Northwestern Zhejiang Research Articles

Co-enrichment of selenium and cadmium in soils of southern China and its implication for the safe utilisation of selenium-rich lands

Dietary deficiency of selenium (Se) is a global health threat related to low Se concentrations in crops. Southern China has abundant Se-rich land resources, but the cadmium (Cd) pollution problem is prominent, which may lead to Cd exceeding the safety standard in Se-rich crops. Therefore, it is important to delineate Se-rich land without Cd pollution in order to develop green Se-rich agriculture. Based on soil/sediment geochemical survey data covering 2.3 million km2 of southern China, this study analysed the concentration and spatial distribution of Se and Cd, discussed their enrichment mechanisms and proposed suggestions for the safe use of Se-rich land. The results showed that the soil/sediments in southern China were significantly enriched in Se and Cd, and the median values were 0.31 mg·kg−1 and 221 μg·kg−1, which were 1.8 times and 2.5 times the national soil background values, respectively. In addition, a significant positive correlation was observed between Se and Cd, indicating that Cd contamination in Se-rich soils frequently exceeded the pollution limit. According to statistics, Se-rich land accounted for 32.13 % of southern China. However, due to the co-enrichment of Se and Cd, areas without Cd pollution accounted for only one-third of the total Se-rich area. In particular, the areas with co-enrichment of SeCd are primarily distributed in Yunnan, Guizhou, Guangxi, western Hubei, northwestern Zhejiang, western Hunan, southern Hunan and northern Guangdong. The enrichment of Se is predominantly associated with parent rocks (black and carbonate rocks). At the same time, the enrichment of Cd is influenced by the parent rocks and PbZn mineralisation and mining activities. Three recommendations for managing Se-rich land were proposed: imposing restrictions on the utilisation of heavily contaminated Se-rich land for agricultural production, adopting a rational approach towards utilising lightly polluted Se-rich land and actively promoting the development of Se-rich agriculture in uncontaminated Se-rich areas. In the future, it is necessary to develop technologies that simultaneously enhance Se absorption while inhibiting Cd absorption in order to safely exploit Se-rich lands affected by Cd pollution.

Carexlinanensis (sect. Mitratae), a new species of Cyperaceae from Zhejiang, East China.

Carexlinanensis X.D.Qiu & X.F.Jin, a new species in sect. Mitratae of the sedge family (Cyperaceae) from north-western Zhejiang is described and illustrated. We performed a statistical comparison of the new species with other closely-related species from the same section. Carexlinanensis is similar to Carexsachalinensis F.Schmidt, but differs in having leaf blades 1-2 mm wide (vs. 2.5-3.5 mm wide), utricles longer than pistillate glumes, with beak margin smooth (vs. barbate) and peduncles of lateral spikes enclosed in bract sheaths (vs. exserted from bract sheaths).

Zircon U-Pb Ages, Petrogenesis, and Tectono-Magmatic Evolution of Late Jurassic–Early Cretaceous S-Type Granitoid in Wujinshan Area of Northwestern Zhejiang, South China

Northwest Zhejiang area (NWZJ) is one of the important parts of the large Qingzhou-Hangzhou mineralized belt in South China formed during the Late Jurassic–Early Cretaceous period. Through the study of zircon LA-ICPMS U-Pb dating, whole-rock geochemistry, and Sr-Nd isotopes for the Wujinshan granitoid in NWZJ, two distinct S-type granitic rocks of porphyry type granodiorite and granite were identified, and the two ages of 146.4 ± 1.5 Ma for granodiorite porphyry and 141.9 ± 1.4 Ma for granite porphyries were obtained. These rocks exhibited a geochemical affinity for S-type granitoid, and the two magmatic ages indicate that these rocks were intruded in two magmatic pulses. The Late Jurassic granodiorite porphyry showed moderate SiO2 (64.38–67.89 wt.%) with higher K2O + Na2O (6.22–6.78 wt.%), lower K2O/Na2O (0.57–0.96), moderate Zr (170–215 ppm), high Sr (302–475 ppm), and low Mg# (31–32) contents. The Early Cretaceous granite porphyries contained high SiO2 (69.68–74.85 wt.%), variable K2O + Na2O (4.60–6.99), high K2O/Na2O (1.72–23.53), slightly higher Zr (160–255 ppm), variable Sr (25–412 ppm), and very low to intermediate Mg# (13–44). The granodiorites had intermediate ∑REE (149–177 ppm), while granite samples showed moderate to high ∑REE content (147–271 ppm), and both rocks showed negative Eu anomalies (0.18–0.29). We propose that these two rocks were predominantly generated by the partial melting of Mesoproterozoic metamorphic basement and underwent variable degrees of fractionation and evolution. The Late Jurassic granodiorite porphyry was formed by the partial melting of Mesoproterozoic metamorphic basement with slab-derived melts or basaltic lower crust input following fractional crystallization, while the Early Cretaceous granite porphyries were generated by the partial melting of Mesoproterozoic metamorphic basement and crystal fractionation with variable magma mixing and assimilation in the upper crust. Tectonically, the Wujinshan granitoid formed in a volcanic arc setting largely affected by the subduction and slab rollback of the paleo-Pacific Plate.

Comprehensive Dynamic Influence of Multiple Meteorological Factors on the Detection Rate of Bacterial Foodborne Diseases under Spatio-Temporal Heterogeneity.

Foodborne diseases are a critical public health problem worldwide and significantly impact human health, economic losses, and social dynamics. Understanding the dynamic relationship between the detection rate of bacterial foodborne diseases and a variety of meteorological factors is crucial for predicting outbreaks of bacterial foodborne diseases. This study analyzed the spatio-temporal patterns of vibriosis in Zhejiang Province from 2014 to 2018 at regional and weekly scales, investigating the dynamic effects of various meteorological factors. Vibriosis had a significant temporal and spatial pattern of aggregation, and a high incidence period occurred in the summer seasons from June to August. The detection rate of Vibrio parahaemolyticus in foodborne diseases was relatively high in the eastern coastal areas and northwestern Zhejiang Plain. Meteorological factors had lagging effects on the detection rate of V. parahaemolyticus (3 weeks for temperature, 8 weeks for relative humidity, 8 weeks for precipitation, and 2 weeks for sunlight hours), and the lag period varied in different spatial agglomeration regions. Therefore, disease control departments should launch vibriosis prevention and response programs that are two to eight weeks in advance of the current climate characteristics at different spatio-temporal clustering regions.

Analysis of PM2.5 Characteristics in Yancheng from 2017 to 2021 Based on Kolmogorov–Zurbenko Filter and PSCF Model

Based on the hourly monitoring data including meteorological elements and PM2.5 mass concentration in Yancheng from 2017 to 2021, PM2.5 mass concentration variations, influencing factors and source apportionment were studied by the Kolmogorov–Zurbenko filter and Potential Source Contribution Function Analysis (PSCF) method. The results showed that the mass concentration of PM2.5 in Yancheng showed a decreasing trend from 2017 to 2021, with a decline rate of about 33.8% (2017, 44.79 ± 31.22 μg/m3; 2021, 29.66 ± 21.69 μg/m3); the visibility increased by 18.4% (2017, 11.69 ± 6.46 km; 2021,13.8 ± 6.24 km), which is mainly related to emission reduction measures in China. The mass concentration of PM2.5 has significant seasonal variation characteristics, with the highest in winter, reaching 60.61 μg/m3, and the lowest in summer, only 23.11 μg/m3. The diurnal variation of PM2.5 showed a unimodal distribution, and concentration difference is obvious under the influence of land–sea breeze (36.60 μg/m3, easterly wind; 43.57 μg/m3, westerly wind). Meteorological factors have an important impact on the mass concentration of PM2.5, which fluctuates with seasons. It is calculated to have a good fitting relationship between the visibility and PM2.5 concentration, and the correlation decreases with the increase in humidity (−0.71 ~ −0.41). The relatively clean atmosphere under high humidity conditions is also prone to the obstruction to vision. The corresponding PM2.5 concentration varies significantly under different wind directions and wind speeds in Yancheng, and high values mainly come from the northwest–southeast–southwest direction. The potential source regions in autumn are mainly distributed in southwestern Jiangsu and northwestern Zhejiang; the potential source regions in winter are mainly located in southwestern Jiangsu, southern Anhui and northern Jiangxi.

The oldest eugaleaspiform fishes from the Silurian red beds in Jiangxi, South China and their stratigraphic significance

• Two new species, Qingshuiaspis junqingi and Anjiaspis ericius , are established. • The eugaleapiforms-polybranchiaspiforms split occurred as early as early Telychian. • The Tangchiawu Formation can be correlated with the Qingshui Formation. • Eugaleapiformes provided key evidence for the correlation of Silurian LRBs in China. • The age of Shuyu should be modified as early Telychian, about 438 million years ago. Two new species of Eugaleaspiformes, Qingshuiaspis junqingi gen. et sp. nov. and Anjiaspis ericius sp. nov., were described from the lower Telychian Qingshui Formation in Wuning, Jiangxi Province. Our phylogenetic analysis reveals that Qingshuiaspis clusters with Shuyu , Meishanaspis , and Jiangxialepis to form the clade Shuyuidae, which is the sister to all other Eugaleaspiformes. These represent the oldest and most primitive fossil occurrences of Eugaleaspiformes in the marine Lower Red Beds of Silurian in South China. The new fossil evidence indicates that the vertebrate assemblages consisting of Shuyu , Meishanaspis , and Anjiaspis from the Silurian marine red beds in northwestern Zhejiang are more comparable to that of the Qingshui Formation (Lower Red Beds) than that of the Xikeng Formation (Upper Red Beds) in Jiangxi Province. The fish-bearing marine red beds in northwestern Zhejiang probably belong to the Tangchiawu Formation rather than the Maoshan Formation, and its age should be modified as early Telychian, about 438 million years ago. The oldest eugaleaspiforms and polybranchiaspiforms from the marine Lower Red Beds of Silurian in South China demonstrate that the two major groups of galeaspids split no later than the early Telychian.

Future projections of rice exposure to cold stress in China throughout the 21st century

Rice exposure to cold stress will be alleviated by the decrease of cold extremes under climate change. The disappearance time of cold exposure and its response to different potential scenes in the 21st century, should be particularly important to make long-term adaptations in China. Given these issues unresolved, here we assessed the decadal changes of rice exposure to cold stress in China throughout the 21st century, and compared the patterns under different combinations of Representative Concentration Pathways (RCP) scenarios, rice phenology shifts and cold tolerance enhancements. Under RCP4.5 with no changes in rice phenology and cold tolerance (i.e., the baseline scene), cold exposure would disappear mainly after the 2030s, 2040s, 2060s and 2080s in Liaoning, Fujian, Jilin and Hunan, respectively. But in Heilongjiang, northern Yunnan, southern Sichuan, western Hunan and northwestern Zhejiang, cold exposure would remain until the end of this century. Compared with the baseline pattern in these provinces, RCP8.5 and cold-tolerance enhancements would make cold exposure disappear 2–3 decades early and reduce the intensity by more than 40%. In southern China, when rice thermal-sensitive stage is moved 10/15 days forward, the disappearance of cold exposure would be 2–4 decades early relative to the baseline pattern. Comparison of the patterns under the baseline scene and other potential scenes suggests cautious optimism about the effectiveness of adjustments in crop phenology and provides quantitative support to the enhancement in cold tolerance. This has broad implications for the research community relative to adaptation planning under climate change.

Basin response to the Jurassic geodynamic turnover from flat subduction to normal subduction in South China

AbstractGrowing evidence supports that the early Mesozoic development of South China was deeply shaped by flat subduction of the paleo-Pacific plate. However, the Jurassic tectonic setting and processes remain controversial. Here, we present new detrital zircon U-Pb ages and sedimentary data from the Jurassic basin in northwestern Zhejiang to constrain the Jurassic tectonic evolution. The continuous Jurassic succession archives an abrupt sedimentary change from a high-energy coastal environment to a proximal and fast-filling terrestrial environment. This lithostratigraphic change was also accompanied by the shift of detrital provenance. Age spectra of the detrital zircons from the bottom of the Jurassic strata show strong 1.0–0.7 Ga and 500–400 Ma populations, which are inferred to be mainly derived from the Yangtze block. In contrast, samples from the overlying Lower–Middle Jurassic were dominated by age groups of 2.0–1.7 Ga and 300–170 Ma, which were probably sourced from the Cathaysia block. The switch of the sedimentary and provenance characteristics reveals that an earliest Jurassic broad sag basin in the inland shifted to an Early–Middle Jurassic retro-arc foreland basin along the coastal region. Abundant Jurassic-aged zircons are compatible with the re-initiation of “normal subduction” in the Early Jurassic. The re-initiation of “normal subduction” resulted in the generation of an accretionary orogeny, continental arcs, and a retroarc foreland basin along the eastern South China margin in contrast to the extensional regime in the inland. The basin response and distinct tectonic regimes of the inland and continental margin in the Early–Middle Jurassic support a geodynamic turnover from flat to normal subduction.

The Yanshanian (Mesozoic) metallogenesis in China linked to crust-mantle interaction in the western Pacific margin: An overview from the Zhejiang Province

The connection between multi-plate convergence and Mesozoic metallogenic explosion in the western Pacific continental margin is a frontier theme of research. A key to understanding of the Mesozoic tectonics in South China involves the spatio-temporal distribution and tectonic control of Mesozoic deposits in this region. The Zhejiang Province in South China is located in the middle segment of the western Pacific metallogenic belt, where tectono-magmatic and metallogenic activities during the Yanshanian Period (Jurassic-Cretaceous) were frequent and intense. This region is an ideal window for investigating oceanic slab subduction and recycling, continental marginal magmatism, deep geological processes, and mineralization in the western Pacific continental margin. Here we present a comprehensive synthesis of information from petrology, isotope geochronology, geochemistry, igneous geology, and tectonics of the Zhejiang metallogenic deposits to evaluate the spatio-temporal distribution and formation mechanism of the Yanshanian mineral deposits. The early Yanshanian deposit types are mainly Fe or Pb–Zn ores, which are distributed in the northwestern Zhejiang region. The ore-bearing magmatic rocks in this period are highly fractionated I-type granites, which originated from continental crust together with depleted mantle materials. In the mid-Yanshanian, Mo deposits are the main type and are distributed throughout the region. Magma types in this period are relatively diverse, most are S-type granites, which were derived from the remelting of old continental crust and mixed with juvenile mantle-derived and crust-derived magmas. The late Yanshanian deposit types are mainly W–Sn, which are distributed in the southeastern part of the Zhejiang Province. The ore-bearing magma has the characteristics of A-type granite with mantle origin. Combined with numerical simulation, we discuss the deep processes of Mesozoic metallogenic explosion in South China. We correlate the early Yanshanian mineralization with flat subduction of the Paleo-Pacific Plate and the foundering of the oceanic slab; the mid-Yanshanian mineralization is associated with the destruction and thinning of lithospheric mantle caused by mantle melting related to the sharp subduction; and the late Yanshanian mineralization witnessed a decrease in the volume of mantle materials and the eastward retreat of the trenches.

Identification of multi-element geochemical anomalies using unsupervised machine learning algorithms: A case study from Ag–Pb–Zn deposits in north-western Zhejiang, China

Identifying significant geochemical anomalies is a fundamental task in mineral exploration. In terms of stochastic process, a specific ore-forming process can be regarded as a small probability event since the deposit type sought rarely occurs in the crust of the earth. Therefore, machine learning algorithms for anomaly detection are suitable for identification of mineralization-related geochemical anomalies. However, identification of significant geochemical anomaly signatures is often hindered by irrelevant and/or redundant variables in a geochemical dataset. It is then necessary to extract significant features by means of dimensional reduction before applying unsupervised machine learning algorithms for anomaly detection. In this study, six unsupervised machine learning methods including isolation forest (IF) and five hybrid models that combined IF with dimensional reduction techniques were implemented and evaluated in identifying Ag–Pb–Zn polymetallic mineralization-related geochemical anomalies using stream sediment geochemical data from north-western Zhejiang Province, China. The five hybrid models involved combining IF with hierarchical clustering (HC-IF), principal component analysis (PCA-IF), stacked denoising autoencoder (SDAE-IF), both HC and PCA (HC-PCA-IF) and both HC and SDAE (HC-SDAE-IF). Anomalies identified by these six methods were evaluated by the receiver operating characteristic (ROC) curve method. The spatial overlay of known mineral deposits and the identified geochemical anomaly maps showed that a strong spatial association existed between the locations of discovered mineral deposits and high geochemical anomaly areas. Furthermore, the area under the curve (AUC) values suggested that the HC-SDAE-IF hybrid model performed best and the HC-IF and HC-PCA-IF models performed better than the IF, PCA-IF and SDAE-IF models. This study demonstrated that: (i) IF is a useful and efficient unsupervised machine learning algorithm for detection of Ag-Pb-Zn polymetallic mineralization-related geochemical anomalies in the study area; and, (ii) the proper manipulation of dimensional reduction and extraction of mineralization-related geochemical variables can not only significantly improve the performance of unsupervised machine learning algorithms including deep learning methods in geochemical anomaly detection, but also be instrumental in clarifying the geological meaning of the identified geochemical anomaly. In this regard, reducing dimensionality and extracting mineralization-related variables (i.e. elements) from raw geochemical data is strongly recommended before applying unsupervised machine learning methods, particularly the sophisticated deep learning algorithms, in geochemical anomaly detection.

Pollution Characteristics and Potential Source Contributions of Gaseous Elemental Mercury (GEM) During Summer and Autumn in Ningbo City

Gaseous elemental mercury (GEM) is commonly known as a hazardous heavy metal in the atmosphere and is harmful to living organisms. GEM is chemically stable and has a long residence time in the atmosphere; hence, it can be transported over long distances with air masses and is regarded as a global pollutant. We study the transportation and transformation mechanisms of GEM and its potential anthropogenic and natural contribution sources. GEM, conventional atmospheric pollutants, and meteorological parameters were monitored at a coastal site in Ningbo during the summer and autumn of 2017. The results were as follows. ① The concentrations of GEM ranged from 0.97-10.95 ng·m-3 and the mean and standard deviation (SD) were (2.32±0.90) ng·m-3, whereby the mean summer concentration was lower than the mean autumn concentration. ② The diurnal variations of GEM, ozone (O3), and gaseous oxidized mercury (GOM) during summer/autumn and sunny/rainy days suggest that higher levels of O3 and that strong solar radiation accounted for the rapid photochemical oxidation of GEM. The intensity of oxidation on sunny days was higher than that on rainy days. ③ Correlation analysis showed that GEM was significantly positively correlated with PM2.5 (R=0.65, P<0.01), PM10 (R=0.47, P<0.01), NO2 (R=0.46, P<0.01), and CO (R=0.57, P<0.01). Local and regional sources of GEM were mainly related to fossil fuel combustion. ④ The photochemical oxidation rate of GEM was influenced by the concentrations of oxidants (e.g., O3), gas-particle partitioning between GEM and particles, and light extinction effects of PM2.5, water vapor, and NO2. ⑤ Potential source contribution analysis (PSCF) indicated that the northwestern Zhejiang Province (including Ningbo City), the southern Anhui Province, and most of Jiangxi Province constitute a triangular area that is a potential source contribution to NBUEORS atmospheric GEM pollution during the summer. Local, regional, and long-range sources all had strong impacts on GEM pollution. During the autumn, the potential sources were mainly in the northern Zhejiang Province, and the source was smaller than that during the summer. GEM pollution during the autumn was mainly influenced by local and regional sources. Therefore, the control of atmospheric GEM pollution in the Yangtze River delta should apply inter-regional prevention and comprehensive control strategies in order to reduce atmospheric mercury pollution.

Mapping Moso bamboo forest and its on-year and off-year distribution in a subtropical region using time-series Sentinel-2 and Landsat 8 data

Moso bamboo is the most widely distributed bamboo forest type in tropical and subtropical areas. Increasing trends in both expansion and logging of Moso bamboo have occurred over the past four decades due to its rapid growth rate and short harvest rotation period. The spatial and temporal distribution of bamboo forest is the basis for the study of the carbon cycle in bamboo forest ecosystems. Previous studies have consistently focused on different influences of scale, data and algorithms for bamboo forest mapping; however, there is still considerable uncertainty in bamboo forest mapping due to the unique on-year and off-year phenomena and their significant differences in spectral characteristics. Northwestern Zhejiang Province has the most widely distributed bamboo forest and was selected as the study area. Based on Sentinel-2 and Landsat 8 time-series data, changes in the spectral characteristics during the growth cycle of bamboo forest were analyzed and the optimum time window for the classification of the bamboo forest was determined. The seasonal index of the bamboo forest based on spectral differences was the proposed approach, and on-year and off-year bamboo forest mapping was conducted seasonally using Landsat 8 and Sentinel-2 data. The results show that (1) the best period to distinguish bamboo forest from other forest types is April–May, followed by December–February, and the best month for distinguishing between on-year and off-year bamboo forests is May; (2) the spectral differences between bamboo forest and other forest types are mainly reflected in the red-edge 3 near-infrared (NIR) and NIR narrow bands (740–865 nm); (3) Sentinel-2 data have obvious advantages over Landsat 8 data in distinguishing the bamboo forest because of better spectral, temporal and spatial resolutions; and (4) the multi-temporal bamboo forest index has a better overall classification accuracy (OA = 91.2) for distinguishing on-year and off-year bamboo forests than the mono-temporal index and can be applied to other regions.

Examining hickory plantation expansion and evaluating suitability for it using multitemporal satellite imagery and ancillary data

Hickory (Carya cathayensis) plantations in northwestern Zhejiang Province, China, have been extensively expanded in the past three decades due to their high economic value; however, improper management has caused serious soil erosion problems. To better manage hickory plantations, it is necessary to accurately map the spatial distribution of hickory expansion and to evaluate land suitability of current hickory plantations, but little research on these issues has been conducted. This research used bi-temporal Chinese satellite Gaofen-1 images in 2015 (leaf-on and leaf-off) in combination with digital elevation model (DEM) data to develop a land-cover map with emphasis on young and mature hickory plantations using the random forest (RF) approach. The distribution data of hickory plantations in 2015 was then used to extract the spectral signatures of the 2010 Landsat imagery. The extracted spectral signatures were classified into different land covers using cluster analysis. The same approach was used with the Landsat imagery in 2005, 2000, 1995, 1990, and 1985 for mapping hickory dynamic change over time. The maximum entropy-based (MaxEnt) model was then used to evaluate the land suitability of these hickory plantations based on the identified factors from DEM, soil, and climate data. The results indicate that (1) the RF classifier based on multisource data can effectively produce a land-cover map with an overall accuracy of 89.5%, in particular, producer's and user's accuracies of 88.7% and 90.2%, respectively, for mature hickory, and 95.2% and 88.9%, respectively, for young hickory plantations; (2) the areas of hickory plantations increased from 157.6 km2 in 1985 to 528.5 km2 in 2015 with the highest average annual increase rate of 25.3 km2 in 2000–2005 and mainly at the cost of coniferous forests, followed by shrub and broadleaf forests; and (3) the MaxEnt model can be effectively used to evaluate suitability for hickory plantations. Three suitability levels—highly suitable, moderately suitable, and marginally suitable—were grouped. The mature hickory forests in 1985 had a higher proportion at the highly suitable level than the expanded hickory plantations between 1985 and 2015. This research provides important results for local governments and farmers to improve the management of young hickory plantations. The approach used in this research may be used for evaluation of land suitability for other cash forests such as Torreya.

Detrital zircon U-Pb geochronology and geochemistry of early Neoproterozoic sedimentary rocks from the Northwestern Zhejiang Basin, South China

Abstract The Jiangnan Orogen in the South China Block collapsed rapidly after the Neoproterozoic assembly of the Yangtze and Cathaysia blocks. Extensional collapse of orogens is generally triggered by post-orogenic extension and/or continental rifting. Detrital zircon U-Pb geochronology and trace elements geochemistry was conducted on sedimentary rocks across the Neoproterozoic angular unconformity in the Northwestern Zhejiang Basin. Detrital zircon U-Pb ages indicate that the Chentangwu Formation (upper Pingshui Group) and the Heshangzhen Group were deposited from 840 to 820 Ma and 810-780 Ma, respectively. The Trace elements geochemistry of early Neoproterozoic detrital zircons suggests that the source rocks of the Chentangwu Formation were derived from continental arcs and oceanic islands whereas those of the Heshangzhen Group (the Luojiamen and the Hongchicun formations) were likely related to continental arcs, oceanic islands and mid-oceanic ridges. This study reveals that the Chentangwu Formation was probably deposited in a Neoproterozoic back-arc basin which was filled by sediments from the Cathaysia Block, the Shuangxiwu Arc, and the Jiangnan Orogen. The source regions of the Hongchicun formations outcrops in the eastern and western Northwestern Zhejiang Basin are the Cathaysia Block and the Jiangnan Orogen, respectively. However, the Shangshu Formation in the west has the same source regions as the underlying Hongchicun Formation in the east. The variations in thickness and source rocks exhibited by the Hongchicun formations in the west and east are controlled by normal faulting along the Dexing-Huangshan fault zone, which is the western boundary fault of the Northwestern Zhejiang Basin. The growth fault resulted in the formation of a ridged rollover anticline in the middle of the Northwestern Zhejiang Basin and prevented ∼810 Ma zircons from being transported to the west during deposition of the Hongchicun Formation. Comprehensive analysis reveals that the extensional collapse of the Jiangnan Orogen resulted from 810 to 780 Ma post-orogenic extension.

The taxonomic revision of Asian Aristolochia (Aristolochiaceae) II: Identities of Aristolochia austroyunnanensis and A. dabieshanensis, and A. hyperxantha—a new species from Zhejiang, China

Through extensive field work and careful examination of specimens, live plant photos, and related publications of Aristolochia, we conclude that A. austroyunnanensis and A. dabieshanensis are distinct species. Meanwhile, Aristolochia hyperxantha, a new species from northwestern Zhejiang, China, is described and illustrated. The new species is similar to A. mollissima in the flower color, but it differs in the indumentum and shape of leaf. Aristolochia hyperxantha is also similar to A. dabieshanensis in the leaf shape, but it differs in the shape and color of flower.

Geochemistry and zircon-apatite U-Pb geochronology of mafic dykes in the Shuangxiwu area: Constraints on the initiation of Neoproterozoic rifting in South China

The Shuangxiwu area of northwestern Zhejiang Province preserves the most complete magmatic records of the Neoproterozoic orogenic cycle at the eastern segment of the Jiangnan Orogen, South China. However, the transition from orogenesis to post-orogenic extension or rifting still remains debated and this led to great confusion on the breakup of Rodinia supercontinent. In this study, we carried out LA-ICP-MS zircon and apatite U-Pb dating and whole-rock geochemical analyses for the mafic dykes that intruded the Shuangxiwu arc volcanic rocks and the Heshangzhen Group in northwestern Zhejiang Province. The U-Pb dating results indicate that the mafic dykes formed at ∼760Ma, rather than ca. 860–850Ma as previously suggested. All the rocks are tholeiitic in compositions and can be divided into three subgroups based on their geochemistry. Group-1 has the lowest TiO2 contents (0.7–1.0wt%) and intermediate Mg# values (40–47), and they show enrichments in large ion lithophile elements and depletions in high field strength elements, resembling typical continental arc basalts. Group-2 has the highest TiO2 contents (1.5–3.6wt%) and Mg# values (50–55), and they do not show anomalies in P, Zr and Hf, similar to ocean island basalts. Group-3 has elevated SiO2 of 58.6–61.2wt%, intermediate TiO2 contents of 1.2–1.5wt%, the lowest Mg# values of 21–30, and negative anomalies in Nb, Ta, Ti and Y. The synthetic studies of Sr-Nd isotopes indicate two end-members for the formations of the three types of mafic dykes: depleted asthenospheric mantle and metasomatized lithospheric mantle. The upwelling of asthenosphere at ca. 760Ma led to partial melting of the pre-existed metasomatized lithospheric mantle to generate the Group-1 rocks with arc-like geochemical features. Continued extension resulted in low-degree partial melting of asthenospheric mantle and subsequent interaction with Group-1 magmas form the Group-2 rocks. The Group-3 rocks were resulted from AFC processes of the Group-2 magmas. Based on our new data and the available U-Pb ages of Neoproterozoic magmatic rocks, the rifting of South China from Rodinia should have not happened before ca. 820Ma.

A spatially weighted singularity mapping method applied to identify epithermal Ag and Pb-Zn polymetallic mineralization associated geochemical anomaly in Northwest Zhejiang, China

The ordinary singularity mapping (OSM) approach utilizing regular square window and ignoring the representativeness of geochemical samples may not characterize the anisotropic geochemical anomaly features. To overcome the abovementioned drawbacks, a spatially weighted singularity mapping (SWSM) method was developed. The SWSM approach focuses more on the spatial anisotropy and the representativeness of samples considering the ore-controlling factors in the mineralization process. In this case study, the stream sediment geochemical data of Ag, As, Pb and Zn, which are the main ore forming elements of epithermal Ag and Pb-Zn polymetallic mineralization in northwestern Zhejiang distinct, China, have been used to illustrate implementation of the SWSM method. Using the spatial weighting factor associated with NE-SW ore-controlling faults system, anisotropic singularity index values for each of the four elements were estimated. Principal component analysis (PCA) was then applied to the anisotropic singularity index to obtain a comprehensive geochemical anomaly. A strong spatial correlation between the integrated anomalies and the known Ag and Pb-Zn polymetallic deposits have been detected through weights-of-evidence modeling. Finally, a comparison of the hybrid geochemical anomaly identification methods including SWSM-PCA (PCA applied to the estimated anisotropic singularity index), OSM-SWPCA (spatially weighted PCA applied to the estimated ordinary singularity index), and OSM-PCA (PCA applied to the estimated ordinary singularity index), has been discussed. The main conclusions are: (1) the SWSM method is applicable for identifying the geochemical anomaly incorporating both singularity and anisotropy that are two significant properties inherent from a nonlinear mineralization system; and (2) compared with the other two hybrid methods, the SWSM-PCA approach provides a better tool to delineate geochemical anomalies for predicting locations of potential mineral deposits.

Petrogenesis of Ore‐Related Granodiorite Porphyry in the Jiande Copper Deposit, SE China: Implications for the Tectonic Setting and Mineralization

AbstractAdakitic rocks and related Cu–Au mineralization are widespread along eastern Jiangnan Orogen in South China. Previous studies have mainly concentrated on those in the Dexing area in northeastern Jiangxi Province, but information is lacking on the genesis and setting of those in northwestern Zhejiang Province. The Jiande copper deposit is located in the suture zone between the Yangtze and Cathaysia blocks of South China. This paper presents systematic LA–ICP–MS zircon U–Pb dating and element and Sr–Nd–Hf isotopic data of the Jiande granodiorite porphyry. Zircon dating showed that the Jiande granodiorite porphyry was produced during the Middle Jurassic (ca. 161 Ma). The Jiande granodiorite porphyry is characterized by adakitic geochemical affinities with high Sr/Y and LaN/YbN ratios but low Y and Yb contents. The absence of a negative Eu anomaly, extreme depletion in Y and Yb, relatively low MgO contents, and relatively high 207Pb/204Pb ratios, indicated that the Jiande granodiorite porphyry was likely derived from partial melting of the thickened lower continental crust. In addition, the Jiande granodiorite porphyry shows arc magma geochemical features (e.g., Nb, Ta and Ti depletion), with bulk Earth‐like εNd (t) values (−2.89 to −1.92), εHf (t) values (−0.6 to +2.8), and initial 87Sr/86Sr (0.7078 to 0.7105). However, a non‐arc setting in the Middle Jurassic is indicated by the absence of arc rocks and the presence of rifting‐related igneous rock associations in the interior of South China. Combined with the regional Neoproterozoic Jiangnan Orogeny, it indicates that these arc magma geochemical features are possibly inherited from the Neoproterozoic juvenile continental crust formed by the ancient oceanic crust subduction along the Jiangnan Orogen. The geodynamic environment that is responsible for the development of the Middle Jurassic Jiande granodiorite porphyry is likely a localized intra‐continental extensional environment along the NE‐trending Jiangshan‐Shaoxing Deep Fault as a tectonic response to far‐field stress at the margins of the rigid South China Plate during the early stage of the paleo‐Pacific plate subduction. In terms of Cu mineralization, we suggest that the metal Cu was released from the subducted oceanic slab and reserved in the juvenile crust during Neoproterozoic subduction along the eastern Jiangnan Orogen region. Partial melting of the Cu rich Neoproterozoic juvenile crust during the Middle Jurassic time in the Jiande area caused the formation of adakitic rocks and the Cu deposit.

U–Pb, Re–Os and Ar–Ar dating of the Linghou polymetallic deposit, Southeastern China: Implications for metallogenesis of the Qingzhou–Hangzhou metallogenic belt

The Qingzhou–Hangzhou metallogenic belt (QHMB) in Southeastern China has gained increasingly attention in recent years. However, due to the lack of reliable ages on intrusions and associated deposits in this belt, the tectonic setting and metallogenesis of the QHMB have not been well understood. The Linghou polymetallic deposit in northwestern Zhejiang Province is one of the typical deposits of the QHMB. According to the field relationships, this deposit consists of the early Cu–Au–Ag and the late Pb–Zn–Cu mineralization stages. Molybdenite samples with a mineral assemblage of molybdenite–chalcopyrite–pyrite±quartz are collected from the copper mining tunnel near the Cu–Au–Ag ore bodies. Six molybdenite samples give the Re–Os model ages varying from 160.3 to 164.1Ma and yield a mean age of 162.2±1.4Ma for the Cu–Au–Ag mineralization. Hydrothermal muscovite gives a well-defined Ar–Ar isochron age of 160.2±1.1Ma for the Pb–Zn–Cu mineralization. Three phases of granodioritic porphyry have been distinguished in this deposit, and LA–ICP–MS zircon U–Pb dating shows that they have formed at 158.8±2.4Ma, 158.3±1.9Ma and 160.6±2.1Ma, comparable to the obtained ages of the Cu–Au–Ag and Pb–Zn–Cu mineralization. Therefore, these intrusive rocks have a close temporal and spatial relationship with the Cu–Au–Ag and Pb–Zn–Cu ore bodies. The presences of skarn minerals (e.g., garnet) and vein-type ores, together with the previous fluid inclusion and H–O–C–S–Pb isotopic data, clearly indicate that the Cu–Au–Ag and Pb–Zn–Cu mineralization are genetically related to these granodiorite porphyries. This conclusion excludes the possibility that this deposit is of “SEDEX” type and formed in a sag basin of continental rifts setting as previously proposed. Instead, it is proposed that the Linghou polymetallic and other similar deposits in the QHMB, such as the 150–160Ma Yongping porphyry-skarn Cu–Mo, Dongxiang porphyry? Cu, Shuikoushan/Kangjiawang skarn Pb–Zn, Fozichong skarn Pb–Zn and Dabaoshan porphyry-skarn deposits are of magmatic-hydrothermal origin and likely formed in a subduction-related setting. This work provides new insight that these intrusion-related deposits (e.g., porphyry and skarn types) of middle to late Jurassic age can be the most important targets for exploration in the QHMB.

Metallogenic efficiency from deposit to region–A case study in western Zhejiang Province, southeastern China

Metallogenic (ore) efficiency can be defined as the ratio of metal reserves to its total supply, and we expanded a typical efficiency-calculation model available at the single mineral scale to the regional scale. A new cell-based model was developed by analogy and by taking some other influences into account: i) a thicker sedimentary cover; ii) regional ore- and rock-controlling structures and their intersections; iii) the crustal heterogeneity unrelated and related to ores; and iv) metallic geochemical anomalies. Finally, a regional contour map of weighted efficiency, which is essential to metallogenic prediction, was obtained. It shows that the efficiency anomalies can provide a much better target area for ore-positioning than do metallic content anomalies, and greater ore efficiency may indicate the likelihood of occurrence of mineral deposits that are larger in size (reserves). Taking northwestern Zhejiang province as a case study, in which the geochemistry of Mesozoic porphyries plausibly show considerable mineralized potential, we found that due to the lower magmatic temperature, delayed exsolution of the hydrothermal solution, and very thick sedimentary cover, the Cu-polymetal ore efficiency associated with granitic plutons in this area is generally low; the relatively higher ore-productivity (efficiency) appears mainly in and around small rock bodies, rock margins, and the contacting zone between different lithologies. Most ore spots, no matter their size, fall into areas with nonzero efficiency values. There seems to be no interdependence between most ore spots of smaller size and ore efficiency, whereas efficiency is essential to regional small- and medium-scaled metallogensis.