cu deposit.  相似文献   

湘西北奥陶系宝塔组灰岩龟裂纹构造特征、成因及其资源意义          下载免费PDF全文

黄乐清  刘伟  柏道远  李泽泓  梁恩云  陈珍宝 《地球科学》2019,44(2):399-414

湘西北上奥陶统宝塔组灰岩的龟裂纹构造在岩序上具有"下密上稀、过渡变形、不穿邻层、似泄水充填"的特点,是地史时期一种特殊的沉积构造.为了查明其成因机制及其与扬子海盆演化过程的内在联系,从湘西北龟裂纹灰岩的岩石学特征、裂缝特征、地球化学特征、盆地模型以及综合对比已知成因的"似龟裂纹构造"等诸多方面入手,经研究后认为龟裂纹构造属于一种受准同生期胶凝缩作用影响形成初始微缝,随后在构造挤压控制下、盆地快速下沉、盆内形成异常高压场的流体环境,驱使下伏富水岩层的灰泥物质向上挤入、充填、改造先期初始裂缝而形成.宝塔组龟裂纹构造的研究,为我们探究构造-流体-岩石多重作用机制提供了岩石学方面的资料;同时,该裂纹疏导功能良好,具有重要的成矿(油藏)意义.  相似文献   

贵州赫章县猪拱塘铅锌矿床主矿体地质特征及找矿标志          下载免费PDF全文

吴大文  何良伦  蔡京辰  王军  柏光辉  杨天  金翔霖  黄庆 《贵州地质》2019,36(4):299-306

贵州赫章猪拱塘铅锌矿床是贵州省内发现的首个中低温热液型超大型铅锌矿床。铅锌矿体严格受北西向断裂构造控制,主要赋存于北西向F1、F2及隐伏F20、F30断裂破碎带及次级断裂破碎带内。根据矿体的空间展布特点,以控容矿断裂作为矿体对比连接的依据,圈定69个铅锌矿体,探明铅锌金属资源量275万吨。Ⅰ-1号主矿体为区内规模最大铅锌矿体,呈似层状、透镜状产出于猪拱塘断层(F1)破碎带内,赋矿围岩建造为二叠系中统栖霞组(P2q)泥灰岩、灰岩、白云质灰岩建造。矿体长度1 640 m,平均厚11. 01 m,铅平均2. 81%,锌平均8. 71%。铅锌资源量182万吨,占矿床总资源量的57%,资源量规模达特大型。通过对Ⅰ-1号主矿体地质特征及找矿标志详细论述,为矿床总体特征及成矿规律总结提供依据。  相似文献   

东昆仑马尼特金矿床赋矿花岗闪长岩锆石U-Pb年龄及岩石地球化学特征     

李积清  王涛  陈静  白宗海  林艳海 《矿物岩石》2019,39(3):69-77

马尼特金矿床位于东昆仑木孜塔格-布青山蛇绿混杂岩带,是近年来在东昆仑发现的与马尔争组地层有关的构造蚀变岩型小型金矿床,矿体主要赋存于晚三叠世花岗闪长岩与围岩的接触部位。本次研究通过对赋矿花岗闪长岩体的LA-ICP-MS锆石U-Pb定年,全岩主量元素、微量元素的研究,探讨了该岩体的形成时代,成因类型及其形成构造环境。结果显示:该花岗闪长岩的锆石U-Pb年龄为213.25 Ma±0.62 Ma(MSWD=0.99),代表其侵入时代为晚三叠世。岩石w(SiO2)在66.96%~68.3%之间,K2O/Na2O=0.54~0.63,相对富钠,贫w(MnO)(平均0.03%),w(P2O5)(0.14%~0.16%)和w(TiO2)(0.4%~0.46%),A/CNK值为1.05~1.16,平均1.106,w(Al2O3)介于15.37%~15.72%之间,里特曼指数δ值为1.43%~1.89%,TFeO/MgO为1.72~1.84,DI为74.19~79.94,表明其为过铝质、钙碱性系列的I型花岗岩。岩石稀土总量较低(ΣREE=110.67×10^-6~121.36×10^-6),表现出轻稀土富集而重稀土亏损的右倾曲线,LREE/HREE=13.54~15.12,[(La/Yb)N=20.42~20.7],轻重稀土分馏明显,负Eu异常中等(δEu介于0.94~0.99之间),大离子亲石元素Rb,Ba,Sr以及U,Th相对富集,高场强元素Nb,Ta及K,P,Ti相对亏损,具有火山弧花岗岩特征。结合其形成时代及区域构造背景,认为其形成于早-中生代巴颜喀拉地块和东昆仑地块后碰撞构造环境。  相似文献   

地面臭氧光化学过程规律的初步研究   总被引：8，自引：2，他引：6  

白建辉  王明星 《气候与环境研究》2001,6(1):91-102

给出了1996年夏季在广东肇庆鼎湖山对光化辐射、地面O3、NO、NO2浓度的观测结果,对影响地面O3、NO、NO2的主要因子进行了分析。晴天,地面O3、NO、NO2浓度有明显的日变化;阴天,它们的日变化比较复杂。晴天和阴天,在lnQUVB/m和lnQvis/m(其中QUVB为紫外B辐射,Qvis为可见光辐射,m为大气质量)与地面O3、NO,NO2浓度、整层大气水汽含量(q1、q2、q3、q4)之间存在着很好的相关关系。利用得到的关系式计算了地面O3浓度,在紫外和可见光波段,计算值与观测值符合得都比较好。  相似文献   

中国中新元古代重要沉积地质事件及其意义   总被引：2，自引：2，他引：0       下载免费PDF全文

旷红伟  柳永清  耿元生  白华青  彭楠  范正秀  宋换新  夏晓旭  王玉冲  陈骁帅 《古地理学报》2019,21(1):1-30

地球曾经历了3次超大陆演化过程,其中2次超大陆(哥伦比亚(Columbia)和罗迪尼亚(Rodinia))旋回涉及中新元古代,并与一系列区域性事件相联系,形成了多成因的超大陆演化模型。华北中东部新元古代沉积事件、扬子和塔里木新元古代裂谷事件、雪球事件等都被视为Rodinia超大陆的裂解响应,它们对定时三大陆块相互关系及定位其在全球超大陆的位置具有至关重要的作用,也反映了重要沉积地质事件在超大陆研究中不可或缺的作用和意义。此外,在中新元古代的Columbia和Rodinia超大陆演化过程中,还伴随发育具有广泛区域性甚至全球意义的巨厚白云岩与碳酸盐岩微生物(岩)、红层与黑色页岩、全球性臼齿亮晶碳酸盐岩和埃迪卡拉纪盖帽碳酸盐岩等沉积事件群及元素(同位素)漂移等地球化学异常事件,也包括特殊且重要的磷块岩、锰、铁矿等沉积成矿事件。由于不断显示出来在全球古大陆重建和古地理恢复方面的重要作用,它们越来越得到学术界的广泛关注和研究。文中通过系统分析中国中新元古代超大陆旋回演化中发育的部分重要或关键地质事件(群)时空发育与分布特征,并结合作者团队的实际资料和测试数据,以期揭示超大陆演化过程与重要沉积地质事件的内在联系,为超大陆聚散旋回演化和时空定位及原型沉积盆地的发育和评价提供科学证据。  相似文献   

Evaluating the contribution of satellite measurements to the re-construction of three-dimensional ocean temperature fields in combination with Argo profiles     

Jian Chen  Hengqian Yan  Senliang Bao  Xindong Cui  Chengzu Bai  Huizan Wang 《海洋学报(英文版)》2022,41(2):65-79

Assimilation systems absorb both satellite measurements and Argo observations. This assimilation is essential to diagnose and evaluate the contribution from each type of data to the reconstructed analysis, allowing for better configuration of assimilation parameters. To achieve this, two comparative reconstruction schemes were designed under the optimal interpolation framework. Using a static scheme, an in situ-only field of ocean temperature was derived by correcting climatology with only Argo ...  相似文献