An intensive study of the geochemical characteristics (including the volatile elements Cl and S) of apatite associated with porphyry deposits was undertaken to address the debate about the crust- or ...mantle-derivation of their copper and gold and to better understand the controls on the transport of metals in magmatic fluids in post-subduction settings. New geochemical data on apatite reveal parameters to discriminate mineralized porphyry systems across Iran and western China (Tibet and Yunnan), from coeval barren localities across this post-subduction metallogenic belt. Apatites in fertile porphyries have higher Cl and S concentrations (reflecting water-rich crystallization conditions) than those from coeval barren ones. Our new isotopic data also indicate these volatiles are likely derived from pre-enriched sub-continental lithospheric mantle, metasomatized by previous oceanic subduction. This study demonstrates that refertilization of suprasubduction lithospheric mantle during previous collision events is a prerequisite for forming post-subduction fertile porphyries, providing an evidence-based alternative to current ore-enrichment models.
•The metabasic rocks in Cathaysia yield U–Pb ages of 969–984Ma and TDM(Hf) of 0.92–1.44Ga.•They originated from a subduction-modified MORB-like source linked to an arc–back-arc setting.•The South ...China Block was created by episodic amalgamation of a series of arc fragments between ∼970 and 820Ma.•The South China Block is an exterior accretionary orogen along the periphery of Rodinia rather than in the interior.
U–Pb geochronology along with elemental and Nd–Hf–Os isotopic data from the earliest Neoproterozoic metabasic rocks within the Cathaysia Block of the South China Block (SCB) constrain the tectonic setting and paleogeography of the block within the Rodinia supercontinent. The metabasic rocks give zircon U–Pb ages of 969–984Ma, ɛHf(t) values of +1.8 to +15.3 and Hf model ages of 0.92–1.44Ga. They are subalkaline basalts that can be geochemically classified into four groups. Group 1 has low Nb contents (1.24–4.33ppm), highly positive ɛNd(t) values (+4.3 to +5.2), and REE and multi-elemental patterns similar to fore-arc MORB-type basalt. Group 2 has Nb contents ranging from 3.13ppm to 6.48ppm, ɛNd(t) of +3.1 to +6.2, low Re and Os contents and high initial Os isotopic ratios, and displays an E-MORB geochemical signature. Group 3 has Nb=7.18–29.87ppm, Nb/La=0.60–1.40, Nb/U=5.0–37, Ce/Pb=1.1–6.6, ɛNd(t)=+2.9 to +7.0, 187Re/188Os=5.87–8.87 and γOs (t)=178–772, geochemically resembling to the Pickle Nb-enriched basalt. Group 4 has strong LREE/HREE and HREE fractionation and high ɛNd(t) values (+2.3 to +5.6), and is characterized by similar element patterns to arc volcanic rocks. Serpentinites coeval to Group 4 show 187Os/188Os of 0.1143–0.1442 and γOs (t) of −7.8 to +0.1. Groups 1 and 2 are interpreted to originate from the N-MORB and E-MORB-like sources with the addition of an arc-like component, genetically linked to fore- and back-arc settings, respectively. Groups 3 and 4 show inputs of newly subduction-derived melt and fluid in the wedge source. These geochronological and geochemical signatures fingerprint the development of an earliest Neoproterozoic (∼970Ma) arc–back-arc system along the Wuyi-Yunkai domain of the Cathaysia Block. Regional relationships indicate that the Wuyi-Yunkai arc–back-arc system was one of a series of separate convergent margin settings, which included the Shuangxiwu (∼970–880Ma) and Jiangnan (∼870–820Ma) systems that developed in the SCB. The formation and closure of these arc–back-arc systems resulted in the northwestwardly episodic amalgamation of various pieces of the Yangtze and Cathaysia to finally form the SCB. These signatures require the SCB to occupy an exterior accretionary orogen along the periphery of Rodinia during 990–820Ma, rather than to have formed through Mesoproterozoic Sibao orogenesis within the interior of Rodinia.
Olivine grains from Songshugou mylonitized peridotite massif record δ18O both lower and higher than in pristine mantle samples in North Qinling Orogen, Central China. Olivines from dunites exhibit ...large variations in δ18O (4.03-7.07 ppm), and some porphyroclasts display negative correlations between δ18O and forsterite content {Fo; 100×Mg/(Mg+Fe2+)}. The porphyroclast cores have low-δ18O values, indicating that they formed in the oceanic lithospheric mantle prior to subduction. We attribute low-δ18O values to seawater-peridotite interaction under high-temperature conditions. The porphyroclast rims and small olivines exhibit high-δ18O values. These features suggest that high-δ18O olivines formed during mylonitization in the exhumation process. Olivines reacted with 18O-rich melt/fluids released from subducted altered oceanic basalts and continental sediments at low temperature (<610-680°C). The 18O-rich melt/fluids selectively affected porphyroclast rims and small olivine grains. Unlike the olivines in the dunites, the olivines and orthopyroxenes in the harzburgites show limited variations in δ18O (4.21-5.45 ppm and 5.5-5.8 ppm, respectively), due to orthopyroxene exchange with melt/fluid at a slower rate than the coexisting olivine. The preservation of the low-δ18O signature in olivines indicates a short residence time (<20 Ma) for subducting peridotites to mantle depths.
Food waste management remains a paramount issue in the field of social innovation. While government-led public recycling measures are important, the untapped role of residents in food waste ...management at the household level also demands attention. This study aims to propose the design of a smart system that leverages sensors, mobile terminals, and cloud data services to facilitate food waste reduction. Unlike conventional solutions that rely on mechanical and biological technologies, the proposed system adopts a user-centric approach. By integrating the analytical hierarchy process and the theory of inventive problem solving, this study delves into users' actual needs and explores intelligent solutions that are alternatives to traditional approaches to address conflicts in the problem solving phase. The study identifies five main criteria for user demands and highlights user-preferred subcriteria. It determines two physical conflicts and two technical conflicts and explores corresponding information and communications technology (ICT)-related solutions. The tangible outcomes encompass a semi-automated recycling product, a mobile application, and a data centre, which are all designed to help residents navigate the challenges regarding food waste resource utilisation. This study provides an approach that considers users' genuine demands, empowering them to actively engage in and become practitioners of household food waste reduction. The findings serve as valuable references for similar smart home management systems, providing insights to guide future developments.
To date, few adakitic rocks have been reported in direct association with contemporary intra-continental extensional structures, which has cast doubt on genetic models involving partial melting of ...the lower crust. This study presents Early Cretaceous (143–129
Ma, new Sensitive high-resolution ion microprobe (SHRIMP) zircon U-Pb ages) adakitic granites, which are directly associated with a contemporary metamorphic core complex (i.e., the Northern Dabie Complex in the Dabie area). These granites exhibit relatively high Sr contents, negligible to positive Eu and Sr anomalies, high La/Yb and Sr/Y ratios, but very low Yb and Y contents, similar to subducted oceanic crust-derived adakites. They are also characterized, however, by very low MgO or Mg
# and Ni values, and Nd–Sr isotope compositions (
ε
Nd(
t)
=
−14.6 to −19.4 and (
87Sr/
86Sr)
i
=
0.7067–0.7087) similar to Triassic continent-derived eclogites subducted in the Dabie–Sulu Orogen. Additionally, late granitic dikes in the adakitic intrusions exhibit low Sr contents, clearly negative Eu and Sr anomalies, low La/Yb and Sr/Y ratios, but relatively high Yb and Y contents, similar to 118–105
Ma granites in the Northern Dabie Complex. Based on composition and geochronology data of Neoproterozoic amphibolites and orthogneisses, Triassic high- to ultra-high pressure metamorphic rocks, and Early Cretaceous mafic–ultramafic intrusive rocks, and the constraints provided by experimental melt data for tonalites, metabasaltic rocks and eclogites, we suggest that the adakitic granites were most probably generated by partial melting of thickened amphibole or rutile-bearing eclogitic lower crust as a consequence of Triassic–Middle Jurassic subduction and thrusting. The late dikes probably originated from plagioclase-bearing intermediate granulites. Moreover, we suggest that late Mesozoic delamination or foundering of thickened eclogitic lower crust is also a more plausible mechanism for the petrogenesis of Early Cretaceous mafic–ultramafic intrusive rocks in the Dabie area, and probably involved partial melting of a mixed source comprising eclogitic lower crust that had delaminated or foundered into upper lithospheric or asthenospheric mantle peridotite. Asthenospheric upwelling in response to post-collisional delamination of lithospheric mantle was likely to have provided the heat source for the Cretaceous magmatism.
Clarifying the mechanism of recycling of pre-existing continental crustal materials into the source of mantle-derived magma is a challenging effort that can be of great value to improving our ...understanding of mantle processes and continental crust growth. This study presents an integrated investigation of whole-rock and mineral geochemical and Nd-Hf-O-Pb isotopic data for dolerites and diorites intruded in the central Lhasa Terrane of Tibetan Plateau at ca. 120 Ma (zircon U-Pb ages). These intrusions have similar distributions of trace elements that are characterized by depletion in Nb-Ta relative to Th, Ba, and U, and moderately negative whole-rock εNd(t) (-5.0 to -1.7) values. Magmatic zircon shows dramatically variable εHf(t) values (from -5.0 to +13.7 in the same rock, including up to 12 epsilon unit variability in single grains). On the other hand, the zircon δ18O values are relatively uniform (+6.0 per mille to +7 per mille0;). The constant 208Pb/206Pb values of clinopyroxene crystallized at ca.-013;900 MPa suggest no contamination with lower continental crust. The lack of covariation between Hf and O isotopes from the same grains, and the lack of relationship between Hf isotopes and trace elements (e.g., Hf, Th/U, and Yb/Gd) in the magmatic zircons, together with the absence of ancient zircon xenocrysts, imply limited upper crustal contamination. In combination with high-whole-rock Th/La(>0.29) ratios, we interpret the zircon Hf isotope heterogeneity as inherited from a depleted asthenospheric mantle with the addition 1-4% Hf from isotopically heterogeneous sediments. Our study therefore emphasizes the need for caution when using complex Hf isotopic zonation in zircon as an argument for intracrustal hybridization of two end-member magmas derived from distinct reservoirs. In addition, the high-Zr/Y ratios and no negative Zr-Hf anomalies of the Aruo intrusions imply a high surface temperature of the down going slab that was able to fully dissolve zircons in the subducted sediments. This requires a special geodynamic condition that was most likely related to the steepening of flatly subducted Neo-Tethyan lithosphere at ca. 120 Ma according to a synthesis of regional tectonic-magmatic-sedimentary records.
Subduction of active spreading ridges most likely occurs throughout Earth's history. Interaction or collision between spreading center and trench, with the active spreading ridge downgoing and ...shallowly being buried in subduction zone, results in low-pressure but high-temperature near-trench magmatism in the forearc and accretionary prism setting. The Central Asian region, a complex orogenic belt created during the evolution and closure of the Paleo-Asian Ocean (PAO) at ~1000–300Ma, provides an ideal place to study the subduction of PAO spreading ridges beneath ancient continental margins. It had been suggested that the low-pressure and high-temperature mafic and intermediate to felsic magmas from the Karamaili ophiolite (KO) in the NE corner of the Junggar basin (NW China) in Central Asia were likely produced by ridge subduction (Liu et al., 2007). In this paper, we combine our new geochemical data with previous results to show that the geochemical characteristics of the bulk of KO mafic rocks range from arc basalt-like to mid-ocean ridge basalt-like and ocean island basalt-like. Their trace element patterns range from depleted to enriched in highly incompatible elements, but depleted in Nb and Ta, indicating a subduction-influenced origin. The KO intermediate to felsic rocks are calc-alkaline and boninitic in composition and have trace element signatures similar to the associated mafic rocks. The low Nb/Ta ratios of some of the mafic rocks and boninitic character of some of the intermediate to felsic rocks reflect a highly depleted source, perhaps due to prior backarc magmatism. Major and trace element models indicate complex fractional crystallization histories of parental KO magmas to generate both the mafic and intermediate to felsic rocks, but in general, crystal fractionation occurred at 1000 to 1200°C and moderate to low (0.5kbar to 10kbar) pressure or <23km depth. We conclude that the KO was formed in a forearc region of a subduction system that experienced ridge subduction.
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•Mafic rocks range from arc- to mid-ocean ridge-like and ocean island basalt-like.•Trace element concentration patterns indicate a subduction-influenced origin.•Silicic rocks are calc-alkalic to boninitic in composition.•The KO was formed in a forearc region of a ridge subduction system.
The magmatic records on passive continental margins are mostly alkaline-tholeiitic series or bimodal volcanic suites commonly induced by active or passive processes. However, the origin of the ...relatively rare pure tholeiitic lavas remains poorly understood. In this paper, we document pure tholeiitic records, the Woniusi rock associations, on the passive northern Gondwana margin. During the Late Paleozoic, accompanied with opening of the Meso-Tethyan Ocean, the Woniusi rock associations made up a unique tholeiitic magmatic flare-up on the Baoshan block, the north tip of Sibumasu. Therefore, the Woniusi rock associations can provide essential insights into the origin of tholeiitic magmatism on passive continental margins and the geodynamics for opening the Meso-Tethyan Ocean. This study reports new whole-rock geochemical, SrNd, and zircon UPb and LuHf isotopic data for the Woniusi rock associations. Combined with previously published data, 234 mafic-ultramafic rocks were used to document a complete record of the Late Paleozoic tholeiitic magmatic activities on the Baoshan block. Our new zircon UPb ages denote the basalts of the Woniusi rock associations emplaced at ∼290 Ma. They are tholeiitic in composition with moderately fractionated rare earth elements, obvious NbTa depletion, and variable εNd(t) values. The high-εNd basaltic rocks were generated by lower degrees of partial melting of a less enriched deeper lithospheric mantle followed by fractional crystallization of olivine, orthopyroxene, and clinopyroxene. In contrast, the low-εNd basaltic rocks were derived from moderate-degree partial melts of the regional more enriched shallower lithospheric mantle, which experienced olivine and orthopyroxene fractional crystallization. Detailed field observations and geochemical studies on the Woniusi rock associations found no solid evidence to support the existence of a mantle plume or oceanic subduction in this region. The pure tholeiitic magmatic flare-up on the passive northern Gondwana margin should be generated in an extensional environment, as evidenced by the sublinear orientated mafic dikes, synchronous development of rift system and half-graben structure, and typical extensional basin depositions. Consequently, the passive extension of the northern Gondwana margin facilitated the opening of the Meso-Tethyan Ocean during the Early Permian. Therefore, the Woniusi rock associations provide direct evidence for the critical role of passive extension in the contribution of tholeiitic magmatic flare-up on the passive continental margin and regional opening of the Meso-Tethyan Ocean.
•The Late Paleozoic Woniusi rock associations are pure tholeiitic in composition.•They were derived from regional heterogeneous lithospheric mantle.•They emplaced on an extensional setting along the passive Gondwana margin.•Passive extension can lead to pure tholeiitic flare-up on passive margins.•This geodynamic process also granted regional opening of the Meso-Tethyan Ocean.
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