Southwestern Sichuan Province Research Articles

The Stress State before the MS 6.8 Luding Earthquake on 5 September 2022 in Sichuan, China: A Retrospective View Based on the b-Value

On 5 September 2022 (BJT), Luding, located in southwestern Sichuan Province, China, experienced an MS 6.8 earthquake. This earthquake occurred within the historical rupture zone of the 1786 MS 7.75 event, part of the southern section of the Xianshui He Fault belt. Given the average 155-year recurrence interval for strong earthquakes in this area, the 236 years since the last event made this earthquake somewhat expected. However, prior to this event, we did not detect any anomalies indicating low surface b-values, which are often indicative of a high-stress state in the source area before strong earthquakes, as highlighted by numerous studies. Our research focused on the northern section of the eastern boundary of the Sichuan–Yunnan sub-block, encompassing the Xianshui He, Anning He, Zemu He, and Daliang Shan fault belts. We meticulously located earthquakes of ML ≥ 1.5 from 2009 to May 2022. The catalog was divided into two periods: 2009–2014 and 2015–May 2022. Using an AIC-constraint method, we analyzed the changes in b-values (Δb) in the latter period compared to the former. Our findings revealed a significant abnormal Δb zone (Δb < −0.3), with a radius of approximately 50 km, when ΔAIC ≥ 2 was selected. Intriguingly, the epicenter of the recent Luding MS 6.8 earthquake fell within this abnormal zone. Furthermore, we calculated the b-value cross-section for the southern section of the Xianshui He fault belt using a directory of precisely located small earthquakes. This revealed that the location, scale, and shape of the abnormally low-b-value area corresponded with the large displacement co-seismic area of the main earthquake, affirming the b-value’s effectiveness in identifying asperities. The b-value’s temporal evolution prior to the mainshock exhibited a nearly decade-long continuous decrease, signifying a long-term stress-loading process akin to that observed before many strong earthquakes. The b-value anomalies observed from different profiles before the Luding earthquake underline the necessity of a comprehensive, multi-dimensional analysis of such anomalies. Finally, our analysis indicates that nine earthquakes with MS ≥ 6.5, including the Luding MS 6.8 event, have contributed to increased Coulomb Failure Stress change (ΔCFS) in the Daofu (DF)–Kangding (KD) section of the Xianshui He fault belt and the northern section of the Anning He fault belt south of Shimian (SM), with amplitudes surpassing the 0.01 MPa threshold. This suggests the potential for strong earthquakes in these zones.

Analysis of Wildfire Danger Level Using Logistic Regression Model in Sichuan Province, China

Sichuan Province preserves numerous rare and ancient species of plants and animals, making it an important bio-genetic repository in China and even the world. However, this region is also vulnerable to fire disturbance due to the rich forest resources, complex topography, and dry climate, and thus has become one of main regions in China needing wildfire prevention. Analyzing the main driving factors influencing wildfire incidence can provide data and policy guidance for wildfire management in Sichuan Province. Here we analyzed the spatial and temporal distribution characteristics of wildfires in Sichuan Province based on the wildfire spot data during 2010–2019. Based on 14 input variables, including climate, vegetation, human factors, and topography, we applied the Pearson correlation analysis and Random Forest methods to investigate the most important factors in driving wildfire occurrence. Then, the Logistic model was further applied to predict wildfire occurrences. The results showed that: (1) The southwestern Sichuan Province is a high-incidence area for wildfires, and most fires occurred from January to June. (2) The most important factor affecting wildfire occurrence is monthly average temperature, followed by elevation, monthly precipitation, population density, Normalized Difference Vegetation Index (NDVI), NDVI in the previous month, and Road kernel density. (3) The Logistic wildfire prediction model yielded good performance, with the area under curve (AUC) values higher than 0.94, overall accuracy (OA) higher than 86%, true positive rate (TPR) values higher than 0.82, and threat score (TS) values higher than 0.71. The final selected prediction model has an AUC of 0.944, an OA of 87.28%, a TPR of 0.829, and a TS of 0.723. (4) The results of the prediction indicate that extremely high danger of wildfires (probability of fire occurrence higher than 0.8) is concentrated in the southwest, which accounted for about 1% of the area of the study region, specifically in Panzhihua and Liangshan. These findings demonstrated the effectiveness of the Logistic model in predicting forest fires in Sichuan Province, providing valuable insights regarding forest fire management and prevention efforts in this region.

Efficacy and safety analysis of angiotensin receptor neprilysin inhibition(ARNI)in patients with heart failure: a real-world retrospective study

BackgroundIn a large randomized controlled trial (PARADIGM-HF), ARNI has been shown to significantly reduce cardiovascular mortality and hospitalization for patients with reduced ejection fraction in heart failure. This study analyzed the efficacy and safety of ARNI on the basis of various types of heart failure patients in southwestern Sichuan Province.MethodsThis study included patients with heart failure who were treated at the Affiliated Hospital of North Sichuan Medical College from July 2017 to June 2021. This study analyzed the efficacy and safety of ARNI in the treatment of heart failure, and analyzed the risk factors for readmission after ARNI treatment.ResultsAfter propensity score matching, a total of 778 patients were included in the study. The readmission rate for heart failure in patients treated with ARNI (8.7%) was significantly lower than that in the standard treatment group (14.5%) (P = 0.023). Both the proportion of patients with increased LVEF and with decreased LVEF were higher in the ARNI treatment group than in the conventional therapy group. Compared with receiving standard medical treatment, combined ARNI treatment resulted in a greater reduction in SBP (-10.00, 95%CI: -24.00-1.50 vs. -7.00, 95%CI: -20.00-4.14; P = 0.016) in HF patients. Combination ARNI therapy did not increase the risk of adverse events. The study found that age (> 65 vs. ≤65 years) (OR = 4.038, 95%CI: 1.360-13.641, P = 0.013) and HFrEF (OR = 3.162, 95%CI: 1.028–9.724, P = 0.045) were independent predictors of readmission in HF patients treated with ARNI.ConclusionPatients with heart failure treated with ARNI can improve clinical symptoms and reduce the risk of readmitted hospital admission. Age > ~ 65 years and HFrEF were independent predictors of readmission in HF patients treated in ARNI group.

Spatio-temporal distribution characteristics of soil-transmitted nematodiasis in Sichuan Province from 2016 to 2021

To investigate the trends in the prevalence of soil-transmitted nematode infections and the spatio-temporal distribution characteristics of soil-transmitted nematodiasis in Sichuan Province from 2016 to 2021, so as to provide the evidence for formulating the soil-transmitted nematodiasis elimination strategy in Sichuan Province. The soil-transmitted nematodiasis surveillance data in Sichuan Province from 2016 to 2021 were collected, and the epidemic trend of soil-transmitted nematode infections was identified. The distribution maps of soil-transmitted nematode infections in Sichuan Province were plotted to identify their spatial distribution characteristics. In addition, the spatial clusters of soil-transmitted nematode infections were detected using globa and local spatial autocorrelation analyses. The prevalence of soil-transmitted nematode infections appeared a decline with time in Sichuan Province from 2016 to 2021 (χ2= 400.24, P < 0.01). Global spatial autocorrelation analysis identified positive spatial autocorrelations in the prevalence of soil-transmitted nematode infections (Moran's I = 0.322, Z = 16.293, P < 0.01), hookworm infections (Moran's I = 0.425, Z = 21.290, P < 0.01), Ascaris lumbricoides infections (Moran's I = 0.102, Z = 5.782, P < 0.01) and Trichuris trichiura infections (Moran's I = 0.084, Z = 6.873, P < 0.01). Local spatial autocorrelation analysis showed that the high-high clusters of soil-transmitted nematode infections were mainly located in 37 counties (cities, districts) of Sichuan Province, and the high-high clusters of hookworm, A. lumbricoides and T. trichiura infections were mainly identified in 39 counties (cities, districts) in mountainous areas around Sichuan Basin and hilly areas, 9 counties (cities, districts) in mountainous areas in southwestern Sichuan Province, and 8 counties (cities, districts) in mountainous areas in southwestern Sichuan Province, respectively. The prevalence of soil-transmitted nematode infections appeared a tendency towards a decline in Sichuan Province from 2016 to 2021, which showed spatial clusters. The management of soil-transmitted nematodiasis requires to be reinforced in high-risk areas of Sichuan Province with adaptations to local epidemiological features.

Features and Formation Mechanism of the Jiaopenba Landslide, Southwestern Sichuan Province, China

The Jiaopenba landslide, which represents a typical large basalt high-speed remote landslide, is located in Emeishan City, southwestern Sichuan province, China. Based on the field investigation, the characteristics of the Jiaopenba landslide have been revealed. The Jiaopenba landslide occurred on the steep Mount Emei. Landslide materials with a volume of approximately 6.75×108 m3 slid down from a high position, forming a large-scale high-speed remote debris flow, with the farthest sliding distance of about 7.5 km. The landslide area is located in the west wing of the Emeishan anticline, which is cut by faults to form a monoclinal fault-block mountain. Although the shear outlet of the landslide is near the slope toe and does not have good free conditions, there are faults passing through the slope toe of the bedding slope of the fault hanging wall, the landslide is affected by the fault activity, and the integrity of the layered slope is poor. When the foot of the slope is empty, the fault zone is compressed and plastic extrusion, which leads to bedding slip of the slope rock mass and greatly weakens the interlayer bonding force. When coupled with long structural planes on both sides to form side crack planes, a large-scale inclined plate structure is formed. Under the action of a strong earthquake and other external forces, the rock mass near the fault can be damaged by tension, and a large-scale high-position landslide can be formed by the mode of compression-slip-tension fracture.

Thalictrum panzhihuaense (Ranunculaceae) is placed in synonymy with T. glandulosissimum, with reduction of T. tsaii to T. glandulosissimum var. tsaii

Based on critical observations on herbarium specimens (including type material) and living plants in the wild, we demonstrate that Thalictrum panzhihuaense (Ranunculaceae), described from Panzhihua city in southwestern Sichuan province, China, is conspecific with T. glandulosissimum and that T. tsaii, described from Weixi county in northwestern Yunnan province, China, is extremely close to T. glandulosissimum. We therefore place T. panzhihuaense in synonymy with T. glandulosissimum and treat T. tsaii as a variety of T. glandulosissimum, i.e. T. glandulosissimum var. tsaii. The identity of T. glandulosissimum var. chaotungense is also discussed. Lectotypification is proposed for T. glandulosissimum.

Evolution of pegmatite ore-forming fluid: The Lijiagou spodumene pegmatites in the Songpan-Garze Fold Belt, southwestern Sichuan province, China

The late to post-tectonic Lijiagou spodumene pegmatites are located in the Ke’eryin orefield, which lies in the Triassic central Songpan-Garze Fold Belt (SGFB) in southwestern Sichuan Province, China. Fluid inclusion petrography, microthermometry and Raman spectroscopic analyses were carried out on quartz and spodumene in granites and four types of pegmatite in the Ke’eryin orefield. A Hydrothermal Diamond Anvil Cell (HDAC) was used to observe the microthermometric behavior of crystal-rich inclusions. Five types of fluid inclusions were identified. Crystal-rich inclusions (Type 1) in spodumene pegmatites were trapped at high temperature (658 to 741 °C) and high pressure (>4.7 kbar). Other inclusion types were found in granite and all types of pegmatite. Triphase CO2-H2O (CO2 + V + L, Type 2) inclusions show medium homogenization temperatures (324 to 339 °C), medium trapping pressures (2.09 to 2.54 kbar) and low to moderate salinities (3.1 to 11.3 wt% NaCl equiv). Biphase aqueous inclusions (L + V, Type 3) show similar homogenization temperatures (319 to 347 °C), and low to moderate salinities (5.5 to 18.0 wt% NaCl equiv). Monophase liquid CO2 (Type 4) inclusions have very low homogenization temperatures (15.4 to 19.1 °C). Monophase liquid H2O (Type 5) inclusions have moderate ice melting temperatures (–18.6 to –9.8 °C), and moderate salinities (18.4 to 18.5 wt% NaCl equiv). The various types of fluid inclusion reveal the P–T conditions of pegmatite formation, which records the transition from a magmatic to a hydrothermal environment and indicate that the ore-forming fluid resulted from the unmixing of magmatic melt. Fluid immiscibility is the key mechanism responsible for formation of the Lijiagou spodumene pegmatites and lithium mineral precipitation occurred from a high to medium temperature CO2-rich fluid. The absence of temperature and salinity gradients between granite and progressively more distal and evolved pegmatite compositions is inconsistent with formation of pegmatite magmas by fractional crystallization of granitic magmas, but consistent with separate anatectic origins of each type of pegmatite magma.

Aggravation of debris flow disaster by extreme climate and engineering: a case study of the Tongzilin Gully, Southwestern Sichuan Province, China

Aggravation of debris flow disaster by extreme climate and engineering: a case study of the Tongzilin Gully, Southwestern Sichuan Province, China

Zircon U–Pb Ages and Lu–Hf Isotope of the Dongchuan Group in Central Yunnan, China, and their Geological Significance

AbstractOn the southwestern margin of the Yangtze Block, the Dongchuan Group consists of slightly metamorphosed sedimentary rocks, including silty slate, argillaceous slate, clayey slate, arkose, dolomite, and minor volcanic rocks. To date, it is still a controversy over the depositional age and stratigraphic sequence of the Dongchuan Group. In this study, we analyzed five samples of meta‐sedimentary rocks and one sample of meta‐tuff from the Yinmin, Luoxue and Etouchang Formations of the Dongchuan Group in the Yuxi region for detrital zircon U‐Pb ages and Lu‐Hf isotope. The detrital zircon ages of the meta‐sediments vary from 3073 to 1703 Ma, mainly clustered at three periods, from 1889 to 1840, 2490 to 2008 and 2878 to 2844 Ma. The youngest age peak of all the samples is ∼1859 Ma, with the∊Hf(t) values of the zircons ranging from –20.3 to +4.3 and more than 90% being negative, indicating that the Paleoproterozoic crustal accretion on the southwestern margin of the Yangtze Block was dominated by reworking of the ancient crustal materials involved in the assembly and breakup of the Columbia supercontinent. Another important age range is between 2490 Ma and 2008 Ma, with∊Hf(t) values from –14.7 to +8.9 and 70% of them are negative, suggesting that the magmatism in the source area was also dominated by reworking and recycling of the ancient crustal materials, with minor juvenile mantle substances added. The detritus was probably derived from the Paleoproterozoic crystalline basement in the southern Yuxi region. The oldest peak age is ∼2847 Ma and the∊Hf(t) values are from –7.7 to +7.0 with 50% of both positive and negative values, demonstrating a possible ∼2.85 Ga ancient continental nucleus on the southwestern margin of the Yangtze Block and substantial growth in juvenile crust materials during this period. Besides, the weighted average age of the zircons from the meta‐tuff of the Etouchang Formation is 1677 ± 14 Ma. Combining the previous research data and this study, we can constrain the depositional age of the Dongchuan Group in central Yunnan Province to the period from the late Paleoproterozoic to early Mesoproterozoic, slightly earlier than that of the Dongchuan Group in the Dongchuan area near to the southwestern Sichuan Province. The depositional age of the Dongchuan Group is older than that of the Kunyang Group.

Geochemistry of source rock–controlled Late Triassic coal: An example from the Dabaoding Coal Mine in Panzhihua, Sichuan Province, southwestern China

The geochemistry of source rock–controlled coals from the Late Triassic Daqiaodi Formation in the Dabaoding Coal Mine of the southwestern Sichuan Province was investigated. A total of 15 coal samples, 6 parting samples, and 4 roof and floor rock samples from the D15–3 and D18 coals were subjected to proximate and ultimate analyses for coal quality, by using LTA-XRD with Siroquant software for minerals, XRF for major element oxides, ICP-MS for trace elements, ICP-CCT-MS for As and Se, ISE for F, and a DMA-80 analyzer for Hg. Results indicate that the Dabaoding D15–3 and D18 coals are classified as low ash and low-volatile bituminous coal. Minerals in coals are dominated by quartz, kaolinite, illite, and dolomite. Most trace elements in the Dabaoding coals are depleted or at normal levels relative to Chinese coals or world hard coals (except for Cr with slight enrichment). The Dabaoding coals and host rocks are characterized by weakly positive Ce and Y anomalies, strongly positive Gd anomalies, and weakly negative Eu anomalies. Based on paleogeographical, mineralogical, and geochemical evidence, the sediment source rocks of the Daqiaodi coal-bearing strata are identified as the Panzhihua trachyte at the top of the Kangdian Upland, which exerted crucial impacts on the Dabaoding coals.

Effects of loose deposits on debris flow processes in the Aizi Valley, southwest China

Loose deposits, rainfall and topography are three key factors that triggering debris flows. However, few studies have investigated the effects of loose deposits on the whole debris flow process. On June 28, 2012, a catastrophic debris flow occurred in the Aizi Valley, resulting in 40 deaths. The Aizi Valley is located in the Lower Jinsha River, southwestern Sichuan Province, China. The Aizi Valley debris flow has been selected as a case for addressing loose deposits effects on the whole debris flow process through remote sensing, field investigation and field experiments. Remote sensing interpretation and laboratory experiments were used to obtain the distribution and characteristics of the loose deposits, respectively. A field experiment was conducted to explore the mechanics of slope debris flows, and another field investigation was conducted to obtain the processes of debris flow formation, movement and amplification. The results showed that loose deposits preparation, slope debris flow initiation, gully debris flow confluence and valley debris flow amplification were dominated by the loose deposits. Antecedent droughts and earthquake activities may have increased the potential for loose soil sources in the Aizi Valley, which laid the foundation for debris flow formation. Slope debris flow initiated under rainfall, and the increase in the water content as well as the pore water pressure of the loose deposits were the key factors affecting slope failure. The nine gully debris flows converged in the valley, and the peak discharge was amplified 3.3 times due to a blockage and outburst caused by a large boulder. The results may help in predicting and assessing regional debris flows in dry-hot and seismic-prone areas based on loose deposits, especially considering large boulders.

Movement and activity of reintroduced giant pandas

Wild populations of giant pandas (Ailuropoda melanoleuca) have steadily increased in the past 2 decades, but the species' distribution remains highly fragmented. Since 2009, an introduction program has worked to rescue the giant panda population of Liziping National Nature Reserve in southwestern Sichuan Province, China. Using Global Positioning System and activity collar data collected between May 2011 and March 2016, we investigated the post-release behavior of the first 5 pandas introduced to Liziping, 4 of which were bred in captivity. Using a change-point analysis, we tested several models of post-release adjustment to the habitat. We found that it took 3–4 months for captive-bred individuals to exhibit movement patterns characteristic of their long-term behavior. Furthermore, we found that, for these individuals, post-adjustment behavior varied by season, with activity levels peaking between May and July, a period of high resource availability. This also corresponded with a decrease in large movement events, where individuals were less likely to travel long distances quickly during these months. Unlike wild giant pandas in more northerly reserves, the 5 pandas released in Liziping (both captive-bred and translocated) did not exhibit any seasonal migration between elevations. Finally, we found that our study individuals had 2 daily periods of activity, which was comparable to those reported in the literature for wild individuals. Our results suggest that captive-bred giant pandas are able to successfully adjust to the wild and, after a period of adjustment, settle into long-term behavior patterns.

Formation mechanism and movement processes of the Aizigou paleolandslide, Jinsha River, China

The Aizigou paleolandslide is a large basalt landslide in the Liucheng section of the Lower Jinsha River, southwestern Sichuan Province, China. Geological investigation and interpretation of remote sensing imagery, in addition to experiments, numerical simulation, and geochronological dating were used to determine the formation and movement of the landslide. Four factors were critical: a substantial height difference between the landslide shearing surface and the foot of the slope; multiple structural defects within the rock mass; a tuff intercalation in the basaltic series with long-term softening due to surface water and groundwater; and seismic activity. The kinematic behavior of the landslide was simulated using a 3-D discrete element model (3DEC), with four stages: (1) Seismic waves in the upper part of the slope were amplified by the mountain topography. When the vibrational energy exceeded the strength of the rock mass, the landslide formed, with deformation and failure by sliding and fracture. (2) Landslide materials with a volume of approximately 3.82 × 108 m3 slid at high speed from a high position, before colliding with the mountainside on the right bank of Aizi Valley. (3) The high-speed debris flow then moved 3 km downstream in Aizi Valley. (4) Landslide materials with a volume of 2.72 × 108 m3 blocked Jinsha River. A lake formed behind the barrier dam; its backwater region reached 75 km upstream. Optically stimulated luminescence dating of the lake sediments suggested that the landslide occurred about 25,000 years ago.

Development of renewable, densified biomass for household energy in China

Recent national strategic plans in China have set renewable energy targets for rural household energy programs, including those that advance the production of densified biomass fuels (e.g. pellets, briquettes) for use in household cooking and heating stoves. There is presently very little information on potential barriers to the successful development of densified biomass for household cooking and heating in China, but such knowledge may be informative in settings that aim to replace unprocessed coal and other polluting fuels with renewable, cleaner-burning energy sources. We designed a case study to coordinate data-gathering efforts at rural field sites in southwestern Sichuan province and northeastern Jilin and Heilongjiang provinces, where production of densified biomass fuels is under development for household end-users. We conducted interviews with factory personnel, local administrative leaders, and sector experts involved in the production and distribution of densified fuel, including pellets and briquettes, for household use. Results from our qualitative textual data analysis yielded several recommendations for improving development of densified biomass fuels for household end-use. These included reducing heterogeneity of feedstocks, increasing financial support for operational costs (e.g. collection, transport, and storage of raw materials; storage and distribution of final products), improving household perceptions of and subsequent demand for densified biomass fuels, and increasing enforcement of national and provincial policies banning the use of coal and open-field biomass burning. Collection and storage of raw materials and the final densified fuel product were consistently noted as critical challenges to scaling up production at all three sites. Finally, the perspectives of factory managers and local village administrators that we present also indicated that production of densified biomass fuels would most likely be more successful and reproducible in places where national-level policies are viewed as obligatory.

A new species of Saxifraga in section Ciliatae subsection Gemmiparae (Saxifragaceae) from Sichuan province, China

Saxifraga viridipetala Z-X. Zhang &amp; Gornall (Saxifragaceae) is described as a new species. Originating from south-western Sichuan province in China, morphological and molecular evidence (based on chloroplast trnL-F and nuclear ITS DNA sequences) indicate that S. viridipetala is closely related to S. gemmipara, in section Ciliatae. The new species can be diagnosed by its narrowly elliptic, pale green petals spotted purple in the proximal 4/5 part.

In situ Pb and bulk Sr isotope analysis of the Yinchanggou Pb-Zn deposit in Sichuan Province (SW China): Constraints on the origin and evolution of hydrothermal fluids

The Yinchanggou Pb-Zn deposit, located in southwestern Sichuan Province, western Yangtze Block, is stratigraphically controlled by late Ediacaran Dengying Formation and contains >0.3 Mt of metal reserves with 11wt% Pb+Zn. A principal feature is that this deposit is structurally controlled by normal faults, whereas other typical deposits nearby (e.g. Maozu) are controlled by reverse faults. The origin of the Yinchanggou deposit is still controversial. Ore genetic models, based on conventional whole-rock isotope tracers, favor either sedimentary basin brine, magmatic water or metamorphic fluid sources. Here we use in situ Pb and bulk Sr isotope features of sulfide minerals to constrain the origin and evolution of hydrothermal fluids. The Pb isotope compositions of galena determined by femtosecond LA-MC-ICPMS are as follows: 206Pb/204Pb=18.17–18.24, 207Pb/204Pb=15.69–15.71, 208Pb/204Pb=38.51–38.63. These in situ Pb isotope data overlap with bulk-chemistry Pb isotope compositions of sulfide minerals (206Pb/204Pb=18.11–18.40, 207Pb/204Pb=15.66–15.76, 208Pb/204Pb=38.25–38.88), and both sets of data plotting above the Pb evolution curve of average upper continental crust. Such Pb isotope signatures suggest an upper crustal source of Pb. In addition, the coarse-grained galena in massive ore collected from the deep part has higher 206Pb/204Pb ratios (18.18–18.24) than the fine-grained galena in stockwork ore sampled from the shallow part (206Pb/204Pb=18.17–18.19), whereas the latter has higher 208Pb/204Pb ratios (38.59–38.63) than the former (208Pb/204Pb=38.51–38.59). However, both types of galena have the same 207Pb/204Pb ratios (15.69–15.71). This implies two independent Pb sources, and the metal Pb derived from the basement metamorphic rocks was dominant during the early phase of ore formation in the deep part, whereas the ore-hosting sedimentary rocks supplied the majority of metal Pb at the late phase in the shallow part. In addition, sphalerite separated from different levels has initial 87Sr/86Sr ratios ranging from 0.7101 to 0.7130, which are higher than the ore formation age-corrected 87Sr/86Sr ratios of country sedimentary rocks (87Sr/86Sr200Ma=0.7083–0.7096), but are significantly lower than those of the ore formation age-corrected basement rocks (87Sr/86Sr200Ma=0.7243–0.7288). Again, such Sr isotope signatures suggest that the above two Pb sources were involved in ore formation. Hence, the gradually mixing process of mineralizing elements and associated fluids plays a key role in the precipitation of sulfide minerals at the Yinchanggou ore district. Integrating all the evidence, we interpret the Yinchanggou deposit asa strata-bound, normal fault-controlled epigenetic deposit that formed during the late Indosinian. We also propose that the massive ore is formed earlier than the stockwork ore, and the temporal-spatial variations of Pb and Sr isotopes suggest a certain potential of ore prospecting in the deep mining area.

Tectonically Induced Anomalies Without Large Earthquake Occurrences

In this study, we documented a case involving large-scale macroscopic anomalies in the Xichang area, southwestern Sichuan Province, China, from May to June of 2002, after which no major earthquake occurred. During our field survey in 2002, we found that the timing of the high-frequency occurrence of groundwater anomalies was in good agreement with those of animal anomalies. Spatially, the groundwater and animal anomalies were distributed along the Anninghe–Zemuhe fault zone. Furthermore, the groundwater level was elevated in the northwest part of the Zemuhe fault and depressed in the southeast part of the Zemuhe fault zone, with a border somewhere between Puge and Ningnan Counties. Combined with microscopic groundwater, geodetic and seismic activity data, we infer that the anomalies in the Xichang area were the result of increasing tectonic activity in the Sichuan–Yunnan block. In addition, groundwater data may be used as a good indicator of tectonic activity. This case tells us that there is no direct relationship between an earthquake and these anomalies. In most cases, the vast majority of the anomalies, including microscopic and macroscopic anomalies, are caused by tectonic activity. That is, these anomalies could occur under the effects of tectonic activity, but they do not necessarily relate to the occurrence of earthquakes.

Residents’ satisfaction with public services in mountainous areas: An empirical study of southwestern Sichuan Province, China

Enhancing the efficiency of public services is essential to residents in mountainous areas. It is also important to promote sustainable development of these regions. Analysing residents' satisfaction with public services in mountainous areas can help in evaluating outcomes of fiscal investment and identifying potential coping approaches for improving public service efficiencies. The residents' satisfaction with public services and the factors that influence such satisfaction were examined in this study. A study of 12 towns located in the southwestern Sichuan Province was performed using an entropy-weighted analytic hierarchy process (EWAHP), the technique for order preference by similarity to ideal solution (TOPSIS) and Tobit regression methods. The results indicate that: 1) the spatial distribution of satisfaction with public services is non-uniform, and the spatial distribution structure varies for different types of public services. 2) Residents' satisfaction with public services is influenced by both objective and subjective factors. Population density, economic distance, social and cultural divisions and elevation are the major objective factors, whereas bounded rationality, the hierarchy of needs and service expectations are the main subjective factors. The most effective strategies for enhancing residents' satisfaction with public services are likely to be clustering the population, choosing supply centres with different public services, regulating the cultural division in ethnic minority towns, selecting supply priorities in accordance with residents' needs, implementing targeted intervention policies and establishing 'bottom-up' and 'top-down' integrated decision-making mechanisms.

Historical and seasonal dynamics of phosphorus mobility in Sancha Lake of Southwest China's Sichuan Province.

Phosphorus (P) fractionations in the surface sediment of Sancha Lake in China's southwestern Sichuan Province were examined to assess the potential P release at the water-sediment interface and to understand its seasonal (2009-2010) and historical dynamics (1989-2010) in the surface water. Elevated P concentrations were detected in the sediment at main reservoir inflow, south canal of the Dujiangyan irrigation network, and intensive cage fish farming area, accounting for 32 and 40% of current total P discharges. The highest total P concentration (11,200μgPg-1) was observed in the upper sediment below intensive fish farming area with a specific enrichment of HCl-P (51% of total P) mainly from fish feeds and feces. These sediments had larger MgCl2-P pools with higher diffusive P fluxes (0.43-0.47mgm-2d-1) from surface sediment than those from other areas (0.25-0.42mgm-2d-1). The general small proportion of MgCl2-P (5.7-10%) and low diffusive P fluxes from surface sediment (<0.02% of sediment P storage (0-1cm)) indicate low mobility and slow release of P from sediments. The sediment as an internal P source led to a 3-4-year lag for P concentration decrease in the surface water after restriction of anthropogenic P discharges since 2005. Thus, the peak P concentration in April and September could be explained as a combined effect of supplementing internal loading via reductive processes in sediments and seasonal water vertical circulation in the early spring and fall. Policy played a crucial role in reducing P inputs to the lake.

Effect of Slope, Rainfall Intensity and Mulch on Erosion and Infiltration under Simulated Rain on Purple Soil of South-Western Sichuan Province, China

Purple soil is widely distributed in the hilly areas of the Sichuan basin, southwest China, and is highly susceptible to water erosion. The triggering of this process is related to slope, rainfall intensity and surface cover. Therefore, this study assesses the effects of different simulated rainfall intensities with different slopes on hydrological and erosional processes in un-mulched and mulched purple soils. Results show that the sediment and water losses increased with an increase of rainfall intensity and slope steepness. Generally, the slope contribution (Sc) on water and sediment losses decreased with increasing rainfall intensity and slope steepness under both un-mulched and mulched soil. In un-mulched conditions, water losses were independent of slope steepness (Sc &lt; 50%) during the highest rainfall intensity. However, in mulched soil, the higher contributions of slope (Sc) and rainfall (Rc) were found for water and sediment losses, respectively, i.e., &gt;50%, except during the increase in slope steepness from 15° to 25° under the highest rainfall intensity (120 mm·h−1). The effectiveness of mulch was more pronounced in reducing sediment losses (81%–100%) compared with water losses (14%–100%). The conservation effectiveness of mulch both decreased and increased with slope steepness for water and sediment losses, respectively, under higher rainfall intensities. Water infiltration and recharge coefficient (RC) decreased with an increase of slope steepness, while with an increase in rainfall intensity, the water infiltration and RC were increased and decreased, respectively, in both un-mulched and mulched soil. On the other hand, mulched soil maintained a significantly (α = 0.05) higher infiltration capacity and RC compared to that of the un-mulched soil.