High eNd Values Research Articles

Petrogenesis of late Permian to Middle Triassic magmatic rocks on northern Hainan Island, South China: Implications for crust–mantle interaction and the tectonic evolution of the Paleo-Tethys

Geochronological, geochemical, and Sr–Nd–Hf isotope data are reported for the late Permian to Middle Triassic Juding gabbros, the Xinxing gabbroic–dioritic rocks, and granites and mafic enclaves from the northern part of Hainan Island, South China. Our data were used to constrain the petrogenesis of these rocks, the crust–mantle interactions involved, and the implications for the tectonic evolution of the area. Zircon U–Pb dating gave crystallization ages of ca. 235 Ma for the Juding gabbros, ca. 252 Ma for the Xinxing gabbroic–dioritic rocks, and 253–238 Ma for the granites and mafic enclaves. The Juding gabbros are characterized by weak negative Nb, Ta, and Ti anomalies, low initial 87Sr/86Sr ratios (0.704603–0.704630), and high εNd(t) values (+3.7 to +3.8). The Juding gabbros are inferred to have been derived by partial melting of depleted asthenospheric mantle, with these melts mixing with melts produced from enriched lithospheric mantle. The Xinxing gabbroic–dioritic rocks have relatively intermediate compositions, with initial 87Sr/86Sr ratios of 0.706600–0.708664, εNd(t) values of −6.3 to −5.1, and εHf(t) values of −3.3 to −0.6. The Xinxing gabbroic-dioritic rocks probably derived by partial melting of enriched lithospheric mantle that was modified by subduction-related melts and/or fluids. The granites from the northern part of Hainan Island have extremely high SiO2, low MgO and Ni contents, with initial 87Sr/86Sr ratios of 0.704794–0.711158, εNd(t) values of −8.5 to −6.6, and εHf(t) values of −15.0 to −1.2. They were probably derived by partial melting of a variety of ancient crustal sources with some addition of mantle material. The mafic enclaves in these granites have relatively low SiO2, high MgO and Ni contents, with initial 87Sr/86Sr ratio of 0.707882, εNd(t) value of −6.4, and εHf(t) values of −9.8 to −3.9. They seem to represent the remnants of a mafic component derived from enriched mantle. The gabbroic–dioritic rocks and gabbros formed in response to the subduction and break off of the Paleo-Tethyan oceanic slab. The late Permian to Middle Triassic magmatic rocks from the northern part of Hainan Island record complex multistage crust–mantle interactions and lithosphere–asthenosphere interaction, probably related to subduction during closure of the Paleo-Tethys Ocean and the consequential collision of the South China and Indochina blocks.

Development prospect of natural gas industry in the Sichuan Basin in the next decade

The Sichuan Basin is the earliest natural gas discovery and utilization area in the world, where China's modern natural gas industry started. Through nearly 7 decades of development, a natural gas industrial system with complete upstream, midstream and downstream industry chain has been established, and its natural gas production has been among the top in China for half a century. And it has played an important role in the process of improving the primary energy consumption structure and constructing a “beautiful China”. The evaluation result of national oil and gas resources in the 13th Five-Year Plan shows that the natural gas resource extent in the Sichuan Basin is 39.94 × 1012 m3, ranking the first in petroliferous basins of China. In addition, the proven rate of natural gas resource is only 15% and it is still in the early and middles stages of exploration. Therefore, the Sichuan Basin has great potential in natural gas exploration and development. The natural gas production in the Sichuan Basin in 2020 is 565 × 108 m3 (including all production enterprises of PetroChina and Sinopec in the Sichuan Basin), taking the first place in China major gas producing areas. Over the next decade, the China puts forward new development concepts from the perspective of development circumstances. The construction of Chengdu–Chongqing economic circle will be promoted and a national natural gas strategic production base with yearly gas production of 1000 × 108 m3 will be built up in the Sichuan Basin, which marks a new golden development age of natural gas industry in the Sichuan Basin. From the perspective of development potential, deep and ultra-deep marine carbonate gas reservoirs, deep shale gas and continental tight sandstone gas will be the key exploration and development fields to search for giant gas fields in the Sichuan Basin. It is recommended to strengthen core technology researches according to the thoughts of “coordinated development of marine and continental, conventional and unconventional, structural and lithologic” and relying on theoretical and technological progress. In the future, it will enter a booming development period when the quality of natural gas resources will be continuously improved and the production rate will be increased continuously. In the meantime, take advantage of the opportunities of prosperity development to break through the development bottleneck of increasingly complex work objects, incomplete pipeline network system and insufficient high end and high additional value industries. Under the situation of normalized low oil price, construct a new-type industrial system with the coordinative development of natural gas production, transportation, storage and marketing and the innovation and efficiency improvement in the whole industrial chain. It is predictable that the natural gas industry in the Sichuan Basin will start in a new peak growth period and a high-quality development period in the next decade, and its yearly natural gas production will exceed 1000 × 108 m3, and the yearly natural gas production of PetroChina Southwest Oil & Gasfield Company will reach 800 × 108 m3 in 2030. Obviously, the Sichuan Basin will be a world-class natural gas production and supply base.

Compositional signatures of ophiolitic rocks from the Dongco massif: Novel insights into the evolution of the central Tibetan Meso-Tethyan oceanic plateau

The role of the Meso-Tethyan oceanic plateau in the growth of the Tibetan Plateau is debated. In this paper, we report coexistence of large-scale mid-ocean ridge basalt (MORB)-like and enormous ocean island basalt (OIB)-type mafic rocks from the Dongco ophiolitic rocks of the Bangong–Nujiang Suture Zone. The MORB-like rocks host tholeiitic geochemical characterizes, and have supra-subduction zone affinity such as enrichments in large ion lithophile elements (LILEs), depletions in high field strength elements, high εNd(t) values (+6.5 to +9.5) and low initial 87Sr/86Sr ratios (0.7033–0.7050). The OIB-type rocks have an alkaline affinity and are characterized by enrichments in LILEs and light rare earth elements, strongly negative Sr anomalies, variable εNd(t) values of −3.7 to +7.3, and low initial 87Sr/86Sr ratios ranging from 0.7034 to 0.7050. Metamorphic zircons from amphibolites in the sole of the ophiolitic rocks yielded UPb ages of 104–100 Ma. Detrital zircons from the upper Cretaceous sandstone of the Abushan Formation (K2ab) yielded young UPb ages of 100–86 Ma. Considering the regional geology, we suggest that the Dongco MORB-like rocks were derived from a depleted mantle source and formed from an intra-oceanic subduction-related setting, representing remnants of normal oceanic crust, whereas the OIB-type rocks were derived from an enriched mantle source representing remnants of a Meso-Tethyan oceanic plateau. Our preferred hypothesis is that the Meso-Tethyan oceanic plateau experienced a phase of accretion at 104–100 Ma, which probably increased local subduction erosion of the upper plate and providing provenance for the deposition of the K2ab sandstone. The maximum depositional ages of K2ab sandstone constraint the minimum ages for closure of the Bangong–Nujiang Tethys Ocean most likely at 100–86 Ma.

Basalt from the Extinct Spreading Center in the West Philippine Basin: New Geochemical Results and Their Petrologic and Tectonic Implications

We present geological, bulk-rock geochemical and Sr–Nd–Hf isotopic data for mafic rocks from the West Philippine Basin (WPB). These mafic rocks comprise pillow basalts characterized by a vesicular structure. The mid-ocean ridge basalt (MORB)-normalized trace element patterns of basalts from the study area display depletions in Nb. In addition, the chondrite-normalized lanthanide patterns of basalts from the WPB are characterized by significant depletions in the light lanthanides and nearly flat Eu to Lu segments. The investigated rocks have initial 87Sr/86Sr ratios (87Sr/86Sr(i)) of 0.703339–0.703455 and high εNd(t) values (8.0 to 8.7). Furthermore, basalts from the WPB have 176Hf/177Hf ratios that range from 0.28318 to 0.28321 and high εHf(t) from 15.2 to 16.3. Semi-quantitative modeling demonstrates that the parental melts of basalts from the study area were derived by ~20% adiabatic decompression melting of a rising spinel-bearing peridotite source. The Sr–Nd–Hf isotopic compositions of basalts from the WPB indicate that their parental magmas were derived from an upper mantle reservoir possessing the so-called Indian-type isotopic anomaly. Interpretation of the isotopic data suggests that the inferred mantle source was most likely influenced by minor inputs of a sediment melt derived from a downgoing lithospheric slab. Collectively, the petrographic and geochemical characteristics of basalts from the study area are analogous to those of mafic rocks with a back-arc basin (BAB)-like affinity. As such, the petrogenesis of basalts from the WPB can be linked to upwelling of an Indian-type mantle source due to lithospheric slab subduction that was followed by back-arc spreading.

Genesis and mechanisms of metal enrichment in the Baimazhai Ni-Cu-(PGE) deposit, Ailaoshan Orogenic Belt, SW China

ABSTRACT The ∼259 Ma Baimazhai Ni-Cu-(platinum-group element) deposit is located in the Ailaoshan-Red River fault zone on the southwest margin of the Yangtze Plate in the Jinping area of southeastern Yunnan Province. The intrusion is lenticular (∼530 m long × 190 m wide × 24–64 m thick) and concentrically zoned (margin to core) from gabbro through pyroxenite to peridotite. It contains ∼50 kt of Ni-Cu-(platinum-group element) mineralization, concentrically zoned (margin to core) from disseminated through net-textured to massive sulfides with an average grade of 1.03 wt.% Ni, 0.81 wt.% Cu, and 0.02∼0.69 ppm Pd+Pt. The sulfide assemblage comprises pyrrhotite, chalcopyrite, and pentlandite, with lesser magnetite, violarite, galena, and cobaltite. The mineralization is enriched in Ni-Cu-Co relative to the platinum-group elements and the host rocks are enriched in highly incompatible lithophile elements relative to moderately incompatible lithophile elements with high Th/Yb and intermediate Nb/Yb ratios. These host rocks, and those at most other Ni-Cu-platinum-group element deposits in the Emeishan Large Igneous Province, have high γOs and intermediate εNd values, indicating that they crystallized from a magma derived from a subduction-modified pyroxenite mantle source and modified by crustal contamination. The initial concentrations of metals in the primary magma are estimated to have been on the order of 200 ppm Ni and 100 ppm Cu, but only 0.4 ppb Pd, 0.2 ppb Pt, 0.005 ppb Rh, 0.02 ppb Ru, and 0.01 ppb Ir. The δ34S values of ores and separated sulfides range from 5.8‰ to 8.6‰, between the ∼10‰ value of sulfides in the metasedimentary country rocks and the 0 ± 0.5‰ value expected for magmas derived from MORB-type mantle, or the –2.5 ± 0.3‰ value expected for subduction-modified mantle, consistent with equilibration at magma:sulfide mass ratios (R factors) of 100–1000. Variations in Ir100 and Pd100 (metals in 100% sulfide) are consistent with 40–60% fractional crystallization of monosulfide solid solution to form Ni-Co-intermediate platinum-group element (Ru, Os, Ir)-rich massive ores and Cu-palladium/platinum-group elements (Pt, Pd, Rh)-Au-rich residual sulfide liquids. This process is also recorded by magnetite: Type I (early magmatic), type II (late magmatic), and type III (secondary) magnetites exhibit progressively lower Cr-Ti-V concentrations. The platinum-group element contents in base-metal minerals are low, and only pentlandite, violarite, and cobaltite contain detectable concentrations of Pd, Rh, and Ru. There is abundant textural evidence for metamorphic-hydrothermal alteration of sulfides in the Baimazhai intrusion, with secondary violarite, chalcopyrite, and pentlandite being enriched (Ag, Sb, Au, Pb) or depleted (Sn) in more mobile chalcophile elements. The different tectonic and petrogenetic settings of the Baimazhai and other deposits in China highlight the potential of Ni-Cu-platinum-group element deposits to occur in subduction or post-subduction settings and demonstrate that the key controls are magma flux and access to crustal S. Exploration potential remains for the Ailaoshan orogenic belt to host additional magmatic Ni-Cu deposits.

Geographical drivers of geochemical and mineralogical evolution of Motianling peatland (Northeast China) exposed to different sources of rare earth elements and Pb, Nd, and Sr isotopes

Geochemical shifts triggered by surface runoff and atmospheric fallout in a Chinese peatland were investigated by using Pb, Sr, and Nd, REE and by SEM mineralogical analysis. Motianling peatland (Northeast China) is located at 1670 m a.s.l., near the China–Mongolia border. Based on division of profile into two phases of different trophy, the total ∑REE value determined for the minerotrophic part of the profile (from 62 to 46 cm) varied from 67 to 31 mg·kg−1 and mineralogical analysis revealed the occurrence of weathered volcanic rocks, supported by a high εNd value (−3.26). After the transition from minerotrophic to more ombrotrophic conditions, the peatland became independent of the local bedrock weathering, which was manifested by a much lower concentration of REE (7–20 mg·kg−1) and lower εNd values (−7.37; −8.11). Moreover, PAAS-normalized pattern of REE distribution in the bottom part revealed the highest Eu/Eu* value (1.24), as well as a slight enrichment in Eu. The anthropogenic effect was visible from 1964, during which period the spheroidal aluminosilicate particles (SAP), produced by coal-fired power-plant activity, appeared for the first time, followed by an abrupt decrease in 206Pb/207Pb isotopic signature to 1.167. The dimensions of SAP (~1.5 μm), as well as the time of first appearance, indicated long-range transport. The REE ratios obtained in this study are characteristic of the eolian deposition signature, which is like the Gobi and northern Chinese deserts. The anthropogenic activity was manifested by a slight enrichment in Gd during reduced delivery of natural dust. Both, North Chinese and Asian part of the Russian industry supply anthropogenic dust. Topography, wind direction, and patterns of precipitation, as well as the initial phases of Asian industrial development, are the most important drivers promoting the deposition of chemical elements.

International Tourists’ Perceptions on Spice Markets: A Guideline to Introduce Spice Market Concept into Sri Lankan Context

Purpose: The possibilities of syndicating spice and tourism industries to exploit its fullest potentials to achieve wider benefits have been rarely discussed and such attempts have been rarely made by previous scholars. In such an environment, our main focus was to introduce the “spice market concept” to the Sri Lankan context to strengthen the weak link that exists between the two industries. Research Method: First phase of the study was designed to explore issues associated and strategies adopted by Cochin, Turkey and Dubai spice markets through the analysis of 715 customer views. Second phase of the study was shaped by the insights obtained from the key industry informants/experts through interviews and focus group discussions. Both qualitative and quantitative techniques were instrumental in data analysis. Findings: Product strategy varied from raw spices, organic spices, fair trade spices to high end value additions like nutraceuticals. Cochin and Turkey spice markets were recognized as reliable sources of high-quality spices with the consensus of 80% and 66.7% of the reviewers. Women cooperatives, Arabian, Egyptian, Indian, Iranian, and Syrian marketing channels were the focal sources of spices. Competitive and discount pricing strategies were common to all studied market places. Promotional strategies varied from on-site special promotions to e-marketing. Ethical, customer friendly, caring and trustworthy services were main customer demands. Bentota, Hikkaduwa and Kandy would be promising locations to establish spice markets. Limitations: Lack of firsthand experience on Turkey and Dubai spice markets was a constraint during the study. Originality/value:If implemented in the planned way, the proposed spice market concept could generate a momentous contribution to the country’s socio-economic development through the diversification of the tourism and spice industries.

Recycling of continental crust in the southern North China Craton: Constraints from the Sr–Nd–Pb–Hf–O isotopic compositions of Early Cretaceous Funiushan granites

This paper reports new zircon U–Pb ages, whole-rock geochemistry, and Sr–Nd–Pb–Hf–O isotopic compositions for the Funiushan (FNS) pluton of the southern North China Craton (NCC). These data and statistical analyses of previously reported compositions of late Mesozoic granites from the southern NCC are used to constrain late Mesozoic continental recycling and geodynamic processes. The FNS pluton includes coexisting early Early Cretaceous (140 Ma), late Early Cretaceous (130–116 Ma) and highly evolved granites (HEGs; 126–125 Ma). The early Early Cretaceous granites have high Sr contents (332–566 ppm), high Sr/Y (53–138) and (La/Yb)N (29–52) ratios, and low MgO contents (0.15–0.48 wt%). They have relatively low (87Sr/86Sr)i values (0.7051–0.7054), relatively high εNd(t) values (−4.11 to −3.96) and variable εHf(t) values (−22.9 to −0.53). They are also characterized by high initial 206Pb/204Pb values (17.893–17.975) and relatively low δ18O values (5.34‰–7.48‰) as well as Neoproterozoic (851–734 Ma) inherited zircons, suggesting that they have an adakitic affinity formed by recycling of subducted continental crust of the Yangtze Craton (YC) with input from a mantle component. In contrast, the late Early Cretaceous granites have relatively high (87Sr/86Sr)i values (0.7077–0.7085), low εNd(t) values (−14.2 to −12.0), relatively high initial 206Pb/204Pb values (17.398–17.497), εHf(t) values of −23.7 to −10.7, and δ18O values of 5.76‰–6.55‰. These data, and the Neoproterozoic zircon ages (716–702 Ma), indicate that the primary magmas formed from recycled YC crust with a minor contribution from the NCC basement. The late Early Cretaceous HEGs have relatively high εNd(t) values (−9.33 to −8.70), high initial 206Pb/204Pb values (17.656–17.885), intermediate εHf(t) values (−12.3 to −6.18), and relatively low δ18O values (5.22‰–6.72‰), indicating that they formed from subducted YC and mantle material. Previous work on granites of the southern NCC has established two phases of granite formation. Late Jurassic to early Early Cretaceous I-type granites (160–130 Ma) occur throughout the southern NCC. These are adakitic and formed from thickened lower continental crust (LCC). Late Early Cretaceous A-type granites (130–110 Ma) formed from thinned LCC. The differences between Late Jurassic to early Early Cretaceous granites and late Early Cretaceous granites reflect a transformation in tectonic regime from thickening to thinning, which is attributed to rollback of the subducting Paleo-Pacific Plate.

Cu-Ni mineralization in Early Permian mafic complexes in the Kalatage area of eastern Tianshan (NW China): Petrogenetic constraints from geochronology, geochemistry, and Hf-Sr-Nd-Os isotopes

The Early Permian was a critical period in the long history of accretion and collision of the southern Altaid orogen. Early Permian mafic-(ultramafic) intrusions and mafic–ultramafic-related sulfide Cu-Ni deposits are common in the eastern Tianshan, but the sulfide Cu-Ni deposits related to the mafic intrusions are still poorly studied, and yet provide key information on the ambient tectonic evolution. In order to help understand their petrogenesis, we report new data on the Early Permian mafic intrusions and related sulfide Cu-Ni deposits in the Dananhu arc of the eastern Tianshan in NW China. The ore-bearing Yueyawan complex is a well-differentiated, zoned mafic intrusion consisting of troctolite, olivine gabbro, layered gabbro, gabbro, and leucogabbro from the bottom upwards. The ore bodies are primarily strata-bound within olivine gabbros and troctolites at the bottom of the complex. The ores are more enriched in Cu than Ni than the more enriched, disseminated, veined and massive equivalents. Gabbros from the mafic complex yield zircon crystallization ages that range from 265 Ma to 273 Ma. The gabbros are tholeiitic and characterized by typical subduction-related geochemical signatures with low TiO2 contents, enrichments in Rb, Ba, U, K, Pb, and Sr, depletion in Nb and Ta, positive Eu and Ti anomalies, high εNd(t) values of +7.44 to +8.06, zircon εHf(t) values of +11.68 to +20.58, and low (87Sr/86Sr)i (0.703322–0.703416). The gabbroic rocks have positive correlations between SiO2 and TiO2, Al2O3, CaO, Nb, and Y, and negative correlations between SiO2 and MgO, Ni, and Co. The (187Os/188Os)i and γOs values of sulfides from the Yueyawan complex that contains Cu-Ni deposits range from 0.266 to 0.372 and 112 to 197, respectively. These geological, petrological, and geochemical characters indicate that the gabbros were mantle-derived, and that fractionation and crustal contamination were essential for the genesis of the magmatic Cu-Ni sulfide deposits. After integrating our data with those of previous investigations, we conclude that the protoliths of the sulfide deposits were probably derived from an asthenospheric garnet-free mantle in a subduction setting in the Early Permian. Oblique ocean-ridge subduction and a resultant slab window plausibly induced asthenospheric upwelling that gave rise to the generation of the mantle-derived melts, which likely moved into strike-slip faults through a slab window in the supra-subduction zone. Strong fractionation, crustal contamination, and multi-stage eruptions led to formation of the Cu-Ni sulfide deposits.

The Silurian to devonian magmatic evolution of the Eastern Tianshan Terrane: New insights from geochemistry, geochronology, and Sr–Nd–Hf isotopes of new-discovered Sidingheishan porphyry Cu–Mo deposit, NW China

The Sidingheishan porphyry Cu–Mo deposit is located in the northeastern margin of the Kanggur–Huangshan Shear Zone of the Eastern Tianshan Terrane (ETT) in the Xinjiang Province of northwestern China. Laser Ablation–Inductively Coupled Plasma–Mass Spectrometry (LA–ICP–MS) zircon U–Pb dating of rocks in the area yielded an emplacement age of 427 ± 3 Ma for the ore-bearing granodiorite, which is intruded by 406 ± 3 to 397 ± 4 Ma gabbro, and a 382 ± 4 Ma monzogranite. These rocks have a tholeiitic to calc–alkaline and metaluminous geochemical affinities, with A/CNK values ranging from 0.65 to 1.14. The Silurian granodiorite and Carboniferous monzogranite are enriched in LREEs and LILEs (i.e. K, Ba, Pb and Sr), depleted in HREEs and HFSEs (i.e. Nb, Ta and Ti), and slightly positive Eu anomalies (Eu/Eu* = 0.94–1.39) indicative of crystal fractionation. The granodiorite and monzogranite have elevated MgO assays (0.36–1.85 wt%) and Mg# values (34–52), low (87Sr/86Sr)i ratios of 0.70320–0.70435, high εNd(t) values (5.9–6.9), TDM2 Nd model ages between 687 and 568 Ma, and εHf(t) values between + 8.37 and + 17.44. The geochemistry of the Early Devonian gabbro is characterised by its low SiO2 assays of 47.69–51.34 wt% and high Al2O3 assays of 18.07–22.91 wt% and MgO assays of 2.29–7.09 wt% (with Mg# values of 38–64), εNd(t) values of 4.7–6.9, εHf(t) of 8.04–17.97, and (87Sr/86Sr)i values of 0.70371–0.70420. The gabbro samples are enriched in LILEs, depleted in HFSEs, and have positive Eu anomalies. Combined with the regional geological history and above mentioned data, we suggest that the Sidingheishan granodiorite and monzogranite were formed during partial melting of subducted oceanic crust interacting with the lithospheric mantle. We also proposed that the Devonian gabbro developed during an extensional tectonic setting involving subduction–related magmatism in a continental arc margin rather than during mantle plume activity in the post–collisional extensional tectonic setting. The Sidingheishan granodiorite and associated porphyry Cu–Mo mineralisation were generated in an arc setting, associated with the N-dipping subduction of the Palaeo–Tianshan oceanic plate beneath the Dananhu–Tousuquan island arc.

Parameterization of Biot–Willis Effective-Stress Coefficient for Deformation and Alteration of Porous Rocks

The effective stress coefficient is an essential geomechanical parameter required for estimation of the effective stress acting upon the subsurface reservoir porous rock formations and affecting their petrophysical properties. The values of the effective stress coefficient for various rock properties depend on the complex phenomena involving various types of rock deformation and alteration processes. This paper presents a discussion of the relevant factors and an effective method for accurate correlation of the Biot–Willis effective stress coefficient by means of a kinetics-based phenomenological model. This is accomplished by developing a modified power-law equation which describes the variation of the effective stress coefficient by various rock deformation and alteration processes at a macroscopic scale. This equation has five parameters which can be determined using the experimental data obtained by rock testing. The modified power-law equation is derived in a manner to satisfy the low- and high-end limit conditions of the effective stress coefficient exactly, which are the zero and unity values, respectively, for the Biot–Willis effective stress coefficient associated with the bulk volumetric strain. However, many empirical correlations presented in the literature cannot satisfy the low- and high-end limit values of the effective stress coefficient. The modified power-law equation is applied for correlation of the Biot–Willis effective stress coefficient associated with the bulk volumetric strain as functions of porosity, permeability, permeability/porosity ratio, and stress using the experimental data of various porous subsurface rock formations and artificial porous materials. The quality of the correlations is determined by means of the coefficient of regression or correlation and the root mean-square of the difference of the correlation values relative to the measured data. The correlation of the Biot–Willis coefficient with porosity yields the best results compared to the correlations obtained with permeability and permeability/porosity ratio. The stress dependence of the Biot–Willis effective stress coefficient of heterogeneous rock formations involving the slope change and hysteresis effects is correlated to describe the slope discontinuity caused by the deformation process transition and the hysteresis caused by the inertial and delay effects, fully elastic pre-damage, and/or irreversible rock damage during loading/unloading.

Superimposed mineralization in the deformed Yulekenhalasu porphyry Cu-Mo deposit (Northwest China): Rb-Sr geochronology, S isotope, and trace element analysis of chalcopyrite

The Yulekenhalasu porphyry Cu–Mo deposit is located ca. 40 km southwest of Qinghe, in the Chinese Altay-East Junggar section of the Central Asian Orogenic Belt, NW China. The belt preserves multistage tectonic-hydrothermal and porphyry Cu-Mo mineralization events associated with arc to syn- and post-collision environments over 87 m.y. The 359 Ma deformed granitic porphyries are characterized by positive εNd(t) (+0.62 to + 3.77) and (87Sr/86Sr)initial values (0.704304–0.705960), and old crustal model ages of 747 to 1216 Ma, whereas a 272 Ma sample from late chalcopyrite–molybdenite–pyrite–magnetite–feldspar–calcite–gypsum veins yielded (87Sr/86Sr)initial values of 0.704415 to 0.705764, high εNd(t) values (+5.81 to + 5.88) and young crustal model ages (715 to 614 Ma) suggesting an increasingly juvenile mantle source over time. Seven fragments of a single deformed chalcopyrite grain yielded an Rb-Sr isochron age of 358.6 ± 4.8 Ma (2σ, MSWD = 1.8), which is consistent with the 360 Ma recrystallized zircon grains in the deformed host granitic porphyries. Eight fragments of chalcopyrite from the chalcopyrite–molybdenite–pyrite–magnetite–feldspar–calcite–gypsum veins formed along cleavage planes yielded a younger Rb-Sr isochron age of 272.2 ± 2.6 Ma (2σ, MSWD = 1.8). The younger age is interpreted as the lower age limit for the Mo and Cu mineralization in the post-collisional stage. The heterogeneous initial Sr isotopic compositions of chalcopyrite in the Yulekenhalasu deposit are likely the result of phyllosilicate inclusions. Disseminated chalcopyrite crystals in the granitic porphyry have different trace elemental contents than chalcopyrite in the deformed granitic porphyry and late chalcopyrite veins. Our Rb-Sr and trace element data for chalcopyrite grains constrain the age and geochemistry of multistage mineralization in porphyry Cu-Mo deposits. In-situ S isotope data of chalcopyrite from the deformed granite porphyries and chalcopyrite-feldspar-quartz-muscovite veins display a similar mantle origin. The 272 Ma mineralization event at Yulekenhalasu is coeval with the formation age of the Cu-Ni-(PGE) sulfide deposit in the Chinese Altay, indicating that hydrothermal mineralization like that in porphyry deposits can form proximal to ultramafic–mafic rocks and potentially may have a genetic relationship with mantle-derived Cu-Ni-(PGE) sulfide deposits.

Petrogenesis of Late Carboniferous-Early Permian mafic-ultramafic-felsic complexes in the eastern Central Tianshan, NW China: The result of subduction-related transtension?

Knowledge of the Late Paleozoic accretionary processes responsible for the Altaids (or southern Central Asian Orogenic Belt) is critical for a better understanding of continental growth in Central Asia. Here, we systematic study the Late Carboniferous mafic-ultramafic-felsic complexes in eastern Central Tianshan to understand the tectonic evolution of the southern Altaids. Two gabbros yield zircon crystallization ages of 301.5 ± 2.3 Ma and 300.7 ± 2.6 Ma and one granite is dated as 301.6 ± 1.5 Ma. The gabbros are tholeiitic and characterized by typical subduction-related geochemical signatures with low TiO2 contents, enrichments in Rb, Ba, U, K, Pb and Sr, negative Nb and Ta anomalies, and negative to positive Eu and Ti anomalies. The granites are the A2-type granites with high contents of SiO2, K2O + Na2O, Ga, Zr, Nb, Y, HFSE, REE, and high ratios of Fe/Mg and Y/Nb (>1.2). The gabbros and granites have high εNd(t) values of +1.64 to +5.03, zircon εHf(t) values of −2.8 to +9.1, and low (87Sr/86Sr)i (0.704007–0.705437) values. These geochemical characters demonstrate that the rocks in the complexes are fractionation genesis and that the A-type granitic rocks are the highest fractionation facies of tholeiitic mafic rocks. These results suggest that they were originated from the asthenospheric garnet-free mantle in a supra-subduction zone. Combined with regional data, we suggest that the oblique subduction with slab break-off of the Southern Tianshan oceanic plate plausibly induced asthenospheric upwelling to form the tholeiitic magma, and which intrude along the strike-faults the Central Tianshan-Yamansu arc. Accordingly, these results reveal the Paleo-Asian Ocean continued to subduct at the southern Altaids in the Late Carboniferous.

Tracking the Tectonic Evolution of the Junggar-Balkhash Ocean: A Case Study from the Post-Collisional Takergan Pluton in the West Junggar, Xinjiang

The Late Carboniferous and Early Permian igneous rocks are widely developed in the West Junggar, Xinjiang, which are considered to be related to the evolution of the Junggar-Balkhash Ocean. However, their tectonic settings have been controversial for a long time. With the aim of providing new evidence for the Late Paleozoic tectonic evolution of the West Junggar, we present petrology, zircon U-Pb chronology, whole-rock major and trace elemental and Sr-Nd isotopic data, to discuss the petrogenesis and tectonic setting of Takergan pluton from the Barleik Mountains in the West Junggar. The Takergan pluton is mainly composed of quartz diorite porphyry and quartz monzonite. The quartz diorite porphyry has low SiO2 (57.76 wt.%–57.81 wt.%), high total alkali contents (Na2O+K2O=6.29 wt.%–6.56 wt.%), and high Mg# values (45–46), with a zircon U-Pb age of 304±5 Ma. The quartz monzonite shows relatively high SiO2 (58.71 wt.%–64.71 wt.%), total alkali contents (7.73 wt.%–9.70 wt.%), and Mg# values (34–47), with the A/CNK values of 0.91–0.98, which belongs to shoshonitic and metaluminous I-type granite series. The quartz monzonite yields zircon U-Pb ages of 302±2 and 296±3 Ma, and is characterized by low initial Sr ratios of 0.703 97–0.704 09, high eNd(t) values of +6.8–+7.0, and young Nd model ages of 551–587 Ma. Both the quartz diorite porphyry and quartz monzonite are enriched in light rare earth elements and Rb, Th, U, K, and depleted in Nb, Ta, Ti, with different degrees of negative Eu anomalies. These features indicate that the Takergan pluton was most likely formed in a post-collisional setting by partial melting of a depleted mantle source that had been metasomatized by subduction-related fluids, with significant fractional crystallization and slightly contaminated by crustal materials. Combined with the widespread distribution of the coeval stitching plutons, the occurrences of terrestrial Late Carboniferous to Permian volcano-sedimentary formations, and the absence of subduction-related rocks later than Early Carboniferous, it is believed that the Junggar-Balkhash Ocean was closed at about 320 Ma, and the central West Junggar has transformed to a post-collisional environment during the Late Carboniferous and Early Permian.

Compositional signatures of dolerite dykes from the Purang ultramafic massif, Tibet: Implications for garnet-bearing components in the Neo-Tethyan mantle

We present geological, whole-rock geochemical, Sr–Nd isotopic and U–Pb geochronological data for the mafic dykes from the Purang ultramafic massif, South Tibet (China). The mafic dykes are composed of dolerite within a mylonitized harzburgite body. These mafic dykes are dated at 138.0–138.5 Ma using zircon and apatite U–Pb methods, and are characterized by enrichments in large-ion lithophile elements (LILEs) and high-field-strength elements (HFSEs), resembling those of typical ocean island basalts (OIB). They have initial 87Sr/86Sr ratios of 0.70612 to 0.70670, initial 143Nd/144Nd ratios of 0.51231 to 0.51233 and high εNd(t) values of −3.1 to −2.6. Geochemical modeling suggests that the parental melts of dolerites were derived by ~50% melting of garnet pyroxenite or eclogite veins in the lithospheric mantle. The formation of the dyke-filling melts can thus be linked to melting of a thin mantle layer containing old low buoyancy plume (LPB)-components in the form of garnet-bearing veins. Our results provide a scenario for the tectono-magmatic evolution of the oceanic lithosphere beneath the Neo-Tethys in the South Tibet. We conclude that the existence of a thermal plume might not be essential to the petrogenesis of the Yarlung-Zangbo Suture Zone (YZSZ) ophiolites.

КЛЮЧОВІ ФАКТОРИ РОЗВИТКУ КОМПАНІЙ В ІННОВАЦІЙНІЙ ЕКОНОМІЦІ

The article is devoted to the key problems of the economic development of companies in the context of globalization, rapid spread of innovations, transformation of the business environment, and improvement of approaches to the regulation of socio-economic processes. There was done comparison of trends and dependency of quantity of business entities and indicators reflecting the nature of the regulatory impact on entrepreneurial activity and protection of property rights. The outstripping positive dynamics of Ukraine’s positions in the international rating of the World Bank Doing Business together with uneven and slow increase in the quantity of business entities related to economic activities with great development potential are identified. It is noted that the creation of a favourable regulatory system is a basic, but not an exclusive factor of economic development in a globalized and innovative economy. Companies striving for success should abandon industrial management models and need to search for solutions focused on improvement the efficiency of the company’s functioning and increasing business value at the end by determining the feasibility of application of value-oriented management. It is emphasized that value-oriented management is based on an understanding of the need to ensure the maximum level of prosperity of owners, investors and other stakeholders, is aimed to form common value chains and, as a result, is crucial for the economic development of the company and socio-economic development of the country. As a result, a hypothesis was formulated about the possibility of use the value potential to ensure the economic development of companies. A cyclical chain of economic development factors from the individual company’s value to macroeconomic indicators has been built. The logic of the relationship between the key factors was defined, in particular, it is indicated that the high end value of business stimulates entrepreneurial activity, attracts of direct or stock market capital from investors, and increases the number of investment projects accepted for financing.

Early Paleozoic tectonic evolution of the South China Block: Constraints from geochemistry and geochronology of granitoids in Hunan Province

The Early Paleozoic Wuyi–Yunkai orogeny in the South China Block (SCB) remains enigmatic. A geochemical and geochronological investigation was carried out for the four poorly-studied granitoid intrusions (i.e., Hongxiaqiao, Xuehuading, Baimashan and Wanyangshan granitoids) in Hunan Province, and within the SCB, to determine their petrogenesis and give enlightening insights into the tectonic evolution of the Wuyi–Yunkai Orogen. The Hongxiaqiao, Xuehuading and Baimashan granitoids have lower SiO2 contents, and total alkali (Na2O + K2O) and A/CNK values, but higher Fe2O3T, MgO and TiO2 contents, compared with those of the Wanyangshan granitoid. All the studied granitoids are strongly depleted in Ba, Nb, Zr, Ti, and HREEs, but are enriched in Rb, Th, U, K, and LREEs, with significant negative Eu anomalies, particularly in the Wanyangshan granitoid. Bulk-rock geochemical compositions indicate that the Hongxiaqiao, Xuehuading and Baimashan granitoids are metaluminous–weakly peraluminous I-type granitoids, whereas the Wanyangshan granitoid is peraluminous and moderately fractionated S-type granitoid. Zircon LA-ICP-MS U–Pb dating results indicate that the Hongxiaqiao, Xuehuading, Baimashan and Wanyangshan granitoids were intruded at 451 ± 1 Ma (MSWD = 1.8), 412 ± 1 Ma (MSWD = 2.4), 415 ± 1 Ma (MSWD = 3.0) and 445 ± 1 Ma (MSWD = 3.9), respectively. The I-type granitoids have variable initial 87Sr/86Sr values of 0.71160–0.72362, high εNd(t) values (−6.5 to −8.1), and young T2DM ages of 1717–1894 Ma. In contrast, the S-type granitoid has consistent initial 87Sr/86Sr values of 0.71448–0.71887, slightly lower εNd(t) values (−9.8 to −10.3), and older T2DM ages (1977–2015 Ma), which suggests that they were derived from partial melting of different Paleoproterozoic basement rocks, without significant crustal contamination. The older Hongxiaqiao and Wanyangshan granitoids were formed in a compressional setting, whereas the younger Xuehuading and Baimashan granitoids were generated in a post-orogenic extensional setting. Integrated with geological evidence, we proposed that the Early Paleozoic Wuyi–Yunkai orogeny in the SCB resulted from intraplate orogenesis triggered by far-field tectonic response to the assembly of the northern East Gondwana, rather than from oceanic subduction–collision.

Genesis of the Lakang'e porphyry Mo (Cu) deposit, Tibet: Constraints from geochemistry, geochronology, Sr-Nd-Pb-Hf isotopes, zircon and apatite

The Lakang'e porphyry Mo (Cu) deposit, intermediate to large in size, is located in the eastern part of the southern Gangdese metallogenic belt. It is associated with a Miocene granodiorite porphyry (GDP). The alteration styles are mainly potassic and phyllic alteration, with minor argillic, chlorite, and carbonation alteration. In this study, we present whole-rock geochemical compositions, zircon LA-ICP-MS U-Pb data, zircon Hf isotope analyses, and zircon and apatite major and trace element compositions for the ore-bearing GDP and postmineralization quartz diorite porphyry (QDP) to constrain the formation of the Lakang'e Mo (Cu) deposit. The ore-bearing GDP, with a zircon U-Pb age of 13.83 ± 0.20 Ma, was intruded after mineralization by the QDP, which was emplaced at 13.00 ± 0.16 Ma. The GDP and QDP are high-K calc-alkaline series rocks with adakite-like features characterized by high contents of K2O and Al2O3, high Sr/Y ratios, strongly fractionated REE patterns, LILE enrichment, and HFSE depletion. The GDP and QDP have relatively low (87Sr/86Sr)i values (0.7051–0.7054) and high εNd(t) values (−0.87 to 0.59). Zircon grains from the QDP have high εHf(t) values (7.0–9.6), while zircon grains from the GDP show large εHf(t) variations ranging from −4 to 9.6, indicating that the magma source of the ore-bearing GDP included more continental crust than that of the postmineralization QDP. The zircon Ce4+/Ce3+ and Eu/Eu* ratios and apatite Mn and SO3 contents indicate that the postmineralization QDP had higher oxygen fugacity than the ore-bearing GDP. The oxygen fugacity of the ore-bearing magma present during apatite crystallization (generally below the Ni-Ni-O (NNO) buffer), was lower than that present during zircon crystallization (above the hematite-magnetite (HM) buffer). The F, Cl, and S contents in apatite show that the GDP and QDP were F and S rich and that the GDP had a higher F content than the QDP. A high oxygen fugacity, a F- and S-rich magma and a Mo-rich crustal source were the key factors for the formation of the Lakang'e porphyry Mo (Cu) deposit.

Petrogenesis of an Early Permian bimodal intermediate‐felsic suite in the East Junggar in Central Asian Orogenic Belt and tectonic implications

The bimodal intermediate‐felsic suites are rare, and their petrogenesis remains unsolved. Here, we report a bimodal intermediate‐felsic magmatic suite from East Junggar (NW China) composed of rhyolites, basaltic andesites, and andesites. The basaltic andesites and andesites are porphyritic with phenocrysts predominantly of plagioclase. The rhyolites are porphyritic with phenocrysts of alkali‐feldspar, quartz, and minor plagioclase. LA–ICP–MS zircon U–Pb dating yielded an age of 284 ± 2 Ma for rhyolites. The basaltic andesites and andesites show SiO2 ranging from 54.67 to 58.26 wt%, and exhibit moderate TiO2 (1.45–1.77 wt%), and K2O (1.59–2.07 wt%) with low MgO (1.51–2.25 wt%). They display enrichment in HFSE and LILE together with negative Th, Nb, Ta, Ti anomalies, and exhibit low 87Sr/86Sr(t) ratios (0.7040–0.7046), high positive εNd(t) values (+5.82 to +6.16) and young TDM ages (<0.6 Ga). The rhyolites exhibit highSiO2(>75 wt%), negative Nb, Ta anomalies and significant depletion in Ba, Eu, Sr, Ti, and P. They also show high εNd(t) values (+5.51 to +7.08) and young TDM ages (<0.6 Ga), which are close to those of the intermediate rocks. Except for elements dominantly controlled by fractional crystallization, the other trace elements of the bimodal suite display similar patterns. Based on these characteristics, the MELTS simulation further suggests that the felsic rocks were possibly evolved from the intermediate magmas through fractional crystallization of feldspar, clinopyroxene, iron‐titanium oxide, and apatite. In contrast, the magmas parental to basaltic andesites were derived from the remelting of basaltic rocks underplated beneath the lower crust. The petrogenesis of this bimodal suite also provides new insights into Permian crustal reworking in the East Junggar, and suggest that the Junggar Ocean was closed prior to the Early Permian.

Neo‐Tethyanslab tearing constrained by PalaeoceneN‐MORB‐like magmatism in southern Tibet

Southern Tibet is a key region for investigating the magmatism that occurredduring the collision between India and Asia. The break‐off of the Neo‐Tethyan slab, after the onset of continental collision at ca. 65–60 Ma, affected the lithospheric thermal regime and led to a series of magmatic and tectonic events. Many magmatic rocks generated by slab break‐off have been reported in southern Tibet; however, which of these record the initial slab break‐off (i.e., slab tearing) is still an open question. The Lianxiang gabbros, which intrude an ophiolite in central‐southern Tibet, provide an ideal opportunity to investigate the footprint of the initial slab break‐off. Zircon U–Pb ages show that the Lianxiang gabbros crystallized at 57–53 Ma, coeval with other mafic dikes in southern Tibet. The Lianxiang gabbros are characterized by high Na2O (2.13–5.42 wt%), Al2O3(13.86–17.13 wt%), and V (188–346 ppm) contents and moderate Mg# (40.8–65.9). The gabbrosare slightly depleted in light rare earth elements [LREE; (La/Yb)N= 0.45–0.76], similar to normal mid‐ocean ridge basalt (N‐MORB). They also have low87Sr/86Sriratios (0.703538–0.705698) and highεNd(t) values (9.49–10.68), indicating that they were derived mainly from a shallow asthenospheric mantle source. Combining our results with data from other magmatism at ~57 Ma in the southern Lhasa Terrane, we propose that the N‐MORB‐type rocks reflect the tearing of the Neo‐Tethyan slab. The process of slab break‐off differed between western and eastern southern Tibet, possibly as a result of different lithospheric structures and compositions.