A visual basic spreadsheet macro for geochemical background analysis

A Visual Basic macro entitled BACKGROUND calculates geochemical background values of chemical parameters and estimates threshold values separating background data from anomalies. The macro uses two statistical methods, the iterative 2-sigma technique and the calculated distribution function, and integrates these model-based objective methods into a widely accessible platform (i.e., MS Excel). The macro offers the possibility for automated processing of geochemical data and enables an automated generation of background range and threshold values for chemical parameters.     

Origin,organic geochemistry,and estimation of the generation potential of Neogene lacustrine sediments from the Valjevo-Mionica Basin,Serbia

This paper reports an investigation of 60 samples of lacustrine sedimentary rocks of Neogene age lying at depths of 0–400 m in the Valjevo-Mionica Basin, Serbia. The goal of the study was to determine the origin and type of primary organic matter (OM), the degree of thermal alteration, the generation potential of OM from the rocks of this basin, and conditions in the sedimentation environment during the formation of the rocks. The potential of OM of the rocks was estimated on the basis of the thermolysis of a representative sample after its preliminary debituminization.     

四川盆地晚三叠世碎屑组分对物源分析及印支运动的指示

沉积物源分析是认识盆山演化的重要途径.四川盆地上三叠统的砾岩碎屑、砂岩骨架颗粒、碎屑重矿物组分显示,晚三叠世存在5大物源,它们分布于龙门山北段-中段、大巴山、龙门山南段、盆地东南和盆地南部.碎屑物源总体以"再旋回造山带"和"大陆板块"类型为主,其中,龙门山北段-中段和龙门山南段以"再旋回造山带"类型为主,而盆地东南部和南部以"大陆板块"类型为主."再旋回造山带"类型可细分为"混合造山带"及"碰撞造山和褶皱冲断带"两种类型,龙门山北段和龙门山南段均以"混合造山带"及"碰撞造山和褶皱冲断带"类型为特征.盆地物源分布存在阶段性特征:早期,龙门山北段-中段、大巴山物源规模较大,盆地东南和南部规模较小;晚期,盆地东南和南部规模增大,各方向呈均衡分布格局,这与周缘板块构造活动的阶段性有关.晚三叠世,龙门山北段由西北向东南方向挤压,构造活动强度总体具有弱-强-弱的演变趋势.须二期,龙门山北段逆冲-推覆开始形成,并暴露水面遭受剥蚀,向盆地提供物源;须四期为盆地最活跃期,龙门山北段进一步挤压抬升剥蚀,盆内沉积中心也由西北向东南迁移;须四期后,龙门山北段剥蚀区继续向东南推进,但构造活动强度渐趋和缓.     

鲁西新泰孟家屯2.7Ga变质沉积岩与黑云斜长片麻岩锆石Hf同位素特征

对出露于山东新泰孟家屯2.7Ga的孟家屯岩组中石榴石石英岩(M08)、含十字石石榴石黑云母石英片岩(D242-Y2)和黑云斜长片麻岩(M03)(TTG质片麻岩)进行锆石Lu-Hf同位素分析。石榴石石英岩锆石核部176Lu/177Hf、176Hf/177Hf变化范围为0.001730～0.002546、0.281249～0.281360,锆石变质边部176Lu/177Hf、176Hf/177Hf变化范围为0.000123～0.002070、0.281241～0.281318;含十字石石榴石黑云母石英片岩锆石核部176Lu/177Hf、176Hf/177Hf变化范围为0.001334～0.002169、0.281226～0.281324,锆石变质边部176Lu/177Hf、176Hf/177Hf变化范围为0.000445～0.001375、0.281227～0.281309;黑云斜长片麻岩锆石176Lu/177Hf、176Hf/177Hf变化范围为0.000315～0.000847、0.281186～0.281265。孟家屯岩组石榴石英岩、含十字石石榴石黑去母石英片岩中碎屑(岩浆)锆石和黑云斜长片麻岩中岩浆锆石的εHf(t)分别为3.75～7.26、2.31～7.26和3.21～6.27,同时TDM1与其U-Pb年龄非常接近,表明它们起源于新生地壳的部分熔融。结合区域研究资料认为,2.7Ga是鲁西重要的一期构造岩浆热事件,也可能是华北克拉通重要的构造岩浆活动时期。变质沉积岩中许多变质增生锆石相对于核部岩浆锆石低176Lu/177Hf、高176Hf/177Hf,显示变质作用过程中石榴石的存在对锆石的Lu-Hf同位素体系有很大影响。     

内蒙古中部四子王旗地区晚二叠-早三叠世过铝花岗岩定年及成因

研究区位于华北板块北缘中段,紧邻兴蒙造山带,是研究古生代—中生代地壳增生演化的重要地区。本文对区内三个花岗岩体进行了锆石LA-ICP-MSU-Pb定年及岩石地球化学研究。结果表明阿玛乌苏花岗闪长岩形成于267±9Ma(MSWD=9.7);布龙二长花岗岩和格尔图白云母正长花岗岩分别侵位于239±4Ma和238±6Ma(MSWD=0.91);而侵入格尔图白云母正长花岗岩的白云母二长花岗岩脉则获得了224±8Ma(MSWD=5.7)的侵位年龄。岩石地球化学特征显示阿玛乌苏花岗闪长岩为岩浆混合成因,暗示大规模岩浆底侵作用的存在;格尔图白云母正长花岗岩具明显的稀土元素"四分组"效应,是分异岩浆与流体作用的结果,可能经历一定程度的地壳混染,非真正意义上的S型花岗岩,属于造山后岩浆热事件,应代表造山的结束。格尔图白云母正长花岗岩及白云母二长花岗岩脉均受到热液流体作用,说明在中三叠世(224～238Ma),区内一直存在有大量的热液流体活动,且热液流体可能富含F和Cl,区内产出的大规模的萤石矿是否为该期流体活动的产物尚需进一步工作。     

Occurrence and geochemistry of arsenic in the groundwater of Eastern Croatia

In order to examine the extent of the As enrichment and the factors influencing this enrichment in the groundwater of Eastern Croatia, groundwater samples were collected from 56 production wells in two counties, Osijek-Baranja and Vukovar-Srijem, suspected to be more affected. Hydrochemical analyses were performed at all locations including in situ As speciation at 32 locations. Arsenic was detected in 46 out of 56 groundwater samples with total As concentrations up to 491 μg/L. Thirty-six of the studied wells yielded groundwater with total As concentrations that exceeded the WHO Maximum Contaminant Level for arsenic in drinking water of 10 μg/L. Only inorganic As species were detected with arsenite As(III) as the predominant form. The spatial distribution of As in the groundwater was significantly linked with geological, geomorphological and hydrogeological development of the alluvial basin of the Drava and Sava rivers. The most probable groundwater As sources are deeper sediments from the Middle and Upper Pleistocene. The results obtained suggest that biogeochemical processes controlling As concentration in the groundwater are complex and location-specific. Reductive dissolution of Fe oxides, desorption of As from Fe oxides and/or clay minerals as well as competition for the sorption sites with organic matter and phosphate could be the principal mechanisms that control As mobilization. The extent of those processes vary in the different parts of the Drava and Sava depressions and could be linked to different site related parameters, such as lithology, mineralogy, local hydrology and hydrogeology; thus different processes of As mobilization have been proposed for the different types of water in relation to groundwater evolution.     

Annual and seasonal variability of precipitation in Vojvodina,Serbia

Annual and seasonal variability of precipitation observed at 92 stations in Vojvodina (Serbia) were analyzed during the period 1946–2006. The rainfall series were examined by means of the empirical orthogonal functions (EOF). The first set of singular vectors explains from 68.8 % (in summer) to 81.8 % (in winter) of the total variance. The temporal variability of the time series associated with the main EOF configurations (the principal components, PCs) was examined using the Mann–Kendall test and the spectral analysis. The time series of PC1 revealed decreasing trend in the winter and spring precipitation and increasing trend in the autumn, summer, and annual precipitation. The relationships between the first PC and circulation patterns, such as the North Atlantic Oscillation (NAO), the East Atlantic (EA) pattern, and East Atlantic/West Russia pattern, were also investigated. The PC1, displaying temporal behavior of the first mode, demonstrated evident correspondence with the NAO index in analysis of the annual, winter, and autumn precipitation. Power spectra of the PC1 show statistically significant oscillations of about 3.3 years for the spring precipitation and about 8 and 15 years for the winter precipitation. Comparisons with spectral analysis of authors for some regions in Europe, most of them in the Mediterranean domain, show that similar periodicities are detected.     

2D geological–geophysical model of the Timok Complex (Serbia,SE Europe): a new perspective from aeromagnetic and gravity data

The study reports new aeromagnetic and gravity data for the northern part of the Timok Magmatic Complex (TMC), East Serbia. The TMC is part of the Tethyan Eurasian metallogenic zone well known for hosting large copper and gold deposits. The complex formed by continuous volcanic activity 90–78 Ma ago, that developed in roughly three phases: Turonian andesites, Santonian–Campanian andesites/basaltic andesites (both mostly volcanic) and Campanian latites/monzonites (mostly shallow intrusive). The aeromagnetic measurements included acquiring total magnetic intensity data that were corrected for diurnal variations, leveling, microleveling, calculated normal field values, calculated anomaly values of total magnetic field intensity and reduction to the pole. The gravity measurements were carried out in an irregular grid with relative gravity values obtained using a Worden gravity meter. 2D modeling reveals that the subsurface extension of the Campanian Valja Str? pluton is ten times larger than it is indicated by its surface outcrops. This implies that the area south and southeast from the pluton can be interesting in terms of finding new porphyry systems. The model indicates that this intrusive body should not be considered as a deeply dissected pluton. This sheds new light onto its potential with respect to epithermal gold mineralization, as well. The model also suggests that there are larger non-exposed bodies of Santonian–Campanian volcanics and near-surface hydrothermally altered rocks than it is inferred from geological maps. The results of our study suggest that further interdisciplinary investigations in the TMC, in particular those integrating geophysics and geology, may have potential of advancing the existing exploration models.     

A critical evaluation of using bulk sediment instead of fine fraction in environmental marine studies, investigated on example of Rijeka harbor, Croatia

This work tested the preferential use of fine (<63 μm) or bulk sediment (<2 mm) in environmental research of marine sediments in the Eastern Adriatic. Fine fraction sediment containing silt and clay (<63 μm), predominating in the studied area, was examined to evaluate past and present anthropogenic inputs and to test our hypothesis that investigation of bulk sediment should be preferred. Following aqua regia digestion, chemical analyses of 58 elements were performed by ICP/OES, ICP-MS and cold vapor AAS, and statistical analysis was performed. The concentrations of the majority of the analyzed elements increased with age of the sediment, except for Ag and Sn, which had higher concentrations in recent sediments. The previous main sources of metal contamination in Rijeka harbor were now abandoned municipal-sewage outflow and oil refinery, and continuing harbor activities and antifouling paint use. All activities except of antifouling paint use have been decreasing significantly. Anomalies of selected elements were determined by the box-plot method. More anomalies were found in the bulk sediment than in the fine fraction. Results of Q-modality clustering and factor analysis in the fine fraction almost correlate with that applied on bulk sediments. Thus, it can be said that the differences between the element distribution in the bulk and fine fraction are not statistically significant. Our conclusion is that analysis of bulk marine sediment gives a better insight into the state of pollution and supports previous recommendations to use bulk sediment as a chosen media for environmental studies.