Tourmaline from the Archean G.R.Halli gold deposit,Chitradurga greenstone belt,Dharwar craton （India）： Implications for the gold metallogeny

Tourmaline occurs as a minor but important mineral in the alteration zc,ne of the Archean orogenic gold deposit of Guddadarangavanahalli （G.R.Halli） in the Chitradurga greenst~ne belt of the western Dharwar craton, southern India. It occurs in the distal alteration halo of the G.R.Halli golcl deposit as （a） clusters of very fine grained aggregates which form a minor constituent in the natrix of the altered metabasalt （AMB tourmaline） and （b） in quartz-carbonate veins （vein tourmaline）. ~[＇he vein tourmaline, based upon the association of specific carbonate minerals, is further grouped as （i） albite-tourmaline-ankerite-quartz veins （vein-1 tourmaline） and （ii） albite-tourmaline-calcite-quartz veins （vein-2 tourmaline）. Both the AMB tourmaline and the vein tourmalines （vein-I and vein-2） belong to the alkali group and are clas- sified under schorl-dravite series. Tourmalines occurring in the veins are zoned while the AMB tour- malines are unzoned. Mineral chemistry and discrimination diagrams 1eveal that cores and rims of the vein tourmalines are distinctly different. Core composition of the ve：n tourmalines is similar to the composition of the AMB tourmaline. The formation of the AMB tourmaline and cores of the vein tour- malines are proposed to be related to the regional D1 deformational event associated with the emplacement of the adjoining ca. 2.61 Ga Chitradurga granite whilst rims of the vein tourmalines vis-a- vis gold mineralization is spatially linked to the juvenile magmatic accretion （2.56-2.50 Ga） east of the studied area in the western part of the eastern Dharwar craton.     

Kiel Ⅳ-IRMS双路在线分析微量碳酸盐的碳氧同位素

石笋能重建百年、十年的气候事件,为达到空间高分辨率,对微量碳酸盐的检测提出了更高要求,传统磷酸酸解法的样品用量大(约10 mg)已经无法满足微量样品的分析,而激光探针质谱分析方法需对检测结果进行校正。本文采用KielⅣ-IRMS双路在线分析技术对微量碳酸盐样品的碳、氧同位素进行检测研究其可行性,并以GBW 04405和NBS 19为例研究了不同样品量的碳酸盐标准样品在不同反应时间对同位素分馏的影响。结果表明,由于标准样品所需的反应时间不同,从而导致同位素分馏值的差异。对样品量为4~85μg的标准样品GBW 04405进行检测,δ13C、δ18O测量值分别为0.574‰±0.027‰、-8.519‰±0.065‰,与推荐值0.57‰±0.03‰、-8.49‰±0.14‰基本一致,表明该方法能够满足微量碳酸盐测试的要求。将KielⅣ-IRMS双路在线分析技术与GasbenchⅡ-IRMS检测方法进行对比,对于标准样品GBW 04405,KielⅣ-IRMS所用样品量约为50μg,δ13C、δ18O测量值分别为0.576‰±0.012‰、-8.501‰±0.050‰,GasbenchⅡ-IRMS所用样品量约为140μg,δ13C、δ18O测量值分别为0.569‰±0.034‰、-8.590‰±0.099‰。表明KielⅣ-IRMS方法相比于GasbenchⅡ-IRMS方法所需样品量少,精度高,结果重现性好,该方法在碳酸盐样品的应用上能达到空间高分辨率。     

花岗岩型热液铀矿床C、O同位素研究---以甘肃省龙首山芨岭矿区为例

龙首山地区是西北重要的花岗岩型热液铀矿产区之一,区内控矿条件复杂。研究选取甘肃省龙首山芨岭矿区内的矿床和部分矿点的热液碳酸盐样品并测定其C、O同位素组成：δ13C VPDB的值在-1.50‰～-6.33‰之间,δ18OSMOW值为-2.577～5.051‰之间。进一步研究结果表明,成矿流体中矿化剂ΣCO2主要来源于与区域深大断裂有关的幔源脱气作用,同时伴有海相碳酸盐来源;成矿同时期伴随的强烈流体脱气(CO2)作用对矿质沉淀至关重要。成矿热液的水源主要为岩浆热液与大气降水混合特征,但以大气降水形成为主。     

土库曼斯坦阿姆河盆地卡洛夫-牛津阶储层特征及控制因素分析

土库曼斯坦东北部的阿姆河盆地,是中亚地区最重要的含油气盆地之一。根据钻井岩芯和分析化验资料,确定阿姆河盆地卡洛夫-牛津阶为碳酸盐台地相沉积,具有特征的前缘缓斜坡沉积模式,可划分为蒸发台地、局限台地、开阔台地、台地边缘、前缘缓斜坡和盆地6个相带。其中台内、台地边缘和前缘缓斜坡为储层发育相带,尤以发育于台地边缘、开阔台地和前缘缓斜坡相带中的礁、滩微相最有利于储层发育。沉积微相和岩性对储层类型及物性有直接控制,特点为高能环境条件下沉积的块状礁灰岩和中-厚层状滩相颗粒灰岩以发育原生孔隙保存良好的孔隙型和裂缝-孔隙型储层为主,而较低能环境条件下沉积的(含)颗粒微晶灰岩、隐藻灰岩和泥-微晶灰岩以发育基质岩物性很差的裂缝型储层为主。通过综合分析,认为储层发育受沉积微相、岩性和成岩作用复合控制,以各相带内的礁、滩微相灰岩为高效勘探开发目标的"甜心"位置。     

南京下蜀黄土记录的250~100ka期间的环境演化信息

下蜀黄土记录了东亚季风环境演变的重要信息,是全球气候变化研究的重要载体。通过对南京仙林(XL)剖面下蜀黄土地球化学元素、风化指标和磁化率指标的综合分析,讨论了南京下蜀黄土的化学风化程度及沉积环境。研究结果表明,南京下蜀黄土的常量元素与上陆壳化学组分接近,显示其物质来源比较稳定,在堆积以前经历了充分的混合。XL地区的沉积环境比洛川黄土沉积环境要湿润,与洛川古土壤、镇江下蜀黄土的沉积环境接近,处于较为湿润条件下形成的中等风化阶段。在250~100ka期间,XL剖面的沉积环境经历了冷干-暖湿-冷湿-暖湿的变化特征。同时,长江中下游地区在此期间具有风化成壤作用逐渐增强、气候逐渐暖湿、东亚夏季风逐渐增强的特点。     

花岗闪长岩风化层土壤及其盐水与酸不溶物元素变化行为研究:以热液成矿指示元素为例

从土壤到水系沉积物风化过程中微量元素含量的变化行为对化探异常的圈定和解释具有重要参考价值。以北京西南房山花岗闪长岩体发育的土壤为研究对象,通过盐水及盐酸溶液去除土壤中的活动态微量元素,以模拟含盐水系及酸性水系,实验查明从土壤到水系沉积物风化过程中微量元素的变化行为。实验结果发现从土壤到盐水不溶物再到酸不溶物,花岗岩风化指数(WIG值)逐渐降低,表明WIG是表征其风化程度的良好地球化学指标。样品粒度越细其风化程度越高,热液成矿元素含量从粗粒级到细粒级含量逐渐升高,建议采样粒度为80~100目。     

Mobilization and redistribution of elements in soils developed from extreme weathering basalt on Hainan Island

Major, trace and organic elements of a South China were reported to investigate elements laterite profile developed on Neogene basalt on Hainan Island, mobilization and redistribution in tropical regions. The results indicate that strong acid environment and organic matter （OM） can remarkably improve the transfer of insoluble elements. Among all the elements, Th is the least mobile. As for the general conservative elements during incipient chemical weathering, such as Ti, Zr, Hf and Nb, the removals are up to 30%-40% in the upper profile. And for Fe, A1, Cu and Ni, that tend to be combined with secondary minerals and to be retained in temperate zone, they are re- moved from the upper profile, transferred downwards, and then precipitated in the lower profile. In addition, atmos- pheric inputs, including sea salt aerosols and dust, have a profound effect on the budgets of elements that are susceptible to leaching losses （e.g. K, Na and Sr）. Excluding the possibilities of groundwater and erosion, the remarkable increase of K, Na and Sr concentrations in the upper profile, together with dramatically upward increasing trends of the percentage changes of Sr/Th, K/Th and Na/Th ratios, show that atmospheric inputs, especially sea salt aerosols, contribute much extraneous seawater derived elements, such as K, Na and Sr to the soils. The overall elemental be- haviors in this profile suggest that organic matter and atmospheric inputs play a very important role in the mobiliza- tion and redistribution of elements during extreme weathering in tropical regions.     

Paleoclimate and Paleoenvironment of Gonghe Basin, Qinghai-Tibet Plateau, During the Lastdeglacial: Weathering, Erosion and Vegetation Cover Affect Clay Mineral Formation

With the analysis of the sources and formation mechanism of the clay minerals in the sediment core from the Dalianhai lake in the Gonghe Basin,northeastern Tibet-Qinghai Plateau,clay mineral composition proxies,grain-size and carbonate contents have been employed for high-resolution study in order to reconstruct East Asian Summer Monsoon （EASM） over the northeastern Tibet-Qinghai Plateau during the lastdeglacial.The study also extended to establish a relationship between vegetation cover changes and erosion during the last 14.5 ka with pollen record and clay mineral proxies.Smectite/kaolinite and smectite/（illite＋chlorite） ratios allow us to assess hydrolysis conditions in lowlands and/or physical erosion process in highlands of the Gonghe Basin.Before 12.9 Cal ka BP,both mineralogical ratios show low values indicative of strong physical erosion in the basin with a dominant cold and dry phase.After 12.9 Cal ka BP,an increase in both mineralogical ratios indicates enhanced chemical weathering in the basin associated with a warm and humid climate.The beginning of Holocene is characterized by high smectite/（illite＋chlorite） and smectite/kaolinite ratios that is synchronous as with deposition of many peat laminae,implying the best warm and humid conditions specifically between 8.0 to 5.5 Cal ka BP.The time interval after 5.0 Cai ka BP is characterized by a return to high physical erosion and low chemical weathering with dry climate conditions in the basin.Comparing variations of clay mineral assemblages with previous pollen results,we observe a rapid response in terms of chemical weathering and physical erosion intensity to a modification of the vegetation cover in the basin.     

高频红外法测定碳酸盐型石墨矿中固定碳的研究

针对用直接法(或非水滴定法)测定碳酸盐型石墨矿中固定碳时,碳酸盐等杂质分解不完、遇酸分解易飞溅、检测效率低以及用间接法不能准确测定低含量碳酸盐型石墨矿中固定碳的难题,建立用硝酸前处理样品—高频红外吸收法测定碳酸盐型石墨矿中固定碳的方法,并建立校准曲线。从样品的称样量、助溶剂的加入量、酸溶剂及其浓度的选择等方面对该方法进行详细研究。精密度、准确度符合石墨矿中固定碳的分析实验要求,并用国家一级标准物质对其进行了验证(RSD%,n=10)3.37%~0.70%;(RE%,n=10)-1.03%~0.00%。不同检测方法比较发现,本法与直接法、间接法进行比较,具有操作简单、稳定好、快速等特点,提高了石墨矿中固定碳含量的检测效率,适合碳酸盐型石墨矿固定碳的分析测定。