Trace Element Modeling Research Articles

Geochemistry, Sr-Nd isotopes and zircon U-Pb dating of magmatic rocks from the Talesh range, western Alborz: New insights into Late Cretaceous evolution of the southern Eurasian margin

The eastern flank of the Talesh range of western Alborz, northwestern Iran, exposes volumetrically significant Late Cretaceous volcanic and volcaniclastic associations as well as cross-cutting dykes and minor subvolcanic equivalents. The volcanic units appear as massive to pillowed flows interlayered with volcaniclastic beds and subordinate limestones. We present new field data, zircon UPb ages, bulk-rock major and trace element geochemistry, and SrNd isotopes on the igneous rock suite. Geochemical data show that the lava units and dykes are mainly basaltic in composition with minor basaltic andesites and trachytes. They form two contrasting series of arc-related calc-alkaline (Group 1) and OIB-like (Group 2) rocks. The zircon UPb age of Group 1 rocks is 95.6 ± 1.8 Ma (2σ), whereas for Group 2 rocks, cross-cutting relationships and stratigraphic constraints indicate a somewhat younger age. Group 1 rocks have 87Sr/86Sr(i) varying from 0.7038 to 0.7070 and εNd(t) values ranging from +0.5 to +5.0. Group 2 rocks have 87Sr/86Sr(i) = 0.7040–0.7065 and εNd(t) from −3.0 to +3.7. Trace element and isotopic modelling shows that the primitive Group 1 magmas were derived from a metasomatized mantle source enriched by the addition of ∼6–10 % sediment melt component, while Group 2 rocks are consistent with melts of an asthenospheric mantle source enriched by ∼1–5 % EMII component. Trace element modelling indicates that Group 1 rocks formed from ∼6–13 % partial melts of a spinel-garnet lherzolite with garnet:spinel ratios of 45:55 to 10:90, whereas primitive Group 2 melts were generated through ∼1–3 % partial melting of a garnet-spinel-lherzolite with garnet:spinel ratios of 90:10 to 80:20. We propose a geodynamic model in which a north-dipping Neotethyan slab beneath the western Alborz (Talesh area) continental margin produced arc assemblages of Group 1 rocks and subsequent slab rollback led to the upwelling of an asthenospheric mantle to generate OIB-like magmatism of Group 2 rocks in an extensional intra-arc to back-arc setting.

Major, trace elements and Sr–Nd–Pb isotopes systematics of mafic dykes from the Figuil (northern Cameroon) and Léré (southwestern Chad) areas

In this study, field descriptions of the dolerite dykes cross‐cutting the Pan‐African basement (DPB) and the dolerite and gabbroic dykes cross‐cutting the Cretaceous sedimentary basin (DGCSB) are used together with petrographic, bulk‐rock geochemistry, as well as Sr–Nd–Pb isotopic data to constrain the geodynamic setting and origin of these mafic (basanite, basalt and basaltic andesite in composition) rocks that outcrop in the Figuil–Léré area. The DPB dykes are alkaline with SiO2 of 46.63–49.03 wt% and MgO of 3.93–7.11 wt%. In contrast, the DGCSB dykes are subalkaline with SiO2 ranging between 50.24 and 53.16 wt% and MgO fluctuating between 5.22 and 7.90 wt%, comparable to dykes described in other regions of the Cameroon Line (CL). The rocks studied belong to the tholeiitic series and were emplaced in within‐plate basalts (WPB) and mid‐ocean ridge basalts (MORBs) setting. The variations in major and trace elements from the basanite to basaltic andesite compositions are dependable with fractional crystallization (FC) of different mineral phases such as opaque minerals, olivine, clinopyroxene, amphibole and alkali feldspar. Most samples exhibit negative Nb–Ta and positive Sr anomalies, which together with the negative correlation between MgO and 87Sr/86Sr, and isotopic ratio of 206Pb/204Pb <19.5 (18.27–19.49) suggests interactions of crustal components. Nevertheless, this contamination seems limited because there is a positive correlation between SiO2 and 143Nd/144Nd plot and low Ba contents (72–210 ppm) of the samples compared to the mid‐continental crust (259–628 ppm). Trace element modelling proposes a derivation of the Figuil–Léré dykes from parental melts generated by 4%–15% partial melting of a source containing garnet peridotite in the mixed lithospheric–asthenospheric mantle. The isotopic data of the dykes studied with hybrid magma composition are characterized by more radiogenic 87Sr/86Sr, 143Nd/144Nd and 206Pb/204Pb isotopic ratios with a dominant mixing of depleted MORB mantle (DMM)–enriched mantle 1 (EM1)–enriched mantle 2 (EM2), like those of other mafic dykes of the CL.

Advancing Forensic Chemical Analysis to Classify Wild and Captive Turtles

The diets and environments that individuals experience can vary greatly within and among wildlife populations. These individual experiences can be compared using the chemical signatures of animal tissues, which can differentiate animals into groups, including those raised in the wild versus those held in captive facilities. In this study, we compared different combinations of four stable isotope ratios and 15 trace elements derived from the claw tips of captive wood turtles throughout the eastern U.S. and wild wood turtles (Glyptemys insculpta) from Maine to develop predictive models used to determine their origins. The purpose of this work is to develop an objective statistical tool that law enforcement can use to help prosecute poachers. We found that the chemical signatures of 14 (12 trace elements and 2 stable isotope ratios) of the 19 markers we explored were different between wild and captive wood turtles, thus reflecting the differences in their diets and environments. We found that our stable isotope ratio model had nearly perfect predictive accuracy in classifying wild wood turtles as wild and captive wood turtles as captive, whereas our trace element and combined model were 100% accurate, thus validating this statistical approach for determining the origins of confiscated wood turtles from Maine.

Neoarchean crustal reworking inferred from granitoids in the western Dharwar Craton: Constraints from Nd isotopic composition, trace elements, and phase equilibrium modelling

The granitoid magmatism in the Chitradurga greenstone belt implies crustal reworking in the western Dharwar Craton during the Neoarchean. High-K granites and low-K trondhjemites are studied for their petrogenesis using the whole-rock elemental and Nd isotopic composition and compared with the earlier works. These granitoids were formed by partial reworking of older crust, which includes TTG gneisses and metabasites. Low Sr/Y ratios (0.1–7.6) and zircon saturation temperatures (< 850 °C) suggest that crustal anatexis occurred at the shallower crustal levels by low-T fluid-present melting. Phase equilibrium and trace element modelling show that the potassic granites were formed by partial melting of TTG gneisses at shallower depths corresponding to 4–6 kb pressures and melt extraction in batches leaving a final residue comprising ∼66% plagioclase, ∼ 30% quartz, ∼ 3% orthopyroxene, and ∼ 1% ilmenite. Monzogranite was formed from the melt extracted at a higher temperature with some entrained minerals, whereas the early batches of water saturated melt modified by fractional crystallization during the ascent formed syenogranites. The low-K trondhjemites were formed by 10–12% partial melting of metabasites at 4–5 kb pressures, leaving residual assemblages with plagioclase (42–46%), amphibole (24–26%), orthopyroxene (20–21%), ilmenite (4–5%), and garnet (2–9%). The partial melting of various crustal source rocks at different crustal levels indicates a reworking event in the terrane, which was likely triggered by mafic underplating and H2O dominated fluid flux.

Fate of an oceanic plate in the Neo-Tethys intra-oceanic subduction system: Evidence from elemental and Rb/Sr – Sm/Nd isotopic systematics

We report the coexistence of normal mid-ocean ridge basalt (NMORB)-type and alkaline ocean island basalt (OIB)-type mafic volcanics from the Zildat Ophiolitic Mélange (ZOM), Indus Suture Zone (ISZ), eastern Ladakh Himalaya. Trace element modeling portrays chemically heterogeneous mantle sources, wherein blueschists and sub-alkaline mafic volcanics depict almost flat REE-patterns [(La/Sm)N = 1.04–2.9] and respectively <20 % and >20 % degrees of partial melting from a depleted spinel-lherzolite mantle source. In contrast, alkaline mafic volcanics depict enriched LREE-patterns [(La/Yb)N = 35–48] with <5 % degrees of partial melting from a transitional garnet-spinel lherzolite enriched mantle source. Since the prevalent hypothesis considers seamounts and island arc rocks of the subducting oceanic plate within the Neo-Tethys Ocean to be the protolith for the contemporaneous Shergol Ophiolitic Melange (SOM) blueschists. In contrast, ZOM blueschists depict different protolith signatures. The εNd(t = 140 Ma) values for ZOM blueschists (+3.7 to +7.4) and sub-alkaline mafic volcanics (+9.2 to +9.3) are analogous to present-day Indian Ocean NMORB, while for OIB-type mafic volcanics (+3.7 to +4.3) are comparatively lower and analogous to Hawaii and Kerguelen OIB. Therefore, the observed protolith decoupling in the contemporaneous blueschists suggest the involvement of different protolith contenders, which were partially off-scraped from of the subducting plate during prolonged deep subduction followed by exhumation along the ISZ.

Carboniferous back-arc bimodal rocks in West Kunlun during northward subduction of the Paleo-Tethys

ABSTRACT The widespread occurrence of Carboniferous Wuluate Formation volcanic rocks in the West Kunlun is closely related to the evolution of the Paleo-Tethys but has received little attention. In this study, we conducted detailed fieldwork on the Wuluate Formation in West Kunlun and performed zircon U‒Pb dating, whole-rock major and trace element analysis, whole-rock Sr-Nd isotope analysis, and in situ zircon Hf isotope analyses. The Wuluate Formation is characterized by a bimodal volcanic suite. Zircon U‒Pb dating indicates that the rhyolites erupted at ca. 348–353 Ma, which is coeval with the zircon U‒Pb dating result of 354 Ma for the basalt. The basalts show a tholeiitic magmatic evolution trend with flattened REE patterns and depleted whole-rock Sr-Nd and zircon Hf isotopes, indicating geochemical affinity to back-arc basin basalt (BABB). Trace element modelling results indicate that the primitive basaltic compositions fit well with the products of the DMM + sediments + H2O source under melting conditions of asthenospheric temperature and thin lithosphere thickness, and the REE modelling results show that the basalts underwent 40% to 95% crystallographic differentiation of olivine, monazite, hornblende, plagioclase, and magnetite. The silicic rocks are calcic to calcic-alkaline and meta/peraluminous. They exhibit flattened REE patterns and slightly enriched zircon Hf isotopes, which could originate from Precambrian metaigneous sources of West Kunlun. The Kungai bimodal suite is likely to have formed in a back-arc setting corresponding to the northward subduction of Paleo-Tethys. The subduction of Paleo-Tethys had already occurred, and a back-arc basin had developed before the Early Carboniferous.

Fertile mantle domains with different metasomatic features beneath the eastern North China Craton: Transformation from variably auto-metasomatized asthenospheric upwelling

The eastern North China Craton is known for replacement of refractory lithospheric mantle by fertile one relevant to the (Paleo-) Pacific subduction. However, the formation mechanism of the fertile mantle domain remains enigmatic, thus hindering profound understanding of the associated lithosphere-asthenosphere interaction. To explore the deep dynamic processes, we present petrology, in-situ element and Sr isotopic data on spinel peridotite xenoliths entrained by the Cenozoic basalt in the Qingyuan county, Liaoning Provence.The Qingyuan mantle xenoliths can be categorized into two groups based on textural characteristics and mineral compositions. Group A peridotites consist of lherzolites containing patch of fine-grained aggregates and have low olivine Fo (100×Mg/(Mg + Fe) ≤ 89, atomic ratios) and mineral major-element composition trends deviating from residual mantle. The coarse-grained clinopyroxenes outside the patch and the patch-hosted fine-grained clinopyroxenes and amphiboles display similar light rare earth element (LREE)-enriched patterns and comparable 87Sr/86Sr ratios (0.7035–0.7039, 0.7040–0.7062 and 0.7029–0.7033, respectively). These characteristics suggest that Group A peridotites may represent fragments of lithospheric mantle strongly modified by melt impregnation. In contrast, Group B xenoliths, typically lherzolites, have protogranular texture without the patches of fine-grained aggregates. The olivines have moderate Fo (ca. 90–91) and mineral major-element compositions highly resembling melting residua. The melting is estimated to occur at about 1370–1590 °C and 2–4 GPa, corresponding to mantle potential temperatures of around 1450–1550 °C. The clinopyroxenes show variably enriched REE patterns and depleted 87Sr/86Sr ratios (0.7020–0.7044). These peridotites are thus interpreted as fragments of residual lithospheric mantle transformed from small-scale asthenospheric upwelling. Diffusion modeling of trace elements in clinopyroxenes suggests ubiquitous Mesozoic-Cenozoic metasomatism in the studied peridotites.Combining with other Cenozoic basalt-borne peridotite xenoliths from the eastern NCC and associated tectonic setting, we conclude that the fertile lithospheric mantle domains with different metasomatic features may be transformed from variably auto-metasomatized asthenospheric upwelling. That is, the subduction-related small-scale upwelling not only leaves behind residual domains with weak metasomatism but also produces mantle regions strongly infiltrated by the decompressional melts. This model links the mantle domains of different formation mechanisms to coherent geodynamic processes and emphasizes the complex mantle processes associated with the fluctuated lithosphere-asthenosphere boundary.

Complexity and ambiguity in the relationships between major lunar crustal lithologies and meteoritic clasts inferred from major and trace element modeling

Clasts of feldspathic lithologies such as magnesian anorthosites, anorthositic troctolites, and granulites in lunar meteorites have greatly expanded knowledge of the lithologic diversity of the lunar crust. However, their origins and relationships to other major crustal lithologies such as the ferroan anorthosites, magnesian-suite, and alkali-suite are not fully understood. Here we present the results of phase equilibrium modeling using the MELTS and MAGFOX programs designed to investigate the origins of lunar crustal lithologies and petrologic connections between them. We show that the major and trace element compositions of the Mg- and alkali-suites are consistent with partial melting of hybridized sources and are inconsistent with decompression melting + assimilation models. Our results also show that the vertical trend in Mg# in mafic silicates vs. An# in plagioclase characteristic of feldspathic meteoritic lithologies and ferroan anorthosites can be produced by fractional crystallization of KREEP-free Mg-suite melts, but that these melts are not likely to contribute significantly to the composition of the global crust. Furthermore, we calculated potential parental melt compositions for these crustal lithologies using the abundances of REEs in plagioclase in FANs, the Mg- and alkali-suites, and clasts in feldspathic meteorites. Our results show that despite low bulk rock abundances of incompatible trace elements in many feldspathic lunar meteorites, parental melts with overall REE abundances similar to or in excess of KREEP are needed to reproduce the REE abundances in plagioclase in clasts from feldspathic lunar meteorites. However, the lack of a Na enrichment trend in their plagioclase compositions with decreasing Mg# requires very Na-depleted melts without a KREEP component. The available data regarding magnesian anorthosites, anorthositic troctolites, and granulites in lunar meteorites, and inferences made here regarding their parental melt compositions, lead to contradictory and ambiguous conclusions regarding their origins.

Late Cryogenian–Ediacaran magmatism in southern Borborema Province, NE Brazil: Ages, sources, petrogenesis, and tectonic setting

The Sergipano Orogenic System (SOS) in southern Borborema Province (NE Brazil) hosts voluminous Neoproterozoic plutonism related to the Brasiliano/Pan-African Orogeny. This paper presents comprehensive whole-rock geochemical data, titanite U-Pb ages, and the first combined zircon U-Pb and Lu-Hf isotope results for plutonic rocks from the Macururé Domain to constrain their sources, petrogenesis, and tectonic setting. Three magmatic episodes are recognized and record the evolutionary stages of the orogen. (i) Early-collisional magmatism (643–628 Ma) comprises gabbros and diorites with minor tonalites characterized by well-developed tectonic foliation and evidence of solid-state deformation. These rocks are magnesian, high-K calc-alkaline, LILE- and LREE-enriched and provide subchondritic εHf(t) values (−6.5 to −4.7) and Orosirian Hf-TDMC model ages (1.83–1.94 Ga). Such features indicate derivation from a lithospheric mantle source metasomatized by incorporating crustal components through subduction processes prior to magma generation, possibly related to the Rhyacian Orogeny (2.20–1.96 Ga). Extensive mixing/mingling between basaltic and crust-derived magmas took place at lower crustal depths, producing coeval hybrid diorites and quartz-diorites. (ii) Syn-collisional magmatism (630–624 Ma) encompasses biotite- and muscovite-bearing granodiorites and monzogranites, preserving their structures parallel to the schistosity of the country rocks. These rocks are leucocratic, weakly metaluminous to peraluminous, and contain abundant surmicaceous enclaves. Petrographic features and geochemical composition suggest an origin related to the partial melting of graywacke protoliths with a subordinate igneous component. (iii) Late-collisional magmatism (625–600 Ma) includes undeformed and isotropic monzonites and granodiorites, which truncate the regional foliation. These rocks are consistently metaluminous and magnesian, showing affinities with the high-K calc-alkaline to shoshonite series. Trace element modeling with subchondritic εHf(t) values (−8.3 to −4.1) and Paleoproterozoic Hf-TDMC model ages (1.77–2.03 Ga) demonstrate that reworking of ancient lower mafic crust played an important role at this time. The integration of our data with previously published results leads us to conclude that the geodynamic evolution of the SOS along the western Gondwana margin is better explained by large-scale lithospheric extension followed by basin inversion and continental collision.

The different responses of trace elements to equilibrium and disequilibrium melting: Implications for crustal differentiation and granite compositions

Equilibrium and disequilibrium meltings are two common mechanisms in the geochemical differentiation of the continental crust. However, responses of trace elements to the two melting processes are still not fully understood in granite petrogenesis. To address this, we conducted trace element modelling of open system melting using phase equilibrium calculations combined with solubility equations for accessory minerals and mineral–melt partition coefficients based on three melt-reintegrated felsic granulite compositions. The results indicate systematic differences between the compositions of disequilibrium (Type I) and equilibrium (Type II) melts involving water-present melting reaction, fluid-absent melting reaction involving biotite, and fluid-absent melting reaction in the absence of biotite. Type I melts generally have higher Rb, Ba, Co, Ni, V, and Cr contents, and Rb/Sr and Nb/Ta ratios, and lower Sr, P, Th, U, and light rare earth element contents than Type II melts. Significantly, disequilibrium melting involving biotite can produce melts with high Nb contents and super-chondritic Nb/Ta ratios, which may be a reservoir for the missing Nb on Earth. Compared with Type II melts, the trace element contents and ratios of Type I melts exhibit a larger range, more complex trends, and are more sensitive to changes in melting reaction types and melt loss. This suggests that, in addition to petrogenetic processes such as crystal entrainment, fractional crystallization and magma mixing, the disequilibrium melting would also contribute to the compositional diversity of granites. The modelling results also show that the trace element signatures of granites that are commonly used to determine their petrogenetic processes and tectonic setting may lead to erroneous conclusions if the granitic melts were produced by disequilibrium melting.

GIS-based Spatial Variability and Water Quality Index (WQI) Modeling of Trace Elements in Groundwater of Jamshedpur, Eastern India

Abstract The present study investigated the spatial variability and water quality index (WQI) modeling of groundwater for drinking purposes. Thus, the sample from 30 locations in Jamshedpur city was collected to explore the hydrochemical characteristics. The range of values of trace elements was well complied with the Bureau of Indian Standards (BIS) except Co (0.1 to 13.87 µg/L), Cu (0.12 to 64.62 µg/L), Mn (20 to 1461 µg/L), and Sr (30 to 544 µg/L).The water table of this region showed tremendous variation (0.44 to 4.90 mbgl) as monitored by a sensor-based water level recorder. The WQI model revealed that only 4% of the water in this region is under the excellent categories, followed by good (86%) and poor (10%). Human health risk assessment of trace elements in contaminated groundwater was also performed according to the United States Environmental Protection Agency (USEPA). The estimated hazard index (HI) value (4.85E-02 to 1.61E+00) indicated the non-carcinogenic risk. The study provides immense help for public health decision-makers to prevent the communities health risks.

Role of Depleted-MORB Mantle in the Genesis of Basalts from the Neoarchean Eastern Felsic Volcanic Terrane of the Sandur Greenstone belt, Dharwar Craton, India

Abstract The mafic volcanic rocks from the eastern felsic volcanic terrane (EFVT) of the Neoarchean Sandur greenstone belt of Western Dharwar Craton (WDC) are studied to evaluate their geochemical characteristics and tectonic implications. Characterised as sub-alkaline, tholeiitic basalts, they display moderate SiO2 (49.82-53.74 wt.%), Al2O3 (9.08-15.91 wt.%), TiO2 (0.25-0.66 wt.%) and total alkalies (Na2O+K2O= 0.60-3.97 wt.%) with Mg# ranging from 37-55 at low Cr (7-33 ppm), Ni (8-24 ppm) and V (252-612 ppm). Their rare earth and trace element patterns are coherent exhibiting moderate fractionation (La/Yb=0.16-1.09), slight negative Eu anomalies indicating limited plagioclase fractionation (Eu/Eu*= 0.69-0.96), negative Nb, Ta, Ti and Zr-Hf anomalies revealing their arc signatures. The Nb-Th and Zr-Y relationships of these basalts suggest their derivation from the partial melting of depleted mantle in an intra-oceanic arc setting. Trace element modelling of these basalts indicates their genesis by ~15% partial melting of depleted MORB-mantle and depletion of the source is attributed to previous melting events. These basalts are geochemically similar with the depleted arc and forearc basalts of the Phanerozoic Tonga and Izu-Bonin-Mariana arcs emphasising the operation of analogous tectonic processes during the Archean era.

Differentiation of an upper crustal magma reservoir via crystal-melt separation recorded in the San Gabriel pluton, central Chile

AbstractCrystal-melt separation has been invoked as a mechanism that generates compositional variabilities in magma reservoirs hosted within the Earth’s crust. However, the way phase separation occurs within such reservoirs is still debated. The San Gabriel pluton of central Chile is a composite pluton (12.82 ± 0.19 Ma) with wide textural/compositional variation (52–67 wt% SiO2) and presents a great natural laboratory for studying processes that occur in upper crustal magma reservoirs. Geochemical and geochronological data supported by numerical models reveals that shallow magma differentiation via crystalmelt separation occurred in magma with intermediate composition and generated high-silica magmas and cumulate residues that were redistributed within the reservoir.The pluton is composed of three units: (1) quartz-monzonites representing the main hosting unit, (2) a porphyritic monzogranite located at the lowest exposed levels, and (3) coarse-grained quartz-monzodiorites with cumulate textures at the middle level of the intrusive. Calculations of mass balance and thermodynamic modeling of major and trace elements indicate that &amp;lt;40 vol% of haplogranitic residual melt was extracted from the parental magma to generate quartz-monzonites, and 50–80 vol% was extracted to generate quartz-monzodiorites, which implies that both units represent crystal-rich residues. By contrast, the monzogranites are interpreted as a concentration of remobilized residual melts that followed 30–70 vol% fractionation from a mush with 0.4–0.55 of crystal fraction. The monzogranites represent the upper level of a pulse that stopped under a crystal-rich mush zone, probably leaving a mafic cumulate zone beneath the exposed pluton. This case study illustrates the role of the redistribution of residual silicic melts within shallow magma reservoirs.

A peridotite source for strongly alkalic ultrabasic HIMU lavas of the Oslo Rift, Norway

High alkali (Na2O + K2O) low SiO2 lavas generally have highly fractionated trace element compositions and their petrogenesis is debated. Both pyroxene-rich (pyroxenite) and olivine-rich (peridotite) mantle sources have been proposed for such lavas. HIMU (high 238U/204Pb) lavas usually have such compositions and are often interpreted as being derived from garnet-pyroxenite (eclogite) residue of subducted recycled oceanic crust, possibly including a carbonate component. In some cases, an origin from a garnet peridotite source has also been considered.We present new Mg, Pb, Nd, and Sr isotopic data and elemental data for alkalic ultrabasic lavas (melilitites, nephelinites) from the Oslo Rift, Norway. The magmatic province of the Permo-Carboniferous Oslo Rift is interpreted as part of the much larger Skagerrak-Centered Large Igneous Province (SCLIP) which may be related to a mantle plume source originating from the African Large Low Shear Velocity Province (LLSVP) at the core-mantle boundary. The range of δ26Mg is narrow (−0.32 to −0.28) and is similar to typical mantle values, and therefore is inconsistent with a carbonated source as has been suggested for other similar lavas. The 206Pb/204Pb values of all the lavas are high, which identifies them as HIMU lavas. The εNd of +1 to +2 are substantially lower than for typical HIMU lavas, and in the εNd-εSr diagram they plot on the LoNd array between HIMU and EMI. The lavas are more like archetypal kimberlites (formerly, Group I kimberlites), as these also have εNd slightly higher than the chondritic value and Pb isotopes consistent with a HIMU source. The REE patterns of the lavas are also almost as fractionated as in Group I kimberlites.We used major and trace elements to infer the primary magma composition of these lavas. This primary magma composition is compared with experimental melts of both carbonated peridotite and carbonated eclogite source compositions and shows that their major element compositions are only consistent with either a very high degree of melting of eclogite or a very low degree melting of garnet peridotite. The strongly fractionated REE patterns of the lavas can only be made by low-degree melting of either eclogite or garnet peridotite, which therefore effectively rules out eclogite as a major component of the mantle source of these lavas. Further trace element modeling points to a mantle source composition with >97% garnet peridotite that was lightly carbonated (<0.5 wt% CO2) and melted to a very low degree (∼0.4%) to produce these lavas. The modeled source trace element pattern was constrained by the Nd, Sr, and Pb isotopic compositions of the lavas. The measured high Ti contents of these lavas (3.8–6 wt%) are quantitatively shown to be the result of enrichment by both partial melting and fractional crystallization, using experimentally determined DTi for melting of this type of source. We also show that a low degree of melting of a slightly carbonated source is sufficient to result in the likely very high CO2 content (10–15 wt%) of the primary magma.The rather uniform Pb isotope composition of HIMU magmas suggests that the HIMU source is rather uniform in composition, but the Pb isotope composition requires this source to form late in Earth's history. The similarity of these lavas and kimberlites suggests a very deep source, possibly in the LLSVP that gave origin to the SCLIP. This means that LLSVPs do not represent some primordial layer around the core that escaped homogenization of the mantle by the Moon-forming giant impact. Instead, this layer must have formed late in Earth's history. The constraint that this source contains <3% of garnet-pyroxenite (eclogite) residue of recycled basaltic oceanic crust shows that this layer is primarily not a subducted slab graveyard. The process by which the LLSVPs formed, however, remains obscure.

Origin of silicic rocks of the Deccan Traps continental flood basalt province: Inferences from field observations, petrography, and geochemistry

The origin of silicic rocks (SiO2 > 65 wt%) in Continental Flood Basalt (CFB) provinces could be attributed to complex petrogenetic processes. The 65.5–66 Ma old Deccan Traps CFB contains eight sporadic but significant silicic rock exposures that are studied here in a comprehensive framework using field observations, petrography, major oxides (n = 56), and trace element chemistry. Rhyolite and granophyre, as well as subordinate felsite, ignimbrite, trachyte, pitchstone, and microgranite coexist with volcanic and plutonic mafic rocks such as basalt, basaltic andesite, and gabbro. Multiple isolated and circular/semi-circular hills and linear dykes of silicic rocks are present in the form of lavas with prominent flow folding, rheomorphic ignimbrite, and tuffs. The ‘Rheological Agpaitic Index’ (RAI) indicates that most of the silicic rocks in the Deccan Traps are effusive in nature, except for Rajpipla, Alech, Bombay, and Osham silicic rocks, which are marked by explosive volcanism. Thermodynamic-based Rhyolite-MELTS modelling suggests that the major oxide composition of Pavagadh and Barda basalt is a likely candidate for the parental melt composition of the silicic rocks of the Deccan Traps. Ba, Sr, P, Zr, and Ti anomalies are consistent with the fractionation of K-feldspar, plagioclase, apatite, zircon, and Fe-Ti oxides, respectively. Two broad REE patterns are noticed in the Deccan Traps silicic rocks: a flat pattern for Barda, Alech, and Chogat-Chamardi silicic rocks, and a steep REE pattern for Osham, Rajula, Pavagadh, Rajpipla, and Bombay silicic rocks. Trace element modelling reveals that 5–10 % partial melting of a spinel peridotite source could produce an REE pattern and abundances similar to the associated basalts. Further extensive fractional crystallization (60–90 %) of the parental mafic melt at a deeper depth (where spinel is stable) could produce the REE composition and pattern observed in most silicic rocks except for those of Barda, Alech, and Chogat-Chamardi, which require fractional crystallization of the same parental melt at a shallower depth (where spinel is not stable). The geochemical variability of Deccan Traps silicic rocks reveals an origin from a mantle-derived parental mafic melt that evolved via the assimilation and fractional crystallization (AFC) process to form the silicic exposures, which is typical of silicic volcanism in other global CFBs.

Petrogenesis of Mesozoic Magmatic Suites in the Jiaodong Peninsula: Implications for Crust-Mantle Interactions and Decratonization

Abstract The North China Craton (NCC) has thick lithosphere in the Paleozoic (&amp;gt;200 km) but appears to be decratonized in the Mesozoic. However, the actual processes operated in the lower crust-deep mantle are still unclear. The Mesozoic granitic rocks can provide important clues to the NCC decratonization mechanism. Here, we conducted trace element modeling to check whether partial melting of the Archean lower crust can generate these Mesozoic magmatic suites. Meanwhile, zircon Hf isotope analysis was conducted to reveal crust-mantle interaction processes and further give constraints on the decratonization of the NCC. Zircon Hf isotope data of the Linglong, Guojialing, and Aishan suites, the mafic microgranular enclaves (MMEs) in the Guojialing suite, and mafic dykes display minor differences: the Linglong (160–150 Ma), Guojialing (~130 Ma), and Aishan (118–116 Ma) suites have zircon εHft=–25.4 to –14.5, –15.3 to –10.4, and –23.1 to –11.9, respectively. The Cretaceous mafic dyke (126 Ma) has a highly negative εHft value (–22.8 to –17.7). Meanwhile, the MMEs (in the Guojialing granodiorite, DCW-2A, 129 Ma) have zircon εHft=–13.0 to –8.9. Temperature-pressure conditions calculated using amphibole compositions for both the Guojialing granodiorite and its MMEs are basically identical, implying possible magma mixing. Our modeling results show that certain trace elements (e.g., Tb, Yb, and Y) have to be retained in the source to match the composition of the Linglong suite, which requires substantial garnet residues (high-pressure melting) in the Jurassic. The Early Cretaceous garnet-dominated lower crust is Yb-/Y-enriched but depleted in elements like Sr and La. Therefore, it could not form geochemical features like high Sr/Y and La/Yb ratios akin to the Guojialing suite. Integrating the modeling results and zircon Hf isotope data, we propose that the crust in the eastern NCC had thickened and partially melted by dehydration to produce an eclogitic residue containing a large amount of garnet (&amp;gt;50% by weight) during the Jurassic (Linglong granite), whereas upwelling of hot and hydrous mafic magma from the asthenospheric mantle induced fluxed melting of both the lower crust and lithospheric mantle in the Early Cretaceous, during which the lithospheric mantle and part of the lower crust in the Jiaodong were removed by the convective mantle. About 10 Mys later while the Aishan suite formed, the crust was not thick anymore, and melting occurred under moderate pressure which does not necessarily require abundant garnet as the residue phase.

The earliest stage of mantle-melt evolution during subduction initiation: Evidence from the Neo-Tethyan Mirdita Ophiolite, Albania

Mantle-melt evolution processes in the earliest stage of subduction initiation (SI) are still ambiguous. Here, we report the systematic petrogeochemical and physical records of the SI processes demonstrated by the Gomsiqe massif, Mirdita ophiolite. The Gomsiqe ultramafic body consists of basal lherzolites, upper harzburgites containing lentoid dunites and disseminated chromitites, displaying transition of petrological (Cr# of spinels range from 12.7 to 47.1) and geochemical signatures. Clinopyroxene trace element modeling indicates that lherzolites and harzburgites have undergone variable garnet-facies melting prior to spinel-facies melting. Harzburgites encountered higher degrees of spinel-facies melting compared with those of lherzolites (~ 8–10% vs. ~ 3–5%), and late-stage MORB melt metasomatism. Lherzolites escaped metasomatism. The dunites and chromitites formed by interactions between the harzburgitic lithosphere and MORB-like transitional magmas continued, but with limited hydrous fluid involvement during subduction. The transitional characteristics of metasomatic melt composition and physical condition (i.e., oxygen fugacity [ f o 2 ]) of different lithologies are consistent with the corresponding archive in the Izu-Bonin-Mariana forearc. Lherzolites and harzburgites have comparable f o 2 to that of the abyssal peridotites. The dunites are apparently more oxidized compared to the associated chromitites, further supporting a hypothesis that sulfur-saturated MORB melts were responsible for the formation of chromitites and reduced Cr# of chromitite spinels. Thermometry showed that lherzolites preserved higher equilibration temperatures than harzburgites. Both experienced a later lower-temperature re-equilibration process. Thus, the Mirdita ophiolite preserves multi-stage mantle-melt evolution processes, which are the comprehensive physicochemical responses of the earliest stage of SI. • Gomsiqe mantle rocks reveal time-progressive mantle-melt evolution process. • Gomsiqe massif records the earliest subduction initiation-related signatures. • Ophiolitic mantle provide complementary insights of subduction initiation process.

Evaluation among trace elements, clinical parameters and type 1 diabetes according to sex: A new sight of auxiliary prediction in negative insulin auto-antibodies population

BackgroundType 1 diabetes (T1D) exhibited sex-specific metabolic status including oxidative stress with dynamic change of trace elements, which emphasized the importance of the evaluation of trace elements according to sex. Besides, the most significant characteristic, insulin auto-antibodies, could not be found in all T1D patients, which needed the auxiliary prediction of clinical parameters. And it would benefit the early detection and treatment if some high-risk groups of T1D could predict and prevent the occurrence of disease through common clinical parameters. Hence, there was an urgent need to construct more effective and scientific statistical prediction models to serve clinic better. This study aimed to evaluate the sex-specific levels of trace elements and the relationship between trace elements and clinical parameters in T1D, and construct sex-specific auxiliary prediction model combined with trace elements and clinical parameters. MethodsA total of 105 T1D patients with negative insulin auto-antibodies and 105 age/sex-matched healthy individuals were enrolled in First Hospital of Jilin University. Inductively Coupled Plasma Mass Spectrometry was performed for the measurement of calcium (Ca), magnesium (Mg), zinc (Zn), copper (Cu), iron (Fe), selenium (Se) in the serum, and the data of clinical parameters were received from medical record system. The lambda-mu-sigma method was used to evaluate the relationship between abnormal clinical parameters and trace elements. Training set and validation set were divided for the construction of predictable models in males and females: clinical parameters model, trace element model and the combined model (clinical parameters and trace elements). Goodness fit test, decision curve analysis and other related statistical methods were used to perform data analysis. ResultsLower levels of Mg, Ca, Fe in the serum were found in T1D population in females compared with healthy population, while levels of Fe, Zn and Cu of serum in T1D individuals were higher than those of healthy population in males. Levels of serum Mg, Fe and Cu in T1D group were found with significant sex difference for (P < 0.05), and the levels of Fe and Cu in serum of males were higher than those of females, level of serum Mg in males was lower than those of females. Levels of serum Mg and Zn showed fluctuation trend with increased numbers of abnormal clinical parameters (NACP) in males. Serum Zn in females showed consistent elevated trend with NACP; serum Se increased first and then decreased with NACP in males and females. The auxiliary prediction model (Triglyceride, Total protein, serum Mg) was found with the highest predicted efficiency in males (AUC=0.993), while the model in females (Apolipoprotein A, Creatinine, Fe, Se, Zn/Cu ratio) showed the best predicted efficiency (AUC=0.951). The models had passed the verification in validation set, and Chi-square goodness-of-fit test, DCA results both confirmed their satisfactory clinical applicability. ConclusionSex-specific difference were found in serum Mg, Fe and Cu in T1D. The combination of triglyceride, total protein and serum Mg for males, and apolipoprotein A, creatinine, Fe, Se, Zn/Cu ratio for females could effectively predict T1D in patients with negative anti-bodies, which would provide alarm for the population with high-risk of T1D and serve the T1D prediction in patients with negative anti-bodies.

Architectural and Compositional Diversity of Early Earth Ocean Floor Evidenced by the Paleoarchean Nondweni Greenstone Belt, South Africa

Abstract The nature of the early Archean ocean floor remains a topic of important debate. There are relatively few well-preserved occurrences worldwide where such terrains may be studied in detail because of structural dismemberment, metamorphic overprinting and pervasive early stage hydrothermal alteration to recent weathering. The 3.41-Ga dominantly mafic formations of the Nondweni Greenstone Belt (NGB) covering 270 km2 in the south-eastern Kaapvaal Craton comprise submarine volcanics that exhibit a wide range of textural features, including pillows, chill zones and brecciated flow tops, and various spinifex textures, including the rare platy pyroxene type, cumulate layers, and tuffs. Channelized subaqueous lava lakes that underwent fractionation are capped by thick spinifex-textured units and pillows. Early stage seafloor alteration is regionally variable, ranging from intense to minimal, with preservation of original mineralogy in many areas. Mafic volcanic rocks of the NGB contrast with those of the Barberton Greenstone Belt both in the style of volcanism and in the associated compositional range of komatiitic basalt to basalt with a complete absence of high-Mg komatiites. Olivine-phyric rocks, or derivatives thereof, are largely absent and pyroxene is the main controlling phase with orthopyroxene in the most primitive komatiitic basalts and clinopyroxene in the evolved lava lake sequences. The abundance of orthopyroxene typifies the long-standing silica-enriched character of the Kaapvaal Craton. Three exceptionally well-preserved and well-exposed sequences were studied utilizing hand-drilled samples and deep coring providing unprecedented stratigraphic and textural detail and field controls for more than 400 samples. A unifying feature of the mafic volcanics of the NGB is the range of compositions and ratios of incompatible elements most clearly illustrated by a series of high- and low-Ti compositional lineages reflecting differing sources or degrees of mantle partial melting. Sharp boundaries between high- and low-Ti flow successions indicate sudden changes in the melting regimes or the interaction of flow sequences from different volcanic centres. Th/Nb ranges from 0.1 to 0.2 and reveals crustal contamination of primitive lavas. The primary magma that gave rise to the most primitive komatiitic basalts with 19.5% MgO was derived from partial melting of a mantle plume source in the garnet stability field. Trace element modeling shows that the sequences studied in detail have been modified by fractionation and crustal contamination with the most likely contaminant being the Ancient Gneiss Complex (3.43–3.66 Ga), which is extensively exposed in Eswatini and probably underlies the Paleoarchean terrains in the southern Kaapvaal Craton. The geotectonic setting was likely that of a submerged felsic crustal platform as enclaves within an oceanic plateau.

Temporal evolution of 142Nd signatures in SW Greenland from high precision MC-ICP-MS measurements

Measurements of 142Nd isotope signatures in Archean rocks are a powerful tool to investigate the earliest silicate differentiation events on Earth. Here, we introduce a new analytical protocol that allows high precision radiogenic and mass-independent Nd isotope measurements by MC-ICP-MS. To validate our method, we have measured well-characterized ∼3.72 to ∼3.8 Ga samples from the Eoarchean Itsaq Gneiss Complex and associated supracrustal belts, as well as Mesoarchean greenstones and a Proterozoic dike in SW Greenland, including lithostratigraphic units that were previously analyzed for 142-143Nd isotope systematics, by both TIMS and MC-ICP-MS. Our μ142Nd values for ∼3.72 to ∼3.8 Ga rocks from the Isua region range from +9.2 ± 2.6 to +13.2 ± 1.1 ppm and are in good agreement with previous studies. Using coupled 142,143Nd/144Nd isotope systematics from our data for ∼3.8 Ga mafic-ultramafic successions from the Isua region, we can confirm previous age constraints on the earliest silicate differentiation events with differentiation age of 4.390−0.060+0.045 Ga. Moreover, we can resolve a statistically significant decrease of 142Nd/144Nd isotope compositions in the ambient mantle of SW Greenland that already started to commence by Eoarchean time, between ∼3.8 Ga (μ142Nd = +13.0 ± 1.1) and ∼ 3.72 Ga (μ142Nd = +9.8 ± 1.0). Even lower but homogeneous μ142Nd values of +3.8 ± 1.1 are found in ∼3.4 Ga mantle-derived rocks from the Ameralik dike swarms. Our study reveals that ε143Nd(i) and εHf(i) values of Isua rocks scatter more than it would be expected from a single stage differentiation event as implied from nearly uniform μ142Nd values, suggesting that the previously described decoupling of Hf and Nd isotopes is not a primordial magma ocean signature. Instead, we conclude that some of second stage processes like younger mantle depletion events or recycling of subducted material affected the 147Sm143Nd isotope systematics. The preservation of pristine whole-rock isochrons largely rules out a significant disturbance by younger alteration events. Based on isotope and trace element modelling, we argue that the temporal evolution of coupled 142,143Nd/144Nd isotope compositions in the ambient mantle beneath the Isua rocks is best explained by the progressive admixture of material to the Isua mantle source that must have had present-day-like μ142Nd compositions. In contrast, Mesoarchean mafic rocks from the ∼3.08 Ga Ivisaartoq greenstone belt and the 2.97 Ga inner Ameralik Fjord region as well as a 2.0 Ga Proterozoic dike within that region all have higher μ142Nd values as would be expected from our simple replenishment model. This argues for reworking of older Isua crustal material that carried elevated μ142Nd compositions.