GSA Annual Meeting in Seattle, Washington, USA - 2017, 2017
The low δ 26 Mg feature of the LOMU-like potassium-rich lavas was induced by the incorporation ... more The low δ 26 Mg feature of the LOMU-like potassium-rich lavas was induced by the incorporation of recycled oceanic crust in the source region. The correlations between δ 26 Mg, (Gd/Yb) N , Sr and Pb isotopes indicate a multistage preconditioning of the mantle source. Magnesium isotopes can be used as a tracer of recycled oceanic crust in the source region of mantle-derived magmas.
With single-column chemical purification, highly accurate δ7Li values for eight international ref... more With single-column chemical purification, highly accurate δ7Li values for eight international reference materials are presented together with seventeen Chinese geological reference materials from NRCG using the Nu Sapphire.
Cr-spinel [(Mg, Fe2+)(Cr, Al, Fe3+)2O4)] is a common mineral in the ultramafic core of the Duke I... more Cr-spinel [(Mg, Fe2+)(Cr, Al, Fe3+)2O4)] is a common mineral in the ultramafic core of the Duke Island complex in southeastern Alaska, US. Cr-spinel grains with an unmixed texture have been observed in dunite and wehrlite of the complex. Inhomogeneous Cr-spinel with a ratio of Cr/(Al + Cr + Fe3+) <0.37 is prominent in dunite. The inhomogeneous Cr-spinel consists of two completely different compositions: Al-rich Cr-spinel, and Fe3+-rich Cr-spinel with a wide range of Cr content (from 11.8 wt.% to 28.6 wt.% Cr2O3). The unmixed texture is complex, and three subtypes of inhomogeneous Cr-spinel are recognized: Type B1 Cr-spinel showing complete separation, crystallographically oriented type B2 Cr-spinel, and irregular Al-rich Cr-spinel rimmed type B3 Cr-spinel. The unmixed texture was achieved by an unmixing process at around 600 °C due to the miscibility gap of spinel between Al-rich and Fe3+-rich phases. The unmixed patterns of inhomogeneous Cr-spinel are controlled by the initial c...
Here we present new occurrences of amphibole in a suite of chromitites, dunites, and harzburgites... more Here we present new occurrences of amphibole in a suite of chromitites, dunites, and harzburgites from the mantle sequence of the Lycian ophiolite in the Tauride Belt, southwest Turkey. The amphibole occurs both as interstitial grains among the major constituent minerals and as inclusions in chromite grains. The interstitial amphibole shows generally decreasing trends in Na2O and Al2O3 contents from the chromitites (0.14–1.54 wt% and 0.04–6.67 wt%, respectively) and the dunites (0.09–2.37 wt%; 0.12–11.9 wt%) to the host harzburgites (<0.61 wt%; 0.02–5.41 wt%). Amphibole inclusions in chromite of the amphibole-bearing harzburgites are poorer in Al2O3 (1.12–8.86 wt%), CaO (8.47–13.2 wt%), and Na2O (b.d.l.–1.38 wt%) than their counterparts in the amphibole-bearing chromitites (Al2O3 = 6.13–10.0 wt%; CaO = 12.1–12.9 wt%; Na2O = 1.11–1.91 wt%). Estimated crystallization temperatures for the interstitial amphibole grains and amphibole inclusions range from 706 to 974 °C, with the highe...
Magmatic Ni-Cu sulfide deposits in orogenic belts have distinct petrological and geochemical feat... more Magmatic Ni-Cu sulfide deposits in orogenic belts have distinct petrological and geochemical features compared with world-class intraplate magmatic deposits. One such feature is the presence of abundant primary hydrous minerals such as phlogopite and amphibole, indicating a H 2 O-rich parental magma. However, the origin and nature of the fluids have not been established. In the southern Central Asian Orogenic Belt, the Permian Baishiquan and Tianyu mafic–ultramafic intrusions host magmatic Ni-Cu sulfide deposits. Both intrusions are composed of lherzolite, olivine websterite, gabbronorite, gabbro, and diorite. The main ore-host rocks are lherzolite and websterite, with disseminated, net-textured, and massive ores comprising the dominant primary ore types. Low zircon ε Hf (− 6.9 to 7.9 ‰) and varying δ 18 O values (5.2 to 6.6 ‰), as well as both arc-type and MOR-type zircon Nb/Yb (0.0013–0.011) and U/Yb (0.33–10.22), identify an altered lower oceanic crust component in the mantle source. A combination of altered lower oceanic crust and upper crust can account for the zircon Hf–O isotopic characteristics. A mixing model further reveals that the Baishiquan and Tianyu magmatic sulfide deposits originated from a depleted mantle source that experienced two stages of subduction metasomatism with a 30% addition of altered oceanic crust in the first stage and 20% in the second. In the second stage, > 10% oceanic sediment with high δ 18 O must also have been added to result in olivine δ 18 O values higher than those in mantle. This staged evolution is reflected in both the olivine and zircon signatures with olivine from disseminated and net-textured ores at the Tianyu deposit having high δ 18 O (4.6 to 6.3 ‰) with a similar range to zircon and high δ 7 Li isotopic compositions (12.03 to 19.46 ‰). Contamination in the source by oceanic sediment with high δ 18 O values can account for the olivine δ 18 O values (4.8 to 5.7 ‰ at Baishiquan) being higher than those in the mantle, while the addition of brine (5% at the Baishiquan deposit) can explain the olivine δ 7 Li values (20.96 to 31.01 ‰). The results suggest that H 2 O content, Li content, and δ 7 Li and δ 18 O isotopic signatures in olivine and zircon are good indicators of mantle metasomatism and olivine fluid processes in magmatic Ni-Cu sulfide deposits.
Abstract Olivine is a ubiquitous mineral in mafic-ultramafic rocks and has been widely used as a ... more Abstract Olivine is a ubiquitous mineral in mafic-ultramafic rocks and has been widely used as a mineral marker in various geological processes. However, its development of trace elements is limited. Here we present newly-obtained trace element data 7Li, 27Al, 29Si, 31P, 43Ca, 45Sc, 49Ti, 51V, 53Cr, 55Mn, 59Co, 60Ni, and 66Zn of olivine in typical mantle xenoliths, mantle peridotites in ophiolites, and plutonic rocks from layered and Alaskan-type intrusions to develop trace element proxies for the petrogenesis, mineralization and discrimination of various mafic-ultramafic rocks. Residual olivine grains in mantle xenoliths and ophiolitic peridotites, which represent residues of mantle melting, have higher Ni/Co (>20) and Ni/Mn (>2) ratios than magmatic olivine (Ni/Co 2 ppm, V/Sc > 0.5) from ophiolitic peridotites (V
Although a mantle origin of carbonatites has long been advocated, a few carbonatite bodies with c... more Although a mantle origin of carbonatites has long been advocated, a few carbonatite bodies with crustal fingerprints have been identified. The Eppawala carbonatites in Sri Lanka are more similar to orogenic carbonatites than those formed in stable cratons and within plate rifts. They occur within the Pan-African orogenic belt and have a formation age of ca. 475 Ma newly obtained in this study with no contemporary mantle-related magmatism. These carbonatites have higher (87Sr/86Sr)i ratios (0·70479–0·70524) and more enriched Nd and Hf isotopic compositions than carbonatites reported in other parts of the world. Model ages (1·3–2·0 Ga) of both Nd and Hf isotopes [apatite ɛNd(t) = −9·2 to −4·7; rutile εHf(t) = −22·0 to −8·02] are in the age range of metamorphic basement in Sri Lanka, and the carbon and oxygen isotopic compositions (δ13CPDB = −2·36 to −1·71; δ18OSMOW = 13·91–15·13) lie between those of mantle-derived carbonatites and marble. These crustal signatures are compatible with ...
Secondary ion mass spectrometry (SIMS) requires matrix‐matched reference materials to calibrate m... more Secondary ion mass spectrometry (SIMS) requires matrix‐matched reference materials to calibrate mass fractionation during oxygen isotope measurement. Over one thousand SIMS oxygen isotope measurements were conducted on eleven natural mineral samples (five olivines, three clinopyroxenes and three orthopyroxenes) in nineteen sessions using CAMECA IMS 1280 SIMS instruments to evaluate their potential as SIMS reference materials. The obtained results reveal oxygen isotope homogeneity of these samples. No matrix effect was measured for the same variety of mineral samples with limited Mg‐number variations (89.6–94.2, 90–91.9 and 90.1–92.1 for olivine, clinopyroxene and orthopyroxene, respectively). The recommended oxygen isotope compositions of these samples were determined using laser fluorination. These samples are therefore suitable to be used as reference materials for in situ oxygen isotope microanalysis.
Carbonatite metasomatism plays an important role in modifying the composition of Earth's mantle, ... more Carbonatite metasomatism plays an important role in modifying the composition of Earth's mantle, however, its effect on mantle Mg isotopic composition is poorly constrained. Here, we report highprecision mineral Mg isotope data for three suites of mantle peridotite xenoliths that experienced variable degrees of carbonatite metasomatism. The δ 26 Mg values of minerals in these xenoliths are variable and range from −0.32 to −0.11h in olivine, from −0.28 to −0.09h in orthopyroxene, from −0.27 to −0.05h in clinopyroxene, from 0.06 to 0.44h in spinel and from −0.61 to −0.37h in garnet. Calculated bulk-rock δ 26 Mg values of the peridotites vary from −0.27 to −0.10h, falling within and slightly higher than the normal mantle range (−0.25 ± 0.07h). The coexisting minerals are in isotopic equilibrium, with clinopyroxene δ 26 Mg values correlated with the carbonatite metasomatic indices such as MgO and Na 2 O in orthopyroxene. These results suggest that carbonatite metasomatism does not produce light Mg isotopic signature in mantle peridotites as previously suggested, instead it might slightly elevate their δ 26 Mg values. Therefore, carbonatite-metasomatized peridotites in the mantle cannot be the primary source rocks of low-δ 26 Mg mantle-derived magmas. Instead, fractional crystallization and accumulation of chromite during ascent of the basaltic magmas may explain the isotopically light basalts, as supported by the covariations of δ 26 Mg with chemical indices of chromite crystallization (e.g., Cr, V, Fe and Ti). Consequently, chromite crystallization may significantly influence the physiochemical processes on the genesis of basalts, which would require comprehensive evaluation in future studies.
To better understand the mechanism of Mg isotopic variation in magma systems, here we report high... more To better understand the mechanism of Mg isotopic variation in magma systems, here we report high precision Mg isotopic data of 17 bulk rock samples including dunite, clinopyroxenite, hornblendite and gabbro and 10 pairs of dunite-hosted olivine and chromite separates from the well-characterized Alaskan-type Xiadong intrusion in NW China, which formed by continuous and high degree of lithological differentiation from mafic magmas. Chromite separates have highly variable d 26 Mg values from À0.10‰ to 0.40‰, and are consistently heavier than coexisting olivine separates (À0.39‰ to À0.15‰). Both mineral d 26 Mg values and the degrees of inter-mineral fractionation are well correlated with geochemical indicators of magma differentiation, indicating that these inter-sample and inter-mineral Mg isotope fractionations are caused by magma evolution. The d 26 Mg values range from À0.20‰ to À0.02‰ in the dunite, À0.43‰ in the clinopyroxenite, À0.43‰ to À0.28‰ in the hornblendite, 0.18‰ in the chromite-bearing hornblendite, and À0.56‰ to À0.16‰ in the gabbro. The Mg isotopic variations in different types of rocks are closely related to fractional crystallization and accumulation of different proportions of oxides vs. silicates. Chromite crystallization and accumulation is the most important factor in controlling Mg isotope fractionation during the formation of the Xiadong intrusion. Compared to basaltic and granitic magmas, differentiation of the Alaskan-type intrusions occurs at a relatively high oxygen fugacity, which favors chromite crystallization and consequently significant Mg isotope fractionations at both mineral and whole-rock scales. Therefore, Mg isotope systematics can be used to trace the degree of magma differentiation and related-mineralization.
Dithiocarbamate-grafted polyurethane (PU) composites were synthesized by anchoring dithiocarbamat... more Dithiocarbamate-grafted polyurethane (PU) composites were synthesized by anchoring dithiocarbamate (DTC) as a chelating agent to the polyethyleneimine-polydopamine (PE-DA)-functionalized graphene-based PU matrix (PE-DA@GB@PU), as a new adsorbent material for the recovery of Cu2+, Pb2+, and Cd2+ from industrial effluents. After leaching with acidic media to recover Cu2+, Pb2+, and Cd2+, dithiocarbamate-grafted PE-DA@GB@PU (DTC-g-PE-DA@GB@PU) was decomposed and PE-DA@GP was regenerated. The latter was used to recover Pd2+, Pt4+, and Au3+ from the copper leaching residue and anode slime. The present DTC-g-PE-DA@GB@PU and PE-DA@GB@PU composites show high adsorption performance, effective separation, and quick adsorption of the target ions. The morphologies of the composites were studied by scanning electron microscopy and their structures were investigated by Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy. The effects of pH values, contact time, and initial metal...
Reduced porphyry Cu deposits are scarce and their origins remain enigmatic. The Late Carboniferou... more Reduced porphyry Cu deposits are scarce and their origins remain enigmatic. The Late Carboniferous Baogutu reduced porphyry Cu deposit in the western Junggar Terrane, NW China, provides an opportunity to address this issue. In this study, we conducted systematic analyses in terms of petrography, mineral chemistry, major elements, trace elements and Fe isotopes to investigate the redox state of its primary magma and further constrain the origin of Baogutu copper deposit. Based on the petrological observation and mineral chemistry, two magmatic stages have been recognized during the formation of ore-forming diorite. The early stage is characterized by the crystallization of magnetite and high Mg # [Mg/(Mg + Fe 2+)] hornblende under oxidized condition (ΔNNO > 2.36, calculated by the equation given by Scaillet and Evans, 1999). The late stage is characterized by the crystallization of ilmenite and low Mg # biotite under reduced condition (ΔNNO <-0.6). The large *
To determine whether fractionation of Li isotopes could occur at high temperatures, we examined m... more To determine whether fractionation of Li isotopes could occur at high temperatures, we examined major element and Li isotopic compositions of olivine from the Xiadong intrusion, an Alaskan-type complex in the Central Asian Orogenic Belt. Olivine in thirteen dunites, displaying characteristic cumulus textures, yielded large variations in Li concentration (0.10 to 11.18 ppm) and isotopic composition (δ 7 Li =-7.18 to +34.41‰). These variations are too large to be attributed entirely to diffusive processes. The correlations between Li elemental or isotopic composition and differentiation indices such as Fo and MnO contents of olivine, and NiO content of chromite, suggest probable Li isotope fractionation during early stage of differentiation. We speculate that while Li behaves mildly incompatible during differentiation, 7 Li is preferentially
Cenozoic basalts in SE China may be derived from a mixture of depleted MORB mantle (DMM) and enri... more Cenozoic basalts in SE China may be derived from a mixture of depleted MORB mantle (DMM) and enriched mantle 2 (EM2) sources, but whether these basalts share a common mantle source or magmatic history remains unknown. To investigate these unresolved issues, this study sampled basalts from Niutoushan and Mingxi (Fujian province), Xilong (Zhejiang province), and Penghu (Taiwan) for geochemical analysis. The basalt samples show OIB-like trace element patterns and have low PGE contents, with 0.02-0.7 ppb Ir and Pd, 0.05-1.4 ppb Ru, 0.01-0.2 ppb Rh, and 0.06-1.1 ppb Pt. All samples have high Cu/Pd ratios ranging from ~69,000 to 3,500,000, and low Cu/Zr ratios ranging from 0.1 to 0.8, suggesting sulfur-saturated fractionation. Model calculations indicate that the basalts are depleted in PGE due to the retention of 0.001% to 0.1% sulfide in the mantle and the removal of up to 0.0022% sulfide during magma ascent. The crystallization of olivine and spinel, and partial melting are insufficient to account for the observed PGE variation in these basalts. Thus, the distinct PGE patterns in basalts with different ages may reflect the heterogeneity of the mantle source beneath SE China. The source heterogeneity may be due to compositional heterogeneity, particularly variations in oxygen fugacity and PGE mineral phases, or due to variable fluid/melt metasomatic agents in the sub-continental lithospheric mantle. This heterogeneity is possibly related to the westward subduction of the Paleo-Pacific Plate.
ABSTRACT Ultrapotassic igneous rocks can generally be divided into two sub-groups based on the te... more ABSTRACT Ultrapotassic igneous rocks can generally be divided into two sub-groups based on the tectonic settings in which they formed. The orogenic sub-group occurs in subduction-related tectonic settings, while the anorogenic sub-group is confined to stable continental regimes. The Pleistocene Xiaogulihe ultrapotassic volcanic rocks outcrop in the western part of Heilongjiang province, northeast China, and are of intraplate origin with respect to its tectonic settings. Previous elemental and isotopic investigations have suggested that the mantle source of these volcanic rocks had been modified by continental-derived sediments resulting from an ancient subduction (at least older than 1.5 Ga). In this contribution, we performed in-situ oxygen isotope analysis on olivine grains in these ultrapotassic rocks using secondary ionization mass spectrometry (SIMS). The olivine grains generally have higher δ18O values and CaO contents than those of mantle peridotite xenoliths in the nearby Keluo potassic rocks and show linear correlations between major and trace elements, and Fo, suggesting that they are cognate phenocrysts resulted from fractional crystallization processes. The restricted and non-correlated variations in δ18O with the Fo of these olivine grains imply that the fractional crystallization processes might have negligible influence on their δ18O values. The relatively higher δ18O values of the olivine phenocrysts than the normal mantle imply the addition of an 18O-rich crustal component into their mantle source after ruling out the crustal contamination of the host magmas. We propose that the high-δ18O feature of the olivine phenocrysts was inherited from the subducted crustal component in their mantle source. Given the rapid oxygen isotopic diffusion under high temperature and the long period between mantle metasomatism event and volcanic eruption, it is postulated that the high-δ18O signature could only be preserved in the relatively cold and stable subcontinental lithospheric mantle. Such speculation is consistent with our previous inference that the Xiaogulihe ultrapotassic volcanic rocks were mainly generated from the lower subcontinental lithospheric mantle which had been metasomatized by potassium-rich silicate melts derived from ancient subducted continental-derived sediments.
This study based on compiled worldwide garnet peridotite data confirms the GST in high P and T co... more This study based on compiled worldwide garnet peridotite data confirms the GST in high P and T conditions, which was obtained from Al-free experimental system (MgO-Cr 2 O 3-SiO 2) by Klemme (2004). A new spinel-phase peridotite zone, garnet peridotite discontinuous zone, is defined, and another GST, although no experimental data, is principally and presumably proposed to exist. The garnet inclusion-bearing spinel harzburgite from Lashaine (Tanzania) provides the first evidence for the existence of ultra-high spinel zone and is explained as recrystallized minerals hosting the interacted residue of ancient oceanic lithosphere subducted into the great depth of more than 220km. These previously unexpected findings are generating great challenges to phase transition in extreme conditions and to our understanding of layered-structure of the Earth. In addition, coexistent five-phase peridotite is suggested to be naturally useful tool to constrain the GST.
Ages and tectonic implications of the mafic-ultramafic-carbonatite intrusive rocks and associate ... more Ages and tectonic implications of the mafic-ultramafic-carbonatite intrusive rocks and associate Cu-Ni, Fe-P and apatite-vermiculite deposits from the Quruqtagh district, NW China
GSA Annual Meeting in Seattle, Washington, USA - 2017, 2017
The low δ 26 Mg feature of the LOMU-like potassium-rich lavas was induced by the incorporation ... more The low δ 26 Mg feature of the LOMU-like potassium-rich lavas was induced by the incorporation of recycled oceanic crust in the source region. The correlations between δ 26 Mg, (Gd/Yb) N , Sr and Pb isotopes indicate a multistage preconditioning of the mantle source. Magnesium isotopes can be used as a tracer of recycled oceanic crust in the source region of mantle-derived magmas.
With single-column chemical purification, highly accurate δ7Li values for eight international ref... more With single-column chemical purification, highly accurate δ7Li values for eight international reference materials are presented together with seventeen Chinese geological reference materials from NRCG using the Nu Sapphire.
Cr-spinel [(Mg, Fe2+)(Cr, Al, Fe3+)2O4)] is a common mineral in the ultramafic core of the Duke I... more Cr-spinel [(Mg, Fe2+)(Cr, Al, Fe3+)2O4)] is a common mineral in the ultramafic core of the Duke Island complex in southeastern Alaska, US. Cr-spinel grains with an unmixed texture have been observed in dunite and wehrlite of the complex. Inhomogeneous Cr-spinel with a ratio of Cr/(Al + Cr + Fe3+) <0.37 is prominent in dunite. The inhomogeneous Cr-spinel consists of two completely different compositions: Al-rich Cr-spinel, and Fe3+-rich Cr-spinel with a wide range of Cr content (from 11.8 wt.% to 28.6 wt.% Cr2O3). The unmixed texture is complex, and three subtypes of inhomogeneous Cr-spinel are recognized: Type B1 Cr-spinel showing complete separation, crystallographically oriented type B2 Cr-spinel, and irregular Al-rich Cr-spinel rimmed type B3 Cr-spinel. The unmixed texture was achieved by an unmixing process at around 600 °C due to the miscibility gap of spinel between Al-rich and Fe3+-rich phases. The unmixed patterns of inhomogeneous Cr-spinel are controlled by the initial c...
Here we present new occurrences of amphibole in a suite of chromitites, dunites, and harzburgites... more Here we present new occurrences of amphibole in a suite of chromitites, dunites, and harzburgites from the mantle sequence of the Lycian ophiolite in the Tauride Belt, southwest Turkey. The amphibole occurs both as interstitial grains among the major constituent minerals and as inclusions in chromite grains. The interstitial amphibole shows generally decreasing trends in Na2O and Al2O3 contents from the chromitites (0.14–1.54 wt% and 0.04–6.67 wt%, respectively) and the dunites (0.09–2.37 wt%; 0.12–11.9 wt%) to the host harzburgites (<0.61 wt%; 0.02–5.41 wt%). Amphibole inclusions in chromite of the amphibole-bearing harzburgites are poorer in Al2O3 (1.12–8.86 wt%), CaO (8.47–13.2 wt%), and Na2O (b.d.l.–1.38 wt%) than their counterparts in the amphibole-bearing chromitites (Al2O3 = 6.13–10.0 wt%; CaO = 12.1–12.9 wt%; Na2O = 1.11–1.91 wt%). Estimated crystallization temperatures for the interstitial amphibole grains and amphibole inclusions range from 706 to 974 °C, with the highe...
Magmatic Ni-Cu sulfide deposits in orogenic belts have distinct petrological and geochemical feat... more Magmatic Ni-Cu sulfide deposits in orogenic belts have distinct petrological and geochemical features compared with world-class intraplate magmatic deposits. One such feature is the presence of abundant primary hydrous minerals such as phlogopite and amphibole, indicating a H 2 O-rich parental magma. However, the origin and nature of the fluids have not been established. In the southern Central Asian Orogenic Belt, the Permian Baishiquan and Tianyu mafic–ultramafic intrusions host magmatic Ni-Cu sulfide deposits. Both intrusions are composed of lherzolite, olivine websterite, gabbronorite, gabbro, and diorite. The main ore-host rocks are lherzolite and websterite, with disseminated, net-textured, and massive ores comprising the dominant primary ore types. Low zircon ε Hf (− 6.9 to 7.9 ‰) and varying δ 18 O values (5.2 to 6.6 ‰), as well as both arc-type and MOR-type zircon Nb/Yb (0.0013–0.011) and U/Yb (0.33–10.22), identify an altered lower oceanic crust component in the mantle source. A combination of altered lower oceanic crust and upper crust can account for the zircon Hf–O isotopic characteristics. A mixing model further reveals that the Baishiquan and Tianyu magmatic sulfide deposits originated from a depleted mantle source that experienced two stages of subduction metasomatism with a 30% addition of altered oceanic crust in the first stage and 20% in the second. In the second stage, > 10% oceanic sediment with high δ 18 O must also have been added to result in olivine δ 18 O values higher than those in mantle. This staged evolution is reflected in both the olivine and zircon signatures with olivine from disseminated and net-textured ores at the Tianyu deposit having high δ 18 O (4.6 to 6.3 ‰) with a similar range to zircon and high δ 7 Li isotopic compositions (12.03 to 19.46 ‰). Contamination in the source by oceanic sediment with high δ 18 O values can account for the olivine δ 18 O values (4.8 to 5.7 ‰ at Baishiquan) being higher than those in the mantle, while the addition of brine (5% at the Baishiquan deposit) can explain the olivine δ 7 Li values (20.96 to 31.01 ‰). The results suggest that H 2 O content, Li content, and δ 7 Li and δ 18 O isotopic signatures in olivine and zircon are good indicators of mantle metasomatism and olivine fluid processes in magmatic Ni-Cu sulfide deposits.
Abstract Olivine is a ubiquitous mineral in mafic-ultramafic rocks and has been widely used as a ... more Abstract Olivine is a ubiquitous mineral in mafic-ultramafic rocks and has been widely used as a mineral marker in various geological processes. However, its development of trace elements is limited. Here we present newly-obtained trace element data 7Li, 27Al, 29Si, 31P, 43Ca, 45Sc, 49Ti, 51V, 53Cr, 55Mn, 59Co, 60Ni, and 66Zn of olivine in typical mantle xenoliths, mantle peridotites in ophiolites, and plutonic rocks from layered and Alaskan-type intrusions to develop trace element proxies for the petrogenesis, mineralization and discrimination of various mafic-ultramafic rocks. Residual olivine grains in mantle xenoliths and ophiolitic peridotites, which represent residues of mantle melting, have higher Ni/Co (>20) and Ni/Mn (>2) ratios than magmatic olivine (Ni/Co 2 ppm, V/Sc > 0.5) from ophiolitic peridotites (V
Although a mantle origin of carbonatites has long been advocated, a few carbonatite bodies with c... more Although a mantle origin of carbonatites has long been advocated, a few carbonatite bodies with crustal fingerprints have been identified. The Eppawala carbonatites in Sri Lanka are more similar to orogenic carbonatites than those formed in stable cratons and within plate rifts. They occur within the Pan-African orogenic belt and have a formation age of ca. 475 Ma newly obtained in this study with no contemporary mantle-related magmatism. These carbonatites have higher (87Sr/86Sr)i ratios (0·70479–0·70524) and more enriched Nd and Hf isotopic compositions than carbonatites reported in other parts of the world. Model ages (1·3–2·0 Ga) of both Nd and Hf isotopes [apatite ɛNd(t) = −9·2 to −4·7; rutile εHf(t) = −22·0 to −8·02] are in the age range of metamorphic basement in Sri Lanka, and the carbon and oxygen isotopic compositions (δ13CPDB = −2·36 to −1·71; δ18OSMOW = 13·91–15·13) lie between those of mantle-derived carbonatites and marble. These crustal signatures are compatible with ...
Secondary ion mass spectrometry (SIMS) requires matrix‐matched reference materials to calibrate m... more Secondary ion mass spectrometry (SIMS) requires matrix‐matched reference materials to calibrate mass fractionation during oxygen isotope measurement. Over one thousand SIMS oxygen isotope measurements were conducted on eleven natural mineral samples (five olivines, three clinopyroxenes and three orthopyroxenes) in nineteen sessions using CAMECA IMS 1280 SIMS instruments to evaluate their potential as SIMS reference materials. The obtained results reveal oxygen isotope homogeneity of these samples. No matrix effect was measured for the same variety of mineral samples with limited Mg‐number variations (89.6–94.2, 90–91.9 and 90.1–92.1 for olivine, clinopyroxene and orthopyroxene, respectively). The recommended oxygen isotope compositions of these samples were determined using laser fluorination. These samples are therefore suitable to be used as reference materials for in situ oxygen isotope microanalysis.
Carbonatite metasomatism plays an important role in modifying the composition of Earth's mantle, ... more Carbonatite metasomatism plays an important role in modifying the composition of Earth's mantle, however, its effect on mantle Mg isotopic composition is poorly constrained. Here, we report highprecision mineral Mg isotope data for three suites of mantle peridotite xenoliths that experienced variable degrees of carbonatite metasomatism. The δ 26 Mg values of minerals in these xenoliths are variable and range from −0.32 to −0.11h in olivine, from −0.28 to −0.09h in orthopyroxene, from −0.27 to −0.05h in clinopyroxene, from 0.06 to 0.44h in spinel and from −0.61 to −0.37h in garnet. Calculated bulk-rock δ 26 Mg values of the peridotites vary from −0.27 to −0.10h, falling within and slightly higher than the normal mantle range (−0.25 ± 0.07h). The coexisting minerals are in isotopic equilibrium, with clinopyroxene δ 26 Mg values correlated with the carbonatite metasomatic indices such as MgO and Na 2 O in orthopyroxene. These results suggest that carbonatite metasomatism does not produce light Mg isotopic signature in mantle peridotites as previously suggested, instead it might slightly elevate their δ 26 Mg values. Therefore, carbonatite-metasomatized peridotites in the mantle cannot be the primary source rocks of low-δ 26 Mg mantle-derived magmas. Instead, fractional crystallization and accumulation of chromite during ascent of the basaltic magmas may explain the isotopically light basalts, as supported by the covariations of δ 26 Mg with chemical indices of chromite crystallization (e.g., Cr, V, Fe and Ti). Consequently, chromite crystallization may significantly influence the physiochemical processes on the genesis of basalts, which would require comprehensive evaluation in future studies.
To better understand the mechanism of Mg isotopic variation in magma systems, here we report high... more To better understand the mechanism of Mg isotopic variation in magma systems, here we report high precision Mg isotopic data of 17 bulk rock samples including dunite, clinopyroxenite, hornblendite and gabbro and 10 pairs of dunite-hosted olivine and chromite separates from the well-characterized Alaskan-type Xiadong intrusion in NW China, which formed by continuous and high degree of lithological differentiation from mafic magmas. Chromite separates have highly variable d 26 Mg values from À0.10‰ to 0.40‰, and are consistently heavier than coexisting olivine separates (À0.39‰ to À0.15‰). Both mineral d 26 Mg values and the degrees of inter-mineral fractionation are well correlated with geochemical indicators of magma differentiation, indicating that these inter-sample and inter-mineral Mg isotope fractionations are caused by magma evolution. The d 26 Mg values range from À0.20‰ to À0.02‰ in the dunite, À0.43‰ in the clinopyroxenite, À0.43‰ to À0.28‰ in the hornblendite, 0.18‰ in the chromite-bearing hornblendite, and À0.56‰ to À0.16‰ in the gabbro. The Mg isotopic variations in different types of rocks are closely related to fractional crystallization and accumulation of different proportions of oxides vs. silicates. Chromite crystallization and accumulation is the most important factor in controlling Mg isotope fractionation during the formation of the Xiadong intrusion. Compared to basaltic and granitic magmas, differentiation of the Alaskan-type intrusions occurs at a relatively high oxygen fugacity, which favors chromite crystallization and consequently significant Mg isotope fractionations at both mineral and whole-rock scales. Therefore, Mg isotope systematics can be used to trace the degree of magma differentiation and related-mineralization.
Dithiocarbamate-grafted polyurethane (PU) composites were synthesized by anchoring dithiocarbamat... more Dithiocarbamate-grafted polyurethane (PU) composites were synthesized by anchoring dithiocarbamate (DTC) as a chelating agent to the polyethyleneimine-polydopamine (PE-DA)-functionalized graphene-based PU matrix (PE-DA@GB@PU), as a new adsorbent material for the recovery of Cu2+, Pb2+, and Cd2+ from industrial effluents. After leaching with acidic media to recover Cu2+, Pb2+, and Cd2+, dithiocarbamate-grafted PE-DA@GB@PU (DTC-g-PE-DA@GB@PU) was decomposed and PE-DA@GP was regenerated. The latter was used to recover Pd2+, Pt4+, and Au3+ from the copper leaching residue and anode slime. The present DTC-g-PE-DA@GB@PU and PE-DA@GB@PU composites show high adsorption performance, effective separation, and quick adsorption of the target ions. The morphologies of the composites were studied by scanning electron microscopy and their structures were investigated by Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy. The effects of pH values, contact time, and initial metal...
Reduced porphyry Cu deposits are scarce and their origins remain enigmatic. The Late Carboniferou... more Reduced porphyry Cu deposits are scarce and their origins remain enigmatic. The Late Carboniferous Baogutu reduced porphyry Cu deposit in the western Junggar Terrane, NW China, provides an opportunity to address this issue. In this study, we conducted systematic analyses in terms of petrography, mineral chemistry, major elements, trace elements and Fe isotopes to investigate the redox state of its primary magma and further constrain the origin of Baogutu copper deposit. Based on the petrological observation and mineral chemistry, two magmatic stages have been recognized during the formation of ore-forming diorite. The early stage is characterized by the crystallization of magnetite and high Mg # [Mg/(Mg + Fe 2+)] hornblende under oxidized condition (ΔNNO > 2.36, calculated by the equation given by Scaillet and Evans, 1999). The late stage is characterized by the crystallization of ilmenite and low Mg # biotite under reduced condition (ΔNNO <-0.6). The large *
To determine whether fractionation of Li isotopes could occur at high temperatures, we examined m... more To determine whether fractionation of Li isotopes could occur at high temperatures, we examined major element and Li isotopic compositions of olivine from the Xiadong intrusion, an Alaskan-type complex in the Central Asian Orogenic Belt. Olivine in thirteen dunites, displaying characteristic cumulus textures, yielded large variations in Li concentration (0.10 to 11.18 ppm) and isotopic composition (δ 7 Li =-7.18 to +34.41‰). These variations are too large to be attributed entirely to diffusive processes. The correlations between Li elemental or isotopic composition and differentiation indices such as Fo and MnO contents of olivine, and NiO content of chromite, suggest probable Li isotope fractionation during early stage of differentiation. We speculate that while Li behaves mildly incompatible during differentiation, 7 Li is preferentially
Cenozoic basalts in SE China may be derived from a mixture of depleted MORB mantle (DMM) and enri... more Cenozoic basalts in SE China may be derived from a mixture of depleted MORB mantle (DMM) and enriched mantle 2 (EM2) sources, but whether these basalts share a common mantle source or magmatic history remains unknown. To investigate these unresolved issues, this study sampled basalts from Niutoushan and Mingxi (Fujian province), Xilong (Zhejiang province), and Penghu (Taiwan) for geochemical analysis. The basalt samples show OIB-like trace element patterns and have low PGE contents, with 0.02-0.7 ppb Ir and Pd, 0.05-1.4 ppb Ru, 0.01-0.2 ppb Rh, and 0.06-1.1 ppb Pt. All samples have high Cu/Pd ratios ranging from ~69,000 to 3,500,000, and low Cu/Zr ratios ranging from 0.1 to 0.8, suggesting sulfur-saturated fractionation. Model calculations indicate that the basalts are depleted in PGE due to the retention of 0.001% to 0.1% sulfide in the mantle and the removal of up to 0.0022% sulfide during magma ascent. The crystallization of olivine and spinel, and partial melting are insufficient to account for the observed PGE variation in these basalts. Thus, the distinct PGE patterns in basalts with different ages may reflect the heterogeneity of the mantle source beneath SE China. The source heterogeneity may be due to compositional heterogeneity, particularly variations in oxygen fugacity and PGE mineral phases, or due to variable fluid/melt metasomatic agents in the sub-continental lithospheric mantle. This heterogeneity is possibly related to the westward subduction of the Paleo-Pacific Plate.
ABSTRACT Ultrapotassic igneous rocks can generally be divided into two sub-groups based on the te... more ABSTRACT Ultrapotassic igneous rocks can generally be divided into two sub-groups based on the tectonic settings in which they formed. The orogenic sub-group occurs in subduction-related tectonic settings, while the anorogenic sub-group is confined to stable continental regimes. The Pleistocene Xiaogulihe ultrapotassic volcanic rocks outcrop in the western part of Heilongjiang province, northeast China, and are of intraplate origin with respect to its tectonic settings. Previous elemental and isotopic investigations have suggested that the mantle source of these volcanic rocks had been modified by continental-derived sediments resulting from an ancient subduction (at least older than 1.5 Ga). In this contribution, we performed in-situ oxygen isotope analysis on olivine grains in these ultrapotassic rocks using secondary ionization mass spectrometry (SIMS). The olivine grains generally have higher δ18O values and CaO contents than those of mantle peridotite xenoliths in the nearby Keluo potassic rocks and show linear correlations between major and trace elements, and Fo, suggesting that they are cognate phenocrysts resulted from fractional crystallization processes. The restricted and non-correlated variations in δ18O with the Fo of these olivine grains imply that the fractional crystallization processes might have negligible influence on their δ18O values. The relatively higher δ18O values of the olivine phenocrysts than the normal mantle imply the addition of an 18O-rich crustal component into their mantle source after ruling out the crustal contamination of the host magmas. We propose that the high-δ18O feature of the olivine phenocrysts was inherited from the subducted crustal component in their mantle source. Given the rapid oxygen isotopic diffusion under high temperature and the long period between mantle metasomatism event and volcanic eruption, it is postulated that the high-δ18O signature could only be preserved in the relatively cold and stable subcontinental lithospheric mantle. Such speculation is consistent with our previous inference that the Xiaogulihe ultrapotassic volcanic rocks were mainly generated from the lower subcontinental lithospheric mantle which had been metasomatized by potassium-rich silicate melts derived from ancient subducted continental-derived sediments.
This study based on compiled worldwide garnet peridotite data confirms the GST in high P and T co... more This study based on compiled worldwide garnet peridotite data confirms the GST in high P and T conditions, which was obtained from Al-free experimental system (MgO-Cr 2 O 3-SiO 2) by Klemme (2004). A new spinel-phase peridotite zone, garnet peridotite discontinuous zone, is defined, and another GST, although no experimental data, is principally and presumably proposed to exist. The garnet inclusion-bearing spinel harzburgite from Lashaine (Tanzania) provides the first evidence for the existence of ultra-high spinel zone and is explained as recrystallized minerals hosting the interacted residue of ancient oceanic lithosphere subducted into the great depth of more than 220km. These previously unexpected findings are generating great challenges to phase transition in extreme conditions and to our understanding of layered-structure of the Earth. In addition, coexistent five-phase peridotite is suggested to be naturally useful tool to constrain the GST.
Ages and tectonic implications of the mafic-ultramafic-carbonatite intrusive rocks and associate ... more Ages and tectonic implications of the mafic-ultramafic-carbonatite intrusive rocks and associate Cu-Ni, Fe-P and apatite-vermiculite deposits from the Quruqtagh district, NW China
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