Low Concentrations Of Trace Elements Research Articles

Gold source and deposition in the Sanakham gold deposit, SW Laos: Constrains from textures, trace element geochemistry and in-situ sulfur isotopes of pyrite

The Luang Prabang (Laos) – Loei (Thailand) metallogenetic belt is endowed with major porphyry-skarn, and epithermal gold deposits. The Sanakham gold deposit is a newly discovered hydrothermal vein-type orogenic gold deposits (10.6 t Au @ 3.05 g/t) in the belt, and consist of a series of quartz-sulfide veins that are controlled by secondary structures of the regional NNE-trending brittle-ductile shear zone. Its mineralization can be divided into four stages: (I) quartz–pyrite–arsenopyrite, (II) quartz–pyrite–pyrrhotite–chalcopyrite, (III) quartz–pyrite–base-metal sulfide, and (IV) quartz–carbonate. Three pyrite generations were identified: py1 (stage I) as disseminated euhedral to subhedral coarse grains; py2 (stage II) as subhedral to anhedral fine grains occur around the cataclastic and corrosion textures in py1; py3 (stage III) as subhedral to anhedral fine grains occurred in sulfide veins or veinlets that overprint the existing quartz-sulfides. All three generations of pyrite have low trace-element contents including very low lattice-bound gold (py1: 0.040 ppm; py2: 0.098 ppm; py3: 0.028 ppm) and arsenic (py1: 227 ppm; py2: 133 ppm; py3: 13.3 ppm) contents. Visible gold grains are sited in textures of pyrite grains that relate to brittle cataclastic deformation. Considering the relatively low contents of pyrite in the ores of Sanakham, it is impossible to derive the high-gold grade orebodies through local remobilization of originally lattice-bound gold in pyrite. The py2 might be formed during hydrothermal overprinting and dissolution of py1 led by continuous supply of ore fluids with relatively higher contents of Au, Ag, Cu, Sb, Te, Pb, and Bi. A reduction reaction related to reduced carbon species in wallrock is an assignable cause for gold deposition, even though the fluid-rock interaction and fluid immiscibility processes might be important. The Au- and As-poor pyrites have similar δ34S values (py1: –2.58 to –0.83 ‰; py2: –2.17 ‰ to + 0.25 ‰; py3: –1.24 to –0.60 ‰ ppm) that close to 0 ‰, indicating the sulfur may have been originated from magmatic or mantle sources. Therefore, we propose that the Sankham gold deposit is a member of the orogenic deposit class, but notably characterized by the low concentrations of invisible gold in the relatively As-poor pyrite lattice.

Chemical elements in Elaeis guineensis materials and derived oil

The production of oil palm (Elaeis guineensis) in Southeast Asia is vital to the economies of Indonesia and Malaysia. Both fertilisers and pesticides used in palm production can contain elevated concentrations of Trace Elements (TEs) which may accumulate in soils and leaf tissues of plants. We hypothesised that leaves from oil palms may be deficient in essential elements, while containing elevated concentrations of non-essential TEs commonly found in agrichemicals. Samples of plant materials (leaves and fruitlets) were collected from active and former plantations in Sumatra, Indonesia, and analysed for essential and non-essential elements. Indonesian palm oil samples were sourced in New Zealand and their elemental concentrations determined. Leaf materials from both active and abandoned production sites were deficient in N, K, S and Mo, while leaf materials from abandoned sites were deficient in P. These deficiencies may have been a contributing factor to the abandonment of production at these sites. Concentrations of non-essential elements were below or comparable to average plant concentrations and no evidence of contamination was found in plant tissues. Palm oil contained low concentrations of TEs, which did not pose any toxicity risks. However, Na and Al were present in concentrations of 1198 and 159 mg kg−1 respectively, which were higher than have been previously reported. Tropical oil palm production could benefit from the determination of bioaccumulation factors for fertiliser contaminants in E. guineensis, to limit the transfer of contaminants to plants and products if increased fertiliser applications were used to correct nutrient deficiencies.

Textural and chemical variations of sphalerite in the Giant Shuangjianzishan Ag-Pb-Zn deposit, South Great Xing’an Range, China: Implications for ore-forming processes

The Shuangjianzishan vein-type Ag-Pb-Zn deposit (145 Mt of ore grading 128.5 g/t Ag, 1.8 wt% Pb and 0.5 wt% Zn) in the South Great Xing’an Range (NE China) is hosted in NW- and NE-trending veins crosscutting the Lower Permian Dashizhai Formation, which is intruded by a granite porphyry. Although Ag-Pb-Zn sulfide mineralization has been extensively studied, the detailed ore-forming processes remain unclear. We have identified four stages of sulfide assemblages containing three generations of sphalerite: (1) Quartz arsenopyrite sphalerite (Sp1) stage; (2) Galena Ag-minerals sphalerite (Sp2) stage; (3) Ag-minerals pyrrhotite sphalerite (Sp3) stage; and (4) Pyrite calcite stage. Stages 2 and 3 are economically important. The textures of Sp1, Sp2, and Sp3 directly record the ore-forming processes, and the mineralization of silver shows an evolution trend from simple sulfides to complex sulfosalts. LA-ICP-MS trace element analyses showed that the Sp1 contains low content of silver and other trace elements (Fe, Mn, Sn, Cu, and Pb), indicating an anoxic to an euxinic environment. Stage 2 contributed largely to the silver endowment, with relatively high silver content in sphalerite or Ag-bearing mineral inclusions in Sp2a, Sp2b, and galena. Most of the silver minerals were deposited during stage 3, with sulfide and sulfosalt assemblages (e.g., pyrargyrite + canfieldite + tetrahedrite with minor pyrrhotite) replacing Sp2b. Selenium is significantly enriched in Sp3 and selenium-rich canfieldite from Stage 3. Sulfur isotopes determined by in situ LA-multicollector (MC)-ICP-MS analyses of sphalerite vary significantly from −9.6 to 2.2 ‰ (δ34SSp1 = -4.1 ∼ 1.1 ‰; δ34SSp2 = -4.2 ∼ 2.2 ‰; δ34SSp3 = -9.6 ∼ -2 ‰). Sulfur was possibly derived from the magmas forming the granite porphyry (δ34S = 1.4 ‰) and the magmatic sulfur reservoir was oxidized by mixing with the Dashizhai stratum sulfur (δ34S: −4.9 to −6.5 ‰). This resulted in lowering of the fluid δ34S value during the deposition of Sp3. The textural, chemical and isotopic data indicate distinct ore-forming episodes at Shuangjianzishan. We suggest that the deposition of abundant Ag-bearing minerals was induced by a new volume of Ag-rich ore-forming fluids and triggered by extensive decompression and cooling during Stage 3. The sulfur isotope and chemical geothermometers suggest the involvement of relatively high-temperature (>330 °C) hydrothermal fluid during Stage 2. Unlike a single cooling mineralization process, the superposition of relatively high-temperature mineralizing fluids may be an important factor in the large-scale Ag-Pb-Zn mineralization at Shuangjianzishan.

Tracking carbonatitic melt infiltration in the Miaoya carbonatite–syenite complex (central China) from zircon textures and geochemistry

The Miaoya carbonatite-syenite complex, located at the Qinling Orogenic Belt (central China), which hosts both Nb and REE mineralization. We studied the relationship of zircon grains within the carbonatitic and syenitic matrix by scanning electron microscope and optical microscopy combined with cathodoluminescence (SEM– and OM–CL) to identify primary versus secondary features. The primary zircon grain zones with magmatic oscillatory zoning and dull CL luminance crystallized at a relatively early stage of magma differentiation. In contrast, the secondary zones of zircon grains showing bright CL luminance were formed by recrystallization and contained numerous fractures with micro-inclusions of calcite and apatite, etc. The complicated texture of zircons strongly implies that zircons in both syenite and carbonatite had experienced solid-state recrystallization and dissolution-reprecipitation processes, respectively. Temperatures calculated using the Ti-in-zircon thermometer are ∼ 600 ℃ for the secondary zircons both in syenite and carbonatite. Hence, recrystallization processes were probably caused by varying degrees of metasomatic reactions involving late-stage residual carbonatitic melts, which were initially generated by silicate–carbonate liquid immiscibility at an earlier stage of magma evolution. The metasomatic reactions led to distinct geochemical and isotopic compositions of the secondary zircon. For instance, the secondary zircon is characterized by relatively lower concentrations of trace elements (e.g., REE, Th, U and Pb), LREE/HREE ratios, disturbances of the U–Pb ages and heterogeneous εHf(t) values (0.41 to 10.2). Our results imply that metasomatism due to infiltration of late-stage residual carbonatitic melts could play an important role in the evolution and of carbonatite-syenite system and related mineralization.

Geochemistry (TE, REE, Oxygen) of Zircon from Leucogranites of the Belokurikhinsky Massif, Gorny Altai, as Indicator of Formation Conditions

The present contribution deals with the isotopic-geochemical study (by Electron Probe Microanalysis (EPMA) and Method of Secondary Ion Mass Spectroscopy (SIMS) of zircons from Belokurikhinsky massif leucogranites, which resulted in the determination of two morphological varieties of zircons (zonal and porous). Zonal zircons exhibit low content of trace elements, a “magmatic” type of REE distribution spectra, and geochemical indices consistent with those of magmatic zircons. Anomalously high REE (up to 38 800 ppm), Y (up to 50 700 ppm) and U (up to 24 700 ppm) contents, as well as elevated Hf, P, F, Cl, and water contents (up to 3.5 wt %) were found in porous zircons. They display gently flattened REE distribution spectra with no Ce-anomaly and the persistence of negative Eu-anomaly, as well as geochemical parameters that differ from typical zircons of magmatic origin. The obtained geochemical characteristics of porous zircons reflect the process of enrichment of the magmatic melt with rare and rare earth elements, and indicate a high fluid saturation of the melt. The δ18О determined value for porous zircons is in the range of 9.22 to 12.54‰, which significantly exceeds a mantle value and seems to be caused by influence of external fluids interacting with sedimentary rocks surrounding leucogranites. The detailed isotopic-geochemical study of zircon samples suggests that their crystallization from leucogranites of a third (final) phase in the evolution of the Belokurikhinsky massif took place from fluid-saturated melt with elevated incompatible element concentrations.

In Situ Trace Element and Sulfur Isotope Composition of Pyrite from the Beiwagou Pb-Zn Deposit, Liaodong Peninsula, Northeast China: Implications for Ore Genesis

The Beiwagou Pb-Zn deposit, located in the western part of the Liaodong Peninsula, is a carbonate-hosted stratiform deposit with a Pb + Zn reserve of 0.08 Mt @ 4.14% (Pb + Zn). The orebodies occur as conformable layers and lenses and are strictly controlled by strata (the Paleoproterozoic Gaojiayu and Dashiqiao Formations) and lithology (plagioclase amphibolite and dolomitic marble). Given that previous studies have focused only on the mineralization features and mineralogy of deposits, herein, we report in situ trace element analyses of pyrite using LA-ICP-MS, together with in situ sulfur isotopes of pyrite, to constrain the composition, substitution mechanisms, source of sulfur, and sulfate reduction pathways of pyrite in the Beiwagou deposit. Based on pyrite morphology, texture, and chemistry, four pyrite types were identified: subhedral, porous-to-massive pyrite (Py1) related to chalcopyrite; subhedral, porous crushed pyrite (Py2) associated with fine-grained sphalerite; rounded and porous pyrite (Py3) related to the Zn-rich part of the laminated ore; and anhedral, porous-to-massive pyrite (Py4) associated with pyrrhotite, arsenopyrite, sphalerite, and galena. Py1 is characterized by high As, Ag, Cd, In, Au, Cu, and Zn concentrations and low Te, Bi, and Mo concentrations, whereas Py2 has high concentrations of Co and Ni and low concentrations of other trace elements, such as Cu, Zn, Bi, and Te. Py3 is characterized by elevated As concentrations, low Co, Ni, In, W, Te, and Tl concentrations, and varying Pb concentrations, whereas Py4 has low Ag, Cd, In, Zn, Cu, and Mn concentrations and varying W, Co, Ni, Pb, Sb, and As concentrations. Significant correlations between some elements in each pyrite type suggest substitution mechanisms, such as (Zn2+ + Cu2+ + Mn2+ + Cd2+) ↔ 2Fe2+, Ag+ + (Sb)3+ ↔ 2Fe2+, and (Te+ + Ag+) + Sb3+ ↔ 2Fe2+, and the existence of a negative correlation between Co and Ni implies competition between both elements. The strongly positive δ34S values (12.11‰–23.54‰) are similar to that of seawater sulfates and likely result from thermochemical sulfate reduction (TSR). In conclusion, the Beiwagou Pb-Zn deposit is a typical SEDEX deposit and mineralization likely occurred during diagenesis.

FORMATION OF THE COMPOSITION OF TRACE ELEMENTS OF SNOW DUST IN TYUMEN AND TOBOLSK USING HIERARCHICAL CLUSTER ANALYSIS

Link for citation: Zakharchenko A.V., Pasko O.A., Tigeev A.A. Formation of the composition of trace elements of snow dust in Tyumen and Tobolsk using hierarchical cluster analysis. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 8, рр. 110-120. In Rus. The relevance: search for new methodological approaches and techniques for assessing the aerosol migration of substances and characterizing air pollution. The purpose of the work is a comparative analysis of clusters of the content of microelements of the solid phase of snow in the closely located cities of Tyumen and Tobolsk with respect to clean background and areas subject to technogenic impact. The materials: the trace elements of solid phase of the snow cover. The methods: chemical-analytical for determining the content of trace elements, hierarchical cluster in the analysis of geochemical spectra, probabilistic-statistical. Results. The background dust load in Tobolsk is less, and the inner city load is higher compared to Tyumen. A cluster data structure of 8 clusters has been established with the allocation of two large groups that combine the Tobolsk and Tyumen sites, which are divided into clusters with low and high content of trace elements. Conclusions. The conditionally background cluster C6 is present in Tobolsk (22,6 %) and Tyumen (11,7 %), and C5 – 13 % in Tobolsk and 8 % in Tyumen. A specific Tobolsk cluster C8 with a predominance of scattered elements (48 %) was found at 2 sites in Tyumen, which may indicate a possible transfer of aerosols between these cities. Some technogenic clusters contained heavy metals, while others were dominated by Sc, Cr, Ni, Zn, and Cd. Technogenic clusters (C7, C1) differ in the shape of the geochemical spectrum: heavy metals predominate in some, trace elements (C8) predominate in others; the same applies to conditionally background samples. The specific technogenic Tyumen cluster C4 is distinguished by high values of Cu and Mo. Conditionally isolated background clusters had a low content of microelements. To identify environmental conditions, we moved from the standardized values of cluster analysis to their material content. It is shown that some clusters contain heavy metals, while others contain Sc, Cr, Ni, Zn, and Cd. Conditionally isolated background clusters had a low content of microelements. Using the content of microelements of the C5 cluster as a background, the environmental index of pollution Zc was calculated, which in Tobolsk reaches a high and dangerous level of pollution 60,8–83,7, in Tyumen – an average, moderately dangerous level Zc (32–64). The use of cluster analysis makes it possible to determine the trace elements pollution of snow dust and the territory as a whole.

A systematic evaluation of titanite reference materials for optimizing trace element and U[sbnd]Pb analysis by LA-ICP-MS

Titanite (CaTiSiO5) is a commonly occurring and versatile accessory mineral with broad applications in petrochronology. In situ U-Pb and trace element analyses via SIMS and LA-ICPMS are routinely performed using a matrix-matched reference material for U-Pb and standard glasses (non-matrix matched reference material) for elemental abundance determination. We report U-Pb isotopic ratios and major and trace element concentrations for three titanite samples (Ecstall, McClure and FCT) which are commonly used as reference materials in petrochronology studies. In addition, we characterize two new samples which can potentially serve as matrix-matched reference materials for titanite trace element geochemistry (BLR-2 and BRA-1). Based on electron microprobe analysis, samples BLR-1 and BLR-2 are homogeneous and suitable for use as a primary reference material for trace element concentrations. Whereas Ecstall, McClure, and FCT titanite reference materials show high intra-grain heterogeneity, yielding relative standard deviations for most trace elements between 5% and 40%, with higher standard deviations for U of 70% for Ecstall (n = 26), 265% for McClure (n = 22), and 202% for FCT (n = 26). Therefore, we suggest that these grains are unsuited to serve as reference materials for trace element quantification. The BRA-1 titanite has low trace element concentrations and is chemically heterogeneous (total REE abundances of 40 ppm for the rim and 95 ppm for the core of the grain), thus is not suitable for standardization of chemical composition using LA-ICPMS. It is commonly asserted that a matrix-matched standardization provides a more robust downhole fractionation correction compared to a non-matrix matched standardization. However, it remains unclear which standardization approach (matrix-matched vs non-matrix matched/glass) is more accurate for titanite trace element quantification. To resolve this, we tested several standardization approaches for trace element quantification, comparing matrix-matched (BLR-1) and non-matrix-matched (NIST612) standardizations with different internal elemental standards (IES; Ca, Si and Ti) and without internal standardization (semi-quantitative). To provide an independent constraint on the accuracy of the various trace element standardization techniques we compared results to trace element concentrations obtained via solution Q-ICPMS on crushed BLR-2 and BRA-1 aliquots. The matrix-matched standardization using Si as the IES yields the best reproducibility of trace element concentrations followed by the matrix-matched reduction using Ti as the IES. Moreover, the matrix-matched semi-quantitative correction yielded the lowest weighted percentage of difference compared to reference trace composition quantified by solution ICPMS. Finally, in this contribution we also benchmark sampling-size for precise U-Pb dating of common-Pb rich phases like titanite.

In situ characterization of pyrite from multiple microenvironments in middle Jurassic strata, northeastern Ordos Basin, China: Evaluation of synsedimentary/diagenetic fluid evolution

The sulfur isotopic composition and trace element content recorded in sedimentary pyrite have been widely used as a proxy to establish the geochemistry of pyrite-forming fluids. However, a continuous and complete evolution process of these fluids from the sedimentary period to diagenetic period remains not well constrained. The middle Jurassic strata (the Yan'an Formation containing coal seams and its overlying Zhiluo Formation hosting U deposits in the sandstone) in the northeastern Ordos Basin contain four kinds of microenvironments favorable for pyrite formation, namely coal, carbonaceous debris in barren gray sandstone, barren gray sandstone without carbonaceous debris and U mineralized gray sandstone from bottom to top, providing a good opportunity to decode pyrite formation in response to synsedimentary/diagenetic fluid evolution. In these microenvironments, pyrite named as PC, PD, PB and PM respectively, displays a variety of micro morphologies (framboidal, euhedral, infilling, irregular and cement) formed during sedimentary and diagenetic stages. PC has δ34S values ranging from −36.1 to +26.5 ‰ and low contents of total trace elements (from 6.7 to 58 ppm of Co + Ni + As + Se + Mo). PD and PB present δ34S signatures from −33.6 to +14.4 ‰ and from +9.7 to +22.2 ‰, respectively, with moderate trace element contents (from 21 to 111 ppm and from 23 to 80 ppm, respectively). PM resulting from the oxidation of PD and PB shows negative δ34S values (from −16.9 to −11.1 ‰ for framboidal pyrite and from −56.7 to −34.8 ‰ for euhedral pyrite + pyrite cement) and high trace element contents varying from 350 to 931 ppm. Detailed sulfur isotope and trace element microanalyses indicate that S involved in the formation of pyrite is derived from the fractionation process of organic sulfur in the coal, while Fe and trace elements originate from the surface-derived meteoric water. A paragenetic sequence from early PC, to PD and PB, and finally PM implies an evolution trend of δ34S values increasing first and then decreasing (bacterial sulfate reduction for framboids and Ostwald ripening for euhedral pyrite and pyrite cement of PM) and gradual enrichment of trace elements from synsedimentary to diagenetic fluids. The quantitative results can contribute to a better understanding of synsedimentary/diagenetic fluid evolution both locally and regionally for sedimentary strata in the low-temperature system.

Genetic implications, composition, and structure of trioctahedral micas in xenoliths related to Plinian eruptions from the Somma-Vesuvius volcano (Italy)

Abstract The present work is part of a systematic mineralogical and petrographic characterization of mica-bearing xenoliths from Somma-Vesuvius volcano (Roman Magmatic Province, southern Italy). Skarns, composite skarns-marbles and cumulates from Pompeii Plinian eruption (AD 79), and skarns and syenite from Avellino eruption (3945 ± 10 cal yr BP) were investigated to define the crystal chemistry of the Somma-Vesuvius trioctahedral micas and to draw inferences on petrogenetic processes to which they were subjected. Xenoliths were characterized by means of polarized optical microscopy, scanning electron microscopy (SEM-EDS), X-ray powder diffraction (XRPD), and bulk-rock geochemical analyses. Mica crystals were studied using electron microprobe analysis (EMPA) and single-crystal X-ray diffraction (SCXRD). Micas from skarns are variably associated with Mg ± Ca silicates (clinopyroxene, vesuvianite, humite, clinohumite, chondrodite, forsterite, and garnet), other sporadic silicates (anorthite, sodalite, titanite, and britholite), apatite, calcite, various types of oxides, as well as rare sulfides and halides. In composite skarn-marble rocks, the mineral assemblages show some differences compared to skarns, as a lack of clinopyroxene and the presence of dolomite. Cumulate samples consist of mica and clinopyroxene, whereas syenite is mainly composed of mica, K-feldspar, feldspathoids, and clinopyroxene. Together with mica, apatite occurs in all the lithotypes. Trace element arrays are scattered for skarn and composite skarn-marble samples. The REE patterns have a general enrichment in light (La, Ce, Pr, Nd) and medium (Sm, Eu, Gd, Tb, Dy) rare earth elements, in some cases with slight positive Gd anomaly. Cumulate samples generally have low amounts of Ba, Sr, Zr, and Th, while syenite exhibits low concentrations of trace elements, except for Rb, Cs, and Tl. Mica crystals occurring in the studied xenoliths are phlogopite with different Al and Mg contents at the octahedral site, a negligible tetraferriphlogopite component and variable dehydrogenation degree. All samples belong to the 1M polytype (C2/m and C2 space group) and have a wide range of unit-cell parameters, especially of the c axis [5.3055(1) ≤ a ≤ 5.3218(1) Å, 9.1893(1) ≤ b ≤ 9.2188(4) Å, 10.1803(2) ≤ c ≤ 10.2951(2) Å]. The shortest c-cell parameter pertains to de-hydrogenated phlogopite from Avellino skarn, whereas OH-rich phlogopite from Pompeii composite skarns-marbles has a c-cell parameter that approximates that of the end-member phlogopite. Overall, it is observed that the crystal chemistry of the micas studied here extends the known range of the other Vesuvian micas from the literature. The Ti-depletion and the wide degree of dehydrogenation of phlogopites from skarns and composite skarns-marbles suggest that the studied samples originated under variable pressure conditions. In addition, the presence of humite in the mineral assemblage seems to indicate the occurrence of devolatilization reactions. The scarce mica occurrence in cumulate and mainly in syenite, instead, may depend on pressure conditions in the magma storage system exceeding the mica stability.

Mineralization and genesis of the orogenic gold system in the Kalamaili area, East Junggar, Xinjiang, northwestern China

There are many lode gold deposits and occurrences in the Kalamaili area of the East Junggar, northwestern China. However, little is known about the specifics of ore geology and geochemistry of these gold deposits because of very limited exploration and research work in this region. Field geology, fluid inclusions, stable isotopes, trace elements in quartz, and hydrothermal zircon U-Pb dating are combined in this study to constrain the nature and source of ore fluids, the timing of mineralization, and the mechanism of gold precipitation in Kalamaili. The gold deposits are confined to a narrow zone between two regional NW- to NWW-trending shear zones and are structurally controlled by secondary, high-angle faults of the shears. The orebodies occur in the Middle Devonian and Lower Carboniferous, zeolite to lower greenschist facies clastic sedimentary and pyroclastic rocks. Gold mineralization occurs as auriferous quartz-sulfide ± tourmaline veins/veinlets and disseminated ores in the immediate altered wall rocks. The ore mineralogy is relatively simple and dominated by quartz with minor to trace amounts of sulfides (pyrite and arsenopyrite), sericite, calcite, and native gold. Quartz of various generations contains three types of fluid inclusions, including predominant H2O-CO2-NaCl inclusions and subordinate H2O-NaCl inclusions and CO2 ± CH4 ± N2 inclusions. The mineralizing fluid is uniformly characterized by a medium to high homogenization temperature (mostly 240−330 °C), low salinity (typically <6 wt% NaCl equivalent), reduced, and CO2-rich-H2O-NaCl ± CH4 fluid. The hydrogen and oxygen isotope data (δ18OH2O = +5.6‰ to +14.3‰, δDH2O = −99‰ to −62‰) indicate a metamorphic origin for the mineralizing fluid. The majority of sulfide δ34S values range between 0‰ and +10‰, indicative of a largely sedimentary rock reservoir of sulfur in the ore-forming fluids. Geochemically, the auriferous quartz is characterized by low concentrations of most trace elements including Ti, Al, Li, Ge, and Sb. Laser ablation−inductively coupled plasma−mass spectrometry U-Pb isotope dating of hydrothermal zircons from the auriferous quartz vein yielded a weighted mean 206Pb/238U age of ca. 313 Ma. Phase separation of ore fluids and fluid-rock interaction are suggested as key mechanisms for the gold precipitation. Integrated geological and geochemical evidence indicates that formation of the orogenic gold system in Kalamaili is related to the transition from compressional to transcurrent deformation during the Late Carboniferous. Target gold exploration in this region should focus on the northeast side of the Kalamaili fault zone, where there exist suitable structural and stratigraphic trap sites with high fluid flux and potential gold mineralization.

Geochemistry of color-zoned apatite from the Chadormalu iron oxide-apatite deposit, Central Iran: Insights into REE mobility during hydrothermal alteration

Apatite in the ‘Kiruna-type’ iron deposits is known as potential resource of rare earth elements (REEs). The present study describes large color-zoned apatite crystals in the Chadormalu magnetite-apatite deposit, Central Iran, to obtain insights into the behavior of REEs and trace elements during apatite mineralization and subsequent hydrothermal alteration. The zoned apatite consists of a beige-colored core and surrounding reddish and white polycrystalline domains. The beige-colored core is optically single crystals, but shows a replacement texture of the early-stage apatite (Ap-I) by the later-stage apatite (Ap-II) with abundant monazite inclusions. Ap-I is characterized by higher REEs, Y, Na, Si, S and Cl contents than Ap II. Both Ap II and reddish/white polycrystalline domains show similar compositions with very low contents of REEs and trace elements. These textural and chemical relations suggest that initial apatite mineralization (Ap-I) was followed by an intensive hydrothermal event, which has resulted in dissolution of Ap-I and precipitation of Ap-II and surrounding polycrystalline domains. REEs in Ap-I were leached into the fluid and precipitated as monazite inclusions in Ap-II and interstitial monazite in the reddish domain of polycrystalline apatite. Parts of REEs leached in the fluid are also incorporated into cores of the polycrystalline apatite. It is concluded that, although the later hydrothermal event remobilized REEs, it did not significantly affect the total REE budget of the investigated apatite-magnetite ore deposit.

Source of gold and ore-forming processes in the Zarshuran gold deposit, NW Iran: Insights from in situ elemental and sulfur isotopic compositions of pyrite, fluid inclusions, and O−H isotopes

The Zarshuran gold deposit (155 t Au, average grade: 2.63 g/t), NW Iran, provides a new paradigm for understanding the multicomponent ore-forming processes and metallogeny of gold during the evolution of hydrothermal fluids. It is characterized by auriferous quartz veins and gold coexisting with disseminated Fe-As-S sulfide minerals that are hosted in a sequence of Early Cambrian metasedimentary rocks. A complex paragenesis is defined by five sulfide stages: pre-ore stage pyrite (Py0), early ore-stage pyrite (Py1 and Py2), middle ore-stage pyrite (Py3a, Py3b, and Py3c), late ore-stage pyrite (Py4), and post ore-stage pyrite (Py5). Py0 with framboidal texture is characterized by relatively low concentrations of As, Au, Cu, and Sb, and has a broad range of negative δ34S values from −28.2 to −3.7 ‰, indicating microbial reduction of marine sulfate. Py1 and Py2 show porous texture with As-rich bright bands also having high Au (mean: 18.4 ppm). Similarly, narrow ranges in δ34S from −3.6 to +3.2 ‰ likely suggest a deep-seated magmatic sulfur source. In the middle ore-stage, Py3a cryptocrystalline cores have a range of positive δ34S (+5.4 to +26.7 ‰) values and high concentration of As(-Au), whereas later well-crystallized outer rim Py3c is Co(-Ni) rich, has a much more restricted δ34S range (−2.9 to +1.4 ‰), indicating an evolution of fluid composition from As-rich to Co-rich. Most of the gold (mean: 20.2 ppm) and trace elements (Hg, Ag, Sb, and Tl) were deposited in Py4, whose δ34S values (+5.4 to +26.7 ‰) show that ore fluid sulfur in this stage was mainly sourced from a mixture of magmatic sulfur with minor input of reduced sedimentary rocks. Low gold and trace element content with slightly negative δ34S values (–8.5 to –4.2 ‰) of Py5 show that they were likely formed from a metal-poor oxidizing fluid.The mineralizing fluid system can be described as carbonic-aqueous with low to moderate salinity (3.2–15.1 wt% NaCl equiv.) and medium temperature of 285 to 317 °C (early ore-stage) and 255 to 290 °C (late ore-stage), which suggests that phase separation was responsible for gold precipitation during late ore-stage As-Hg-Sb sulfide veins. The δ18Ofluid ranges from −7.8 to +4.2 ‰, and the δD values for fluid inclusions in mineral range from −105 to −65 ‰, suggesting involvement of meteoric water during late- to post ore-stages. Our results indicate that the Zarshuran is a distal disseminated gold deposit formed during southward subduction of the Proto-Tethys oceanic lithosphere beneath the northern margin of Gondwanan terranes through the early Cambrian.

Accumulation of Plastics and Trace Elements in the Mangrove Forests of Bima City Bay, Indonesia.

Pollution with microplastics (MPs), nanoplastics (NPs) and trace elements (TEs) remains a considerable threat for mangrove biomes due to their capability to capture pollutants suspended in the water. This study investigated the abundance and composition of plastics and TEs contained in the soil and pneumatophores of Avicennia alba sampled in experimental areas (hotel, market, river mouth, port, and rural areas) differentiated in anthropopressure, located in Bima Bay, Indonesia. Polymers were extracted and analyzed with the use of a modified sediment isolation method and Fourier transform infrared spectroscopy. Trace elements were detected by inductively coupled plasma optical emission spectrometry. The lowest and highest quantities of MPs in soil were recorded in rural and hotel areas, respectively. The rural site was characterized by distinct MP composition. The amounts of sediment-trapped MPs in the tested localities should be considered as high, and the recognized polymers partly corresponded with local human activity. Concentrations of seven plastic types found in plant tissues did not entirely reflect sediment pollution with nine types, suggesting a selective accumulation (particularly of polyamides and vinylidene chloride) and substance migration from other areas. Very low concentrations of non-biogenic TEs were observed, both in sediments and pneumatophores. The results highlight the relevance of environmental contamination with plastics.

CONTRIBUIÇÕES MINERALÓGICAS E GEOQUÍMICAS SOBRE A ORIGEM DO MINÉRIO DE MANGANÊS DO MORRO DO URUCUM (CORUMBÁ, BRASIL)

This article was prepared in 2011 and its publication at this time represents a reminder to Prof. doctor Herbert Pöllmann, who contributed to the field and analytical activities. The manganese ore from Urucum, in Mato Grosso do Sul, constitutes an important reserve of this mineral good and in recent years has been the scene of many constant researches in several publications, mainly in the last five years, with emphasis on both Mn and Fe. At the time we analyzed the few samples of this unpretentious article, publications were still scarce. Our analyzes are restricted to a few samples and the sampling is not representative of the different levels at which Mn ore occurs. The mineralogical and chemical results of these samples indicate mineralogy dominated by cryptomelana and low concentrations of most trace elements, especially REE. Anomalous are mainly Ba, Sr and Co. The origin o this ore is undoubtedly sedimentary, with little or no terrigenous contribution.

Дундговь болон Хэрлэнгийн төмрийн металлогений бүсэд тархсан төмрийн ордууд

Iron Oxide Apatite and Iron Oxide Copper Gold deposits generally consist of Fe and Cu-Au ore, and some deposits occasionally are recognized P, REE, Co, Ag and U. IOCG deposits are divided into magnetite and hematite subtypes by general ore mineral. Magnetite type IOCG has Na-Ca or, Na and potassic alteration zones, ore bodies are breccia and veins in shapes, ore-forming fluid was δ18O light supplied by magmatic and metamorphic waters. Hematite IOCG has a little potassic alteration zone, and ore bodies are formed breccia and lens in shapes in sericitic-chloritic alteration zone. Ore-forming fluid was δ18O heavy supplied by magma with a significant contribution of meteoric water. Banded Iron Formation is divided into Algoma, Superior and Rapitan sub types. The Algoma type BIF has δ18O of primary silica changed from +8‰ to +20‰ at temperatures below 100°C during diagenesis, indicating that although O isotope exchange occurs during diagenesis, low concentrations of rare earth and trace elements in siliceous shale do not change in ocean water-derived fluids. The Rapitan type, when the Earth’s oceans were almost completely covered by ice and cut off from the atmosphere, the ferruginous quartzite was deposited in the water at a time when the oceans were re-oxygenated. Prominent deposits of superior-type ferruginous quartzite occur in Paleoproterozoic sedimentary basins or in shallow-water sedimentary rocks of the continental shelf (Dartsagt, Ereen). Iron skarn deposits are divided into calcic, magnesian, and scapolite (albite) by their general chemical composition. Calcic iron skarn is developed at contact of carbonate bearing rocks and basic intrusion, and ore consists of magnetite, chalcopyrite, cobaltite, and pyrrhotite. Host rocks of magnesian iron skarn are typically dolomite, or limestone, quartzite, and schist associated with dolomitic. Ore minerals are recognized as magnetite, chalcopyrite, pyrite, sphalerite, arsenopyrite, and pyrrhotite in these type deposits (Bargilt). Host rocks are andesite, tuff, limestone, argillite at the scapolite (albite) iron skarn, then magnetite, hematite, pyrite, marcasite, chalcopyrite, sphalerite, pyrrhotite, and arsenopyrite are ore minerals.

Recycling of bottom sediment to agriculture: effects on plant growth and soil properties

PurposeThe use of bottom sediments in agriculture reduces the storage of excavated material and allows the nutrients it contains to be applied for soil fertilisation and improvement. However, the direct application of sediments to soil may cause numerous problems. Therefore, the addition of other waste materials may be a promising and useful method in the production of bottom-sediment-based growing media. The aim of the study was to evaluate the effect of growing media prepared on the basis of bottom sediments and various waste materials on the properties of soil as well as on the yield and chemical composition of courgette biomass.MethodsThe growing media were prepared with substrates in the form of mixtures with bottom sediments taken from the Rożnów reservoir. The effect of mixtures on plant growth was determined in a laboratory pot experiment. Air-dry mixtures (M1—bottom sediment with water treatment sludge (BS + SW); M2—bottom sediment with biomass ash (BS + BA); M3—bottom sediment with coffee hulls (BS + CH)) were mixed with soil (S) in the following proportions: combination I—25%, combination II—50%, combination III—75%, and combination IV—100% mixture.ResultsThe media did not have harmful effects on the plant or the soil environment. They had deacidifying properties; high contents of calcium, magnesium, potassium, and phosphorus; low total trace element content; and posed little risk of metal mobility. Heterocypris incongruens was the organism most sensitive to the substances contained in the studied media. The use of bottom-sediment-based media reduced the biomass of the test plant and, at the same time, limited the accumulation of trace elements in its aboveground parts.ConclusionMost of the analysed media were low-toxic to the test organisms and can potentially be used in agriculture, horticulture, or the reclamation of degraded land.

Polycyclic soils with Bt and Bw developed on mafic rocks in a forest cerrado transition environment in Roraima, northern Amazon, Brazil

In the extreme north of Brazil, in Roraima, there is an important set of mafic, volcanic or plutonic rocks, associated with the Juro-Cretaceous magmatism, and one of the most extensive areas is the Colônia do Taiano region, the first agricultural colony of Roraima. In addition to basalts, many diabases and diorites occur, forming an extensive patch of soils with good agricultural suitability, in the cerrado-forest transition. Two soil profiles developed from diabase were studied, after selecting the most representative pedons of the area. P1, an Argissolo Vermelho Eutrófico latossólico (Ultisol) and P2 an Argissolo Vermelho Eutrófico típico (Ultisol), were described and collected. Morphological, physical, chemical, mineralogical analyses, and extraction of Fe, Al, Ti and Si oxides by sulfuric attack were carried out; Fe2O3, Al2O3, TiO2, and SiO2, by plasma emission spectrometry; and Fe-DBC (dithionite-citrate-bicarbonate) and Fe ammonium oxalate. The soils presented a typical latosolic morphology at the base of the profile, with the top of the B horizon showing waxiness varying from moderate to abundant, thus revealing a polycyclic genesis of Bt superimposed on Bw, formed in a previous cycle. The SiO2 contents indicated a desilication process, and the low contents of trace elements and TiO2 showed mafic materials poor in magnetite, and reworking of the parent material by pediment in a drier climate. The Feo/Fed ratio proved to be atypical for the Amazon region, consistent with the mafic lithology.

Trace Element Geochemistry of Alluvial TiO2 Polymorphs as a Proxy for Sn and W Deposits

The Segura mining field, the easternmost segment of the Góis–Panasqueira–Segura tin–tungsten metallogenic belt (north–central Portugal), includes Sn-W quartz veins and Li-Sn aplite-pegmatites, which are believed to be genetically related to Variscan Granites. Sediment geochemistry indicates granite-related Ti-enrichments, locally disturbed by mineralization, suggesting magmatic and metamorphic/metasomatic titaniferous phases. Therefore, Segura alluvial samples and the geochemistry of their TiO2 polymorphs (rutile, anatase, and brookite) were investigated, and their potential as exploration tools for Sn and W deposits was evaluated. The heavy-mineral assemblages proved to be good proxies for bedrock geology, and TiO2 polymorph abundances were found to be suitable indicators of magmatic and/or metasomatic hydrothermal processes. The trace element geochemistry of Segura’s alluvial rutile, anatase, and brookite is highly variable, implying multiple sources and a diversity of mineral-forming processes. The main compositional differences between TiO2 polymorphs are related to intrinsic (structural) factors, and to the P-T-X extrinsic parameters of their forming environments. Anomalous enrichments, up to 9% Nb, 6% Sn and W, 3% Fe, 2% Ta, and 1% V in rutile, and up to 1.8% Fe, 1.7% Ta, 1.2% Nb, 1.1% W 0.5% Sn and V in anatase, were registered. Brookite usually has low trace element content (<0.5%), except for Fe (~1%). HFSE-rich and granitophile-rich rutile is most likely magmatic, forming in extremely differentiated melts, with Sn and W contents enabling the discrimination between Sn-dominant and W-dominant systems. Trace element geochemical distribution maps show pronounced negative Sn (rutile+anatase) and W (rutile) anomalies linked to hydrothermal cassiterite precipitation, as opposed to their hydrothermal alteration halos and to W-dominant cassiterite-free mineralized areas, where primary hydrothermal rutile shows enrichments similar to magmatic rutile. This contribution recognizes that trace element geochemistry of alluvial TiO2 polymorphs can be a robust, cost- and time-effective, exploration tool for Sn(W) and W(Sn) ore deposit systems.

Mineralogy and geochemistry of serpentinized peridotites of the Northern Nubian Shield: The origin of compositionally banded olivine and implications for Neoproterozoic supra-subduction zone metasomatism

A sequence of Neoproterozoic ultramafic rocks — serpentinized peridotite, serpentinite, and clinopyroxenite — outcrop in Wadi El-Mireiwa in the south Eastern Desert of Egypt. They represent the mantle and lowermost crustal section of a fragmented ophiolite, emplaced by thrusting above metasedimentary rocks and an island arc assemblage and later intruded by a granite mass. In samples of the serpentinized peridotite, back-scattered electron images of olivine reveal banded zoning, defined by straight and parallel Mg-enriched (Fo ∼ 96) lamellae within typically magnesian host crystals (Fo ∼ 89). The presence of clinopyroxene, the relatively low whole-rock Mg# (∼88), the low NiO content of olivine (0.1–0.32 wt%), and the relatively high TiO2 content of fresh Cr-spinel (∼0.3 wt%) are all consistent with a cumulate origin for the serpentinized peridotite and serpentinites. On the other hand, some associated serpentinite has higher whole-rock Mg# (92) and low TiO2 in Cr-spinel (∼0.01 wt%), consistent with a residual origin by high-degree melt extraction in the fore-arc region of a supra-subduction zone (SSZ) environment. The formation of Mg-enriched bands in olivine is attributed to the enhancement of metasomatic Mg-Fe exchange with high-Mg/Fe2+ fluids along crystallographically-oriented subgrain boundaries produced by high strain-rate dislocation creep. Such high-Mg/Fe2+ fluid metasomatism also explains reverse zoning of MgO in Cr-spinel, whereas the low whole-rock concentrations of REE and other trace elements exclude a significant role for melt-rock interaction. The evidence for high-Mg/Fe2+ fluid metasomatism in this suite indicates that SSZ fluids and high fore-arc strain rates affect not only the mantle wedge but also overlying ultramafic cumulates. The oxygen fugacity [ΔlogƒO2(FMQ)] values calculated from unmetasomatized (+2.48 to +2.67) and metasomatized (+3.75 to +4.53) samples reflect the oxidized nature of Neoproterozoic SSZ magma and the even more oxidizing character of the metasomatic fluids. Banded zoning has also been recorded in olivine from Mariana fore-arc peridotite and Phanerozoic SSZ ophiolites; the Neoproterozoic Wadi El-Mireiwa case shows that rapid mantle flow has been a persistent feature of the tectonic environment where fore-arc ophiolites develop.