Source of ore-forming material and metallogenic age of the Zheboshan gold deposit, western Sichuan Province, China

The Zheboshan gold deposit, which is located in the “Gold Triangle” area on the borders of Sichuan. Gansu and Shaanxi provinces, is a very complicated micro-fine disseminated gold deposit. Considering the ICP-MS measurements and Rb and Sr isotope data, it is suggested that the orcforming materials may have come from the quartz-amphibole porphyrite dykes. It is also suggested that the age of ore depasit is generally consistent with the age of formation of the quartz-amphibole porphyrite. It is further deduced that the deposit is a magmatic hydrothermal ore deposit.     

Intergrowth texture in Au-Ag-Te minerals from Sandaowanzi gold deposit, Heilongjiang Province: Implications for ore-forming environment

Sandaowanzi gold deposit,Heilongjiang Province,is the only single telluride type gold deposit so far documented in the world,in which 90% of gold is hosted in gold-silver telluride minerals.Optical microscope observation,scanning electron microscope,electron probe and X-ray diffraction analysis identified abundant intergrowth textures in the Au-Ag-Te minerals,typified by sylvanite-hosting hessite crystals and hessite-hosting petzite crystals.The intergrown minerals and their chemistry are consistent,and the hosted minerals are mostly worm-like or as oriented stripes,evenly distributed in the hosting minerals,with clear and smooth interfaces.These suggest an exsolution origin for the intergrowth texture.With reference to the phase-transformation temperature derived from synthesis experiments of tellurides,the exsolution texture of Au-Ag-Te minerals implies that the veined tellurides formed at 150-220℃.The early stage disseminated tellurides formed at log f(Te 2) from 13.6 to 7.8,log f(S 2) from 11.7 to 7.6,whereas the late stage veined tellurides formed at log f(Te 2) ranging from 11.2 to 9.7 and log f(S 2) from 16.8 to 12.2.     

He-Ar isotope geochemistry of the Yaoling-Meiziwo tungsten deposit,North Guangdong Province: Constraints on Yanshanian crust-mantle interaction and metallogenesis in SE China

Isotopic abundances and ratios of He and Ar found in inclusion fluids in pyrites formed in the Yaoling-Meiziwo tungsten miner-alization epoch show that the concentration of 4He varies widely,from 1.54×10-7 cm3 STP/g to 2609×10-7 cm3 STP/g.3He is 0.759×10-12 cm3 STP/g-3.463×10-12 cm3 STP/g.3He/4He is 0.0043-4.362 Ra,varying from crustal to mantle values.The concen-tration of 40Ar ranges from 0.624×10-7 cm3 STP/g to 8.89×10-7 cm3 STP/g.The 40Ar/36Ar varies extensively,from 330 to 2952,between atmospheric and crustal or mantle radiogenic values.Mantle-derived He is present in ore-forming fluids and the calcu-lated average proportion of the mantle He is 22%;the maximum is 67%.Our research results show that mantle-derived fluids play a significant role in tungsten mineralization.The fractionation of He and Ar indicate that there was 4He-enriched air-saturated water(MSAW) in the ore-forming fluid.The ore-forming fluid was a mixture of mantle fluid,crustal magmatic fluid and MSAW.The occurrence of a mantle component in ore-forming fluid indicates the large-scale W and Sn mineralization,including Yaol-ing-Meiziwo,in southeastern China was the result of crust and mantle interaction.The underplating or intrusion of voluminous basaltic magma formed by partial melting of the upper mantle provided the necessary heat to cause partial melting of the crust and the generation of voluminous S-type granitic magmas.Crustal magmatic fluid and mantle fluid with high 3He/4He were released from magma crystallization and fractionation,mixed with the circulating modified air-saturated water,and filled the extensional tectonic fractures,leading to the formation of world-class W and Sn deposits in southeastern China.     

Re-Os isotope dating of pyrite from the footwall mineralization zone of the Xinqiao deposit,Tongling, Anhui Province: Geochronological evidence for submarine exhalative sedimentation

The Xinqiao deposit is located in the Tongling area,Anhui Province.This deposit is dominantly composed of stratiform sulfide orebodies,which are restricted to the transitional zone from clastic rocks to carbonates at the base of the Late Carboniferous Huanglong Formation.There are discordant veinlets or networks of mineralization in the footwall rocks below the stratiform sulfide orebodies.The underlying discordant mineralization zones coexist with conformable stratiform sulfide orebodies,which are considered to be the most representative features of massive sulfide deposits formed by submarine exhalative sedimentation.This study reports a pyrite 187Re-187Os isotopic age of 319±13 Ma(MSWD=16) for the footwall mineralization zone.This isochron age is consistent with the interval of strata hosting the conformable stratiform sulfide orebody,and provides direct geochronological evidence for Carboniferous exhalative sedimentary mineralization.     

广东石人嶂钨矿床黑钨矿铁锰成分的变化规律初步研究*

黑钨矿铁锰含量在不同空间、时间状态下变化不同。以石人嶂钨矿为例,通过电子探针实验和扫描电镜能谱分析,探讨黑钨矿铁锰成分含量的变化。黑钨矿铁锰成分在空间上表现为:黑钨矿中FeO含量随深度的增加而增大,MnO含量则与之相反,黑钨矿由两极分异型变为中间成分的钨锰铁矿;矿化强度较高的矿脉黑钨矿的FeO含量较高;与硫化物共生的黑钨矿FeO含量大于MnO含量,H/F值小于1,黑钨矿偏向于锰钨铁矿。在时间上表现为晶体核部富铁,边部富锰,推测存在环带结构。通过对黑钨矿铁锰成分变化规律分析,认为主要控制因素是黑钨矿晶体内部结构和成矿条件的变化。     

小流域中-低频泥石流与山洪输沙比例的讨论:以金沙江支流海子沟为例

泥石流山洪输沙比是工程防治设计的重要参数。本文以金沙江支流海子沟为例,调访了近115a的泥石流活动历史,查明了1996年一次最大规模泥石流运动参数,采用雨洪法计算了不同的泥石流发生频率下泥石流的流量、总量。通过对1899年至今海子沟堰塞坝泥沙淤积的测定,得出海子沟流域每年泥沙淤积量为1.23×10~5 m~3,总输沙量为1.42×107 m~3,流域平均剥蚀速率为1.5mm/a。由不同泥石流频率下海子沟泥石流的固体物质总量,计算出自1963年以来海子沟泥石流输沙量为1.67×10~6 m~3,而此期间山洪泥石流的总输沙量为6.65×10~6 m~3,由此确定海子沟泥石流的输沙量占山洪泥石流输沙总量的25%。而官坝河泥石流、白龙江流域泥石流、蒋家沟泥石流输沙量分别占总输沙量的29.5%、62.9%、99%,泥石流输沙量随着泥石流频率的增加而增加。高频率泥石流工程拦挡仅考虑泥石流输沙量;类似白龙江流域松散固体物质丰富的半干旱气候区泥石流防治拦挡工程需考虑山洪输沙量;而类似官坝河、海子沟中等频率的泥石流沟,需更多考虑山洪输沙量。     

基于GIS的区域适居性评价研究--以青海省为例

目的对区域每一点的适居性进行综合评价。方法采用AHP法对因子赋权。结果首先构建了区域适居性评价因子体系，接着利用图文数据源，在地理信息系统空间分析模块的支持下，通过单因子空间分析、布尔逻辑运算和复合叠置分析对区域适居性进行综合评价。结论运用GIS空间分析技术能实现多数据源处理、多指标叠合分析、多维度显示，这些功能为适居性评价提供了科学、客观、高效、直观的方法支持，今后应进一步提高评价的可靠性。     

Dating of sediment-hosted disseminated-type gold deposit by using ~(40)Ar/~(39)Ar laser probe: A case study of Changkeng large-scale gold deposit, China

Ore-forming age is one of the most important data in studying the genesis of mineral deposits. Dating of sedi-ment-hosted disseminated-type gold deposits, which areone of the most important types of gold deposits in theworld, is always a difficult task for ore geologists. Themajor reason is that most of the ores in this type deposit are of various siliceous and are composed of extremely fine-grained minerals, thus it will be very difficult to de-termine their ages by using conventional isotopi…     

Oxygen isotope geochemistry of phosphorite and dolomite and palaeo-ocean temperature estimation: A case study from the Neoproterozoic Doushantuo Formation, Guizhou Province,South China

The Neoproterozoic Doushantuo Formation at Weng'an in Guizhou Province of South China consists of phosphorites and dolomites.Three types of samples are recongnized for the phosphate-bearing rocks.In Type I samples, interstitial phosphates occur within the dolomite rocks, whereas in Type III samples, interstitial dolomites occur within the phosphorites; both of them may have diagenetic origin.The Type II samples are interbedded phosphorites and dolomites.Oxygen isotopic compositions of phosphate and coeval carbonate were analyzed.Phosphates of Type I and II samples show similar low δ18Ophos (SMOW) values of 10.9‰～12.1‰ and 10.7‰～12.8‰, respectively, whereas Type III phosphates show higher δ18Ophos (SMOW) values of 13.2‰～15.0‰.Dolomites from Type I and II samples have δ18Ocarb (PDB) and δ13Ccarb (PDB) values of -6.2‰～-3.4‰ and -2.2‰～-0.7‰, respectively, whereas interstitial dolomites from Type III samples show lower δ18Ocarb (PDB) and δ13Ccarb (PDB) values of -12.9‰～-8.6‰ and -4.4‰～-2.6‰.Petrology and oxygen isotope data suggest that diagenetic alteration may have partially affected the studied rocks, but the dolomites from Type I and phosphates from Type III samples represent the most pristine isotopic compositions of primary carbonates and phosphates precipitated from seawater.Calculations of palaeocean temperatures from the most 18O enriched dolomite and phosphate indicate a temperature range of 32.2 ℃ to 34.0 ℃ for the seawater of the Doushantuo Formation period.Ce anomaly also suggests more oxic conditions and possibly shallower water depth in the upper strata of the Doushantuo Formation at Weng'an, Guizhou Province.     

基于空间数据库的生态环境综合信息图谱的指标体系研究--以莆田市为例

根据莆田市生态环境的现状、社会经济的发展以及建立生态环境综合信息图谱谱系的要求,确定该区生态环境综合信息图谱的指标体系。同时把空间数据库技术和现代多媒体技术结合起来,实现在空间数据基础上的多媒体信息查询。这不但丰富了属性数据的查询,也提高了指标的可视化。     

叠前多重降维复杂岩性预测技术——以元坝西部须三段为例

川东北元坝西部地区上三叠统须家河组第三段岩性复杂多样,储层岩性以钙屑砂岩为主,不同类型岩性地球物理响应特征差异小,岩性预测难度大.针对上述难点,开展叠前多重降维复杂岩性预测技术研究.多重坐标变换逐次降维可将2个弹性参数合并成1个岩性区分能力最大的新弹性常数,用于识别目标岩性.提出了基于叠前多重降维分析的岩性预测的实现流程,以岩石物理分析为基础,多重坐标交换降维为核心,对相控约束叠前弹性参数反演得到的弹性参数数据体进行多重降维,从而实现复杂岩性分布预测.元坝西部须三段钙屑砂岩预测的应用分析证实了该方法预测精度高、实用性强.     

Dating of sediment－hosted disseminated－type gold deposit by using ^40Ar／^39Ar laser probe： A case study of Changkeng large－scale gold deposit, China

Hydrothermal clay minerals that formed in the main metallogenic stage of the Changkeng disseminated-type gold deposit in central Guangdong were analyzed by the 40Ar/39Ar laser probe. The results give Ar-Ar isochron ages of 109.9 1.4 to 110.1 1.3 Ma, which are 30 to 50 Ma older than the age of silver ore bodies in the deposit. Both gold and silver mineralizations were not related to hidden granite batholith in the mining district, but probably related to evo-lution of sedimentary basins. This study shows that the 40Ar/39Ar laser probe is a sound dating tool applicable to sediment-hosted disseminated-type gold deposit.     

Analysis of the ecological environment around 10000 a BP in Zhaitang area,Beijing: A case study of the Donghulin Site

The transition from Paleolithic to Neolithic around 10000 a BP was a significant event in human history. We have analyzed the paleoenvironment in the Zhaitang area (Beijing) based on samples from an early Neolithic site at Donghulin. This site is considered to demonstrate the Paleolithic-Neolithic transition in this area. The site yielded burials with several human skeletons, known as "Donghulin man". We conducted a geomorphological and quaternary geological investigation in the Donghulin area, and also analyzed sediments and pollen, enabling us to discuss the living environment of the local people. Donghulin man lived mainly from 11100-9600 cal a BP; a period of warming following the Younger Dryas. The climate was good, the land was covered by dry temperate grassland, and later, wet temperate meadow steppe. "Donghulin man" usually inhabited the floodplain; this was flat, warm, and wet, with abundant plants and animals for a favorable living environment. Our research helps to rebuild the living environment of humans in the Beijing area around 10000 a BP, and to understand more about the environmental setting in north China during the Paleolithic-Neolithic transition.     

Geochemical characteristics and petrogenesis of Mesozoic basalts from the North China Craton： A case study in Fuxin, Liaoning Province

Occurrence of Cretaceous basalts in Fuxin County, Liaoning Province provides us an opportunity to understand Mesozoic mantle processes beneath the northern margin of the North China Craton (NNCC). Fuxin Jianguo basalts occur as volcanic channel phases with well-developed columnar jointings and contain few spinel lherzolite and pyroxenite xenoliths. They are poor in silica and rich in alkalis, Ti and Al, belonging to alkaline basalts. In trace element compositions, Jianguo basalts are moderately enriched in LREE and LILE, but not depleted in HFSE. They have low Sr and high Nd and Pb isotopic ratios. These geochemical characteristics suggest that Jianguo basalts originated from the depleted asthenosphere, representing an undifferentiated and uncontaminated primitive magma. Presence of these basalts indicates that the lithosphere beneath the region had thickness less than 65 km at the time of basalt eruption and was mainly composed of fertile pargasite-bearing spinel Iherzolite and plagioclase pyroxenite. The voluminous basaltic-andesitic magmatism during the early Jurassic-late Cretaceous time indicates that the commencement and accomplishment of lithosphere thinning in the NNCC was much earlier than that in the southern margin, since the mafic-intermediate volcanism only occurred at the Cretaceous time in the southern margin and the basalts with an asthenosphere isotopic signature at the Tertiary. This shows that highly spatial and temporal heterogeneity existed in the Mesozoic lithosphere evolution.     

乡村振兴背景下秦巴山区农村居民点整理潜力与分区研究——以陕西省山阳县为例

农村居民点作为农户社会经济活动的重要载体,对其进行空间重构与优化是实现乡村振兴的有效途径。以陕西省山阳县238个村为研究单元,从自然资源、土地区位、社会经济三个维度选取20项评价因子,构建山阳县农村居民点整理潜力评价指标体系,并借助由粒子群优化的BP神经网络模型,对山阳县农村居民点的整理潜力指数进行综合测度,最后运用层次聚类法划分居民点整理分区,进一步探讨相应的整理途径。结果表明:①山阳县居民点整理潜力指数值介于8. 80～57. 29之间,其中高值区大多集中在地势平坦,交通便利,靠近中心城区,并且社会经济发展良好的地区。②基于层次聚类分析结果和农村发展现状,将山阳县划分为城镇发展区、优先整理区、重点整理区、适度整理区和控制调整区等居民点用地整理类型,并按照分区统筹的原则,因地制宜地提出相应的整理策略和优化途径,以期为城乡统筹和乡村振兴提供参考依据。     

广东山区水果经作规模开发地理环境研究——以梅州市蕉岭县为例

广东省山区地处南亚热带与中亚热带间的气侯区(带)，既适宜发展部分热带果作，也适宜栽培部分温带果作．发展热带果作是山区高效农业生产项目，但冬季易受寒害，风险大．为保证山区热带果作的顺利发展，必须根据山区地形复杂、地域差异形成各种不同小环境的特点，选择避免出现使热带果作受害的生存极限温度的小环境，适地适种．为此，我们进行了该项研究．利用冷空气入侵本省出现的晴冷天气，对山区垂直分布的极端低温进行了野外观测，分析取得了山区寒天“冷湖效应”和逆温约分布规律，并利用逆温现象进行山区热带果作布局规划，为我省山区发展热带果作规模生产提供了科学依据．     

Coral cover as a proxy of disturbance:A case study of the biodiversity of the hermatypic corals in Yongxing Island, Xisha Islands in the South China Sea

The Yongxing Island is the biggest island of Xisha Islands in the middle part of the South China Sea. It occupies 1.8 square kilometers of land area and has permanent residence on it. There are only a few papers on the coral community of the Xisha Islands, reporting the species composition, structure and zonations of the hermatypic coral community in 1970s. The present study describes the hermatypic coral community based on the quadrat survey after almost 30 years in Yongxing Island in August 2002. It was the first time to present the percent cover data of live corals of Yongxing Island via a systematic scheme of quantitative quadrat sampling. The average total percent cover of the live coral is 68.4%. We found the total percent cover (TPC) could be an idea proxy of the overall disturbance regime impinging on the coral community. TPC can be used as an integrated measure of disturbance to coral reef. Using this surrogate, the best fit relation between TPC of the live corals and species richness, species diversity, or the species evenness is the unimodal second-order polymorphic parabola equation. This result is expected by the intermediate disturbance hypothesis (IDH). From the fitted parabola equations, we calculated the best TPCs corresponding to the maximal species richness, the highest species diversity, or the most evenness respectively. They are surprisingly stabilized between 55% and 58%. Coralcover is the basic parameter widely available for most observation, research or monitoring programs. The good qualitative characteristics of percent cover provide powerful tool for the experimental, theoretical and modeling studies of coral reef in response to the disturbance.     

基于CVM的城市绿色生态系统游憩服务支付意愿及影响因素研究——以武昌区为例

利用二元Logistic模型、有序Ordinal模型及CVM调查数据,研究居民对武昌区城市绿色生态系统游憩服务的支付意愿与影响因素,并对其游憩服务价值进行评估.主要结论如下:1) 58. 33%的居民有支付愿意,支付金额为39. 74元/人·年,其中武昌区居民支付意愿略高于非武昌区居民.2)居民收入对支付意愿(P 0. 05)与支付金额(P 0. 01)有显著正影响,居民的关注度(P 0. 01)、满意度(P 0. 05)和是否重游(P 0. 01)对支付意愿亦有显著正影响,受教育水平(P 0. 01)对支付金额有显著负影响.表明居民支付行为不仅受经济因素收入水平的影响,也受认知水平、满意度、观念、受教育水平等非经济因素的重要影响.3)武昌区城市绿色生态系统游憩服务2016年总经济价值约为2. 13亿元,约占当年GDP总量的0. 22%,随着武汉生态园林城市的建设与居民收入水平的提高,城市绿色生态系统游憩服务的潜力会越来越大.