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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‰), 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 (

The study of Carboniferous magmatism in northern West Junggar plays an important role in understanding the tectonic evolution of that part of the Central Asian Orogenic Belt. In this study, we present petrology, zircon U–Pb geochronology, mineral and whole-rock geochemistry, and the Sr–Nd–Hf–Pb isotope compositions of volcanic rocks from the Hamutusi area of northern West Junggar. LA–ICP–MS zircon U–Pb analysis of a representative andesite yielded an early to late Carboniferous age of 324.4 ± 6.9 Ma. The volcanic rocks are calc-alkaline, with high SiO2 (54.2–57.8 wt%), MgO (5.97–8.33 wt%), Mg# (60–69), Cr (147–448 ppm), and Ni (29.1–120 ppm) contents, and are enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE), but depleted in high field strength elements (HFSE), these characteristics are similar to those of typical sanukitoids within the Setouchi volcanic belt in Japan. All samples have radiogenic initial Sr and Pb isotopic compositions, and low eNd(t) and eHf(t) values, indicating the sanukitoids were generated by partial melting of subducting sediments in which the melts interacted with the mantle. Geochemical modeling calculations indicate a proportion of 3–10% sediment melt and slab-derived fluids were mixed with the depleted mantle to produce the bulk of the Hamutusi rocks. We conclude that the studied rocks from north West Junggar record the initiation of ridge subduction related to a transition from normal subduction to subduction of young and hot oceanic lithosphere between the early and late Carboniferous.

Adakitic rocks occur in a variety of tectonic settings and are key to understanding the tectonic evolution and geodynamics of orogenic belts. We investigated latest Oligocene (23.5–22.5 Ma) quartz monzonites and granites from the western segment of the Urumieh–Dokhtar magmatic belt in Iran, which are likely to have formed in response to the early stages of Arabia–Eurasia collision. The studied rocks have the geochemical characteristics of typical adakites, such as high SiO 2 (60.18–68.82 wt%) and Sr (499–793 ppm) contents, low Y (8.90–17.1 ppm) and Yb (0.88–1.58 ppm) contents, and high Sr/Y (26.1‒67.8) and (La/Yb) N (21.9‒32.9) ratios. They have variable K 2 O (3.88–5.09 wt%), MgO (0.44–2.74 wt%; Mg# = 33.7–52.5), Cr (4.27–40.59 ppm), Ni (4.28–35.68 ppm) and Th (9.56–59.59 ppm) contents, and relatively depleted Sr–Nd isotopic compositions [( 87 Sr/ 86 Sr) i = 0.70450–0.70516; ε Nd ( t ) = 2.1–2.7]. These characteristics indicate that the quartz monzonites were derived from the partial melting of delaminated lower crust that interacted with mantle peridotite with high MgO, Cr and Ni contents and depleted Sr–Nd isotopic compositions and suggest that the granites were formed by the fractional crystallization of quartz monzonitic magma. The geochemical features of the studied adakitic rocks could therefore have been affected by magmatic processes (e.g. fractional crystallization), which might be misleading in interpretations of their petrogenesis and related tectonic settings. The geochemical features of the studied rocks indicate that the crust of the western segment of the Urumieh–Dokhtar magmatic belt was thickened to c. 50 ± 4.43 km during the latest Oligocene ( c. 23.5 Ma) as a result of Arabia–Eurasia collision. Supplementary material: Whole rock geochemical and Sr–Nd isotopic compositions, and zircon U–Pb and Lu–Hf isotopic data are available at https://doi.org/10.6084/m9.figshare.c.6188328

Two new homosioflavonoids, ophiopogonanone I (1) and methylophiopogonanone C (2) were isolated from the tuberous roots of Ophiopogon japonicus. Their structures were elucidated on the basis of extensive spectroscopic analyses. The absolute configuration of compounds 1 and 2 were assigned on the basis of CD method. In addition, compounds 1–2 were tested for their cytotoxic activities against HL-60, SMMC-7721, and MCF-7 human cancer cell lines, and compound 2 showed significant cytotoxic activity against HL-60 cell line with IC50 value of 14.42 μM.

Garnet-bearing peridotites commonly occur in the deeper parts of mature or thickened oceanic lithosphere, and are rarely exhumed and emplaced onto the seafloor. The Purang ophiolitic peridotites in south Tibet contain rare symplectite pseudomorphs after garnet, offering a unique window into the still poorly understood evolution of the deep oceanic lithosphere. Here, integrated petrologic and Os-Li isotopic data are used to constrain the evolution and dynamics of emplacement for these garnet peridotite protoliths. The Purang peridotites show wide variations of chemical compositions (spinel Cr#: 0.2–0.8) and Os model ages (up to 2.0 Ga), thus representing a piece of heterogeneous oceanic mantle lithosphere. Dunite channels show two distinctive groups of Cr# of spinels and Os-isotope compositions, with the low- to medium-Cr# (0.2–0.6) and high-Cr# (0.7–0.8) dunites reflecting the reaction of host lherzolites/harzburgites with percolating mid-ocean ridge basalt–like and boninitic melts, respectively. This confirms recent subduction initiation-related melt percolation in the Purang peridotites. Coexisting olivines and pyroxenes in the peridotites show systematic Li elemental and isotopic disequilibrium, suggesting fast cooling of the peridotites to Li closure temperature shortly after the melt percolations, likely during exhumation of the peridotites onto the seafloor. This supports a close link between subduction initiation and tectonic emplacement of the Purang peridotites. Combined with other geological evidence, we suggest the Purang peridotites may originate from the deep part of old, thick oceanic lithosphere of the Neo-Tethys. This thick oceanic lithosphere was progressively weakened and thinned likely during widespread plume-lithosphere interaction, triggering the transformation of garnet peridotite protoliths to spinel peridotites. Subsequently, initiation of a new subduction zone along the lithospheric weakness caused rapid ascent and emplacement of the Purang peridotites at a nascent forearc.

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.

This study used clinopyroxene (cpx) compositions and zircon Hf-O isotopes of Eocene adakitic rocks (EARs) from the Qiangtang block to resolve the mechanism(s) responsible for the formation of the central Tibetan Plateau. The two leading and opposing hypotheses for the origin of these rocks are (1) partially molten foundered lower crust, and (2) partial melting of continentally subducted upper crust. The consensus is that some crustal sources within the mantle have reached eclogite facies, while evidence remains insufficient. Reverse zonation for cpx in high Mg# andesitic samples shows a low Mg# core with lower Sr and Sr/Y than the high Mg# rim, suggesting derivation of parent magma by interaction between some eclogite-derived felsic melts and mantle peridotite. Overall, the mantle-like zircon δ18O (mean value of ∼5.9‰) and εHf(t) (up to +6.7) values argue for a mafic source rather than buried upper-crustal rocks. Given the EARs were formed within a short time span after the end of crustal shortening, the original felsic melts were most likely derived from the foundered and eclogitized lower crust. The foundering process explains the early Eocene low-relief topography and the intermediate, eclogite-free modern crustal composition of central Tibet. Surface uplift as a response to lithosphere removal, however, was likely negligible, based on various lines of evidence, including sediment provenance, isotope paleoaltimetry, and thermochronology, perhaps because the central Tibetan crust was weak.

To better understand the origin of voluminous silicic rocks in a convergent continental margin, we conducted an integrated study in which we have obtained geochronological, mineralogical, and isotopic (including whole-rock Sr–Nd–Pb, in-situ zircon Hf) data of the Heri batholith in West Qinling on the NE Tibetan Plateau. The batholith is composed of metaluminous to weakly peraluminous granodiorites (235–233 Ma) and porphyritic granodiorites (230–223 Ma) with an I-type affinity. Both lithologies share similar major, trace elemental and Sr Nd isotopic compositions. Detailed elemental data demonstrate that these granodioritic rocks underwent fractional crystallization of hornblende and apatite, with plagioclase (i.e. sieve-textured plagioclase cores) accumulation to some extent. Except for porphyritic granodiorites, the Pb isotopes for other analyzed samples are characterized by high radiogenicity and uniformity ((206Pb/204Pb)t: 17.263–18.472, (206Pb/204Pb)t: 15.571–15.591, and (206Pb/204Pb)t: 38.032–38.304), together with limited variations in initial Sr ((87Sr/86Sr)t: 0.707251–0.708103) and Nd (eNd(t) = −7.1 to −6.3) isotopes with two-stage model ages (TDM2) of 1.58–1.52 Ga. These factors collectively point to a derivation from the Mesoproterozoic basement rocks at the lower crustal level, or a comprehensive mixing of different-age components that generated an average crustal residence age. The Sr Nd isotopic compositions of the porphyritic granodiorites are strikingly similar to those of granodiorites. Compared with the experimental melt compositions of amphibolites, the Heri granitoids are probably derived from an amphibolitic source under fluid-absent conditions due to the incongruent breakdown of amphibole and biotite. Based on the temporal–spatial distribution of granitic intrusions in West Qinling and the regional tectonic evolution, our interpretation is that the Heri batholith was formed during the initial collision between the North China Craton (NCC) and the South China Craton (SCC), which was accompanied by the closure of the Paleotethyan Ocean. Considering both previously published data and our new data, we propose that the Heri granitoids were mainly generated by the partial melting of lower crustal amphibolites, with minor mantle-derived melts.

Orthopyroxene-bearing granitic rock (e.g. charnockite) is relatively rare but provides an excellent opportunity to probe the thermal and tectonic evolution of deep orogenic crust because of its distinct mineral assemblage. Here we present petrological, mineralogical, elemental, and Sr–Nd–Hf–O isotopic data for late Eocene (ca. 36 Ma; zircon U–Pb ages) volcanic rocks exposed in the Ejiu region in the southern Qiangtang Terrane to investigate how the central Tibetan crust evolved to its modern thickness and thermal state. The Ejiu volcanic rocks (EVRs) are trachydacites with anhydrous mineral assemblages (i.e. two pyroxenes, sanidine, plagioclase, and ilmenite, without amphibole and biotite) and geochemical characteristics (e.g. high P2O5 and TiO2) that resemble those of charnockite-type magmatic rocks. Mineral and whole-rock thermometry and hygrometry suggests that the parent magma crystallized under hot (~1000°C) and dry (H2O 1.5 GPa) and high temperature (>1000°C) generated the EVRs. Based on a synthesis of independent geological and geophysical data, we further suggest that the southern Qiangtang Terrane crust of the central Tibetan Plateau was thick, dry, and elevated during the Late Cretaceous to early Eocene time, and that it became abnormally hot owing to the ascending asthenosphere after lithospheric foundering during the middle Eocene.

The Kerguelen large igneous province (LIP) has been related to mantle plume activity since at least 120 Ma. There are some older (147–130 Ma) magmatic provinces on circum-eastern Gondwana, but the relationship between these provinces and the Kerguelen mantle plume remains controversial. Here we present petrological, geochronological, geochemical, and Sr–Nd–Hf–Pb–Os isotopic data for high-Ti mafic rocks from two localities (Cuona and Jiangzi) in the eastern Tethyan Himalaya igneous province (147–130 Ma). Zircon grains from these two localities yielded concordant weighted mean 206Pb/238U ages of 137.25 ± 0.98 Ma and 131.28 ± 0.78 Ma (2σ), respectively. The analyzed mafic rocks are enriched in high field strength elements and have positive Nb–Ta anomalies relative to Th and La, which have ocean island basalt-like characteristics. The Cuona basalts were generated by low degrees of melting (3–5 %) of garnet lherzolites (3–5 vol% garnet), and elsewhere the Jiangzi diabases were formed by relatively lower degrees of melting (1–3%) of garnet lherzolite (1–5 vol% garnet). The highly radiogenic Os and Pb isotopic compositions of the Jiangzi diabases were produced by crustal contamination, but the Cuona basalts experienced the least crustal contamination given their relatively low γOs(t), 206Pb/204Pbi, 207Pb/204Pbi, and 208Pb/204Pbi values. Major and trace element geochemical and Sr–Nd–Hf–Pb–Os isotope data for the Cuona basalts are similar to those for products of the Kerguelen mantle plume head. Together with high mantle potential temperatures (>1500 °C), this suggests that the eastern Tethyan Himalaya igneous province (147–130 Ma) was an early magmatic product of the Kerguelen plume. A mantle plume initiation model can explain the temporal and spatial evolution of the Kerguelen LIP, and pre-continental breakup played a role in the breakup of eastern Gondwana, given the >10 Myr between initial mantle plume activity (147–130 Ma) and continental breakup (132–130 Ma). Like studies of Re–Os isotopes in other LIPs, the increasing amount of crustal assimilation with distance from the plume stem can explain the variations in radiogenic Os.

The mechanism of magma generation during continental collision remains enigmatic. Appinite–granite suites commonly occur within collisional orogenic belts, providing an opportunity to monitor lithospheric evolution and the geodynamic processes involved. This paper presents geochronological, mineralogical, and geochemical data for the Eocene (~50 Ma) Pengcuolin appinite–granite suite, which is the first such suite to have been found in the southern Lhasa Terrane, southern Tibet. Two distinct populations of plagioclase are observed in the appinitic rocks: high-An plagioclases that crystallized as an early phase from H2O-saturated mafic magmas, and low-An plagioclases that formed as a late phase at pressures of ~3 kbar and ~5 kbar, as calculated from equilibrium thermobarometry using low-Al and high-Al amphiboles, respectively. The amphibole-rich appinitic rocks have low SiO2 contents and moderate values of Mg#, and are enriched in large ion lithophile elements and depleted in high field strength elements. They have homogeneous initial 87Sr/86Sr ratios of 0.705174–0.705330, eNd(t) values of 0.85 to 1.47, and zircon eHf(t) values of 3.3 to 7.9. These features suggest the appinites were derived from the melting of mantle peridotites that had been permeated by slab-derived fluids. Whole-rock geochemical data, equilibrium melting calculations, and ABS5 modeling results indicate that the primary melts of the appinitic rocks were generated from garnet-stabilized mantle, and that the melts then ascended with crystallization taking place under H2O-saturated conditions and under variable temperatures and pressures. The associated granites have a high and narrow range of SiO2 contents, and they exhibit a high-K calc-alkaline character, and low A/CNK ratios and Mg# values. These geochemical characteristics, plus their widespread distribution and depleted isotopic compositions (87Sr/86Sri = ~0.705, eNd(t) = 1.12–1.59, and zircon eHf(t) = 6.9–9.2), are comparable to those of Cenozoic granitoids elsewhere in southern Tibet and consistent with the partial melting of juvenile mafic lower-crustal materials. This appinite–granite suite not only attests to a flux of slab fluids through the lithospheric mantle during breakoff of the Neo-Tethyan slab, it also sheds light on the vertical profile of magma evolution from the deep mantle to the shallow crust. The emplacement of the appinite–granite suite was facilitated by regional faults, but the rising hydrous basaltic magmas were often trapped by the thick overlying continental crust, and those underplating magmas provided the heat and water that caused the partial melting of the continental crust, finally leading to the widespread Cenozoic felsic (and rare mafic) magmatic rocks of southern Tibet.

There is considerable controversy over the nature of (strongly) peraluminous granitoids and their relationship with coeval metaluminous granitoids. The origin of peraluminous granitoids is of great importance for an understanding of granite petrogenesis, as well as the formation and evolution of the continental crust. This study reveals the presence of contemporaneous metaluminous granitoids and muscovite-bearing peraluminous granitoids in the Guomaying composite pluton (GCP) at approximately 243–242 Ma in West Qinling in the NE Tibetan Plateau. The Middle Triassic granitoids in the GCP can be petrographically and geochemically divided into two groups. The group I samples are characterized by slightly higher K2O/Na2O ratios and are metaluminous with lower Zr-saturation temperatures (740–756 °C). In contrast, the group II samples have lower K2O/Na2O ratios and mostly strongly peraluminous compositions, with marginally higher Zr-saturation temperatures (762–778 °C). Both groups share similar trace elements and Sr–Nd–Pb–Hf isotopic compositions, pointing to middle to lower crustal origins with an amphibolitic residue. The metaluminous granitoids are interpreted as partial melting of amphibolites in the middle to lower crust beneath West Qinling, and the muscovite-bearing peraluminous granodiorites were also generated by partial melting of an amphibolitic source, with addition of a feldspar-rich component in the source. The hydrous basaltic melts derived from partial melting of a metasomatized mantle wedge source were also incorporated into the magma mush. It is inferred that disparate magma sources, entrained peritectic assemblages, and various degrees of antecryst recycling collectively exerted influence on the granitic magma chemistry of the GCP. Consequently, our data suggest that muscovite-bearing strongly peraluminous granitoids, which are widely regarded as the products of recycled metasedimentary rocks, can also originate from an amphibolite-dominated source with involvement of a feldspar-rich component.

Successively erupted intermediate-felsic rocks with variations in their geochemical compositions indicate physical changes in lower-crust conditions, and the variations can provide important insights into the regional tectonic setting. What triggered the late Early Cretaceous tectonic transition of the central-north Lhasa Terrane remains controversial, hindering the understanding of the mechanisms behind the formation of the central Tibetan Plateau. The sodic Dagze volcanic rocks in the north Lhasa Terrane are characterized by high contents of SiO2 and Na2O, low contents of MgO, Fe2O3, and K2O, and low values of Mg#. However, the trace element compositions of the whole-rocks and their zircons allow the rocks to be divided into two groups. The Group I rocks (ca. 105 Ma) have higher contents of Sr and Ba, higher Sr/Y and La/Yb ratios, and lower contents of Y, Yb, Ti, and Zr than Group II rocks (ca. 100 Ma). Besides, the zircons from Group I rocks have higher values of Yb/Gd and U/Yb, lower values of Th/U, and lower Ti contents than the zircons from Group II rocks. However, the rocks of both groups have identical depleted whole-rock Sr-Nd and zircon Hf isotope values. The geochemical data indicate that rocks of both groups were generated by partial melting of a juvenile lower crust, but the differences in the two groups reflect a transition from deep-cold melting to relatively shallower-hotter melting in the period from ca. 105 to 100 Ma. This transition was synchronous with the rapid cooling of granitoids, topographic uplift, and the shutdown of magmatism in the central-north Lhasa Terrane, and followed by sedimentation and the resumption of magmatism in the south Lhasa Terrane. The above observations collectively indicate that the central-north Lhasa Terrane was under an extensional setting in late Early Cretaceous, and we tentatively suggest that it was in response to lithospheric drip during roll-back of the northward-subducting Neo-Tethyan oceanic plate.

The scale and extent of isotopic heterogeneities in the Paleo-Asian oceanic mantle remain poorly constrained. Here, we report Os isotopic data for mantle peridotites from the Paleozoic Gangou and Kumishi ophiolites, which are preserved in the western Chinese Tianshan sutures (Xinjiang, China) and considered to sample the Paleo-Asian oceanic upper mantle. These heavily serpentinized peridotites display positive correlations between Al2O3, Ti, and Yb contents, indicating variable degrees of melt extraction from fertile mantle sources. However, enriched light rare-earth element patterns in the peridotites are inconsistent with simple residues of partial melting, thus reflecting the effect of post-melting melt percolation. Peridotites from both ophiolites show wide variation of Os isotopic compositions, several of which are characterized by highly unradiogenic 187Os/188Os values (0.117–0.118), reflecting Proterozoic melt depletion. Such feature is common in modern oceanic peridotites and most Phanerozoic ophiolites, meaning that Os-isotopically ultradepleted domains should be widespread in the Paleo-Asian oceanic mantle. The overall similarity of Os-isotope distribution between the Paleozoic Tianshan ophiolites and modern oceanic peridotites suggests that they derive from the same heterogeneous upper mantle reservoir. This might support the hypothesis that isotopically ultradepleted domains are inherent components of the convecting upper mantle and have not been sufficiently homogenized by convection. Alternatively, Re-depletion ages (TRD) for these ancient domains are broadly coincident with the major peaks in crustal zircon ages that are thought to reflect episodes of continental crust growth in the adjacent Yili–Central Tianshan microcontinents. This suggests that the ultradepleted mantle domains in some of the Tianshan ophiolites may derive from ancient subcontinental lithospheric mantle, which detached and were exhumed to form the substrate of ocean basins.

The northward subduction of the Neo-Tethys oceanic lithosphere and subsequent collision between India and Asia continents gave rise to the Tibetan Plateau. However, how and when oceanic subduction started to transform to an intraplate environment are still open questions. The granitoids distributed in Lhasa Terrane of south Tibet offer a unique chance for us to investigate the deep geodynamic processes. Here, we present zircon U–Pb–Hf isotope, whole-rock major and trace element and Sr–Nd isotope data of granitoid intrusions in the Sangsang area of the southern Lhasa Terrane. The Sangsang granodiorites and granites were crystallized at ca. 54 Ma, while the emplacement age of the quartz monzonites is ca. 47 Ma. The granodiorites are characterized by relatively high Mg# values (35.3–41.1) and Fe2O3t (5.16–6.26 wt%) contents, and low Na2O + K2O contents (6.4–6.9 wt%) and A/CNK values (0.91–0.99), which are similar to the geochemical characteristics of I-type, high-K calc-alkaline rocks. They have high 87Sr/86Sri ratios (0.706455–0.706490), and low eNd(t) (− 3.58 to − 2.96) and zircon eHf(t) (− 3.4 to 0.3) values, indicating they were derived from a hybrid source of ancient mafic crust and juvenile lower crust. The coeval granites have lower Mg# values (22.5–27.25) and similar zircon eHf(t) values (− 2.6 to 1.1), suggesting they were probably differentiation productions of the granodiorites. The quartz monzonites have higher Na2O + K2O contents (9.18–9.59 wt%) and A/CNK values (0.98–1.03), higher zircon eHf(t) values (− 2.2 to 2.6) and more depleted Sr and Nd isotopes than the granodiorites and granites. The quartz monzonites were probably produced by melting of mixed juvenile crustal materials and metagreywacke. The new geochronological and geochemical data help constrain the geodynamic processes in the Lhasa Terrane during the Early Cenozoic, as the Sangsang granitoids represent the change from subduction termination to intraplate extension at the southern margin of the Lhasa Terrane.

Crustal thickening and uplift of southern Tibet have been widely associated with India-Asia continental collision during the Cenozoic. However, recent studies indicated that the crust of the northwestern (NW) Lhasa Terrane was thickened during the late Mesozoic. Here we report geochronological and geochemical data for the Gaerqiong diorite porphyries (GPs) and Xiongma plutons (XPs) in the NW Lhasa terrane, southern Tibet. Zircon U-Pb dating suggests that these intrusive rocks were generated at ca. 85 and ca. 88 Ma, respectively. The GPs are characterized by high MgO, Cr, and Ni contents, and they have adakitic affinities. These geochemical features, combined with their depleted εNd(t) (+1.7 to +2.0), 87Sr/86Sr(i) (0.705103–0.705259), and zircon εHf(t) (+5.2 to +10.2) isotopic compositions, indicate that the GPs were produced by partial melting of the delaminated juvenile continental crust. In contrast, the XPs are composed of host granites and mafic microgranular enclaves (MMEs). The MMEs have low SiO2 and high MgO contents, and low εHf(t) (–14.0 to –5.8) values, indicating that their parental magmas were derived from an enriched mantle. The host granites have high SiO2 and low MgO contents, and variable εNd(t) (–7.4 to –6.3) and zircon εHf(t) (–11 to –4.1) values. These observations, combined with the presence of MMEs in the Xiongma granites, suggest that the host granites were the result of mixing of crust- and mantle-derived magmas. Detailed study of these two plutons, combined with the previous researches, suggests that Late Cretaceous (ca. 90 Ma) magmatism in the NW Lhasa Terrane occurred in a post-collisional extensional setting related to delamination of the regionally thickened lithosphere after collision of the Lhasa-Qiangtang Terranes. We propose that the crust of the NW Lhasa Terrane reached a maximum thickness (average of >50 km) before the Late Cretaceous (ca. 90 Ma). This crustal thickening was caused by underplating of mafic magmas during slab roll-back and break-off of the southward-subducting Bangong-Nujiang oceanic lithosphere and subsequent tectonic thrusting during Qiangtang-Lhasa Terrane collision, respectively. Given that crustal thickening generally results in elevated terrain, the regional uplift (driven by isostasy due to crustal thickening) probably commenced before the Late Cretaceous (ca. 90 Ma).

National Key Research and Development Project of China [2016YFC0600304]; Major State Basic Research Program of the People's Republic of China [2015CB452602]; Natural Science Foundation of China [41730427, 41803030, 41873037]; US National Science Foundation [EAR 1725002]; Romanian Executive Agency for Higher Education, Research, Development and Innovation Funding projects [PN-III-P4-ID-PCE-2016-0127, PN-III-P4-ID-PCCF-2016-0014]

The separation of the Indian Plate from the Australia–Antarctic Plate and its accretion to the Eurasian Plate is the key to understanding the evolutionary history and paleogeographic reconstruction of Eastern Gondwana in the Jurassic–Cretaceous. In this paper, zircon U–Pb dating indicates that the Charong Dolerites (~ 142 Ma) are newly recognized Lower Cretaceous magmatic rocks in the central Tethyan Himalaya in southern Tibet. These dolerites are characterized by moderate contents of SiO2 (49.9–56.9 wt%), high contents of MgO (4.66–9.69 wt%) and TiO2 (2.20–2.81 wt%), high Zr/Y ratios (7.5–13.1), enrichments in Rb and Th, moderately negative Nb–Ta anomalies, and no Zr–Hf anomalies. Taking into account the narrow range of whole-rock initial 87Sr/88Sr ratios (0.7068 to 0.7086), the negative values of eNd(t) (− 2.4 to − 4.1), and the geochemical makeup of the zircons, the Charong Dolerites are akin to continental basalts, indicating that the central Tethyan Himalayan area was in an extensional setting during the Early Cretaceous. Although the Charong Dolerites indicate a relatively high mantle-melting temperature (~ 1469 ± 44 °C), this is still lower than the temperature required for a mantle plume origin. In combination with the Lower Cretaceous mafic rocks in the eastern Himalaya and the coeval volcaniclastic sediments, we suggest that the Charong Dolerites were partial melts of a rising asthenospheric mantle, this process having been triggered by rifting between the Indian Plate and the Australia–Antarctic Plate. This episode of continental lithospheric extension may have led to the opening of a post-Neotethyan oceanic basin that extended between the Indian Craton and the Tethyan Himalaya during the late Early Cretaceous, a feature that is highly significant in paleogeographic reconstructions of Eastern Gondwana.

The subduction history of the Neo-Tethys is critical for understanding the early-stage tectonic evolution of the Qinghai–Tibetan Plateau. Arc volcanics, which usually record the subduction process, thus can help trace the evolution of the Neo-Tethys. In this paper, we report for the first time zircon LA-ICP-MS U-Pb ages, whole-rock major and trace element geochemistry, as well as Sr–Nd–Hf isotopic data for the volcanic rocks from the Danshiting Formation at the southern edge of the Lhasa Terrane. Two samples collected from the Danshiting Formation volcanic rocks yield zircon U-Pb ages of 97.1 ± 0.8 Ma and 90.1 ± 0.7 Ma, respectively. The volcanic rocks of the Danshiting Formation are composed dominantly of basalts and andesites characterized by depletion of high-field-strength elements, low (87Sr/86Sr)i ratios (0.7042–0.7045), high eNd(t) (+2.1 to +2.7) and high eHf(t) values (mean + 11.6). These rocks show geochemical affinity of arc volcanic rocks. The volcanic rocks of the Danshiting Formation may have formed during the northward subduction of the Neo-Tethys. This paper, combined with the previous data, briefly divide the northward subduction of the Neo-Tethys into four periods: the Jurassic (195–150 Ma), when the magmatic activity was controlled by the northward high-angle subduction of the Neo-Tethys that produced volcanics of the Yeba and Bima formations; the Late Jurassic to Early Cretaceous (150–110 Ma), when the Neo-Tethys subducted at low-angles; the Late Cretaceous (110–80 Ma), when subduction was of the Andean-type and produced volcanic rocks of the Danshiting Formation; the Paleogene (70–40 Ma), when there was transition from ocean-to-continent subduction to continent–continent collision that produced volcanic rocks of the Linzizong Group.

Figures A1–A5 and Tables A1–A7.

Osteoporosis is a common aging-related disease diagnosed primarily using bone mineral density (BMD). Extracellular vesicles (EVs) remain unexplored in the context of osteoporosis. Towards this, EVs were isolated from plasma of a discovery cohort with 8 non-osteoporotic and 8 osteoporotic individuals, and nanoparticle tracking analysis (NTA) revealed a significantly higher EV concentration in osteoporotic individuals (P = 0.003). Moreover, EVs concentration showed a linear correlation with bone mineral density (BMD) values (linear correlation coefficient r = 0.9542, deviation from zero, p < 0.001). Results using a mouse model of osteoporosis confirmed that the number of EVs in mice from hindlimb unloading group was significantly higher than that from the age-matched control group (p = 0.015). TaqMan Real-Time PCR demonstrated that miR-335-5p, -320a, -483-5p, and miR-21-5p, were significantly higher expressed in osteoporotic patients compared with non-osteoporotic individuals. Quantitative real-time PCR shown that Wnt1, Wnt5a, Wnt7a, and Wnt9a mRNAs were lower expressed in osteoporosis derived EVs. In vitro functional assay indicated that osteoporosis derived EVs resulted in reduced mineralization in SaOS-2 cells. In conclusion, these results suggest that osteoporosis increased the secretion of EVs which carry higher expression of miRNAs and decreased expression of Wnt signals, further decreased the mineralization capacity in human osteoblasts.

The Machangqing porphyry Cu-Au deposit is located in the Sangjiang region, Jinshajiang-Ailaoshan metallogenic belt, southeastern Tibet. It has three main phases of felsic-mafic intrusions: barren granites, ore-forming porphyry intrusions, and mafic lamprophyres. U-Pb zircon dating shows that these intrusions were emplaced over a period of ~3 m.y., with lamprophyres at 36.50 ± 1.6 Ma (1σ), porphyry intrusion at 34.26 ± 0.22 Ma (1σ), and granite intruded at 34.00 ± 0.26 Ma (1σ). The in situ Rb-Sr analysis of phlogopite and amphibole, primary minerals in the lamprophyres, also gives a date of 36.5 ± 1.5 Ma (2σ), regarded as the emplacement age of the lamprophyre, earlier than the ore-forming porphyry intrusions. The magmatic phases have significantly different sulfur and chlorine contents. The SO3 contents of igneous apatite microphenocrysts from the mineralization-related porphyry intrusions are higher (0.24 ± 0.14 wt %, 1σ, n = 82) than those from the barren granites (0.08 ± 0.07 wt %, 1σ, n = 30). The chlorine contents in apatite grains from the porphyry intrusions (0.18 ± 0.16 wt %, 1σ) are also higher than those from granites (0.04 ± 0.02 wt % Cl, 1σ). The apatite in lamprophyres have higher sulfur (0.68 ± 0.19 wt %, 1σ, n = 40) and chlorine (0.48 ± 0.13 wt %, 1σ). The large difference of Cl and S in lamprophyres might suggest that elevated magmatic volatile contents derived from the mafic magma were important for ore formation in the Machangqing porphyry systems. The in situ Sr and O isotopes in apatite phenocrysts from the porphyry intrusions (87Sr/86Sr: 0.70593–0.70850; δ18O: 6.0–7.0) are similar to those in the lamprophyres (87Sr/86Sr: 0.70595–0.70964; δ18O: 5.4–6.9), consistent with similar origins for their volatile contents. These data may indicate that the deeper magma chamber was recharged by a relatively S-Cl-rich mafic magma similar to the lamprophyres, triggering the ore-forming magmatic event. This study also suggests that origin of apatite Sr and also volatile contents, combined with in situ Sr and O isotopes, could be useful for fingerprinting fertile intrusions associated with mineralization within drainage source areas or in outcrops.

The Lhasa Terrane in southern Tibet is the leading edge of the Tibet-Himalaya Orogen and represents a fragmentary record of terminal oceanic subduction. Thus, it is an ideal region for studying magmatism and geodynamic processes that occurred during the transition from oceanic subduction to continental collision and/or oceanic slab breakoff. Here we examine a suite of early Cenozoic mafic rocks (ca. 57 Ma) within the central part of Lhasa Terrane, southern Tibet, which erupted during a transitional phase between the onset of India-Asia continental collision and Neo-Tethyan slab breakoff. These rocks display a geochemical affinity with magmas produced by fluid-fluxed melting of the mantle wedge within a subduction zone environment. The whole-rock element and Sr-Nd isotope compositions of these mafic rocks are similar to those of Cretaceous subduction-related magmatism in southern Tibet, demonstrating the sustained influence of the Neo-Tethys Ocean slab on the mantle wedge during the onset of the collision of India and Asia. The results of our geochemical forward modeling constrain the conditions of melt generation at depths of 1.3−1.5 GPa with significant fluid additions from the Neo-Tethyan slab. These results provide the first petrological and geochemical evidence that slab flux-related magmatism continued despite the commencement of continental collision. While existing studies have suggested that magmas were derived from melting of the Neo-Tethyan slab during this period, our new results suggest that additional magma generation mechanisms were active during this transitional phase.

Experimental methods, Figures S1–S5, and Tables S1–S8.

The ~1500-km-long, (N)NW–(S)SE-trending, Yushu–Yidun Arc delineates the configuration of subducted Paleo-Tethyan oceanic lithosphere in the central–eastern Tibetan Plateau. At its southern termination, widespread Late Triassic arc-like rocks are associated with coeval, minor amounts of E-MORB/OIB-like basalts (EOB) and porphyry Cu (±Mo, ±Au) deposits developed to the north of the southwestern extension of the Longmenshan Fault. This association of tectonic, magmatic, and ore deposit features, along with the coeval dextral slip of the Longmenshan Fault and NE–SW-trending granitic belt to the northwest, were likely related to the active proto-Longmenshan Fault. This was a weakened conservative plate boundary located between the subducted Garze–Litang oceanic lithosphere and Yangtze Craton. Upwelling asthenospheric mantle along the subducted conservative plate boundary underwent decompression partial melting and formed the parental melts of the EOB, which triggered partial melting of the subducted slab and metasomatized mantle wedge and formed the ore-forming magmas and arc-like andesites, respectively.

The Precambrian origin and evolution of the Lhasa Terrane remain unclear. Here, we present new zircon U–Pb isotopic and whole-rock geochemical data for the RenTso gabbros of the central Lhasa Terrane. These data indicate that these gabbros formed during the early Neoproterozoic (∼925 Ma) and have affinities with high-Fe–Ti basaltic rocks, given that they contain low concentrations of SiO2 (39.8–49.0 wt%) and high concentrations of FeOT (11.3–23.5 wt%), TiO2 (2.19–5.70 wt%), and V (333–1204 ppm). These gabbros also have N-MORB-like trace element features such as low (La/Sm)N ratios (0.50–0.57) and the absence of negative Nb–Ta anomalies. Combining these features with the high whole-rock eNd(t) (+5.04 to +7.55) and zircon eHf(t) (+7.8 to +13.0) values for these samples indicate that the RenTso gabbros formed by the partial melting of depleted asthenospheric mantle. The Fe–Ti enrichment in these gabbros reflects conditions of low oxygen fugacity during magma fractionation. These gabbros are spatially associated with troctolite and peridotite units, indicating that together these units form a typical ophiolitic lithological assemblage. These geochemical and field observations suggest that the study area contains a subduction-unrelated-type ophiolite that most likely represents the embryonic crust of the Mozambique Ocean following continental rifting and breakup. The results therefore indicate that the Lhasa Terrane has a Precambrian affinity with the East African orogen and occupied a different position to the Qiangtang Terrane within the Rodinia supercontinent.

Introduction Oxidative stress is the main cause of osteoarthritis (OA). Lycium barbarum polysaccharides (LBP) have antioxidant properties. Thus, the potential effect of LBP on H2O2-stimulated chondrocytes was examined. Material and methods The cell viability was detected by CCK-8. The reactive oxygen species (ROS) production and apoptosis rates were determined by flow cytometric analysis. The DNA damage was detected by comet assay. Real-time polymerase chain reaction (qPCR) and Western blot assays were performed to examine the expression of histone 2A family member X (γH2AX), checkpoint kinase 1 (Chk1), poly ADP-ribose polymerase (PARP), cysteinyl aspartate specific proteinase (caspase)-3/8/9, and nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and its antioxidant-response element (ARE) dependent factors including heme oxygenase-1 (HO-1) and quinine oxidoreductase-1 (NQO-1). Results Compared to the H2O2 group, LBP inhibited the ROS production and DNA damage caused by H2O2 (p < 0.05), respectively. LBP inhibited the mRNA and protein expressions of γH2AX and Chk1 (p < 0.05). Meanwhile, LBP significantly decreased apoptosis (p < 0.05). And LBP inhibited the expression levels of PARP and Caspase-3/8/9 (p < 0.05). Moreover, LBP increased the expression of Nrf2, HO-1and NQO-1 (p < 0.05). Furthermore, the depletion of Nrf2 that mediated by RNA interference reversed the apoptosis and DNA damage inhibition effect of LBP (p < 0.05). Conclusions LBP protected chondrocytes through inhibiting DNA damage and apoptosis caused by H2O2, in which the Nrf2/ARE signaling pathway played a positive role. It provided an inspiration for clinical application - developing LBP as a therapeutic agent and Nrf2 as a promising candidate.

The giant Pulang porphyry Cu–Au deposit in the Yidun arc, eastern Tibet, formed due to westward subduction of the Garze–Litang oceanic plate in the Late Triassic. The deposit is hosted in an intrusive complex comprising primarily coarse-grained quartz diorite and cored quartz monzonite. Here, we investigate a suite of simultaneous (216.6 ± 1.9 Ma) diorite porphyries within the complex. The diorite porphyries are geochemically similar to mafic magmatic enclaves (MME) hosted in coarse-grained quartz diorite, and both are characterized by low SiO2 (59.4–63.0 wt%) and high total alkali (Na2O + K2O = 7.0–9.2 wt%), K2O (3.5–6.4 wt%), MgO (3.2–5.5 wt%), and compatible trace element (e.g., Cr = 72–149 ppm) concentrations. They are enriched in large-ion lithophile and light rare earth elements (LILE and LREE, respectively), but depleted in high field-strength and heavy rare earth elements (HFSE and HREE, respectively), and yield variably high (La/Yb)N ratios (17–126, average 65) with weak to negligible Eu anomalies. Furthermore, they yield low (87Sr/86Sr)i ratios (0.7054–0.7067), weakly negative eNd(t) (−2.8 to −0.8) values, and variable zircon eHf(t) (−5.4 to +0.8) and δ18O (6.0‰–6.7‰) values. These geochemical features indicate that the diorite porphyry and MME formed through crustal assimilation of a magma produced during low-degree partial melting of metasomatized phlogopite-rich subcontinental lithospheric mantle. In contrast, the coarse-grained quartz diorite and quartz monzonite have relatively high concentrations of SiO2 (61.1–65.3 wt%), K2O (4.1–5.4 wt%), and total alkali (Na2O + K2O = 7.1–8.1 wt%), and low concentrations of MgO (generally

The formation of the Shiquanhe–Yunzhug–Namu Tso ophiolite melange zone (SNMZ) within the Lhasa Terrane, Tibetan Plateau, is key to understanding the Mesozoic tectonic evolution of this terrane, which remains controversial. We show that the Yunzhug ophiolite in the central segment of the SNMZ formed at ~ 150 Ma, based on U–Pb dating of zircons from a gabbroic sample in a well-developed sheeted dike complex. Geochemically, these mafic rocks are dominated by E-MORB-type compositions, along with minor amounts of rocks with P-MORB-type compositions. The samples also exhibit high eNd(t) values and lack negative Nb and Ta anomalies. Data for all the samples plot within the MORB array on a Th/Yb–Nb/Yb diagram. Therefore, these mafic rocks most likely formed in either a slow spreading oceanic setting or an embryonic ocean, and not in a back-arc basin as has been previously assumed. Taking into account the regional geology, we propose that the Yunzhug ophiolite is part of a distinct ophiolitic belt and represents material formed in an embryonic ocean within the Lhasa Terrane, which provides new insights into the Jurassic tectonic evolution of the Lhasa Terrane.

Ophiolites within the South Tianshan orogenic belt directly record the nature and tectonic evolution of the South Tianshan Ocean (STO), which is key for understanding the accretionary history of the Central Asian Orogenic Belt. Here we present petrological and Os isotopic data for the Wuwamen mantle peridotites from the South Tianshan orogenic belt, which provide new insights into the tectonic origin of this ophiolite and evolution of the STO. The lherzolites have low spinel Cr# (0.1–0.2), similar to those of fertile oceanic or continental peridotites that have undergone low degrees of melting. However, the extremely high Na2O (1.5–1.8 wt%) and Al2O3 (5.5–6.2 wt%) contents of the clinopyroxenes are atypical of oceanic peridotites, and resemble those of subcontinental peridotites. The harzburgites have more refractory compositions, suggesting higher degrees of melt extraction. Both the lherzolites and harzburgites have low initial 187Os/188Os ratios (

Continental convergent margins are commonly considered as significant sites for understanding crustal reworking and growth, but the geodynamic processes involving crustal growth remain highly debatable. Triassic intermediate–felsic intrusive rocks are widespread in the northwestern segment of the West Qinling orogenic belt on the NE Tibetan Plateau. These rocks well document the evolution of one branch of the Paleo-Tethys oceans (i.e., the A'nyemaqen Ocean) in East Asia. Here we present a comprehensive study of zircon U Pb and Lu Hf isotopic data, along with whole-rock elemental and Sr Nd isotopic data to decipher the origins of intermediate–felsic intrusions and crustal evolution of the West Qinling in the Triassic. Two episodes of magmatism were detected in this study, i.e., the early high-Mg diorite porphyry–granodiorite–granodiorite porphyry assemblage (Episode #1, ~244–230 Ma), followed by a later monzogranite–granodiorite–granite porphyry assemblage (Episode #2, ~228–203 Ma). These two episodes of magmatism are interpreted as products related to oceanic subduction and continental collision, respectively. In Episode #1, the mafic magmatic enclaves were mainly mantle-derived and were indicative of magma mixing. The high-Mg diorite porphyries were likely derived from partial melting of the mantle wedge metasomatized by sediment-derived melts, whereas the coeval granodiorites and granodiorite porphyries mainly originated from partial melting of amphibolites with significant addition of mantle-derived components. By contrast, the granodiorite porphyries in Episode #2 probably originated from the lower crust-sourced melts with insignificant mantle contribution. The contemporaneous granodiorites and monzogranites were generated by partial melting of the crustal amphibolites or metagreywackes. The proportion of positive zircon eHf(t) values decreased from Episode #1 to Episode #2, indicating a decreasing tendency of the mantle or juvenile component contribution. Our study suggests that the addition of mantle-derived magmas to the continental crust during oceanic subduction processes played an important role in crustal growth.

It is generally believed that andesite–dacite–rhyolite suites and contemporary porphyry Cu deposits are related to subduction in active continental margin settings. However, it is still unclear which tectonic events result in the generation of porphyry Cu deposits and whether asthenospheric mantle material is involved in this process. Widespread andesitic–dacitic felsic intrusions associated with porphyry Cu deposits and rarer basalts have been identified in the Late Triassic southern Yidun arc (SYA) of eastern Tibet. However, few geochronological and geochemical data are available for these basalts, thereby hampering the development of geodynamic models for this magmatic event and the formation of related porphyry Cu deposits in the region. Here we present the first geochemical and SIMS (secondary ion mass spectrometry) zircon U–Pb data of Xiaxiaoliu basalts in the SYA. The age of the Late Triassic Xiaxiaoliu basalts (216.1 ± 2.8 Ma) is consistent with the timing of emplacement of voluminous porphyritic intrusions and the formation of Cu deposits within the SYA (peaking at 215–217 Ma). The Xiaxiaoliu basalts have E-MORB-like trace element patterns that are free of negative Nb–Ta anomalies, and have high 143Nd/144Nd(t) values, suggesting they were sourced from asthenospheric mantle without any arc-type influence. These observations, combined with the fact that some Late Triassic mineralized porphyritic intrusions within the SYA have adakitic affinities, suggest that the basalts and other igneous rocks and associated porphyry Cu deposits within the SYA were produced by tearing of a westward-dipping slab, triggering the upwelling of asthenospheric mantle material during subduction of the Garze–Litang Ocean crust.