Element Distribution Patterns Research Articles

Trace metals in surface sediments from the Laptev and East Siberian Seas: Levels, enrichment, contamination assessment, and sources

Trace metals in Laptev and East Siberian Sea sediments were analyzed to examine the element distribution pattern and to assess sediment contamination using contamination indices. The maximum Cr, Zn, Ni, Cu, and As concentrations occurred in the deeper parts of the East Siberian and Laptev Seas and the estuarine shelves of the Lena and Yana Rivers, and a high Cd content was observed in the sediment of the eastern part of the East Siberian Sea. The increased Cd concentration could be a result of the large number of phytoplankton supplied by the highly productive waters of the Bering Sea and the sorption capacity of Cd precipitation on Fe and Mn oxyhydroxides in seawater. The mean enrichment factors and geoaccumulation index values for Cr, Ni, Cu, Zn, Pb, and Cd showed no contamination by these metals at any sampling locations; however, slight As enrichment was found, possibly originating from natural sources.

Porphyry indicator zircons (PIZ) and geochronology of magmatic rocks from the Malmyzh and Pony Cu-Au porphyry ore fields (Russian Far East)

New data obtained by petrographical, geochemical and U-Pb geochronological studies of magmatic whole rock and zircon samples from the Malmyzh and Pony gold-copper porphyry ore fields are discussed. The trace elements distribution patterns (REE + Y, Hf, Ti, U, Th, Pb) in zircons have been measured by SIMS SHRIMP-IIe instrument in the same spots as for local U-Pb age dating. Geochronological data show a matching Cenomanian crystallization age of the Malmyzh and Pony magmatic rocks: 99–97 and 93 Ma, respectively. ∑REE in zircons from the Malmyzh granitoids varies from 217 to 1,158 ppm, Y – from 718 to 732 ppm, Hf – from 4,524 to 4,928 ppm, Ti – from 4.1 to 16.6 ppm, Pb – from 1.2 to 1.6 ppm, U – from 89 to 112 ppm, Th – from 58 to 76 ppm. Geochemical characteristics of zircons from the Pony monzodiorite-porphyry differ significantly from the Malmyzh granitoid zircons. Concentrations of most trace elements in the Pony zircons, especially LREE and MREE, as well as Y, Pb, U, Th, and Ti are two–three times higher than in zircons from the Malmyzh granitoids. Temperature of zircon crystallization of the Malmyzh granitoids revealed by «Ti in zircon» thermometer is estimated at 680–700 °C, whereas temperature of zircon crystallization of the Pony monzodiorite-porphyry is approximately 784 ± 15 °C. Fertility assessment of magmatic rocks from the Malmyzh and Pony ore fields is based on geochemical characteristics of zircons like Eu/Eu* vs. Dy/Nd and Eu/Eu* vs. (Ce/Nd)/Y plots. These characteristics show that zircons from the Malmyzh granitoids fall into the field of fertile porphyry systems, whereas zircons from the Pony monzodiorite-porphyry plot within the field of barren suites. Comparative analysis of studied samples from the Malmyzh and Pony ore fields with magmatic rocks from porphyry deposits worldwide aids our understanding of the geodynamic framework of their formation and establishes links to adakitic granitoids generated under similar conditions. This result can be utilized during prognostic and metallogenic considerations not only within the limits of Sikhote-Alin territory but also within the whole Russian Far East region.

Petrological and Geochemical Characteristics of the Cretaceous Ngaou Boh Anorogenic Complex (Adamawa Plateau, Cameroon Line): Preliminary Constraints

The Cretaceous Ngaou Boh anorogenic complex (NBAC) located in the far North Adamawa Plateau, the centre domain of the Cameroon Line constitutes a plutonic-volcanic ring association. The whole rock K-Ar datation yields a crystallization age of ca. 74 Ma. Plutonic rocks comprise abundant alkali feldspar granites, scarce clinopyroxene-amphibole gabbros and alkali feldspar syenites. Alkali feldspar granites are leucocratic, coarse to fine-grained; quartz and K-feldspars are the major rock-forming mineral, besides minor oligoclase, biotite and accessory phases as sphene, zircon and opaques. Alkali feldspar syenites are mesocratic coarse-grained, mainly composed of K-feldspars with small amounts of quartz and biotite. Volcanic rocks consist of a basanite-trachyte-rhyolite suite. Basanites contain olivine and diopside phenocrysts and a groundmass essentially composed of plagioclase and titanomagnetite. Biotite-clinopyroxene trachytes and clinopyroxene-amphibole rhyolites have an almost homogeneous modal composition, mainly made up of sanidine and anorthoclase microliths, scarce phenocrysts of quartz, and minor crystals of biotite, clinopyroxene (augite) amphibole (pargasite, sandagaite); Fe-Ti oxides (ilmenite, titanomagnetite) and fibreglass are often isolated in the groundmass. Plutonic rocks are alkaline, weakly metaluminous with some alkali feldspar granites displaying agpaitic or peralkaline feature. Incompatible Trace elements (HFSE and LILE) distribution and chondrite-normalized REE patterns evidence a significant petrogenetic link between clinopyroxene-amphibole gabbros, alkali feldspar syenites and alkali feldspar granites. All the analysed samples are enriched in incompatible elements, indicating melts from spinel and garnet-bearing mantle source close to OIB component. Indeed, the (Tb/Yb)N ratios of both basanites (2.3-2.5) and clinopyroxene-amphibole gabbros (1.4-1.9) suggest different parental magma sources. Alkali feldspar granites appear as residue of magma differentiation led by crystal fractionation of liquid derived from the partial melting of spinel peridotite mantle. Clinopyroxene-amphibole rhyolites and biotite-clinopyroxene trachytes (Mg#=0.0-15.4) derive through fractional crystallization from basanites (Mg#=64.3-60.1), the most primitive mafic parental melt. Both plutonic rocks and lavas trends evidence a bimodality highlighted by a pronounced “Daly gap”.

Geology, alteration geochemistry, and exploration geochemical mapping of the Ertsberg Cu-Au-Mo district in Papua, Indonesia

The Ertsberg-Grasberg district hosts the world's largest Cu-Au(Mo) skarn system. The mineralization is related to the Pliocene Ertsberg- and Grasberg intrusive complexes, which intruded the Jurassic-Cretaceous Kembelangan Group siliciclastics and Cenozoic New Guinea Limestone Group. Despite previous studies, elemental migration across the porphyry-skarn system and across the different ore stages is still unclear. Here, we attempt to tackle this issue by integrating ore deposit geology, alteration/mineralization paragenesis, whole-rock geochemistry of the Ertsberg granitoids and carbonate wallrocks, together with spatial mapping of hydrothermal minerals and target/pathfinder trace elements at the Deep Mill Level Zone of Ertsberg. Ores at Ertsberg are mainly skarn-hosted, whose formation comprises five stages: (I) prograde skarn; (II) retrograde alteration; (III) massive anhydrite replacement; (IV) late hydrothermal veining; (V) supergene alteration. Massive magnetite and main CuAu mineralization occurred in Stage II and III, respectively, although minor Cu mineralization persisted to Stage IV.The Ertsberg granitoids have medium SiO2 and high Al2O3 contents, and consist mainly of (quartz-)monzonite and minor (monzo)diorite. Least-altered samples have upper crust-normalized enrichments in certain large ion lithophile elements (LILEs, e.g., U and K) and depletions in all high field strength elements (HFSEs, e.g., Ti, Y, and Yb). The samples are fresh to moderately-altered, featured by garnet-diopside skarn and/or porphyry-style (potassic, propylitic, phyllic) alterations and anhydrite replacement. Elemental mass balance calculation indicates that the porphyry-style alteration zones are featured by feldspar destruction and the accompanying alkali depletions, although the loss of KRb (in potassic and phyllic zones) and Ca-Ba-Sr (in propylitic zone) are balanced by their respective capturing in secondary K-feldspar-mica and actinolite-epidote-anhydrite. Decarbonation of the dolomitic wallrocks likely released Mg-Ca-Sr, which facilitated the subsequent forsterite-diopside exoskarn and anhydrite alteration. The enrichments of various ore-related target/pathfinder elements in these altered samples are consistent with their mineralized nature, e.g., FeMn (magnetite), Cu-Fe-Bi-Se-Te (bornite), MoRe (molybdenite), Au-Ag-As-Bi-Te (auriferous pyrite/arsenopyrite), Zn-Fe-Mn-Sn-In (sphalerite), and Pb-Ag-Bi (galena).Alteration mineral and target/pathfinder elemental distribution patterns show that the ore fluids were likely originated from the porphyry hydrothermal (potassic) centers near the Ertsberg pluton margin. The fluids then spread out from the potassic centers, forming the surrounding propylitic zone, and migrated along the largely NW-SE-oriented intrusive contact and fault zones. This formed the endoskarn in the Ertsberg pluton, the forsterite-diopside exoskarn in the Waripi Formation dolomite, and the garnet-diopside exoskarn in the Ekmai Formation limestone/calcareous sandstone-siltstone. As the hydrothermal system started to wane, the prograde skarn formation is partially overprinted/enveloped by retrograde serpentine and actinolite/tremolite-epidote-chlorite alterations, and then by magnetite mineralization and massive anhydrite replacement in the carbonate wallrocks. The texturally-destructive skarn formation, and the dissolution of carbonate wallrocks and hydrothermal anhydrite were likely pivotal in creating the highly-fractured Broken Zone, which served as a structural trap for the high-grade Cu-Au-Mo ore deposition.

Weathering profiles developed on gneisses from Batchenga and Doua areas, central Cameroon: Climate and topography controls

Two weathering profiles from Batchenga and Doua areas in Central Cameroun developed under contrasting equatorial climate conditions and located in different morphological units have been selected to constraint the variability of their morphology, mineralogy, and geochemistry. The parent rock is a biotite and amphibole gneiss with a heterogranular granoblastic texture. The weathering profiles are typical lateritic materials formed in a humid tropical climate zone. They comprise, from bottom to top, coarse saprolite, fine saprolite, nodular horizon and loose clayey horizon. The Doua weathered materials are more clay-rich as a result of intense chemical weathering (CIA: 95.0–99.5%) than those of Batchenga (CIA: 51.3–87.8%). The weathering profile of Doua is thicker (12.00 m) than that of Batchenga (6.30 m). The intense chemical weathering and the total leaching of mobile elements as a consequence of good drainage led to the formation of a hard nodular horizon in the Doua weathering profile. The mineral composition is dominated by quartz, kaolinite, muscovite, illite, hematite/goethite, gibbsite and anatase. Illite is particularly abundant in the Batchenga weathering profile. Among trace elements, Ba, V, Zr, Sr, and Cr have high contents while REE show moderate contents with the highest contents in the Batchenga weathering profile. The oxidizing conditions favor positive Ce anomalies while positive Eu anomalies are due to the resistance of Eu mineral bearers. Geochemical mass balance results suggest that climate and topographic position which influence the quality of drainage greatly influence the distribution patterns of major, trace and rare earth elements in the weathering profiles. Apart from Al, Fe, and P, major elements have been much leached than trace elements during chemical weathering. Thus, the important variations are explained by the variation in the annual rainfall and topographic conditions.

Trace element geochemistry of sphalerite and chalcopyrite in arc-hosted VMS deposits

Trace element compositions of sphalerite and chalcopyrite have been investigated for four arc-hosted Cretaceous VMS deposits (María Teresa, Perubar, and Palma in Peru, and Cerro de Maimón in the Dominican Republic) using laser ablation inductively-coupled plasma mass spectrometry. In sphalerite, Fe, Mn, Cd, Hg, Ag, Sb, Se, In, Ge, and Ga are lattice-bound, whereas Sn, Tl, Bi, and Pb occur at least partly as mineral microinclusions. Significant variations in the contents of minor and trace elements are observed in sphalerite grains from individual deposits. A strong negative correlation between Fe (Inter-Quartile Range [IQR] 44,009–18,168 ppm) and Zn indicates a dominant Fe2+ ↔ Zn2+ simple isovalent substitution. Regarding potential high-tech by-products, the contents of In (IQR 42–1.6 ppm, up to 415 ppm) and Ga (IQR 31–5.9 ppm, up to 96 ppm) in the studied sphalerite are normally much higher than those of Ge (IQR 0.85–0.16 ppm, up to 9.3 ppm). Correlation trends suggest Cu+ + In3+ ↔ 2Zn2+, Cu+ + Ga3+ ↔ 2Zn2+, and more complex substitution mechanisms of Zn involving combinations of monovalent (Cu+, Ag+), divalent (Ge2+?), trivalent (In3+, Ga3+, [Sn3+?]), and quadrivalent (Ge4+, Sn4+) cations.As for chalcopyrite, Zn, Ag, Sn, Cd, Se, In, Ga, and Ge are interpreted to be lattice-bound, whereas Mo, Au, Tl, Sb, Pb, and Bi probably occur as microinclusions. Relative to sphalerite, chalcopyrite is depleted in In (IQR 28–8.4 ppm, up to 49 ppm) and Ga (IQR 8.3–2.9 ppm, up to 24 ppm) and enriched in Ge (IQR 5.9–0.70 ppm, up to 80 ppm). Of the other trace elements, Zn (IQR 426–190 ppm) is the most highly concentrated in the studied chalcopyrite, followed by Ag (IQR 136–23 ppm), Se (IQR 64–22 ppm), Sn (IQR 53–1.3 ppm), and Cd (IQR 12–6.0 ppm). General positive correlation trends between Zn, Cd, In, Ge, and Ga in chalcopyrite suggest varied coupled substitution mechanisms of Fe and Cu with fluctuating valences due to covalent bonding.Trace-element distribution patterns in sphalerite and chalcopyrite were studied for the zone-refined Sofía-D massive sulfide body in the María Teresa deposit, which comprises a lower lower portion of dominant pyrite sheathed upward by zones of chalcopyrite (Cu zone), sphalerite (Zn zone) and galena + sphalerite ± fahlore ± barite (Pb – Zn – Ag zone). Bottom to top of the sulfide body, sphalerite records progressive depletion in In, Cu, Mn, and Se, and enrichment in Ge. This distribution pattern agrees with increasing crystallization temperatures and/or volatile magmatic influx towards the lower portion of the massive mineralization. Distribution of trace elements in chalcopyrite is rather uneven except for a sustained enrichment in Se towards the basal portion of the sulfide body. The fact that such trends are preserved in spite of extensive recrystallization during thermal metamorphism in parts of the Sofía-D massive sulfide mineralization suggests i) a closed metamorphic system and ii) that element interdiffusion was prominently local. Accordingly, we propose that sphalerite lattice-bound trace elements distribution patterns described in this article can help determine the polarity of massive sulfide bodies in VMS districts in metamorphosed and tectonized terranes.

Using multivariate statistical analysis in assessment of surface water quality and identification of heavy metal pollution sources in Sarough watershed, NW of Iran.

The Sarough watershed in NW Iran hosts a large amount of mineral occurrences and ore deposits which may be considered as the source of heavy metals in the region. The area has been studied previously; however, the methodology of this paper was less focused on previous studies. This study aimed to assess water quality, determine the spatial distribution pattern, and identify the sources of heavy metals in the main tributaries of Sarough watershed using pollution indexes, multivariate statistical methods, and processing data by geographic information system. Totally, 51 water samples were collected along the main rivers to determine the concentrations of heavy metals by ICP-MS. Regarding the drinking water, agriculture, and freshwater aquatic life guidelines, the rivers were assumed unsafe considering most of toxic elements' content, especially As. The mean values for heavy metal pollution indexes (HPI: 237.32) and metal indexes (MI: 25.37) indicated the intensive heavy metal pollution. The cluster analysis categorized the 51 sampling sites into four clusters with respect to pollution level. The results obtained from the Kruskal-Wallis and multiple comparison tests had the harmony with the results of CA in introducing the most impacted sampling sites and the parameters responsible for water quality degradation. The results of PCA showed the maximum similarity between As, Sb, Se, Fe, and Mn as well as base metals which was attributed to anthropogenic input from mining and mineral processing wastes. Association of Cr and Ni may suggest a lithology source (weathering of metamorphosed ultramafic outcrops). The maps prepared in the GIS system showed the spatial distribution pattern of toxic elements with maximum values nearby mining sites which decreases gradually toward downstream areas. Finally, the results showed that the Sarough River and its tributaries are influenced by high concentrations of heavy metals from the drainages of mining and ore processing sites and naturally occurring metal loadings as well as the geogenic sources such as weathering of geologic formations and hot springs.

Environmental geochemical maps of harmful trace elements in Chinese coalfields

Coal resource utilization and environmental protection is a critical global issue. This study aims to address the need for geochemical maps of harmful trace elements (HTEs) in Chinese coalfields and to extract scientific information from these maps. Based on data extracted from the Trace Elements in Coal of China database, geochemical maps of As, Cd, Cr, F, Hg, Ni, Pb, and Se in Chinese coalfields were generated, for the first time, using the ArcGIS platform. Differences in regional HTE concentrations were attributed to multiple factors, including the type of coal-forming environment, terrigenous debris, and groundwater effect. However, on a national scale, the spatial distribution pattern of HTEs in coal is affected by the abundance of elements in the earth's crust. Herein, the enrichment anomaly of HTEs in coal were found to be significantly correlated with fault locations, and hydrothermal fluid action was characterized as the primary causal factor. HTE abundance in coal is the result of geochemical cycles in the earth's crust. Additionally, stratum fracture zones may serve as conduits and material sources for the migration of HTEs from deep layers to shallow layers, including coal seams. This study provides an essential reference for extensive map applications and coal environmental management while advancing our understanding of the spatial distribution patterns of chemical elements in coal.

Geochemical provenancing and direct dating of the Harbin archaic human cranium

As one of the most complete archaic human fossils, the Harbin cranium provides critical evidence for studying the diversification of the Homo genus and the origin of Homo sapiens. However, the unsystematic recovery of this cranium and a long and confused history since the discovery impede its accurate dating. Here, we carried out a series of geochemical analyses, including non-destructive X-ray fluorescence (XRF), rare earth elements (REE), and the Sr isotopes, to test the reported provenance of the Harbin cranium and get better stratigraphic constraints. The results show that the Harbin cranium has very similar XRF element distribution patterns, REE concentration patterns, and Sr isotopic compositions to those of the Middle Pleistocene-Holocene mammalian and human fossils recently recovered from the Harbin area. The sediments adhered in the nasal cavity of the Harbin cranium have a 87Sr/86Sr ratio of 0.711898, falling in the variation range measured in a core drilled near the Dongjiang Bridge, where the cranium was discovered during its reconstruction. The regional stratigraphic correlations indicate that the Harbin cranium was probably from the upper part of the Upper Huangshan Formation of the Harbin area, which has an optically stimulated luminescence dating constraint between 138 and 309 ka. U-series disequilibrium dating (n = 10) directly on the cranium suggests that the cranium is older than 146 ka. The multiple lines of evidence from our experiments consistently support the theory that the Harbin cranium is from the late Middle Pleistocene of the Harbin area. Our study also shows that geochemical approaches can provide reliable evidence for locating and dating unsystematically recovered human fossils, and potentially can be applied to other human fossils without clear provenance and stratigraphy records.

Spatial Distribution Trends and Influencing Factors of Typical Heavy Metals in Subtropical Alpine Forest Soils: A Case Study from Ailao Mountain in Yunnan Province

In this study, we hypothesized that the distribution patterns of trace metal elements in montane regions would be controlled by the local climate, human activities, vegetation distribution and soil development. Hence, we selected nine forest sites among the elevation of 850 m to 2650 m on the windward (western slope) and leeward (eastern slope) slopes of Ailao Mountain in Yunnan Province of China to determine the typical heavy metal concentrations in forest surface soils, and their differences for distribution trends along with the increasing elevations, and the corresponding environmental factors. The results showed that surface soil Cd, Sb, As, Cr, and Pb had relatively higher concentrations and distinct enrichment factors both on eastern and western slopes. Specifically, the concentrations of Cd and Sb in surface soils of the eastern and western slopes and Pb on the western slope all had obvious altitude distribution trends, which showed their concentrations increased with the increasing elevation. In addition, we found the concentrations of Cd, Sb, As, and Cr in surface soils of the western slope were significantly higher than those of the eastern slope at the same altitude. The correlation analysis and principal component analysis further depicted that the elevation trends of Cd and Sb were mainly controlled by the strong combining effects from long-range atmospheric input and soil organic matter strong absorption, and there was an obvious "cold trapping" effect in high altitude areas. The distribution variations of As and Cr were mainly derived from the weathering difference of soil parent material, while the variations for Pb were controlled by the weathering of bedrock minerals. This study highlights the important role of combining effects from long-range atmospheric input, and from precipitation and vegetation (such as "cold trapping" effect, promoting canopy filtration, litterfall deposition and bedrock weathering) on the distribution trends of trace metals in remote alpine soils.

The Variation in the Stoichiometric Characteristics of the Leaves and Roots of Karst Shrubs

Currently, vegetation restoration is being implemented in the ecologically fragile karst areas in southwest China; however, the stoichiometry of the dominant shrubs and their relationship with the environmental factors in the degraded habitats is still unclear. In this study, we investigated the stoichiometry of C, N, and P, their internal correlations, and influencing factors in 23 shrub species in the Huanjiang County in northwest Guangxi Province, China. We found that the mean contents of C, N and P in leaves were higher than those in roots. In addition, the N:P ratio in the leaves was significantly higher than that in the roots, but the opposite was observed for the C:N and C:P ratios. Except for Leaf C and Root C, significant positive or negative correlations were observed across the stoichiometry of the shrub leaves and roots. A factor analysis of variance demonstrated that the differences across species had higher explanatory power than the topography and soil nutrients in terms of the shrub leaf and root stoichiometry. Hence, our results can improve the understanding of the distribution patterns of these vital elements, as well as of the interactions and influencing factors in the different organs of the karst shrubs.

Genesis of carbonatite and associated U–Nb–REE mineralization at Huayangchuan, central China: Insights from mineral paragenesis, chemical and Sr-Nd-C-O isotopic compositons of calcite

The Huayangchuan deposit in the North Qinling alkaline province of Central China is a unique carbonatite-hosted giant U–Nb–REE polymetallic deposit. The mineralization is characterized by the presence of betafite, monazite, and allanite as the main ore minerals, but also exhibit relatively high budgets of heavy rare earth elements (HREE = Gd–Lu and Y). The origin of carbonatites has long been controversial, thus hindering our understanding of the genesis of the deposit. Here, we conducted an in-situ trace elemental, Sr–Nd isotopic, and bulk C–O isotopic analyses of multi-type calcites in the deposit. Two principal types (Cal-I and Cal-II), including three sub-types (Cal-I-1, Cal-I-2 and Cal-I-3) of calcites were identified based on crosscutting relationships and calcite textures. Texturally, Cal-I calcites in carbonatites display cumulates with the grain size decreasing from early coarse- (Cal-I-1) to medium- (Cal-I-2) and late fine-grained (Cal-I-3), whereas Cal-II calcites coexist with zeolite displaying zeolite–calcite veinlets. Geochemically, Cal-I calcites contain relatively high REE(Y) (151–2296 ppm), Sr (4947–9566 ppm) and Na (29–390 ppm) contents, characterized by right- to left-inclined flat distribution patterns [(La/Yb)N = 0.2–4.2] with enrichment of HREE(Y) (136–774 ppm), whereas Cal-II calcites display low REE, Sr and undetectable Na contents, characterized by a right-inclined distribution pattern [(La/Yb)N = 13.5, n = 16]. The U–Nb–REE mineralization, accompanied with intense and extensive fenitization and biotitization, is mainly associated with the Cal-I-3 calcites which show flat to relatively left-inclined flat REE distribution patterns [(La/Yb)N = 0.2–1.0]. Isotopic results show that Cal-I calcites with mantle signatures are primarily igneous in origin, whereas Cal-II are hydrothermal, postdating the U–Nb–REE mineralization. Cal-I calcites (Cal-I-1, Cal-I-2 and Cal-I-3) from mineralized and unmineralized carbonatites, displayed regular changes in REE, Na and Sr contents, but similar trace element distribution patterns and Sr–Nd-C-O isotopic signatures, indicating that these carbonatites originated from the same enriched mantle (EM1) source by low-degree partial melting of HREE-rich carbonated eclogites related to recycled marine sediments. The combination of trace elements and Sr-Nd isotopic composition of calcites further reveals that these carbonatites have undergone highly differentiated evolution. Such differentiation is conducive to the enrichment of ore-forming elements (U–Nb–REE) in the late magmatic–hydrothermal stages owing to extensive ore-forming fluids exsolved from carbonatitic melts. The massive precipitation of the U–Nb–REE minerals from ore-forming hydrothermal fluids may have been triggered by intense fluid–rock reactions indicated by extensive and intense fenitization and biotitization. Therefore, the Huayangchuan carbonatite-related U-Nb-REE deposit may have formed by a combination of processes involving recycled U–Nb–REE–rich marine sediments in the source, differentiation of the produced carbonatitic magmas, and subsequent exsolution of U–Nb–REE–rich fluids that precipitated ore minerals through reactions with wall rocks under the transitional tectonic regime from compression to extension at the end of Late Triassic.

Mineralization of the Tuwu Porphyry Cu Deposit in Eastern Tianshan, NW China: Insights From In Situ Trace Elements of Chlorite and Pyrite

The Tuwu porphyry copper deposit is located on the Dananhu-Haerlik island arc in eastern Tianshan, NW China. Based on geology, petrology, and in situ trace element studies of pyrite and chlorite, we redefined the characteristics of hydrothermal fluids and the following three mineralization stages: premineralization stage (stage Ⅰ), porphyry metallogenic stage (stage Ⅱ), and superimposed transformation stage (stage Ⅲ). Pyrite stage Ⅰ (Py-I) has the highest Co/Ni ratios, and the precipitation crystallization of chlorite (Chl-I2) has the similar rare earth element distribution patterns with those of volcanic rocks Carboniferous Qieshan (CQ), indicating intense volcanic hydrothermal activity. The Co/Ni ratios of Py-II1 and Py-II2 (stage Ⅱ) tend to decrease over time. Moreover, the rare earth element (REE) distribution patterns of Chl-II have similar LREE enrichment, and the Eu anomalies in Chl-II1, Chl-II2, and Chl-II3 range from positive to negative. The initial ore-forming fluid was mainly magmatic hydrothermal fluid, and with the late-stage addition of meteoric water and continuous sulfide precipitation, the trace element composition of the fluid changed, and the whole system became more oxidizing. Py-III (stage Ⅲ) has the lowest Co/Ni ratios, and the REE distribution pattern of Chl-III is characterized by LREE enrichment. Moreover, the Chl-III shows obvious shear deformation characteristics. The results indicate that the host rocks experienced intensely superimposed reformation. By combining and integrating our results with the regional evolution processes in the eastern Tianshan, we propose that the Tuwu porphyry deposit has undergone magmatic hydrothermal and metamorphic hydrothermal processes. Volcanism (stage Ⅰ) provided the space and initial conditions for the emplacement of the metallogenic body. With the emplacement of the plagiogranite porphyry (stage Ⅱ), the main copper mineralization occurred in the porphyry and surrounding rocks. After porphyry mineralization (stage Ⅲ), regional ductile shearing and collisional compression led to a copper reaction, and its accumulation along the faults formed an ore shoot.

Distribution pattern and source apportionment of trace elements in refined petroleum products

The distribution pattern and sources of trace elemental contents of refined petroleum products were determined in this study. Petroleum products comprising of petrol, kerosene, and diesel samples were obtained from different commercial gas stations in Nigeria and analyzed for V, Cr, Mn, Fe, Co, Ni, Cu, and Zn using Atomic Absorption Spectrophotometry. Results showed that Zn had the highest mean concentration of 16.16 ± 2.69 mg/L in petrol while Cu had the lowest mean concentration of 0.70 ± 0.42 mg/L in kerosene. Generally, the contents of the trace elements increased from light to heavy oil. In consonance with the results of correlation matrix, principal component analysis indicated that Cr, Ni, V, and Fe were incorporated as biophile elements during sedimentation while Cu, Mn, Zn, and Co were introduced into refined petroleum products via atmospheric deposition of metal-containing particulates and/or during refining, storage and transportation.

Assessment of dust trace elements in an e-waste recycling area and related children's health risks

Children from Guiyu, an electronic waste (e-waste) recycling town, are exposed to trace elements via dust. However, the source, pathways, and influence factors of house dust and the association of house dust with child inflammation in an e-waste recycling area are not well-known. This study investigated dust trace elements in children's living environment and the associations of house dust trace elements with influence factors and child inflammation. A total of 108 dust samples from children's residences, roads, and kindergartens in Guiyu (an exposed area) and Haojiang and Shantou urban areas (reference areas) were collected and analyzed, as well as children's questionnaire data.The Mann-Whitney U test found there were higher trace element concentrations in road dust (Co, Ni, and Cu), kindergarten dust (Al, V, Mn, Co, Ni, and Zn), and house dust (V, Co, Cu, As, and Cd) in Guiyu than in Haojiang and Shantou urban areas (P < 0.05). Our analysis showed that house dust and road dust have similar distribution patterns of trace elements. Spearman's correlations showed close relationships among quantities of trace elements (P < 0.05).Higher trace element concentrations in dust were found in houses that used indoor shoe cabinets and opened windows frequently (P < 0.05). In houses of children with airway inflammation, higher dust Ba concentrations were found (P < 0.05), and if their fathers did not work with e-waste, we found higher dust Pb concentrations (Mann-Whitney U test, P < 0.05).Health assessments showed a high risk of exposure through ingestion and an acceptable risk of exposure through inhalation of dust trace elements for children. However, relationships between airway inflammation and house dust trace elements showed the inhalation risk might be underestimated. This study suggests trace element exposure via dust poses a health risk for children living in e-waste recycling areas.

New identification and significance of Early Cretaceous mafic rocks in the interior South China Block

Early Cretaceous mafic rocks are first reported in the northern Guangxi region from the western Qin-Hang belt in the interior South China Block. A systematic investigation of zircon U–Pb dating, whole-rock geochemistry, Sm–Nd isotopes and zircon Hf–O isotopes for these mafic rocks reveals their petrogenesis and the mantle composition as well as a new window to reconstruct lithospheric evolution in interior South China Block during Late Mesozoic. Zircon U–Pb dating yielded ages of 131 ± 2 Ma to 136 ± 2 Ma for diabase and gabbro from Baotan area, indicating the first data for Early Cretaceous mafic magmatism in the western Qing-Hang belt. These mafic rocks show calc-alkaline compositions, arc-like trace element distribution patterns, low zircon εHf(t) of − 9.45 to − 6.17 and high δ18O values of + 5.72 to + 8.09‰, as well as low whole-rock εNd(t) values of − 14.27 to − 9.53. These data suggest that the studied mafic rocks are derived from an ancient lithospheric mantle source that was metasomatized during Neoproterozoic subduction. Thus, the occurrence of these mafic rocks indicates a reactivation of Neoproterozoic subducted materials during an extension setting at Late Mesozoic in the western Qin-Hang belt, an old suture zone that amalgamates the Yangtze and Cathaysia blocks.

Depositional Environment and Genesis of the Nabeba Banded Iron Formation (BIF) in the Ivindo Basement Complex, Republic of the Congo: Perspective from Whole-Rock and Magnetite Geochemistry

The Nabeba high-grade iron deposit (Republic of the Congo) is hosted by banded iron formation (BIF) in the Ivindo Basement Complex, which lies in the northwestern part of the Congo Craton. The Nabeba BIF is intercalated with chlorite-sericite-quartz schist and comprises two facies (oxide and a carbonate-oxide). In this study, whole-rock and LA-ICP-MS magnetite geochemistry of the BIF was reported. Magnetite samples from both BIF facies had fairly similar trace element compositions except for the rare earth element plus yttrium (REE + Y) distribution patterns. The high V, Ni, Cr, and Mg contents of the magnetite in the Nabeba BIF could be ascribed to the involvement of external medium-high temperature hydrothermal fluids during their deposition in relatively reduced environment. The Post-Archean Australian Shale (PAAS)-normalized REY patterns of the Nabeba BIF magnetite were characterized by LREE depletion coupled with varying La and positive Eu anomalies. Processing of the information gathered from the geochemical signatures of magnetite and the whole-rock BIF suggested that the Nabeba BIF was formed by the mixing of predominantly anoxic seawater (99.9%) with 0.1% of high-temperature (&gt;250 °C) hydrothermal vent fluids, similar to the formation mechanism of many Archean Algoma-type BIFs reported elsewhere in the world.

Application of compositional data analysis in geochemical exploration for concealed deposits: A case study of Ashele copper-zinc deposit, Xinjiang, China

One of the top priorities of ore body exploration geochemistry is to effectively identifying “anomalies” and separating them from “background” in geochemical data analyses, during which an accurate understanding of geochemical distribution patterns of elements and anomaly separation has been the focus of ore body hunting. However, geochemical data are compositional data with closure effect and require necessary logratio transformation to open closed data for the following statistical analysis. The invested dataset of 13 elements derived from 2264 surface rock samples from the northwestern Ashele mining area was processed and respectively analyzed as the raw data, logarithmically-transformed data, and isometric logratio (ilr) transformed data with exploratory data analysis (EDA) technology. Of which, the ilr transformed data yields an ideal data structure and scale distribution. The data then was analyzed with principal component analysis (PCA) and robust principal component analysis (RPCA), along with the compositional biplots and the first principal component score maps to identify the spatial distribution of element assemblages. After that, a comparative study of the geochemical distribution patterns based on the raw data of mineralized elements and the principal component scores based on ilr transformation data is conducted to explore the connection with mineralization. As a result, four prospecting prediction targets of two types are delineated in the study area.

Geochronology, geochemistry, and isotope compositions of “Grenvillian” S-type granites in the North Qinling unit, central China: Petrogenesis and tectonic significance

An integrated study of whole-rock elements, Sr–Nd isotopes, and zircon U–Pb ages and Hf-O isotopes was carried out for the “Grenvillian” granites from the North Qinling unit, central China. The results not only place clear constraints on the petrogenesis of these granites, but also give insights into the geodynamic evolution of the Qinling orogen during the assemblage of supercontinent Rodinia. LA-ICPMS zircon U–Pb dating of three representative granites from the Dehe, Fangzhuang, and Zhaigen outcrops yielded formation ages of ca. 940–900 Ma. These muscovite-bearing granites have high silica contents (72–79 wt%) and are weak to strong peraluminous (ASI = 1.01–1.15). They exhibit arc-like trace element distribution patterns with enrichment of LREE and LILE (e.g., Rb, K, Pb) but depletion in HFSE (e.g., Nb, Ta, Ti). Besides, they show variable initial 87Sr/86Sr ratios of 0.704 to 0.729 and relatively low εNd(t) values of −3.2 to −6.1, as well as variable zircon εHf(t) and δ18O values (−8.1–+2.6, 7.9‰–12.0‰). These results suggest their derivation from partial melting of a heterogeneous source that dominated by supracrustal components. Furthermore, a few inherited grains give negative εHf(t) values of −9.4 to −18.4 with two-stage Hf model ages up to 2.9 Ga, suggesting the involvement of minor Archean crustal components. Along with their peraluminous features, high zircon δ18O values, and enriched Sr–Nd isotope compositions, these granites were unambiguously derived from partial melting of metasedimentary rocks and thus are of S-type affinity. Geothermometric and compositional approaches suggest these S-type granites were likely generated by dehydration melting of metagraywacke- and/or metapelite-dominated sources. They might be formed in an accretionary orogen associated with the Rodinia-assembly during the early Neoproterozoic, through which the outboard North Qinling terrane was eventually adjacent to the South China Block.

Distribution patterns of natural radioactivity and rare earth elements in intrusive rocks (El Sela area, Eastern Desert, Egypt)

ABSTRACT El Sela is considered as one of the most important occurrences of radioactive elements, radioactive bearing minerals, as well as REE elements in Egypt. The aim of the present work is to study the distribution patterns of natural radioactivity and rare earth elements in 24 intrusive rocks collected from El Sela area, Eastern Desert, Egypt to use in the field of construction and adornment or not and the extent of their impact on those who use them in their homes or for other purposes. The natural radionuclide contents (Raeq), equivalent activities and various hazard indices were also calculated to assess the radiation hazard parameters. On the other hand, the REE concentrations are relatively variable from the host two-mica granite and post-granitic dikes. REEs concentrations are enriched in LREEs relative to heavy ones with higher values of post-granitic dikes. The chondrite normalised REEs exhibit negative Eu anomaly in the studied intrusive rocks, except that the microgranite shows no sign of Eu anomaly.