Petrology, Geochemistry and Zircon U-Pb Geochronology of the Xiangshan Group in the Eastern Hexi Corridor Belt: Implications for Provenance and Tectonic Evolution

The eastern Hexi Corridor Belt（HCB） is located in the transitional belt among the Alxa Block,the Qilian Orogenic Belt and the North China Block. Because of its unique tectonic location, the tectonic setting, provenance, and even the age of the sedimentary strata in the eastern HCB during the Early Paleozoic remain controversial. This study analyzes the provenance of the poorly studied Xiangshan Group, discusses its age of development and tectonic setting in the eastern HCB using a combination of petrological, geochemical and LA-ICP-MS U-Pb zircon dating methods. Based on the youngest age peaks and the fossil evidence, we suggest that the Xiangshan Group is Middle Cambrian to Late Ordovician in age. The complexity of the geochemical characteristics and associated diagrams suggests that the early stage of the Xiangshan Group developed in a passive continental margin environment, late in the backarc basin of the eastern HCB. Based on the sandstone detrital composition, whole-rock geochemistry and detrital zircon ages, we conclude that the Xiangshan Group had an early provenance that was mainly from the Qilian Block and a late provenance from the Qilian Block and the western Alxa Block. The eastern HCB and its northern and southern blocks have similar palaeontology, lithology and basement age characteristics to the South China Block. This indicates that the eastern HCB might not have formed in the intra-continental aulacogen of the North China Block during the Early Paleozoic but has a close affinity to eastern Gondwana.

Timing of Metamorphism and Provenance of the Metamorphic Basement of the Xiangshan Uranium Orefield, Jiangxi Province, China

The origin, age and evolution of the Precambrian metamorphic basement of southern China provide useful insights into early crustal development. Here, we present new laser ablation-inductively coupled plasma-mass spectrometry （LA-ICP-MS） U-Pb age data for detrital zircons from five samples of the Precambrian metamorphic basement of the Xiangshan uranium orefield. Two of these samples, from the northern Xiangshan volcanic basin, yielded a total of 140 U-Pb ages that cluster within the Neoproterozoic （773-963 Ma; 79.3% of data points）, with the rest being scattered through the Paleoproterozoic and Mesoproterozoic, along with a single Archean age. These ages indicate that this basement material is associated with the Cathaysia Block. In comparison, the 172 concordant ages from the other three samples from the southern part of the Xiangshan volcanic basin cluster within the Neoproterozoic （767-944 Ma; 59.8%） as well as the Proterozoic （37.8%） and the Archean （2502-2712 Ma; 14.5%）. These samples are also free of zircons with Grenvillian ages, indicating that these units are associated with the southeastern Yangtze Block. Combining these data with the geochemistry of these units, which suggests that the metamorphosed sedimentary rocks within the northern and southern parts of the Xiangshan basin have a common component from a magmatic island arc that formed during the early Neoproterozoic, we infer that the basin was located along the boundary between the Cathaysian and Yangtze blocks. In addition, the zircons within the samples from the southern and northern parts of the Xiangshan basin show different pre-Neoproterozoic （963 Ma） age populations but similar post- Neoproterozoic zircon populations, indicating that the amalgamation of the Cathaysian and Yangtze blocks occurred after the Neoproterozoic （960 Ma）, with magmatism peaking at 830 Ma and rifting starting at -770 Ma, leading to the subsequent deposition （from bottom to top） of the Shenshan, Kuli, and Shangshi formations.

A numerical study on the effect of tidal flat's slope on tidal dynamics in the Xiangshan Bay, China

The Xiangshan Bay is a semi-enclosed and narrow bay, which is characterized by large scale tidal flats and has been historically utilized through coastal construction and aquaculture engineering. The hydrodynamic model using the Finite Volume Coastal Ocean Model（FVCOM） was constructed to examine the changes of tidal dynamics due to the variation of tidal flat slopes. According to the model results, a decreased slope of a tidal flat would amplify the M2 tidal amplitude and delay the M2 tidal phase in the inner harbor, due to an increased tidal prism, and vice versa. The amplitude of the main shallow-water tide M4 would be amplified/dampened in the entire bay due to the changed bottom friction, if the tidal flat＇s slope were reduced/increased at the Tie inlet. The phase was advanced. The change of a tidal flat＇s slope at the Tie inlet had greater impacts on tidal amplitude,phase and duration asymmetry, than that at the Xihu inlet. The impact of changes of the tidal flat slope at the Xihu inlet was small and was constrained locally. Changes in the tidal flats＇ slopes at the Tie and Xihu inlets changed the tidal duration asymmetry, residual current and tidal energy via modulating tides. The ebb dominance decreased when the tidal flat＇s slope at the Tie inlet was changed. Decreased/increased ebb dominance occurred when the tidal flat＇s slope was reduced/increased at the Xihu inlet. The residual current and tidal energy density was amplified/dampened and more/less tidal energy was dissipated, with reduced/increased slope at both of the inlets. The findings in this study are instructive to coastal engineering and estuarine management.

Geochronology and Tectonic Implications of Diabase Intruded Into Xiangshan Group in the Southeastern Alxa Block, NW China

The southeastern Alxa Block(i.e.,the Hexi Corridor)is a tectonic junction between the North China Block(NCB)to the east,the Alxa Block to the north,and the western Qinling–North Qilian Orogenic Belt to the southwest(Fig.1).The southeastern Alxa Block had undergone

Standing stock of phytoplankton and primary productivity in Penaeus orientalis larval multiplication releasing area of the Xiangshan Bay

The standing stock of phytoplankton (phy. ) and primary productivity (pp) in the Xiangshan Bay were observed in 1992. The results showed higher biological parameters in the bay. The average chlorophyll a (chl a) concentration was (3. 50 5. 93 ) mg/m3 and the primary productivity (444. 5 871. 0) mg/(m2 d). The distribution of chl a and productivity showed distinct spatial and temporal patterns in the bay. The continent influence was Obvious at the top of the bay, lower seawater exchange and higher stability led to higher standing stock of phytoplankton and productivity. At the bay mouth, seawater exchanged continuously with adjacent waters by rapid currents, resulting in fast and unstable exchange and lower standing stock of phytoplankton and primary productivity. The seasonal characters of those parameters were pronounced, in the sequence of spring, summer, autumn and winter. The results of size--fractionated showed that the average contribution of the nano--and picoplankton (< 20pm) to total chl a and productivity were 75 % and 87%, respectively, indicating their importance in phytoplankton community biomass and productivity of the Xiangshan Bay.

Where are the Volcanic Calderas in the Xiangshan Volcanic Basin of Jiangxi？ Implications from Anisotropy of Magnetic Susceptibility

Objective As the world＇s third largest volcanic type uranium ore field,the Xiangshan volcanic basin has attracted much attention for its large industrial value.The ore hosting rocks are mainly the early Cretaceous rhyodacite and porphyroclastic lava,as well as small amounts of high level intrusive acidic rocks and metamorphic rocks.

Analysis on Protection of GI Product Xiangshan Spirit and Suggestions of Its Industrial Supervision

From name, historic stories, reputation, traffic and location factors, and natural factors as production and processing, water, raw material and yeast, this paper firstly analyzes key factors for protection of GI product Xiangshan Spirit. Then, it discusses differences in quality characteristics between Xiangshan Spirit and other rice flavor type spirits. Besides, industrial development of Xiangshan Spirit is analyzed from residues of pesticides, quality of water for making wine, and exclusive use of geographical indication Xiangshan Spirit. Finally, it puts forward following suggestions, including formulating and implementing local standard GI Product Xiangshan Spirit, strengthening quality control over rice raw material, implementing "enterprise + base" industrial model, and support group enterprises with government as leader.

Geochemistry,geochronology,and zircon Hf isotopic compositions of felsite porphyry in Xiangshan uranium orefield and its geological implication

Recently,a new kind of volcanic rock,felsite porphyry,has been revealed by drilling in Xiangshan area,Jiangxi Province,China.To better understand petrogenesis and magmatic evolution sequence of the Xiangshan volcanic-intrusive complex,we studied systematic petrology,geochemistry,LA-ICP-MS zircon U–Pb dating,and Hf isotope results of the felsite porphyry.Results show that the felsite porphyry has similar geochemical characteristics to the porphyroclastic rhyolite,which is the predominant lithology of Xiangshan uranium orefield.Felsite porphyry and porphyroclastic rhyolite have high SiO2,Al2O3,and K2O contents,low Na2O,and MgO contents,and slightly negative Eu anomalies.Moreover,these rocks are relatively depleted in large ion lithophile elements(K,Ba,and Sr)and are enriched in high field strength elements(Th,Zr,and Hf).LA-ICP-MS zircon U–Pb dating of the felsite porphyry yielded a crystallization age of 132.2±0.9 Ma,which is coeval to that of the porphyroclastic rhyolite.These ages signified that Xiangshan volcanic-intrusive complex formed in the Early Cretaceous,during which the entire South China was in the back-arc extension tectonic setting related to the subduction of the Pacific Plate under the Euroasian Plate.In-situ zircon Hf isotope data on a felsite porphyry sample show eHf(t)values from-8.82 to-5.11,while the Hf isotope two-stage model age(TDM2-Hf)ranges from 1513 to 1747 Ma.Combined with petrological,mineralogical,geochemistry,and geochronology results of the felsite porphyry,it is concluded that the felsite porphyry in Xiangshan might be originated from the partial melting of the Mesoproterozoic ancient metamorphic rocks,with possible input of small amounts of mantle materials.

Tide-induced Lagrangian residual velocity and dynamic analysis based on field observations in the inner Xiangshan Bay,China

In the Xiangshan Bay at the east coast of China,coastal marine pollution is conspicuous and severe in recent years.As transport of the pollutants is closely related to the coastal circulation,there is a great practical significance to investigate the circulation in this area.In this work,the surface pattern and vertical profiles of Lagrangian residual velocity(LRV)were studied based on field observation data from the inner Xiangshan Bay.By tracking GPS-GPRS drifters’trajectories,the surface LRV pattern is going out in the central deep trough and flowing inwards near the shoreside.Combined with data from two mooring stations,vertical profiles of LRV is flowing out at surface and flowing in at the bottom,consistent with the gravitational circulation induced by baroclinic effects at the estuary.However,according to the diagnostic analysis,the main mechanism driving the residual current is barotropic rather than baroclinic.The LRV equation is controlled by the tidally-averaged barotropic pressure gradient force,tidal body force and tidally-averaged turbulent stress,while the tidallyaveraged baroclinic pressure gradient force is one order of magnitude less than other forces.Additionally,the tidally mean eddy viscosity coefficient which is used in the expression of tidally-averaged turbulent stress might be not adequate and requires further studies.

A Comprehensive Lagrangian Transport Study in A Long-Narrow Bay,Xiangshan Bay,China

Study on the transport and mixing in coastal waters is of great concern to the ocean resources exploitation and ecological system protection.Lagrangian methods are direct and effective of researching mass transport.Two Lagrangian tools were adopted and combined to describe water transport in a long-narrow bay,Xiangshan Bay,China.Based on the fields of tidal velocity simulated from the 3-D hydrodynamic model,Lagrangian Coherent Structures(LCSs)and synoptic Lagrangian maps(SLMs)were calculated in the study area.Through comparison of the results,the features and relation of the two tools were discussed.The results show that the LCSs act as the separatrix of the water regions with different transport characteristics and can identify the water areas with different transport time scales.The comprehensive application of the Lagrangian tools is helpful to obtain more insight into the water transport process.

Detecting and assessing Spartina invasion in coastal region of China： A case study in the Xiangshan Bay

Spartina alterniflora is one of exotic plants along the coastal region in China. It was introduced as an important engineering approach to ecological restoration in the later 1970 s. However, owing to its good adaptability and strong reproductive capacity, the introduced species is explosively spreading along the coastal region quickly and resulting in a significant impact on the health and safety of coastal wetland ecosystems. It is imperative to quantify the spatial extent and the rate of S. alterniflora sprawl in order to assess its ecological damages and economic impacts. Remote sensing techniques have been used to address these challenges but large unsuccessful due to mixed spectral properties. In this study, a hybrid method was proposed for S. alterniflora detection using medium resolution remote sensing images by integrating both spatial and spectral features of S. alterniflora. The hybrid method consists of two phases：（1） delineation of intertidal zone as the potential area of S. alterniflora distribution and（2） extraction of S. alterniflora fraction distribution with a mixture pixel analysis. The proposed method was tested at the Xiangshan Bay on the east coastal region of Zhejiang Province, China, and mapped the spatial extent of S. alterniflora with Landsat datasets in the 2003, 2009 and 2014. The results showed that, the S. alterniflora has grown exponentially over past 10 years. In 2003, the total area of S. alterniflora was about 590 hm2, but quickly reached to 1 745 hm2 in 2009, and 5 715 hm2 in 2014. With a rate of approximately 10-folds growth within a decade, the invasive species almost occupied all muddy beaches to become the most dominant coastal salt vegetation in this region. It is believed that the strong biological reproductive capacity was the primary reason for such quick spread and at the same time human reclamation activities were also believed to have facilitated the environmental conditions for S. alterniflora sprawl.

MODELING OF THE PALEOGEOTHERMAL FIELD AND ANALYSIS OF THE HEAT SOURCE FOR THE XIANGSHAN URANIUM ORE-FORMING HYDROTHERMALSYSTEM, EAST CHINA

Through the finite-element modeling. a quantitative analysis of paleogeothermal evolution after the main volcanic eruption at Cretaceous period for the Xiangshan uranium ore-field. East China. has been presented. Researches reveal that the energy from the volcanic lava could affect the geothermal field for only three million years after their eruption. and could not provide heat for the Xiangshan uranium ore-foming hydrothermal system because the time gap between the volcanic activities and the uranium mineralizations is longer than 40 million years. The evidences show that the heat energy for the ore-forming system came from anomalously high paleogeothermal gradient in the study area during the mineralization period.

The Relationship between Wang Yangming and Lu Xiangshan in the Light of‘On Eradicating the Root and Source of Evil’

This paper,based on Mencius’s ideas,makes a comparative study of Wang Yangming and Lu Xiangshan in the light of Wang’s“On Eradicating the Root and Source of Evil.”Both Lu and Wang are loyal inheritors of Mencius’s ideas. e author discusses Wang’s inheritance and development of Lu’s theory focusing on two propositions:one is that the intuitive mind is obscured by ma terial desire,and the other,that utilitarian ideas penetrate the innermost mind.Though Wang’s“On Eradicating the Root and Source of Evil”is inspired by Lu,it moves forward to expand Lu’s viewpoints and thinking,and to restructure the framework of his theory.

Xiangshan Spirit Revisited and Emphasized

On March 25,1949,Mao Zedong(1893–1976)led the Central Committee of the Communist Party of China(CPC)to settle in Xiangshan,or Fragrant Hills,in the western suburb of Beiping(now Beijing).This made Xiangshan the headquarters of the CPC in leading China’s War of Liberation(1946–1949)to national victory.

象山矿井主采3^#煤层涌水规律及充水因素分析

为查清矿井的涌水机理,为矿井防治水提供依据,依据大量生产资料,采用相关分析及理论分析相结合的方法,总结了象山矿井及主采3#煤层采面涌水规律,分析了充水因素,开展了煤层顶板含水层充水危险性预测。结果表明,矿井涌水量随着开采条件的变化总体呈现增高的变化趋势,采面涌水量具有背斜区低,向斜区高,回采期间具有先小后大,再由大变小的规律;充水通道主要为采动产生的顶板导水裂隙,充水水源主要来自煤层顶板山西组底部(K4)砂岩含水层与下石盒子组底部砂岩含水层水,涌水量大小与采面所在构造部位、顶板上覆含水层的岩性厚度及煤产量大小有关。在考虑采煤工艺和开采强度相同、同一采区构造类型相同、充水含水层富水性平面差异不够明显及大气降水及地表径流补给不变的情况下,依据顶板导水裂隙带范围内上覆砂岩含水层的岩性与厚度大小对3#煤层顶板含水层充水危险性进行了预测。为避免回采过程顶板突然涌水,应在顶板含水层充水危险性严重区采取事先疏放水措施。

江西相山矿田深部多金属矿化特征

依据江西省相山矿田的深部钻探成果，结合近些年来矿田内零星发现的多金属矿化，确定相山深部埋藏有丰富的多金属矿产资源，成矿潜力深度超过2500m。将相山地区发现的多金属矿化分为两大类，一类为成矿深度相对较浅的铅锌矿，另一类为成矿深度较大的铜矿，认为相山地区的矿化是上铀中铅锌金下铜的成矿空间模式。研究发现铅锌矿主要与碳酸盐脉相伴生产出．铜矿化与硅化关系密切，利用电子探针和扫描电镜发现方铅矿内不均匀的分散有Ag元素，Au元素以均匀质点分散在方铅矿内，以晶格金的形式参与矿物晶格构架。通过分类研究矿化围岩、低品位矿石和高品位矿石各自的硫、铅同位素组成和计算硫同位素平衡温度．认为相山深部多金属成矿以中低温为主，同时局部存在明显的中高温成矿作用。判断成矿物质主要来自于周围的变质岩基底，同时混合部分地幔成矿物质，后期源于上地壳的多次热液改造作用对于Ph、Zn、Cu、Au等元素的富集成矿起到了决定性的作用。对比前人在德兴一遂川多金属矿集区的研究成果，发现相山地区多金属矿化在成矿物质来源上具有矿集区的普遍特征。但在成矿温度方面相山深部多金属成矿以低温为主（114℃-174℃），这与成矿带内以中温（200℃-340℃）为主的成矿作用有较明显的差异，推测它与相山地区勘探深度和不同类型矿化埋深的差异有关。

相山铀多金属矿田赋矿围岩及成矿硫源特征

为了探讨江西相山铀多金属矿区内岩浆岩与成矿(铀矿、铅锌矿)的关系,在野外调查的基础上,对该杂岩体的岩相学、岩石地球化学开展了研究,对其成因类型、源区特征进行了探讨,并对成矿物质来源进行了分析。通过野外及室内分析表明:赋铀矿围岩与赋铅锌矿围岩具有相同的岩性,空间上形成上铀下铅锌的格局。围岩属于富硅高钾钙碱性S型花岗岩,并具有高度分异特征;不同岩性的岩石具有同源性,主要来自于上地壳变质杂砂岩的部分重熔;据岩石地球化学、年代学及区域对比研究推测,在构造演化阶段和形成构造环境上,赋铀矿围岩与赋铅锌矿围岩应该形成于大陆挤压-拉张的过渡环境,地幔提供了部分热源,但主要热源来自地壳的拉张减压增温过程;铅锌矿床的硫源主要来自于花岗质围岩的岩浆热液并受到变质岩系的混染,铀矿床的硫源倾向幔源。

相山铀矿田横涧-岗上英矿区三维预测

在深部找矿过程中,三维地质建模技术起着不可或缺的作用。本次研究以相山矿田横涧-岗上英矿区为例,依托成矿理论、成矿预测理论和矿产资源勘查与评价理论,分析总结横涧-岗上英矿区的成矿地质条件,利用三维地质建模软件GoCAD建立研究区的地形、地层、构造、岩体、矿体和钻探模型,进一步结合勘查开采经验,建立矿区的地质找矿模型,并且采用找矿信息量法圈定成矿有利区段3处。结果表明,横涧-岗上英矿区深部仍有较大的找矿潜力。

象山煤矿中小型地质构造发育规律及其预测

通过对象山井田勘探、建井及采掘生产以来的地质构造资料进行整理、统计和作图分析,系统总结了已采区断层构造的发育特征和展布组合规律,并对井田未采区的地质构造进行了预测。结果显示,象山煤矿煤层中的断层构造极为发育,主采煤层中众多的中小型构造具有明显的方向性,其中断层展布方向主要为NW向,其次为近EW向、NE向和近SN向;断层发育具有明显的成带性,在3号煤层中划分出4个构造带组和16个构造带,在这些构造带内,煤层构造较为复杂,对安全开采影响较大,而在这些构造带之间则为煤层构造相对简单的块段。

宁芜向山地区火山热水沉积黄铁矿矿床地质概念模型

通过对向山地区典型矿床研究表明 ,区内黄铁矿矿床属火山热水沉积型。构造、次火山岩体、古地理环境等为其主要控矿地质条件。找矿标志主要有热水沉积岩、铁帽、围岩蚀变、地球物理异常、地球化学异常等。在此基础上 ,建立了黄铁矿矿床地质概念模型 ,以指导矿区外围的找矿工作。