Quaternary environmental changes in tropical Lake Towuti,Indonesia, inferred from end-member modelling of X-ray fluorescence core-scanning data

Continental and marine sediments are composed of a mixture from different sources and are influenced by a variety of environmental factors and transport processes prior to deposition. For analysis and interpretation, these sources and processes are often challenging to disentangle. We show that end-member modelling of X-ray fluorescence (XRF) core-scanning data helps to overcome these challenges by unmixing different environmental signals from high-resolution sediment geochemical records. We apply this approach to a 100 m long lacustrine succession from Lake Towuti, Indonesia, to separate the regional climate and tectonic history from local ecological and diagenetic processes. The resulting six end-members (EMs) are interpreted to represent changes in ecological (EM1), climatic (EMs 2–4), tectonic (EM 5) and geomorphic (EM6) processes determining changes in sediment composition. Because end-member analysis allows for the tracking of transient and overlapping processes, climatic changes can be followed throughout the 100 m-long succession, suggesting alternating wet and dry periods in Central Sulawesi over long (several 100 000 years) time scales. We show that end-member analysis on elemental data sets offers a detailed and objective means to disentangle depositional processes in sedimentary successions resulting from varying tectonic and environmental factors involved in sediment formation and deposition.     

Removal of selected heavy metals from aqueous solutions using a solid by-product from the Jordanian oil shale refining

 The potential use of treated solid by-product of oil shale to treat aqueous solutions containing several heavy metals, i.e., Cd(II), Cu(II), Cr(III), Ni(III), Pb(II) and Zn(II), was explored. Different experimental approaches including equilibrium batch mode experiments and X-ray fluorescence (XRF) were used to explore the feasibility of this material as a cheap adsorbent for the removal of these heavy metals from predetermined solutions. Results indicate that the solid by-product of oil shale removes Cd(II), Cu(II), Ni(II), and Pb(II), from aqueous solutions by adsorption, but did not remove the other heavy metals investigated in this study. Received: 20 April 1998 · Accepted: 20 November 1998     

High-resolution X-ray fluorescence profiling of hybrid event beds: Implications for sediment gravity flow behaviour and deposit structure

Hybrid event beds form when turbidity currents that transport or locally acquire significant quantities of mud decelerate. The mud dampens turbulence driving flow transformations, allowing both mud and sand to settle into dense, near-bed fluid layers and debris flows. Quantifying details of the mud distribution vertically in what are often complex tiered deposits is critical to reconstructing flow processes and explaining the diverse bed types left by mud-bearing gravity flows. High-resolution X-ray fluorescence core scanning provides continuous vertical compositional profiles that can help to constrain mud distribution at sub-millimetre scale, offering a significant improvement over discrete sampling. The approach is applied here to cores acquired from the Pennsylvanian Ross Sandstone Formation, western Ireland, where a range of hybrid event beds have been identified. Raw X-ray fluorescence counts are calibrated against element concentrations and mineral abundances determined on coincident core plugs, with element and element log-ratios used as proxies to track vertical changes in abundances of quartz, illite (including mica), chlorite and calcite cement. New insights include ‘stepped’ (to higher values) as opposed to ‘saw-tooth’ vertical changes in mud content and the presence of compositional banding that would otherwise be overlooked. Hybrid event beds in basin floor sheets that arrived ahead of the prograding fan system have significantly cleaner sandy components than those in mid-fan lobes. The latter may imply that the heads of the currents emerging from mid-fan channels entrained significant mud immediately before they collapsed. Many of the H3 debrites are bipartite with a sandier H3a division attributed to re-entrainment and mixing of a trailing debris or fluid mud flow (H3b) with sand left by the forward part of the flow. Hybrid event bed structure may thus partly reflect substrate interaction and mixing during deposition, and the texture of the bed divisions may not simply mirror those in the suspensions from which they formed.     

New coring study in Augusta Bay expands understanding of offshore tsunami deposits (Eastern Sicily,Italy)

Tsunami deposits present an important archive for understanding tsunami histories and dynamics. Most research in this field has focused on onshore preserved remains, while the offshore deposits have received less attention. In 2009, during a coring campaign with the Italian Navy Magnaghi, four 1 m long gravity cores (MG cores) were sampled from the northern part of Augusta Bay, along a transect in 60 to 110 m water depth. These cores were taken in the same area where a core (MS06) was collected in 2007 about 2·3 km offshore Augusta at a water depth of 72 m below sea level. Core MS06 consisted of a 6·7 m long sequence that included 12 anomalous intervals interpreted as the primary effect of tsunami backwash waves in the last 4500 years. In this study, tsunami deposits were identified, based on sedimentology and displaced benthic foraminifera (as for core MS06) reinforced by X-ray fluorescence data. Two erosional surfaces (L1 and L2) were recognized coupled with grain-size increase, abundant Posidonia oceanica seagrass remains and a significant amount of Nubecularia lucifuga, an epiphytic sessile benthic foraminifera considered to be transported from the inner shelf. The occurrence of Ti/Ca and Ti/Sr increments, coinciding with peaks in organic matter (Mo incoherent/coherent) suggests terrestrial run-off coupled with an input of organic matter. The L1 and L2 horizons were attributed to two distinct historical tsunamis (ad 1542 and ad 1693) by indirect age-estimation methods using ²¹⁰Pb profiles and the comparison of Volume Magnetic Susceptibility data between MG cores and MS06 cores. One most recent bioturbated horizon (Bh), despite not matching the above listed interpretative features, recorded an important palaeoenvironmental change that may correspond to the ad 1908 tsunami. These findings reinforce the value of offshore sediment records as an underutilized resource for the identification of past tsunamis.     

东坪金矿床的围岩蚀变和流体特征

东坪金矿床围岩蚀变特征、流体包裹体特征与氢氧同位素特征研究表明,成矿流体富集K⁺、Na⁺、Au⁺、Cl^-和CO₂、H₂S,成矿溶液以岩浆热液为主,但有天水的混合。金在溶液中以Au(HS)₂^-和AuCl₂^-形式存在,构造活动引起的压力突变和流岩反应是引起金沉淀的主要因素。围岩蚀变以钾化为主,其次是硫化、钠化和硅化、碳酸盐化。金矿化与K/Al值呈反相关,与Na/Al值和S/Fe呈正相关。K/Al值的最高点与Na/Al值的最低点的对应关系可以用于圈定矿体。     

热液流体中贵金属发生沉淀时硫化物表面特性

热液流体中贵金属发生沉淀时硫化物表面特性ＨＦ＋ＨＣＩ酸的分解作用可用来分离脉金矿床中硅酸盐相和碳酸盐相的矿石矿物。本次研究所选用的矿石为津巴布韦四个太古宙脉金矿床。矿床为中温热液类型（２５０一４００℃）。矿石结构研究表明,在硫化物表面存在一种特殊颗粒...     

The upper Viséan–Serpukhovian in the type area for the Serpukhovian Stage (Moscow Basin,Russia): Part 2. bulk geochemistry and magnetic susceptibility

This study is the summary analysis of bulk XRF geochemistry (233 samples from three sections) of the Oka and Zaborie groups of the type Serpukhovian succession in the Moscow Basin. The siliciclastic wedges in the limestone‐dominated Oka Group are two to three times enriched in Fe, Ti, and Zr compared to Clarke values. Bulk iron strongly correlates with magnetic susceptibility. Iron tends to form ferruginized horizons (original siderites) in finer grained siliciclastic beds associated with coal seams. These beds also tend to be enriched in Cu, Ni, Pb, Zn, and other trace metals (metal enrichment horizons or MEHs). MEHs formed in ponded conditions of coastal low‐pH marshlands vegetated by mangrove‐like lycopsid bushes. Well‐drained environments of palaeokarst formation and alkaline everglades (Akulshino palustrine event) on the other hand did not accumulate Fe and trace metals. The thin shale seam (found close to the Viséan–Serpukhovian boundary in Polotnyanyi Zavod) has unusually high Rb and Sr values, which may contain volcanigenic material useful for absolute dating. The Gurovo Formation (Steshevian Substage of the Serpukhovian) is less enriched in Fe and Ti. In the Gurovo Formation, the transition from the lower montmorillonitic shale (Glazechnya Member) to the upper palygorskitic shale (Dashkovka Member) is expressed by a five‐fold increase in background MgO values, which indicates progressive shoaling and climatic aridization. Phosphorus remains close to 0% in the Oka Group and tends to increase in the Zaborie Group, in agreement with a dramatic increase of conodont numbers and other signatures of a lower Serpukhovian marine transgression. The lower half of the Glazechnya Member exhibits fluctuating enrichment in Fe, Cu, Ni, Pb, Zn, V, Cr, and Co. These fluctuations are mostly inverse to fluctuations of Mn. This pattern has been interpreted as a signature of seafloor oxygen deficiency, where Mn‐rich samples record oxygen‐poor environments (redox barrier level with the sediment surface) and Mn‐poor samples enriched in Fe and trace metals record transitions to anoxic setting. This interval is interpreted as the Lower Serpukhovian highstand. Enrichment in Fe, Ti, and Zr of Oka siliciclastic units of Polotnyanyi Zavod indicates provenance from the ore‐rich Voronezh Land, south of the Moscow Basin. The westerly flux regarded as a possible provenance in previous palaeogeographic reconstructions is discarded for the studied sections. The Gurovo Shale is also linked to the Voronezh province, although Fe, Ti, and Zr concentrations are lower than in the Oka shales. Copyright © 2014 John Wiley & Sons, Ltd.     

Vegetation changes and human impact inferred from an oxbow lake in southwestern Amazonia,Brazil since the 19th century

Pollen and X-ray fluorescence spectrometry (XRF) analyses from a 272 cm-long sediment core of Lago Amapá, an oxbow lake in western Amazonia, reveal the first palaeoecological investigation of late Holocene sediments in Acre state, Brazil. Radiocarbon dating of older sediments failed due to re-deposition of organic material but a historical map suggests that lacustrine deposition started at 1900 AD. We detected two periods of changes in sediment and vegetation, dominated by pioneer taxa especially Cecropia. The first period around 1900 AD is documenting an initial oxbow lake, with regular fluvial input (high Ti) and low accumulation of organic matter (low inc/coh ratio). During that period Andean pollen taxa originating from Peruvian Andean headwaters were deposited. A fully lacustrine phase started about 1950 AD and is characterized by prolonged periods of stagnant water (low Fe/Mn ratio). The increase of pioneer taxa, sedimentation rates and a reduction of most of the XRF element counts point to a period during which Lago Amapá was a more isolated lake which was flooded only during exceptional severe flood events and is catching mainly anthropogenic disturbances. The extensive human influence during this period was assumed by 1) the high occurrence of pioneer taxa and the absence of charcoal which could indicate changes in vegetation possibly as a result of logging, 2) the Ca and Ti/K ratio which reflect changes to a local sediment source, and 3) comparison of Landsat images from the last 30 years which shows broad changes in vegetation cover and land transformation in the peripheral areas of the oxbow lake.     

Chemical composition of the Tertiary black shales of West Sabah, East Malaysia

The X-ray fluorescence and ICP methods were used to analyze 60 outcrop samples of black shale, of which 15 were collected from Belait, 15 from the Setap Shale, 15 from Temburong, and 15 from the Trusmadi formations. The average compositions of the shales from the study area are 64.62%, 63.95%, 62.32%, 63.84% SiO2, 1.84%, 2.14%, 2.04%, 1.99% MgO, 2.55%, 3.12%, 2.89%, 2.72% K2O, 0.32%, 0.30%, 0.32%, 0.53% CaO, 5.86%, 6.06%, 7.14%, 6.60% Fe2O3, 207×10^-6, 180×10^-6, 213×10^-6, 200×10^-6 Rb, and 56×10^-6, 49×10^-6, 50×10^-6, 32×10^-6 Sr for the Setap Shale, Temburong, Belait and Trusmadi samples, respectively. The high Rb/Sr ratios of 3.8, 3.7, 4.2, and 6.1 are attributed to the lowest contents of Sr due to reducing conditions prevailing. The high Rb/K ratio sug- gests either brackish marine or rapid deposition that prevented equilibrium between Rb and K in the shales and marine waters.