南天山萨瓦亚尔顿金矿床稀土微量元素特征及其成因意义

萨瓦亚尔顿金矿位于新疆乌恰县的南天山构造带中,是我国20世纪90年代发现的第一例“穆龙套型”金矿.矿床形成于印支期,矿化与石英脉密切相关,显示了与穆龙套金矿的相似性.成矿流体演化经历了早期高温无矿化石英阶段,中期中低温矿化石英阶段,晚期低温碳酸盐脉阶段.早期无矿石英的稀土及微量元素含量均低于矿化石英.矿化石英包体中流体的稀土元素配分模式显示较一致的轻稀土富集和Eu正异常,指示流体中较高的钙离子或相对还原环境;流体中Pb含量较高,而蚀变强烈的围岩则显示出明显的Ca和Pb流失,这表明成矿流体可能部分来源于与围岩发生交代作用的蚀变流体,矿质沉淀可能与流体混合作用相关.早期石英包体中流体的稀土和微量元素含量较低则指示早期阶段可能未发生流体混合.萨瓦亚尔顿Ⅳ号矿脉为最大矿带,其含矿石英包体中流体微量元素一般高于其它矿脉石英,可能显示较强的流体混合及成矿作用.Ⅱ号矿脉在流体稀土及微量元素含量上显示与Ⅳ脉更为相似.萨瓦亚尔顿金矿稀土微量元素研究表明围岩组分可能为成矿流体主要来源之一,而流体混合则为成矿重要机制,这与前期流体包裹体及同位素研究结论一致,也符合造山型金矿的一般特征.     

Chronology and tectonic significance of Cenozoic faults in the Liupanshan Arcuate Tectonic Belt at the northeastern margin of the Qinghai–Tibet Plateau

The Liupanshan Arcuate Tectonic Belt (LATB) is located at the northeastern margin of the Qinghai–Tibet Plateau. Major strike-slip and thrust faults in the Liupanshan area are prominent Cenozoic structures, which are critical in understanding and reconstructing the tectonic deformation history. This paper not only provides detailed investigations on geometric and kinematic characteristics of these faults in the LATB, but also dates the faults’ movements by electron spin resonance (ESR). The LATB underwent a succession of compression, extension and again compression tectonic deformation processes since the Cenozoic. The Liupanshan Curved Faults first experienced sinistral strike-slip shear during 57–61 Ma. The Liupanshan Curved Faults responded to the deformation caused by the eastward escape of the Qinghai–Tibet Plateau and acted as the northeastern boundary of the deformation. Timing for the formation of the Liupanshan Curved Faults shows that the collision of the Indian and Eurasian plates must have occurred earlier than these faults’ activity because the latter is reflected the far-field effect of the collision.     

http://www.sciencedirect.com/science/article/pii/S1674987112001478

REE composition of the carbonates of the auriferous quartz carbonate veins (QCVs) of the Neoarchean Ajjanahalli gold deposit, Chitradurga schist belt, Dharwar Craton, is characterized by U-shaped chondrite normalized REE patterns with both LREE and HREE enrichment and a distinct positive Eu anomaly. As positive Eu anomaly is associated with low oxygen fugacity, we propose that the auriferous fluids responsible for gold mineralization at Ajjanahalli could be from an oxygen depleted fluid. The observed positive Eu anomaly is interpreted to suggest the derivation of the auriferous fluids from a mantle reservoir. The location of Ajjanahalli gold deposit in a crustal scale shear zone is consistent with this interpretation.     

“丝绸之路经济带”中国段城市潜力的空间格局分异

采用均方差赋权法及模糊隶属度函数方法求解"丝绸之路经济带"中国段城市潜力指数,进而分析了地级城市潜力、县级城市潜力的空间格局分异。结果表明:(1)"丝绸之路经济带"中国段城市潜力整体水平偏低,东部、中部、西部存在明显的差距;(2)"丝绸之路经济带"中国段城市潜力水平呈现由中心城市向四周递减的分布规律;(3)"丝绸之路经济带"中国段城市社会发展水平与城市创新水平制约着城市潜力水平的提升,其中后者的制约因素更为显著,因此,加大城市创新投入是提高城市潜力水平的一种有效途径。     

Simulation and prediction of multi-scenario evolution of ecological space based on FLUS model: A case study of the Yangtze River Economic Belt,China

Journal of Geographical Sciences - Building the Yangtze River Economic Belt (YREB) is one of China’s three national development policies in the new era. The ecological environment of the...     

Diachronic metamorphic and structural evolution of the Connecticut Valley–Gaspé trough,Northern Appalachians

The Connecticut Valley–Gaspé (CVG) trough represents a major, orogen-scale Silurian–Devonian basin of the Northern Appalachians. From Gaspé Peninsula to southern New England, the CVG trough has experienced a contrasting metamorphic and structural evolution during the Acadian orogeny. Along its strike, the CVG trough is characterized by increasing strain and polyphase structures, and by variations in the intensity of regional metamorphism and contrasting abundance of c. 390–370 Ma granitic intrusions. In southern Quebec and northern Vermont, a series of NW–SE transects across the CVG trough have been studied in order to better understand these along-strike variations. Detailed structural analyses, combined with phase equilibria modelling, Raman spectrometry, and muscovite ⁴⁰Ar/³⁹Ar dating highlight a progressive and incremental deformation involving south–north variation in the timing of metamorphism. Deformation evolves from a D₁ crustal thickening event which originates in Vermont and progresses to southern Québec where it peaked at 0.6 GPa/380°C at c. 375 Ma. This was followed by a D₂ event associated with continuous burial in Vermont from 378 to 355 Ma, which produced peak metamorphic conditions of 0.85 GPa/380°C and exhumation in Quebec from 368 to 360 Ma. The D₃ compressional exhumation event also evolved from south to north from 345 to 335 Ma. D₁ to D₃ deformation events form part of a continuum with an along-strike propagation rate of ~50 km/Ma During D₁, the burial depth varied by more than 15 km between southern Quebec and Vermont, and this can be attributed to the occurrence of a major crustal indenter, the Bronson Hill Arc massif, in the New England segment of the Acadian collision zone.     

“一带一路”沿线国家科研合作网络的多元结构及形成机制

科技合作是"一带一路"倡议"民心相通"的重要组成部分,2013年以来取得显著进展。以"一带一路"沿线65国为研究区,运用WOS核心集合论文合作数据构建国家间科研合作矩阵,通过GIS空间分析、社会网络分析以及负二项回归分析法,探究沿线各国2013年和2018年科研合作网络的多元化结构及形成机制,结果表明:①在全球尺度,"一带一路"沿线各国与其他国家之间的知识流动日趋频繁,但内部合作紧密程度不及与沿线以外地区的合作程度。沿线区域对全球的科研合作网络由欧洲、美国和中国"三足鼎立"骨架结构向欧洲、美国、中国、加拿大、日本、澳大利亚等多个密集区构成的"多边形"骨架结构转变。②"一带一路"沿线地区的合作网络的空间结构,由中国、中东欧区组成的"双核发散"向"一区多点"构成的"多极化"空间结构转变;等级结构则呈现典型的"中心-外围"等级层次结构,且由单核心向双核心转变;控制结构呈现出由"单核心"向四周高、中间低的"多超多强"盆地型控制结构转变。③沿线国家的科研实力、经济发展水平、对外开放度等国家主体属性以及地理邻近性、社会邻近性等是沿线科研合作网络形成的主要机制,其中科研实力、社会邻近性的作用最大,地理距离对科研合作的阻碍作用逐渐减弱。     

Stratigraphy of the mid‐ to upper‐Cretaceous System in the Aridagawa area,Wakayama, Southwest Japan

The litho‐ and biostratigraphy of the mid‐ to upper‐Cretaceous System around the Yagumaike Pond in the Aridagawa area, Wakayama, Southwest Japan, were investigated. Many Middle to Late Albian megafossils were found in the strata of a block bounded by faults. It was also revealed that the Upper Cretaceous System of other blocks ranges from the Middle Turonian to Santonian. The Albian megafossil assemblage contains few benthic organisms, in contrast with the abundance of nektons found (e.g. cephalopods). Sedimentological observations of the mudstone profiles also indicate that scarcely or weakly bioturbated, well‐laminated mudstone is dominant among the Albian deposits. These results suggest deposition of the Albian mudstone under a dysaerobic to anoxic environment. It is comparable to the extended oceanic anoxia (OAEs) in mid‐Cretaceous time. Albian deposits with similar characteristics are also known to exist in Shikoku, Southwest Japan. A wide sedimentary basin that was directly affected by global environmental events, such as OAEs, seemed to be formed on the Chichibu Belt in the Albian. The Upper Cretaceous strata in the study area are extremely thin, similar to the coeval deposits on the Chichibu Belt in Shikoku. It is suggested that the sedimentation rate in the sedimentary basin on the Chichibu Belt was extremely low during early Late Cretaceous time.     

蒙古气旋引发辽宁沙尘暴天气过程的数值模拟

从一次发生在辽宁,由蒙古气旋引发的沙尘暴过程入手,利用数值模拟手段,结合常规气象观测资料,围绕蒙古气旋的动力、热力特征以及如何促成此次沙尘暴的发生、发展和维持进行探讨。结果表明,高空气流的辐散抽吸是此次过程的主要起沙动力机制,由蒙古国中部向东南方向延伸至韩国南部的副热带西风急流为此次辽宁沙尘暴过程提供了充足的沙源。此外,蒙古气旋内部的垂直环流与控制辽宁地区的冷平流对此次沙尘暴和降温过程具有一定的触发与维持作用。     

Early Devonian Post-collisional Granitic Magmatism in the North Qilian Orogenic Belt, Western China: Insights into Lithospheric Delamination and Orogenic Collapse

Post-collisional magmatism contains important clues for understanding the reworking and growth of continental crust, as well as lithospheric delamination and orogenic collapse. Early Devonian magmatism has been identified in the North Qilian Orogenic Belt (NQOB). This paper reports an integrated study of petrology, whole-rock geochemistry, Sm-Nd isotope and zircon U-Pb dating, as well as Lu-Hf isotopic data, for two Early Devonian intrusive plutons. The Yongchang and Chijin granites yield zircon U-Pb ages of 394–407 Ma and 414 Ma, respectively. Both of them are characterized by weakly peraluminous to metaluminous without typical aluminium-rich minerals, LREE-enriched patterns with negative Eu anomalies and a negative correlation between P2O5 and SiO2 contents, consistent with geochemical features of I-type granitoids. Zircons from the studied granites display negative to weak positive εHf(t) values (?5.7 to 2.1), which agree well with those of negative εNd(t) values (?6.4 to ?2.9) for the whole-rock samples, indicating that they were derived from the partial melting of Mesoproterozoic crust. Furthermore, low Sr/Y ratios (1.13–21.28) and high zircon saturation temperatures (745°C to 839°C, with the majority being >800°C) demonstrated a relatively shallow depth level below the garnet stability field and an additional heat source. Taken together, the Early Devonian granitic magmatism could have been produced by the partial melting of ancient crustal materials heated by mantle-derived magmas at high-temperature and low-pressure conditions during post-collisional extensional collapse. The data obtained in this study, when viewed in conjunction with previous studies, provides more information about the tectonic processes that followed the closure of the North Qilian Ocean. The tectonic transition from continental collision to post-collisional delamination could be constrained to ~430 Ma, which is provided by the sudden decrease of Sr/Y and La/Yb ratios and an increase in zircon εHf(t) values for granitoids. A two-stage tectonic evolution model from continental collision to post-collisional extensional collapse for the NQOB includes (a) continental collision and crustal thickening during ca. 455–430 Ma, characterized by granulite-facies metamorphism and widespread low-Mg adakitic magmatism; (b) post-collisional delamination of thickened continental crust and extensional collapse of orogen during ca. 430–390 Ma, provided by coeval high-Mg adakitic magmatism, A-type granites and I-type granitoids with low Sr-Y ratios.