蒙古国东南部钨多金属靶区的快速圈定与成矿分析

复杂地表条件下矿产勘探一直是个难题,国外区块更是如此,首次利用XLT一592WZ型便携式XRF分析仪在蒙古国苏赫巴托尔省（额尔德尼查干苏木）13451X草原覆盖地区系统采集数据,分析研究并圈定成矿靶区。初期利用x荧光仪进行扫面勘探,发现有W、As、Ph、Zn、Cu、Fe等元素异常,经过异常查证优选了一个钨多金属找矿远景区。在钨多金属找矿远景区内通过23条探槽和钻探工程进一步揭露发现一条黑钨矿体;钨矿主要以脉状、团块状或是角砾状形式出现,成矿围岩为花岗斑岩,矿石以黑钨矿为主,白钨矿极少,可见硅化、萤石,推测该区成矿类型为高温热液型黑钨矿。综合来看,在野外利用便携式X荧光光谱仪进行定性与半定量分析是有效的,该方法可在同类地区推广应用。     

南海西部54万年以来元素地球化学记录及其反映的古环境演变

通过对南海西部上升流区MD05-2899孔开展高分辨率碳酸盐地层学和XRF岩芯扫描元素地球化学分析,重建了晚第四纪54万来以来东亚夏季风的演化历史,探讨海平面升降对南海西部陆源碎屑供应量的影响。研究选用了ln(Ba/Al)作为该海区古生产力的指标,ln(Br/Al)作为有机物的指标,ln(Ti/Al)作为陆源碎屑供应量的指标。研究结果显示,东亚夏季风在过去54万年以来强度不断增强,具有明显的冰期—间冰期旋回特征,在间冰期强盛和冰期减弱,是控制该海区有机物含量变化的主要因素。东亚夏季风不断强盛可能直接导致了南海周边陆地降雨增强,河流径流量加大,使得南海西部上升流区域的陆源碎屑供应量在间冰期明显高于冰期。研究发现,当相对海平面低于-60 m的时候,大面积暴露的巽他陆架可能向南海西部深水区输入大量陆源碎屑物质,造成研究站位的陆源碎屑供应量在冰盛期出现高值。因此,晚第四纪的东亚夏季风演化和海平面升降共同控制了南海西部上升流区陆源碎屑物质供应量的变化。     

长江三角洲平原湖沼沉积物XRF岩芯扫描结果的可靠性分析

对长江三角洲顶部湖沼相沉积为主的X J02孔(32°19 ′57″N,119°16 ′22″E)进行XRF全岩芯扫描(XRF-cps)分析,同时选取70个样品利用X射线荧光光谱仪(XRF-ppm)进行元素含量测定.通过对两种测试方法所获结果的对比及相关性分析,探讨了XRF岩芯扫描方法测定元素含量的可靠性及其影响因素.结果表明:两种方法所测得的6种元素Ti,Zn,Rb,Sr,Fe和Ca的相关系数很高,XRF扫描强度变化可以很好地反映其含量的变化;XRF扫描强度受含水量的影响,尤其对原子量较小的元素Si等影响比较明显;对于含量较低的元素P和Pb,XRF扫描强度不能真实的反映沉积物中的元素含量.     

High‐resolution synchrotron X‐ray fluorescence investigation of calcite coralloid speleothems: Elemental incorporation and their potential as environmental archives

Synchrotron high‐resolution and micro‐X‐ray fluorescence elemental mapping of two coeval coralloid speleothems from Lamalunga Cave (Italy) are complemented with petrographic, morphological and microstratigraphic studies. The importance of these speleothems relies on their direct and indirect association with a complete Neanderthal skeleton (‘Altamura Man’) found inside the cave. The coralloids grew discontinuously between 64·6 ka and the Holocene and reveal exceptionally high concentrations of Mg, Sr and Si, particularly on convex surfaces, where evaporation is more intense. The incorporation of trace elements depends on several factors including location, shape and geometrical evolution during their growth, as well as climate and environmental parameters. This resulted in calcite precipitation with Sr compositions from 100 to 1200 ppm and an average concentration of 7000 ppm Mg. An unusually high Si content (up to 16%) is possibly derived from volcanic ash transported as particulate and in solution inside the cave. The most common fabrics observed consist of non‐fluorescent elongated columnar calcite forming clean isopachous bands and fluorescent fibre‐like crystals associated with laminated, lenticular bands high in Sr, Mg and Si. Variability in Sr, Mg and Si concentrations appears to induce fabric changes in the coralloids. Elongation and lattice distortion of the crystals was found to coincide with high Mg concentrations. The transition from compact elongated to open to fibre‐like, is here interpreted as due to high concentrations of Si and Sr, which are preferentially incorporated in the speleothem at crystal boundaries and intra‐laminae. It is here inferred that coralloid fabric changes and their elemental content potentially record local rainfall variations through time, with the clean compact calcite marking high infiltration and open fibre‐like and micrite fabrics recording dry periods.     

The petrology and geochemistry of intrusive alkaline rocks of Elchuru,Prakasam District,Andhra Pradesh,India

The Elchuru alkaline igneous intrusion is an arcuate-shaped ring complex, approximately 16 km² in area, cropping out in the Eastern Ghats high grade metamorphic series. It is part of an alkaline province composed of a number of intrusions which range from ijolite-melteigite to alkali gabbro (viz. malignite, melalusitanite, shonkinite) and then to hypersolvus nepheline syenite followed by subsolvus nepheline syenite. The complex is cut by late lamprophyric dykes. A nephelinized alkaline gneiss, within the investigated complex, is the only deformed rock type and is regarded as an older unit not related to the comagmatic series. The remainder of the complex was emplaced post-tectonically. Sovitic carbonatite is a conspicuous Iithologic unit associated with the complex. Chemical analyses of 19 selected samples for 13 major oxides and 5 trace elements (Rb, Ba, Sr, Zr and Nb) are presented to establish a geochemical model for the investigated complex. The mineralogy, petrography and geochemistry of the rocks of the Elchuru Alkaline Complex suggest that it was formed by differentiation of an initially alkali-rich ijolitic magma as reflected in the crystallization of nepheline, kaersutitic amphibole and alkali feldspar. With progressive increase in alkali feldspar content (volume percentage) the ijolite passes to malignite and then nepheline syenites. Amphibole shows sodic enrichment from a dominant calcic variety. Pyroxene, likewise, shows sodic enrichment following the scheme salite-ferrosalite to aegirine-augite. The igneous cycle closes with the intrusion of biotite lamprophyre. There is a systematic increase in total alkalies (Na₂O+K₂O) and decrease in CaO from the early mafic rocks to the syenitic rocks. The alkali-lime index of the complex is 48 indicating its strongly alkaline nature (Peacock 1931), and they are miaskitic in character (agpaicity index <1, Currie 1976). Such miaskitic complexes are associated with carbonatites (Heinrich 1966).     

多参数X荧光测量现场地球化学勘查金矿技术研究与应用

两种微机化携带式Ｘ荧光仪器已经研制成功,它们可以在现场同时测量２至６个元素,获得勘查金矿的多种参数。将Ｘ荧光测量原理与金矿地球化学理论相结合,本文建立了多参数Ｘ荧光测量现场勘查金矿技术。这种技术由携带式Ｘ荧光仪器多元素测试技术,资料整理与异常评价方法构成。由于现场Ｘ荧光测量不仅捕获金的地球化学指示元素,也获取构造与蚀变信息,大大提高了找矿的成功率。     

Environmental responses to Lateglacial climatic fluctuations recorded in the sediments of pre‐Alpine Lake Mondsee (northeastern Alps)

Investigation of the sedimentary record of pre‐Alpine Lake Mondsee (Upper Austria) focused on the environmental reaction to rapid Lateglacial climatic changes. Results of this study reveal complex proxy responses that are variable in time and influenced by the long‐term evolution of the lake and its catchment. A new field sampling approach facilitated continuous and precisely controlled parallel sampling at decadal to sub‐annual resolution for µ‐XRF element scanning, carbon geochemistry, stable isotope measurements on ostracods, pollen analyses and large‐scale thin sections for microfacies analysis. The Holocene chronology is established through microscopic varve counting and supported by accelerator mass spectrometry ¹⁴C dating of terrestrial plant macrofossils, whereas the Lateglacial age model is based on δ¹⁸O wiggle matching with the Greenland NGRIP record, using the GICC05 chronology. Microfacies analysis enables the detection of subtle sedimentological changes, proving that depositional processes even in rather large lake systems are highly sensitive to climate forcing. Comparing periods of major warming at the onset of the Lateglacial and Holocene and of major cooling at the onset of the Younger Dryas reveals differences in proxy responses, reflecting threshold effects and ecosystem inertia. Temperature increase, vegetation recovery, decrease of detrital flux and intensification of biochemical calcite precipitation at the onset of the Holocene took place with only decadal leads and lags over a ca. 100 a period, whereas the spread of woodlands and the reduction of detrital flux lagged the warming at the onset of the Lateglacial Interstadial by ca. 500–750 a. Cooling at the onset of the Younger Dryas is reflected by the simultaneous reaction of δ¹⁸O and vegetation, but sedimentological changes (reduction of endogenic calcite content, increase in detrital flux) were delayed by about 150–300 a. Three short‐term Lateglacial cold intervals, corresponding to Greenland isotope substages GI‐1d, GI‐1c2 and GI‐1b, also show complex proxy responses that vary in time. Copyright © 2011 John Wiley & Sons, Ltd.     

X射线荧光技术在野外勘查金矿中的应用

介绍了现场X射线荧光勘查技术的理论基础、仪器设备和运用X荧光分析仪测量伴生或共生元素含量找金的方法应用。应用X射线荧光法在野外现场直接测定多元素含量的变化,列出金与其指示元素之间密切相关关系,可在野外现场圈定金矿远景区和追索隐伏矿体,具有重要意义。