Equilibrium Ti isotope fractionation factors among major Ti-bearing minerals are critical for understanding Ti isotope fractionation during magmatic processes. We use the first-principles ...calculations based on the density functional theory (DFT) to obtain Ti isotope reduced partition function ratios (103lnβ of 49Ti/47Ti) in a series of important Ti-bearing minerals, including Ti-doped clinopyroxene, orthopyroxene, olivine, and pyrope, geikielite-ilmenite solid solutions, and rutile. There is a large variation in our calculated 103lnβ, which are linearly correlated to their Ti force constants, a parameter related to the average TiO bond length and the Ti valence state. Among all studied minerals, silicates with Ti4+ occupying the tetrahedral Si site have the highest 103lnβ, and rutile has the lowest 103lnβ. The valence state also significantly controls the 103lnβ. Typically, Ti3+-doped silicates have lower 103lnβ than those of Ti4+-doped silicates. At the natural abundance levels, the 103lnβ of Ti4+Si-doped and Ti3+Mg-doped (Ti3+ occupying the Mg site) silicate minerals show no concentration effect. That is, their 103lnβ do not vary with their Ti4+ and Ti3+ contents, respectively. In contrast, the 103lnβ of geikielite-ilmenite solutions significantly decrease with increasing Fe/(Fe + Mg) ratio.
Our calculations predict no significant Ti isotope fractionation among Ti4+Si-doped clinopyroxene, orthopyroxene, olivine, and pyrope (<0.08 % at 1200 K), whereas the 103lnα between geikielite-ilmenite solutions and Ti4+Si-doped clinopyroxene ranges from ∼−0.67‰ to −0.49‰ at 1200 K, supporting the hypothesis that FeTi oxides are important fractionating Ti isotopes during magma differentiation. Finally, the large equilibrium Ti isotope fractionation between geikielite-ilmenite solutions and clinopyroxene suggests that Ti isotopes can be used as a thermometer with precision comparable to that of elemental geothermometer.
Large metal stable isotopic variations have been observed in both extraterrestrial and terrestrial samples. For example, Ca exhibits large mass-dependent isotopic variation in terrestrial igneous ...rocks and mantle minerals (on the order of ∼2‰ variation in 44Ca/40Ca). A thorough assessment and understanding of such isotopic variations in peridotites provides important constraints on the evolution and compositon of the Earth’s mantle. In order to better understand the Ca and Fe isotopic variations in terrestrial silicate rocks, we report Ca isotopic compositions in a set of peridotitic xenoliths from North China Craton (NCC), which have been studied for Fe isotopes. These NCC peridotites have large Ca and Fe isotopic variations, with δ44/40Ca ranging from −0.08 to 0.92 (delta value relative to SRM915a) and δ57/54Fe (delta value relative to IRMM-014) ranging from −0.61 to 0.16, and these isotopic variations are correlated with large Mg# (100×Mg/(Mg+Fe) molar ratio) variation, ranging from 80 to 90. Importantly, NCC Fe-rich peridotites have the lowest 44Ca/40Ca and 57Fe/54Fe ratios in all terrestrial silicate rocks. In contrast, although ureilites, mantle rocks from a now broken differentiated asteroid(s), have large Mg# variation, from 70 to 92, they have very limited δ57Fe/54Fe variation (0.03–0.21, delta value relative to IRMM-014). Our model calculations show that the coupled extremely light Ca-Fe isotopic signatures in NCC Fe-rich peridotites most likely reflect kinetic isotopic fractionation during melt-peridotite reaction on a timescale of several to 104 years. In addition, our new data and compiled literature data show a possible compositional effect on the inter-mineral Ca isotopic fractionation between co-existing clinopyroxene and orthopyroxene pairs.
To better investigate the behavior of titanium (Ti) isotopes during magmatic processes, we report high-precision Ti isotope compositions for 60 terrestrial igneous rocks from different geological ...settings worldwide. Based on their major element compositions and petrographic descriptions, these samples can be subdivided into two groups: Fe-Ti oxide unsaturated and Fe-Ti oxide saturated. The Fe-Ti oxide unsaturated group samples show a narrow δ
49/47
Ti (δ
49/47
Ti = (
49
Ti/
47
Ti)
sample
/(
49
Ti/
47
Ti)
OL-Ti
× 1000) range (− 0.036 ± 0.043‰ to 0.082 ± 0.021 ‰), and no correlation between δ
49/47
Ti and the degree of differentiation is observed. By contrast, Fe-Ti oxide saturated group samples show a remarkable δ
49/47
Ti variation, ranging from 0.005 ± 0.018‰ to 1.914 ± 0.006 ‰, which are positively correlated with SiO
2
contents, and negatively correlated with MgO contents. In particular, multiple SiO
2
vs. δ
49/47
Ti trends are observed in Fe-Ti oxide saturated group, which are controlled by crystal fractionation degrees, magma SiO
2
compositions, and Fe-Ti oxide compositions during magma differentiation.
The Jehol and Yanliao biotas of northern China, two world‐class Lagerstätten with abundant biomass and biodiversity, provide critical clues to Mesozoic terrestrial ecosystems. Their evolution is a ...response to the destruction of the North China craton. However, the impetus for the rapid bloom of the biotas remains a mystery. Mesozoic large‐scale volcanic‐sedimentary strata in northern China are rich in terrestrial organisms. Statistical analyses show that volcanic nutrient element delivery, biomass, and biodiversity in these stratigraphic sequences increase synchronously, while harmful elements have the opposite change with them. These observations reveal the coevolutionary relationship between volcanism and terrestrial biotas. The increased nutrient element supply and inhibited harmful element delivery to terrestrial ecosystems from the voluminous volcanic products, produced under the geodynamic regime of paleo‐Pacific subduction and cratonic destruction, could create a conducive environment for the biodiversity and high prosperity of Mesozoic terrestrial biotas.
Plain Language Summary
The weathering of volcanic products can quickly provide material supply for ecosystems, including nutrient and harmful elements. The availability of these elements in volcanic‐sedimentary sequences can provide key evidence for the intrinsic relations between volcanism and terrestrial biological evolution. Through statistically‐based big data analyses, we determine the changes in nutrient/harmful element delivery, biomass, and vertebrate and entomic diversity of the Mesozoic fossil‐bearing volcanic‐sedimentary strata in northern China. Excluding the interference of pyroclastic flows on the fossil records, the results reveal the significant contributions of elevated volcanic nutrient supply to the flourishing of the Jehol and Yanliao biotas. Meanwhile, the inhibited release of harmful elements has limited impacts on the biotas. This study opens a new path for multidisciplinary investigations to explore the feedback relationship among regional tectonics, volcanism, and terrestrial biotas.
Key Points
Mesozoic terrestrial biotas in northern China coevolved with volcanism during the paleo‐Pacific subduction and cratonic destruction
The increasing supply of volcanic nutrients promoted the flourishing of the Jehol and Yanliao biotas
Inhibited volcanic toxic delivery facilitated the rapid bloom of the terrestrial biotas
This paper reports petrology, major and trace element abundances in bulk-rocks and minerals, and clinopyroxene Sr-Nd-Hf compositions from a suite of mantle xenoliths entrained in Cenozoic Sanyitang ...alkali basalts, Jining County in the Inner Mongolia Suture Zone. The aim is to constrain the nature and evolution of the lithospheric mantle beneath the western North China Craton. The Sanyitang mantle xenoliths are mainly anhydrous spinel lherzolites with subordinate websterites. Petrological and geochemical features of the spinel lherzolites suggest that they are refractory mantle residues formed by variable degrees of melt extraction (3–14%), followed by silicate and carbonatite metasomatism. The Sr-Nd-Hf isotopic compositions (87Sr/86Sr = 0.7031–0.7037, εNd = +5.2 − +11.2 and εHf = +8.4 − +29.3) of clinopyroxene separates from the majority of the spinel lherzolites lie on, or close to, the mantle array defined by the composition of ocean-island basalts and mid-ocean ridge basalts. On the other hand, clinopyroxene separates from a minority of spinel lherzolites (SYT09-01, SYT09-09, SYT11-01) have high 87Sr/86Sr (0.7040–0.7049), εNd (+12.4 − +21.9) and εHf (+58.2 − +67.8), above the mantle array, reflecting long-term depletion of the mantle. The websterites are characterized by lower MgO (18–22 wt%) and higher Al2O3 contents (4.5–5.6 wt%), and lower Mg# (86.2–87.3) than the spinel lherzolites (Mg# = 89.3–90.8; Al2O3 = 0.9–3.6 wt%). Their convex upward rare earth element patterns, along with lower Ni contents (334–389 ppm) indicate that they were cumulates fractionated from basaltic magmas circulating through the upper mantle. The trace element patterns of clinopyroxenes from three phlogopite-free websterites show enrichment in large ion lithophile and negative anomalies for the high field strength elements. In addition, the phlogopite-free websterite clinopyroxene Sr-Nd-Hf isotope ratios plot in the enriched lithospheric field (87Sr/86Sr = 0.7058–0.7061, εNd = −9.2 to −8.4 and εHf = −5.2 to −3.7 respectively), which implies the contribution of recycled lower crustal materials to their source. The presence of phlogopite in some Sanyitang websterites, coupled with strong enrichments in both light rare earth elements and large ion lithophile elements, as well as high 87Sr/86Sr (0.7065–0.7068) and negative εNd (−1.5 to −0.3) and εHf (−6.1 to −4.8) values of clinopyroxene, provide strong evidence for the existence of subduction-related hydrous fluids/melts metasomatism. This study demonstrates that the Sanyitang mantle xenoliths and their component minerals record the complex petrological history and local heterogeneity of the subcontinental mantle lithosphere under the western North China Craton.
•Sanyitang mantle xenoliths are mainly spinel lherzolites with subordinate websterites.•Spinel lherzolites are refractory mantle residues, followed by various metasomatism.•Websterites represent cumulates from mafic melts trapped in mantle depths.•The websterites show existence of subducted crust-derived melt circulation.
This paper reports petrology, major and trace element content, and Fe isotopic composition of minerals from a suite of spinel lherzolites entrained in the Cenozoic Niutoushan basalt from the ...Cathaysia block, South China. The aim is to constrain the nature and evolution of the lithospheric mantle, as well as the factors controlling the fractionation of Fe isotopes beneath the Cathaysia block, South China. Based on the petrographic features and mineral compositions, the Niutoushan spinel lherzolite can be subdivided into two groups. Group 1 lherzolite has a high olivine Fo content (89.3 to 90.6) and both LREE-depleted and LREE-enriched chondrite-normalized REE patterns in clinopyroxene grains, reflecting variable degrees of partial melt extraction (up to 20%) followed by a multistage metasomatic history. The Fe isotopic composition of Group 1 lherzolite minerals shows little variation (δ57/54Fe = −0.05‰ to 0.03‰) with an average of 0.00 ± 0.06‰ (2SD, n =7), close to the suggested δ57/54Fe value of 0.04 ± 0.04‰ for the upper mantle, and there is no significant inter-mineral disequilibria. Compared with the Group 1 lherzolite, the Group 2 lherzolite experienced melt-rock interaction with significant enrichment of Fe as evidenced by relatively lower Mg# (84.9 to 88.2) in olivine and pyroxene grains and LREE-enriched REE patterns in clinopyroxene. Importantly, the Group 2 lherzolite exhibits a large range in Fe isotopic compositions, with δ57/54Fe ranging from −0.48‰ to 0.27‰, and disequilibrium Fe isotope fractionation is noted between most of coexisting Group 2 minerals (Δ57/54FeOpx–Ol = −0.16‰ to 0.25‰ and Δ57/54FeCpx–Ol = −0.16‰ to 0.30‰), reflecting kinetic fractionation during melt-rock interaction. Such processes play an important role in producing inter-mineral Fe isotopic disequilibrium and local Fe isotopic heterogeneity of the subcontinental mantle lithosphere beneath the Cathaysia block, South China, as noted for the subcontinental lithospheric mantle under the North China Craton.
•The Niutoushan spinel lherzolite can be subdivided into two groups.•Group 1 lherzolites are refractory mantle residues later modified by metasomatism.•Group 2 lherzolites are strongly metasomatized and enriched in iron.•Melt percolation result in the Fe isotopic heterogeneity of mantle beneath Niutoushan.
Iron isotopic data of the Cenozoic alkaline basalts and peridotite xenoliths entrained in the Cenozoic and Mesozoic basalts, eastern China, are reported to further constrain the Fe isotopic ...composition of the mantle and investigate the behavior of Fe isotopes during mantle processes. Nine Cenozoic alkaline basalts show limited variation in δ
57Fe that are within the ranges of oceanic basalts, which indicate homogeneous Fe isotope composition of the basalts. The lherzolites from the South China Block also display a limited Fe isotopic variation δ
57Fe of 0.041 to 0.077‰ and an average of 0.060‰
±
0.029‰ (2 SD). This Fe isotopic composition is similar to that of the bulk silicate Earth, indicating that these samples represent mantle residues that underwent just limited degrees of partial melting. In contrast, both the mantle peridotites and their mineral separates from the North China Craton exhibit an extremely large Fe isotopic variation with δ
57Fe ranging from −
1.002‰ to 0.232‰. This may reflect heterogeneous Fe isotopic compositions of the lithospheric mantle beneath the North China Craton. An average δ
57Fe (−
0.066‰) calculated from all the mantle xenoliths in this study is obviously lower than the average value (0.198‰) of δ
57Fe for the Cenozoic alkaline basalts, consistent with the previous observation that basalts generally have heavier Fe isotopes than mantle peridotites. In individual minerals, δ
57Fe of the olivines (−
0.997 to 0.154‰) are systematically lighter than those of the coexisting pyroxenes (−
0.718 to 0.169‰ for orthopyroxene and −
0.642 to 0.304‰ for clinopyroxene, respectively). Phlogopite of apparently metasomatic origin has the heaviest iron isotopic composition amongst the mineral phases with δ
57Fe of 0.302 to 0.376‰. Extreme Fe isotope variation in these peridotites, in particular for the wehrlites, was probably produced by multistage melt–peridotite interactions, consistent with the petrological observation that some of the xenoliths analyzed such as wehrlites were the products of extensive mantle metasomatism. Positive correlations between δ
57Fe and other major and trace element indicators of metasomatism such as CaO and Rb further support the above suggestion. These characteristics suggest that mantle metasomatism or melt–rock interaction can significantly modify Fe isotopes and play an important role in producing Fe isotopic heterogeneity of the lithospheric mantle. Thus, Fe isotopes can provide important information concerning melt–rock interaction and evolution of the lithospheric mantle.
► Fe isotope ratios of basalts and mantle xenoliths from eastern China were measured. ► Cenozoic alkaline basalts show a limited variation in Fe isotopic composition. ► Mantle xenoliths and their mineral separates exhibit an extremely large Fe isotopic variation. ► Positive correlations between δ
57Fe and CaO and Rb suggest that melt–rock interaction can significantly modify Fe isotopes. ► Fe isotopes can provide important information concerning the melt–rock interaction.
Abstract Background The experiences and challenges associated with breastfeeding multiple births can be considerably more complex than those of singletons. Multiple births refer to the delivery of ...more than one offspring in a single birth event. Emphasizing the needs and experiences of mothers with multiple births during breastfeeding can enable healthcare providers to design targeted interventions that enhance breastfeeding rates. However, existing breastfeeding and health education resources and practices do not fully meet the needs of women who breastfeed multiples. This review aimed to review and synthesize qualitative studies on the breastfeeding experiences of women with multiple births. Methods A systematic search was conducted in 10 electronic databases for papers published from the inception of the database to March 2024. The Joanna Briggs Institute Critical Appraisal Checklist for Qualitative Research was utilized to evaluate the methodological quality of the studies included. The thematic synthesis method of Thomas and Harden was employed to integrate and analyze the included literature to derive new categories and conclusions. Findings Eight studies met the inclusion criteria and quality assessment criteria for this study. Through the integration of their results, four themes were identified: the choice and willingness to breastfeed multiple births; the challenges of breastfeeding multiple births; stage management and individualised adaptation of breastfeeding; and the experience of support. Conclusion Throughout the feeding process from pregnancy to the postpartum period, mothers with multiple births often have predominantly negative experiences with breastfeeding. Consequently, hospitals should create a multidisciplinary follow-up team comprising obstetrics, neonatology, psychology, and community services to offer specialized and personalized support to these women at various stages. Systematic review registration https://www.crd.york.ac.uk/PROSPERO/ , identifier PROSPERO 2024 CRD42024520348.
To better understand the behavior of Ti isotope fractionation during alkaline magma differentiation, we studied well characterized alkaline lavas from St. Helena Island (South Atlantic), as well as ...their titanomagnetite separates. The lavas are classified into three groups according to petrographic observations and major element composition. Group 1 and Group 2 samples (5 to > 13 wt.% MgO) have a narrow δ
49/47
Ti range (− 0.02 to 0.05‰), suggesting that Ti isotopic fractionation is insignificant in less evolved basaltic lavas. Conversely, Group 3 samples (MgO < 5 wt.%) are saturated with titanomagnetite and display a wide range in δ
49/47
Ti (− 0.02 to 1.96‰). The δ
49/47
Ti values for Group 3 samples show significant correlation with TiO
2
and SiO
2
content, as well as with Mg and Fe isotopic values. Moreover, titanomagnetite phenocrysts from Group 3 rocks have remarkably lighter δ
49/47
Ti values (− 0.54 to 0.01‰) relative to the corresponding whole rock (− 0.02 to 0.21‰), indicating that titanomagnetite crystallization exerts significant control over the δ
49/47
Ti of Group 3 samples. These observations are further supported by modeling calculations. Together with published Ti isotope data, the results demonstrate that the range in Ti isotopic evolution in alkaline, calc-alkaline and tholeiitic magmatic systems is controlled by fractional crystallization of diverse Fe-Ti oxides with contrasting Ti isotopic compositions. This makes Ti stable isotopes an important geochemical tracer for magma evolution.
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