About 2600 spot analyses of mica (combined electron microprobe and laser ablation ICP-MS) from 120 samples from eight rare-metal granite (RMG) plutons of different geochemical affiliations were ...performed to characterize the contents of major (Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K, F), minor (Li, Rb, Zn), and trace elements (Sc, Nb, Sn, Cs, Ta, W). This allowed to constrain changes in mica chemistry during magma fractionation and to characterize the relation between the trace-element spectra in mica and geochemical specializations of parental granites. The studied samples covered metaluminous to peralkaline A-type granites of the Madeira pluton (Brazil), metaluminous to peraluminous A-type granites (Kimi, Finland; Orlovka, Russia; Cínovec, Czech Republic) and strongly peraluminous S-type granites (Panasqueira and Argemela, Portugal; Beauvoir, France; Nejdek, Czech Republic). Micas from non-mineralized S- and I-type granitoids from the Czech Republic were analyzed for comparison. For the monitored rare metals, the maximum contents are 1200 ppm Sn (Madeira), 350 ppm W (Beauvoir, Nejdek), 2300 ppm Nb (Madeira) and 200 ppm Ta (Orlovka, Cínovec and Nejdek); Sc reaches maximally 300 ppm at Orlovka. Micas from peraluminous RMG are generally rather enriched in W and Cs, while micas from subaluminous A-type granites are relatively enriched in Nb and Sc. Micas from the studied peralkaline rocks are rich in Nb and poor in Cs, Sc and W. With increasing fractionation of the parental magma, the contents of F, Li, and Rb in mica increase, while the contents of high-field-strength elements (HFSE) usually decrease. This can be attributed to the crystallization of late Li-mica after the HFSE accessories rather than to the effect of the mica crystal structure. Micas affected by high-temperature hydrothermal events are usually completely re-equilibrated. By contrast, low-temperature muscovitization connected with washing out of Li and an increase in Sn affected only rims of mica flakes, leaving crystal cores in their original composition. In a succession from early biotite granites to late Li-mica granites, the share of mica in bulk Sn, Nb and Ta contents in the rocks decreases (50–80 → 5–10%, 10–80 → 1–10% and 100 → <5%, respectively), and rutile, cassiterite and columbite/pyrochlore become the main hosts of rare metals.
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•2600 spot mica analyses (EMPA, LA-ICP MS) from rare-metal granites were evaluated.•Contents of rare metals reach 1200 ppm Sn, 350 ppm W, 2300 ppm Nb and 200 ppm Ta.•During fractionation, contents of Li and Rb increase, contents of HFSE decrease.•Micas from S-type RMGs are enriched in W and Cs, micas from A-type in Nb and Sc.•During fractionation, the share of mica on the bulk Sn, Nb, Ta-contents decreases.
The conversion of old brownfield sites into places once again serving society is becoming an upward global trend, especially in urban areas. Due to the increasingly growing pressure on the expansion ...of urban green spaces, such sites can become, for instance, urban parks. The aim of the study was to assess whether the solution is appropriate and if it does not pose a potential health risk. Heavy pollution of soils was found out by means of the example of the urban park newly established in a reclaimed area of a historic mining town. The high average values in the topsoil were found out mainly in As (132 mg/kg), Cd (6.8 mg/kg), Pb (535 mg/kg) and Zn (1604 mg/kg). The assessment of the non-carcinogenic health risk has revealed possible As-related adverse health effects in children even at irregular park visits. According to the carcinogenic risk assessment, As, Cd, Cr and Ni can be ranked in the category of an acceptable total risk for regulatory purposes. The health status of park vegetation as a significant component of the urban ecosystem was also assessed. Soil phytotoxicity brought about severe damage to the seedlings, with a mortality rate of up to 84% locally. The results indicate that heavily polluted brownfield sites with historic mining-related activities are not suitable for establishing urban parks even after reclamation and nature-based solutions may not be invariably appropriate. Based on the findings, the management steps that ought to be implemented in the process of brownfield redevelopment into the urban park even after its establishment have been highlighted in order to minimize the health risk to park visitors while providing the required ecosystem services by vegetation.
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•Newly established park in a reclaimed area was heavily polluted.•The pollution poses possible health risks for children.•Park vegetation health was adversely affected with resulting high mortality.•R or S strategist species are more suitable for afforestation of reclaimed areas.•The study presents steps for safe establishment of urban parks at polluted sites.
Heavy metal pollution is an important concern because of its potential to affect human health. This study was conducted to analyze plants growing on a landfill body and in its surroundings to ...determine their potential for heavy metal accumulation. In addition, the enrichment coefficient (EC) for the plant/soil system was used for determining the environmental contamination from a landfill in terms of heavy metal accumulation. The samples were taken in 2013–2014. Of the analyzed metals, iron achieved the highest values in the samples, i.e. - stalk (103.4–6564.6 mg/kg DM), roots (6563.6–33,036.6 mg/kg DM), leaf (535.1–11,275 mg/kg DM) and soil (12,389–39,381.9 mg/kg DM). The highest concentrations were determined in 2013 for Fe, Mn and Zn. Iron achieved the highest concentrations in the years 2013–2014. Next, EC values were then calculated, with the highest noted for Cd. Cd, as well as Cr, Ni and Zn are accumulated mostly in the leaves, whereas Co, Cu, Fe, Hg, Mn and Pb are accumulated mainly in the roots of T. vulgare.
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•Metal accumulation in T. vulgare growing on landfill body was analyzed.•Enrichment coefficient for plant/soil system was used.•The highest degree of accumulation was found-out for Cd.•The Cd, Cr, Ni and Zn are cumulated most in leaves.•The Co, Cu, Fe, Hg, Mn and Pb are cumulated most in roots.
Subduction is an effective mechanism for deep recycling of supracrustal rocks and mantle refertilization. However, the timing of the onset of modern-style deep subduction is debated. Here we report ...geochronogical and geochemical data for an intrusive suite of ultramafic, syenitic and carbonatitic rocks, a carbonatite-hosted peridotite xenolith, and granulites from the Paleoproterozoic Trans-North China orogen in the North China craton (NCC). The xenolith differs in composition from typical cratonic mantle peridotites. It equilibrated at T ≈ 1100 °C and P ≈ 29 kbar, i.e. under hotter conditions than cratonic mantle xenoliths worldwide. The carbonatites and associated alkaline rocks were emplaced at 1810 ± 3 Ma and are related to the Paleoproterozoic collision between the Western and Eastern segments of the NCC. These intrusions show Sr-Nd isotope compositions consistent with an enriched mantle source (87Sr/86Sr)i = 0.7027–0.7039; εNd(t) = −4 to −6, and contain zircon characterized by unradiogenic Hf isotope compositions εHf(t) = −5 to −9 and high δ18Osmow values (7.9–9.5‰). In contrast, basement granulites and wall-rock granites are enriched in radiogenic Nd and Hf isotopes, but low in 18O. These differences rule out the possibility of crustal contamination. Our results thus suggest that modern-style plate tectonics dates back at least to the Paleoproterozoic Era, and the post-collisional Paleoproterozoic alkaline magmatism in the NCC tapped mantle sources modified by deep sediment recycling.
The enormous tourism boom raises concern about possible negative environmental impacts worldwide. One of the risks posed by tourism may be heavy metal pollution. On the example of the volcanic island ...of Santorini, a popular tourist destination, pollution of soils categorized according to the tourism load was monitored. Significant anthropogenic contamination by heavy metals, especially Cu, Cr and Pb, was found out. This contamination may constitute a moderate ecological risk to the island ecosystems. Tourism has been shown to be a significant pollution factor as evidenced by the contaminated soils near the airport. Simultaneously, airport traffic has been proved to be an important emitter of Co, Cr and especially Zn. The comparison with other volcanic islands has shown that on Santorini the content of heavy metals in soils is significantly lower, despite frequently higher tourism intensity. On this basis, it can be concluded that in case of volcanic islands the dominant factor determining the content of heavy metals in the soil is the parent rock. Given high and ever-increasing intensity of tourism on the island, it can be assumed that soil contamination will continue to rise rapidly. Therefore, without proper steps reducing tourism, increase in soil degradation, growing negative impacts on local ecosystems as well as on the quality of produced wine can be expected on Santorini.
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•The anthropogenic contamination by Cu, Cr and Pb has been found out on Santorini.•The contamination may represent a moderate ecological risk to local ecosystems.•Airport traffic is a significant source of soil pollution on the island.•The dominant factor determining HM content of volcanic island soils is parent rock.•HM monitoring may serve as background for introducing tourist quotas.
•Fengzhen olivine-bearing garnet pyroxenite subducted to ~ 110 km depth.•Cold subduction (272–342 °C/GPa) recorded in lithospheric mantle.•Modern-style subduction initiated prior to ~ 1.8 Ga.
Whether ...modern-style subduction exists in Paleoproterozoic has been hotly debated because of the scarcity of robust petrological evidence. Here, we present a comprehensive study of olivine-bearing garnet pyroxenite xenoliths hosted in the Paleoproterozoic Fengzhen carbonatite. The carbonatite is located in the conjugate area between the Paleoproterozoic Trans-North China Orogen (TNCO) and the Khondalite Belt in North China Craton (NCC) with a dated age of 1810 ± 3 Ma. Petrographically, four-stages of evolution have been identified in the studied olivine-bearing garnet pyroxenite: 1) the formation of the protolith spinel websterite (S1), 2) the prograde metamorphism of spinel-lherzolite facies to garnet-lherzolite facies (M1), 3) retrograde metamorphism to Ariegite subfacies (M2) with formation of symplectite-I, and 4) Seiland subfacies (M3) forming symplectite-II. The clinopyroxene in the xenoliths display high Mg# (Mg2+/(Mg2++Fe2+)*100 = 89–94), strongly depleted HREE (heavy REE) and HFSE (high field strength elements; e.g., Nb, Zr, Ti) and enriched LREE (light REE) and LILE (large ion lithophile elements; e.g., Th and U). Similarly, the whole-rock chemistry exhibits high Mg# (85–88) and high Al2O3 + CaO (20.2–21.9 wt%) with enrichment in LREE and LILE (Th, U) and depletion in HREE and HFSE (e.g., Nb, Ta, Zr, Hf, Ti). The geochemical signatures imply that they might originate from the refractory mantle wedge in subduction zone and have been metasomatized by crust-derived melts. Major mineral thermobarometry yields the peak PT conditions of 26–33 kbar and 890–962 °C corresponding to a cold subduction geothermal gradient (307 ± 35 °C/GPa) with a depth up to 110 km for olivine-bearing garnet pyroxenites, which is also consistent with the results by zirconium-in-rutile and REE thermobarometers. This studies suggest that that the modern-style subduction of the lithospheric mantle was initiated at least since 1.8 Ga.
Laser ablation inductively coupled plasma mass spectrometry is a unique technique designated for in situ analysis of a wide variety of solid samples. Nowadays, LA-ICP-MS is almost routinely used to ...study chemical and isotopic composition of geological materials. This paper reviews our experience with the analysis of tin in geological samples and comprehensively summarizes the limitations that may lead to inaccurate and imprecise outcomes. Experimental results show the extent of cross-contamination given by the ablation of materials containing tenths and tens of %m/m of Sn, and elucidate the impact of contamination on a background progress. Moreover, an analysis is also jeopardized by the occurrence of doubly charged ions of uranium as well as by the matrix effect amplified with operating conditions. Finally, the inhomogeneity of NIST SRM 614 is highlighted via 2D mapping especially within the rim area where tin content reaches up to 8 mg kg−1. Furthermore, a real quartz sample is subjected to LA-ICP-MS analysis to demonstrate the manifestation of discussed negative effects. The true tin content in quartz sample and NIST 614 is verified via GF-AAS. The result of NIST 614 bulk analysis is in a good agreement with GeoReM value.
•Background intensity leads to tenfold overestimation of tin content.•Tin analysis is jeopardized by the occurrence of doubly charged ions of uranium.•Spatial inhomogeneity of tin in NIST SRM 614 reachs up to 8 mg kg−1.
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•Nam Xe REE deposit is of hydrothermal origin.•Nam Xe REE deposit has two episodes of REE mineralization at 45–44 Ma and 35–31 Ma.•Two episodes of REE mineralization coincide with the ...main- and late-collisional periods of the India-Asia convergence, respectively.
Carbonatite-related rare-earth element (REE) deposits are developed in large areas of southwestern China and northwestern Vietnam on the SW margin of the South China block. The ages of REE deposits and their host carbonatite-alkaline rocks in southwestern China have been tightly constrained in the 35–10 Ma interval, but those in northwestern Vietnam remain poorly understood. In this paper, we present new Th–Pb dating results to constrain the timing of mineralization of the Nam Xe REE deposit in northwestern Vietnam, and to reveal its possible relationship to the well-studied REE deposits in southwestern China. The Nam Xe deposit consists of three types of REE ores: Type 1, fine-grained disseminated ores; Type 2, coarse-grained, taxitic ores; and Type 3, REE veinlets. The mineral assemblages and their close relations to hydrothermal alteration, combined with the trace element patterns of the ore minerals, indicate a hydrothermal origin for all the three ore types. Laser ablation-inductively coupled plasma-mass spectrometry Th–Pb dating of monazite yielded weighted-mean Th–Pb ages of 45–44 Ma for type 1 ores and 35–32 Ma for type 2 and 3 varieties, whereas the LA-ICPMS dating of bastnäsite has ages of 35–31 Ma for types 2 and 3, revealing two REE mineralization events at 45–44 and 35–31 Ma in the Nam Xe deposit. The age of type 1 ores overlaps the main-collision period of India-Asia collisional orogeny (65–41 Ma) which confirms carbonatite-related REE mineralization could form in the main-collisional geological setting. The ages of types 2 and 3 ores are consistent with those of the Mianning–Dechang REE metallogenic belt in southwestern China that formed under a late-collision extensional setting (40–26 Ma). Combined with existing geochronological data, results presented here suggest that the Nam Xe REE deposit formed both in the main- and late-collisional settings and represents the southern extension of the Mianning–Dechang REE metallogenic belt.
The present work is a first comprehensive study of the trace-element composition and zoning in clinopyroxene- and amphibole-group minerals from carbonatites, incorporating samples from 14 localities ...worldwide (Afrikanda, Aley, Alnö, Blue River, Eden Lake, Huayangchuan, Murun, Oka, Ozernaya Varaka, Ozernyi, Paint Lake, Pinghe, Prairie Lake, Turiy Mys). The new electron-microprobe data presented here significantly extend the known compositional range of clinopyroxenes and amphiboles from carbonatites. These data confirm that calcic and sodic clinopyroxenes from carbonatites are not separated by a compositional gap, instead forming an arcuate trend from nearly pure diopside through intermediate aegirine–augite compositions confined to a limited range of CaFeSi
2O
6 contents (15–45
mol%) to aegirine with <
25
mol% of CaMgSi
2O
6 and a negligible proportion of CaFeSi
2O
6. A large set of LA-ICPMS data shows that the clinopyroxenes of different composition are characterized by relatively low levels of Cr, Co and Ni (≤
40
ppm) and manifold variations in the concentration of trivalent lithophile and some incompatible elements (1–150
ppm Sc, 26–6870
ppm
V, 5–550
ppm Sr, 90–2360
ppm Zr, and nil to 150
ppm REE), recorded in some cases within a single crystal. The relative contribution of clinopyroxenes to the whole-rock Rb, Nb, Ta, Th and U budget is negligible. The major-element compositional range of amphiboles spans from alkali- and Al-poor members (tremolite) to Na–Al-rich Mg- or, less commonly, Fe-dominant members (magnesiohastingsite, hastingsite and pargasite), to calcic–sodic, sodic and potassic–sodic compositions intermediate between magnesio-ferrikatophorite, richterite, magnesioriebeckite, ferri-nyböite and (potassic-)magnesio-arfvedsonite. In comparison with the clinopyroxenes, the amphiboles contain similar levels of tetravalent high-field-strength elements (Ti, Zr and Hf) and compatible transition elements (Cr, Co and Ni), but are capable of incorporating much higher concentrations of Sc and incompatible elements (up to 500
ppm Sc, 43
ppm Rb, 1470
ppm Sr, 1230
ppm Ba, 80
ppm Pb, 1070
ppm REE, 140
ppm Y, and 180
ppm Nb). In some carbonatites, amphiboles contribute as much as 25% of the Zr
+
Hf, 15% of the Sr and 35% of the Rb
+
Ba whole-rock budget. Both clinopyroxenes and amphiboles may also host a significant share (~
10%) of the bulk heavy-REE content. Our trace-element data show that the partitioning of REE between clinopyroxene (and, in some samples, amphibole) and the melt is clearly bimodal and requires a revision of the existing models assuming single-site REE partitioning. Clinopyroxenes and amphiboles from carbonatites exhibit a diversity of zoning patterns that cannot be explained exclusively on the basis of crystal chemistry and relative compatibility of different trace-element in these minerals. Paragenetic analysis indicates that in most cases, the observed zoning patterns develop in response to removal of selected trace elements by phases co-precipitating with clinopyroxene and amphibole (especially magnetite, fluorapatite, phlogopite and pyrochlore). With the exception of magnesiohastingsite–richterite sample from Afrikanda, the invariability of trace-element ratios in the majority of zoned clinopyroxene and amphibole crystals implies that fluids are not involved in the development of zoning in these minerals. The implications of the new trace-element data for mineral exploration targeting REE, Nb and other types of carbonatite-hosted rare-metal mineralization are discussed.
► Clinopyroxenes and amphiboles are important trace-element hosts in carbonatites. ► Amphiboles contribute a significant share of the bulk-rock Zr, Rb, Ba and REE budget. ► REE exhibit bimodal partitioning. ► Competitive partitioning controls zoning in clinopyroxenes and amphiboles.
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