新疆包古图斑岩铜矿磁黄铁矿和毒砂成因及其成矿指示意义

新疆准噶尔盆地西缘包古图斑岩铜矿是中亚成矿域内首例确认的还原性斑岩铜矿,具有区别于氧化性斑岩铜矿的矿物学特征。包古图斑岩铜矿的成矿闪长岩发育钾硅酸盐蚀变和绢英岩化蚀变及少量青磐岩化蚀变,铜矿化主要集中在钾硅酸盐蚀变阶段和绢英岩化蚀变阶段。钾硅酸盐蚀变和绢英岩化蚀变两阶段发育不同的金属矿物共生组合：前者发育磁黄铁矿,具有黄铜矿+辉钼矿+黄铁矿+磁黄铁矿+钛铁矿+闪锌矿±毒砂组合,黄铁矿主要呈细粒—粗粒五角十二面体,富集Cu而亏损As;后者发育毒砂和碲铋矿物,出现与毒砂共结晶的碲化铋以及不含其他硫化物的独立毒砂脉体,具有辉钼矿+黄铜矿+黄铁矿+毒砂+闪锌矿±碲铋矿物组合,黄铁矿主要呈粗粒立方体,黄铁矿和毒砂中均富集Au+Ag+Te+Bi。钾硅酸盐蚀变和绢英岩化蚀变阶段的硫化物具有不同的组成、结构和成分,反映了绢英岩化蚀变阶段As—Au—Ag—Te—Bi矿化和钾硅酸盐蚀变阶段Cu—Mo—Au—Ag矿化叠加的关系。利用磁黄铁矿和毒砂成分反演了其形成温度和硫逸度,钾化蚀变阶段的温度和硫逸度分别为267~600℃和-1.5~-9.5;绢英岩化蚀变阶段的温度和硫逸度分别为209~325℃和-15.8~-9.7,同时构建了不同阶段的矿物组合相图,结果显示磁黄铁矿的形成和早期低氧逸度流体相关,毒砂的形成与流体温度降低和硫逸度降低相关。同时推断在早阶段Cu—Mo—Au—Ag矿化期和晚阶段As—Au—Ag—Te—Bi矿化期,由于温度和硫逸度存在差异,Cu和As经历了不同的反应沉淀过程。     

Formation of the Permian Taipinggou igneous rocks,north of Luobei (Northeast China): implications for the subduction of the Mudanjiang Ocean beneath the Bureya–Jiamusi Massif

Controversy has long surrounded the tectonic framework and evolution of the Mudanjiang Ocean between the Bureya–Jiamusi–Khanka Massif and Songnen–Zhangguangcai Range Massif, which are located in the easternmost segment of the Central Asian Orogenic Belt. To address these issues, we present zircon U-Pb ages, geochemical data, and zircon Hf isotopic compositions of the Taipinggou amphibolite and metagabbro exposed along the boundary area of Bureya–Jiamusi Massif and Songnen–Zhangguangcai Range Massif. Magmatic zircons from the amphibolite and metagabbro yield ²⁰⁶Pb/²³⁸U ages of 267 ± 2 Ma and 264 ± 2 Ma, respectively, which are interpreted as protolith ages. The geochemical data of the amphibolite samples show transitional characteristics of calcalkaline to tholeiitic series, with high MgO concentrations (9.44–10.48 wt.%) and Mg-numbers (73–75). These samples are enriched in large ion lithophile elements (e.g. Rb, Ba, and K) and light rare earth elements and are depleted in high-field-strength elements (e.g. Nb, Ta, and Ti) and heavy rare earth elements, with εHf(t) values of ?6.63 to ?3.26. It is inferred that the parental magma originated from an enriched lithospheric mantle that had been metasomatized by fluids derived from subducted oceanic slab. During magma evolution, the magma that formed the amphibolite mainly experienced accumulation with a shallow-level evolutionary process involving fractional crystallization. The Taipinggou metagabbro samples are subalkaline series and also characterized by enrichment in large ion lithophile elements (e.g. Rb, Ba, and K) and light rare earth elements and by depletion in Nb–Ta–P–Ti, with εHf(t) values of ?3.09 to +1.16. The Taipinggou metagabbro and amphibolite have similar geochemical and Hf isotopic compositions, indicating a common parental magma source but with different degrees of magmatic differentiation. Based on the new geochronological and geochemical data presented in this study, we propose that both the Taipinggou metagabbro and amphibolite formed in a Middle Permian continental arc setting, closely related to eastward subduction beneath the Bureya–Jiamusi Massif. Combined with previous studies and regional geological observations, we suggest that a double-side subduction model is favoured for the Late Palaeozoic–Early Mesozoic geodynamic processes along the boundary area of Bureya–Jiamusi–Khanka Massif and Songnen–Zhangguangcai Range Massif.     

Late Cretaceous basalts and rhyolites from Shimaoshan Group in eastern Fujian Province,SE China: age,petrogenesis, and tectonic implications

ABSTRACT

Southeastern China is characterized by an extensive Late Mesozoic (Yanshanian) tectono-magmatic-metallogenic event. Although Late Cretaceous volcanism gradually weakened during the epilogue of the Yanshanian event, its petrogenesis and geodynamic processes remain unclear. In this study, we present new zircon U–Pb–Hf isotopic, whole-rock elemental, and Sr–Nd isotopic compositions data, for volcanic rocks from the Zhaixia Formation of the Shimaoshan Group in Fujian Province. The lower member of the Zhaixia Formation consists of basalts and rhyolites, and the upper member is only rhyolites. These volcanic rocks erupted in the early stage of Late Cretaceous, with basalts erupting earlier (ca. 99–98 Ma) than rhyolites (ca. 98–94 Ma). These basalts record high-K calc-alkaline to shoshonitic, light rare earth element (LREE)- and LILE-enrichment, high field strength element (HFSE)depletion with negligible Eu anomalies, and uniform whole-rock ε_Nd(t) (–3 to –6) and zircon ε_Hf(t) (–3.3 to –14.1) values. The overlying rhyolites record peraluminous and high-K calc-alkaline characteristics, LREE- and LILE-enrichment with negative Eu anomalies, and Nb–Ta depletion. The whole-rock ε_Nd(t) and zircon ε_Hf(t) values of these rhyolites both increase from the lower member (ε_Nd(t), –1.5 to –4.7; ε_Hf(t), –5.1 to –16.1) to the upper member (ε_Nd(t), –0.5 to 0.1; ε_Hf(t), –0.3 to –4.3). The features imply that these basalts were derived from the partial melting of the enriched lithospheric mantle and the overlying rhyolites from the melting of the crustal components, respectively. Data from the rhyolites in the upper member indicate that more juvenile, Nd–Hf isotopically depleted materials were injected into their source. During the Late Cretaceous, the new, fast rollback of the subducting slab triggered lithospheric extension and asthenospheric upwelling beneath the coastal regions, which induced the melting of lithospheric mantle and crustal components. As continued, the new round of basaltic underplating provided necessary heat to cause partial melting of the deep crust, including the younger, juvenile, and isotopically depleted crustal components.     

西准噶尔巴音达拉地区卡拉岗组火山岩锆石U-Pb年代学、地球化学及其地质意义

西准噶尔巴音达拉地区发育一套酸性火山岩,被称为卡拉岗组,岩石组合以流纹岩、英安岩、流纹质熔结凝灰岩等酸性火山岩为主。本文对卡拉岗组火山岩进行高精度锆石LA-ICP-MS U-Pb测年,获得英安岩和流纹岩的加权平均²⁰⁶Pb/²³⁸U年龄分别为（294.4±1.3）Ma（n=9,MSWD=0.8）和（298.4±2.5）Ma（n=9,MSWD=3.4）,其形成于早二叠世。岩石地球化学特征表明,卡拉岗组火山岩岩具有高硅（66.69%~75.21%）,富碱（Na₂O+K₂O：6.98%~8.35%）,低MgO（0.18%~1.32%）,贫钙（0.24%~2.49%）的特征,均属过铝质（A/CNK：1.14~1.33）及高钾钙碱性系列。微量元素数据显示,稀土总量为∑REE为83.82×10^-6~197.61×10^-6,（La/Yb）_N=3.15~12.50,轻、重稀土元素分馏比较明显,轻稀土元素（LREE）较为富集,重稀土元素分布相对平坦,球粒陨石标准化配分模式为右倾型。微量元素富集大离子亲石元素（LILE）Rb、Th、U、K,并亏损高场强元素（HFSE）_Nb、Ta、P、Ti。综合最新区域资料及本文研究成果,文章认为研究区早二叠世卡拉岗组火山岩岩浆来源于壳源物质不同程度的部分熔融,残留相中有少量斜长石和角闪石,为后碰撞伸展阶段的产物。     

The effects of aquifer heterogeneity on the 3D numerical simulation of soil and groundwater contamination at a chlor-alkali site in China

The simulation of groundwater flow and solute transport at contaminated sites often neglects the important influence that aquifer heterogeneity can have on the sub-surface distribution of contaminants. In this paper, the method of transition probability for geological statistics (T-PROGS) included in the Groundwater Model System (GMS) was applied to a chlor-alkali-contaminated site that was sampled with 68 soil borings and 15 groundwater monitoring wells. A 3-D groundwater numerical model and solute transport model was developed that was constrained by soil and groundwater data from the site. The spatial distribution of chloroethylene concentrations was simulated for a number of times using the levels measured in the field as a baseline. The results of these simulations showed that shapes and distribution of contaminant plumes are irregular both vertically and horizontally. The solute-transport simulations indicated that much of the contamination will preferentially move in groundwater through silt and fine-sands whereas flow is largely blocked in clays. Consequently, fine sand and silts become the most seriously polluted zones at the site, whereas, areas underlain by clays are largely uncontaminated. Heterogeneous lithologies beneath a site increase the complexity of coupling simulations of soil and groundwater.     

Improvements on the particle-filter-based GLONASS phase inter-frequency bias estimation approach

The carrier phase inter-frequency bias (IFB) of GLONASS between receivers of different types is usually not zero. This bias must be estimated and removed in data processing so that the integer double difference (DD) ambiguities can be fixed successfully. Recently, the particle filter approach has been proposed to estimate the IFB rate in real time. In this approach, the IFB rate samples are first generated and used to correct the phase IFB in the GLONASS observations. Then, the weights of the rate samples are updated with a function related to RATIO which is for ambiguity acceptance testing in integer ambiguity resolution. Afterwards, the IFB rate is estimated according to the weighted particles. This approach can estimate IFB accurately with short convergence time and without prior information. However, when the system noise is set too low, the estimated results are unstable due to the serious problem of particle diversity-loss, even though the system model is accurate. Additionally, the computational burden is dependent on the number of particles, which has to be optimized for the computation at hand. Therefore, this study proposes two improvements for the IFB estimation in regard to the above two aspects. The first improvement is to solve the noise setting problem by employing a regularized particle filter (RPF). The second improvement optimizes the number of particles in the resampling step according to the standard deviation (STD) of the weighted particles via a controlling function. The two improvements result in significantly better performances. The regularization method allows for the system noise to be set as zero without disturbing the estimates, and consequently, more precise estimates can be achieved. In addition, the approach using the controlling function for adapting the number of particles has comparable performance in precision but the computation load is largely reduced.     

过去2000年亚洲气候变化(PAGES-Asia2k)集成研究进展及展望

介绍了国际过去全球变化研究计划(PAGES)过去2000年气候变化研究网络的设立背景、研究目的及亚洲在其中的独特性;总结了过去2000年亚洲气候变化(PAGES-Asia2k)集成研究的主要进展及中国的贡献,分析了当前在亚洲区域开展该项研究的主要问题及难点,并对未来研究进行了展望。亚洲历史悠久,高分辨率的代用资料丰富,是开展过去2000年气候变化研究的理想区域,但目前尚处于起步阶段。已有进展表明:在过去1200年中,亚洲830-1220年相对温暖,1340-1880年明显寒冷,20世纪则快速增暖;但亚洲气候类型多、变化过程复杂、区域差异大。因此,发展气候序列重建的新技术方法,提高重建序列的时、空分辨率、空间覆盖度和重建结果的精度,建立亚洲过去2000年气候代用资料数据库,集成重建过去2000年区域温度变化序列及干湿变化空间型,进而开展区域气候变化驱动机制与气候变化影响及适应研究,是该计划下一步的研究重点。     

Geochemical characteristics and depositional environment of the Middle Permian mudstones from central Qiangtang Basin,northern Tibet

Geochemical characteristics of the Middle Permian mudstones from the Longge Formation in the Jiaomuri area, central uplift zone of Qiangtang Basin have been analysed to constrain their provenance, tectonic setting, depositional redox condition and palaeoclimate. Based on the geochemical parameters like CIA, PIA, ICV values and Th/U, K/Rb ratios indicate that the source rocks were affected by low degree weathering conditions. The U/Th, V/Cr, Ni/Co, V/Sc ratios and U_au, C‐values of samples suggest that the mudstones were formed in an oxic environment, with arid palaeoclimate. Bulk‐rock geochemistry analysis indicates that they are mainly arkose and subarkose, derived from dominantly andesitic rocks, probably a mixing of felsic and mafic provenance. The CIA, PIA and ICV values of these samples suggest that the Longge mudstones are compositionally immature and related to moderate weathering. The tectonic discrimination diagrams, as well as critical trace and REE characteristic parameters imply an oceanic arc or continental arc setting for the depositional basin of mudstones from the Longge Formation, probably back‐arc basin. This study supports an occurrence of archipelagic oceanic basins in the Jiaomuri area in the Middle Permian, which provides evidence for the research of the Longmu Co–Shuanghu–Lancangjiang Suture. Copyright © 2015 John Wiley & Sons, Ltd.     

攀枝花钒钛磁铁矿深部成矿潜力及找矿方向的航磁资料研究

攀枝花钒钛磁铁产出于侵入震旦系大理岩中的海西期辉长岩体,受断裂切割为朱家包包、兰家火山、尖包包、倒马坎等6个区段,累计探明铁矿石储量(A+B+C+D)67.29亿t,是我国重要的矿集区,重要矿段均开展了钻探工作。在航磁异常分析中,攀枝花航磁异常的原因没有得到完全的解释,说明还有一定的找矿潜力。本文以1∶5万航磁数据交互式反演为基础,部分由已完成的由钻孔控制的实测地质剖面资料为约束,结合物性参数和地质信息,对矿体空间分布进行反演,利用10条2.5D反演剖面模拟3D模型,估计了该矿区的深部成矿潜力,为下一步地质勘探提供依据。     

Emergency countermeasures against marine disasters in Qingdao City on the basis of scenario analysis

Storm surge, sea wave, sea ice, red tide and harmful marine creature bloom are main marine disasters occurring in the coast and offshore areas of Qingdao City, Shandong Province, China. Marine disasters mentioned above can be divided into five categories, namely, marine meteorological disasters, marine hydrological disasters, marine geological disasters, marine ecological disasters and man-made marine disasters. Over the past century, the marine disasters in the coast and offshore areas of Qingdao City have caused great economic losses and casualties. In recent years, some problems still exist in emergency management against marine disasters in Qingdao City, such as inaccurate predictions of disasters, untimely early warning and lack of social participation in the emergency management. On the basis of scenario analysis, the authors try to predict different possible scenarios of marine disasters at different early warning levels and propose some optimized emergency countermeasures against marine disaster in Qingdao City. Results of our research can provide a theoretical basis for the revision and improvement of emergency plans and thus guarantee timely and effective emergency management actions against marine disasters in Qingdao City.