Middle Lower Yangtze River Region Research Articles

Geochemical study of the Tongshan intrusion in the Lower Yangtze River metallogenic belt, China: Significances of Cu-Au ore-forming

The Tongshan intrusion is located at the Guichi ore cluster field along the Lower Yangtze River metallogenic belt (LYRB) in eastern China. Elemental data and major elements of biotite are reported for Late Mesozoic plutons in the Guichi ore cluster in the Middle-Lower Yangtze River Region, attempting to explain their diagenetic age, petrogenesis, and tectonic implications. The Tongshan intrusion is dated at 146.3±3.2 Ma, with zircon εHf(t) average value of -5.23, illustrating that the Tongshan intrusion could be derived from crust mantle mixing magmatite provenance. The two-stage Hf model ages between 1184~1422 Ma is indicated magma source relationship with those of the Mesoproterozoic basement in south Anhui. The Tongshan intrusion is high-K calc-alkaline, and exhibit adakite-like geochemical feature, such as high Al2O3, Sr contents, Sr/Y value, low Y and Yb contents. The geochemical and reexplained published isotopic data indicate that these adakites are most likely from partial melting of subducted oceanic crust, and mixed with enriched lithospheric mantle components in the rising process.

Design and Test of Seedbed Preparation Machine before Transplanting of Rapeseed Combined Transplanter

In order to satisfy the soil preparation requirements of a rapeseed combined transplanter in the middle-lower Yangtze River region in China where rice–rapeseed rotation cropping system was performed, a seedbed preparation machine composed of a rotary tillage device, ditch cleaning shovel, and soil leveling auger was designed to realize the function of rotary tillage, stubble ploughing, ditching, and soil leveling. The seedbed preparation machine was designed as the two parts of the middle section and the left–right symmetrical section to realize the need for middle ditching. Based on the principle of active scraping and anti-blocking, the curves of the soil contact section, soil throwing section, and transition section of the ditch cleaning shovel were analyzed. The structure parameters of the soil leveling auger with end reversal structure were designed. In order to further improve the working performance of the seedbed preparation machine, the response surface tests were designed, selecting the forward speed(X1), the rotation speed of rotary tillage blade roller(X2), and the rotation speed of soil leveling auger(X3) as the main influencing factors, taking the soil breaking rate and the straw coverage rate and the soil flatness as the test indexes. The optimal parameter combination was obtained as a forward speed of 0.94 m/s, rotation speed of rotary blade roller of 268 rpm, and rotation speed of soil leveling auger of 204 rpm. Under the optimal parameters combination, the soil breaking rate, straw coverage rate, and soil flatness were 92.06%, 93.01%, and 8.35 mm respectively, which satisfied the agronomic requirements of rapeseed blanket seedling transplanting. This study can provide a reference for the design of a seedbed preparation machine of a rapeseed combined transplanter.

Spatial Patterns and Spatial Autocorrelations of Wetland Changes in China During 2003-2013

Wetlands play an important role in maintaining ecosystem functions. Wetlands in China have suffered intensive human disturbance, especially before 2000, resulting in great losses and degradation. Therefore, two national wetland resource surveys were carried out by the Chinese government during 1998-2003 and 2008-2013 to determine the status of wetlands, understand their dynamics, and provide substantial data that can aid scientific wetland conservation. Based on the survey data, the spatial pattern and spatial autocorrelation were explored using the standard deviation ellipse as well as global and local spatial autocorrelation statistics. GIS mapping was employed to display the results via the visualization of the spatial patterns and relationships. Results indicate that:① Changes in the wetlands of China are significant and exhibit obvious regional differences. The center of the ellipse of the total wetlands has moved to the west, and the degree of spatial differentiation between natural wetlands and artificial wetlands is increasing. There is no significant spatial autocorrelation for changes in artificial wetlands. ② The changes in natural wetlands are significantly spatially autocorrelated and clustered, which are identified by global Moran's I and local Moran's I. The hotspots of natural wetland change are concentrated primarily in Qinghai, Tibet, and Sichuan. The individual hotspot is in Inner Mongolia and the cold spot is in Henan. The difference in spatial autocorrelation between natural and artificial wetland changes indicates that natural wetland changes have shown spatial continuity, while artificial wetland changes have shown strong spatial randomness. ③ Some useful spatial associations are used to delineate wetland conservation effects. Then, three major or five minor effective protection management regions are identified. Wetland conservation efforts should be continuously strengthened and improved, especially in the middle-lower Yangtze River region of central China. The use of Moran statistics helps to reveal spatial autocorrelation and identify the conservation effects in wetland changes, which can provide a basis for decision-making in regional wetland conservation and management systems.

Theoretical performance analysis of a new hybrid air conditioning system with two-stage energy recovery in cold winter

Abstract Energy recovery technologies can effectively improve the energy efficiency of air-conditioning systems and significantly reduce building energy consumption. In this paper, a parametric analysis and energy-saving potential evaluation for a new hybrid air conditioning system (HAC) is carried out theoretically based on developed models. The proposed HAC incorporates into a conventional mechanical vapor compression air conditioning system with an independent fresh air conditioner which is composed of a network of heat exchangers, including a packed bed and three air-water finned coils. Under cold winter climate, in the fresh air conditioner, a packed bed is coupled with a water-air heat exchange coil to form a total energy recovery loop. A run-around sensible energy recovery loop is also integrated in the system to produce a two-stage energy recovery effect. Moreover, a sprayer is installed upstream of the two-stage energy recovery process for fresh air humidification, and a fresh air recirculation duct is equipped for frost-free operation. In the parametric analysis, four independent affecting parameters are included: the air-to-water heat capacity ratio, the indoor temperature, the ambient temperature, and the ratio of recirculation fresh air. The energy-saving potential of the HAC is also evaluated for applications in seven typical cities located in middle-lower Yangtze River region of China over the winter period (December, January and February). The results show that compared with the conventional system with electric humidification, the HAC has an average energy saving rate of 44.0%, and its average power saving per hour is 13.41 W m−2.

Spatial patterns of irrigation water withdrawals in China and implications for water saving

By considering numerical features, spatial variation, and spatial association, the spatial patterns of China’s irrigation water withdrawals in 2001 and 2010 were explored at the regional, provincial, and prefectural scales. In addition, an overlay analysis was used to develop specific water-saving guidance for areas under different levels of water stress and with different degrees of irrigation water withdrawals. It was found that at the regional scale, irrigation water withdrawals were highest in the Middle-Lower Yangtze River region in both years, while at the provincial scale, the largest irrigation water withdrawals occurred in Xinjiang. During 2001–2010, the total of irrigation water withdrawals decreased; however, in the Northeast region, especially in Heilongjiang Province, it experienced a dramatic increase. The spatial variation was largest at the prefectural scale, with an apparent effect. The spatial association was globally negative at the provincial scale, and Xinjiang was the only significant high-low outlier. In contrast, the association displayed a significant positive relationship at the prefectural scale, and several clusters and outliers were detected. Finally, it was found that the water stress in the northern part of China worsened and water-saving irrigation techniques urgently need to be applied in the Northeast region, the Huang-Huai-Hai Plain region, and Gansu-Xinjiang region. This study verified that a multi-scale and aspect analysis of the spatial patterns of irrigation water withdrawals were essential and provided water-saving advice for different areas.

Formation of the Jinshandian Fe skarn ore field in the Edong district, Eastern China: Constraints from U–Pb and 40Ar/39Ar geochronology

The Jinshandian ore field represents one of the largest concentrations of Fe skarn deposits in the Edong district of Eastern China. Orebodies of these deposits occur in skarn along the contacts between quartz diorite or quartz monzonite and Triassic sedimentary country rocks. In this paper, we present new U–Pb geochronological data for magmatic zircon and hydrothermal titanite, as well as 40Ar/39Ar ages on hydrothermal phlogopite, to determine whether multiple magmatic-hydrothermal events associated with formation of the Fe skarn deposits in the Jinshandian ore field. The robust U–Pb zircon ages demonstrate that the quartz monzonite and quartz diorite were emplaced at 130Ma and 127Ma, receptively. The U–Pb and 40Ar/39Ar ages of hydrothermal titanite and phlogopite form the skarn indicate that Fe mineralization also formed at ca. 131–128Ma, but with an additional 118Ma hydrothermal event recorded by phlogopite. This geochronology confirms a causative linkage between granitic intrusion and skarn mineralization. The data also indicate that at least two hydrothermal events took place in the Jinshandian ore field, one at 131–128Ma and the other at ∼118Ma. Integrating these ages from the ore field with previous geochronological data from the broader Edong district, two regional magmatic-hydrothermal events are recognized in the Edong district after 135Ma, with the older one at 131–127Ma in excellent agreement with the ∼131Ma formation age of magnetite-apatite deposits in the eastern part of Middle–Lower Yangtze River region, and the younger one at 122–118Ma post-dating emplacement of the ca. 126Ma A-type granite and syenite in the eastern part of Middle–Lower Yangtze River region. A detailed comparison between the Fe skarn deposits and magnetite-apatite deposits in the Middle–Lower Yangtze River region suggests that these two deposit types not only share similar alteration assemblages and association with the evaporites within the ore-forming systems, but also may have formed during the same Early Cretaceous magmatic-hydrothermal event.

Effect of continuous reduction of nitrogen application to a rice-wheat rotation system in the middle-lower Yangtze River region (2013–2015)

Rice (Oryza sativa L.) and wheat (Triticum aestivum L.) are two stable food crops that play a vital role in national food security. Summer rice-winter wheat double-cropping rotation is the dominant crop rotation practice used in the middle-lower Yangtze River region of China. However, excessive application of nitrogen (N) fertilizer in this region has led to low nitrogen use efficiency (NUE). To our knowledge, no studies have investigated the effects of reducing N fertilizer applications during both the rice and wheat seasons on crop yield, NUE, and soil fertility. In this study, we conducted a two-year field experiment using N fertilizer rates of 180, 240, and 300kgNha−1 during the rice growing season and 135, 180, and 225kgNha−1 during the wheat growing season. No differences in yield were observed among the treatments during the rice growing season; however, reduced N fertilizer application significantly affected yield during the wheat growing season. Reducing the amount of N fertilizer applied during the previous season and current season and the interactions between these seasons (R×W) had no effect on rice yield but did affect wheat yield. In addition, the N application rates significantly influenced N uptake and NUE. During the rice growing season, the N agronomic efficiency (NAE), N physiological efficiency (NPE), N partial factor productivity (NPF), and N recovery efficiency (NRE) increased by 20.6–42.5%, 11.1–15.8%, 23.9–40.2%, and 4.8–28.2%, respectively. During the wheat growing season, the NAE, NPE, NPF, and NRE increased by 20.4–54.9%, 8.2–16.5%, 21.8–58.3%, and 11.6–24.4%, respectively. We applied 15N-labelled urea in the remainder of the soil N fertilization treatments, which indicated that the addition of 15N fertilizer resulted in no difference in the 0–60cm soil profile after rice harvest. Collectively, reducing N fertilizer application rates can effectively improve NUE and decrease N losses, and short-term reductions in N fertilizer application do not affect soil fertility.

Crustal and uppermost mantle velocity structure and its relationship with the formation of ore districts in the Middle–Lower Yangtze River region

In this study, we conduct ambient noise tomography and teleseismic two-plane-wave tomography to probe the crustal and uppermost mantle structures in the Middle–Lower Yangtze River region. The data used include 14 months (from July 2012 to August 2013) of continuous vertical component ambient noise data and 219 teleseismic earthquakes recorded at 138 broadband seismic stations from Chinese provincial networks and 19 temporary seismic stations deployed by China University of Geosciences (Beijing). First, we apply ambient noise tomography to the collected ambient noise data to generate Rayleigh wave group and phase velocity maps at 5–42 s periods and two-plane-wave tomography method to earthquake data to generate intermediate-to-long period phase velocity maps at 20–143 s periods. We then combine the short-to-intermediate period velocity maps from ambient noise and the intermediate-to-long period phase velocity maps from earthquake data to generate broadband phase velocity maps at periods from 5 to 143 s. By inverting these 5–143 s Rayleigh wave velocity maps, we construct a 3-D shear wave velocity model from the surface to ∼250 km depth in the Middle–Lower Yangtze River region. The 3-D model shows that in the upper crust, the basin regions, including the JiangHan, HeHuai, SuBei, HeFei and NanYang basins, are all featured with low velocities, and the mountain regions with high velocities. In the uppermost mantle, a low-velocity zone at ∼100–200 km depth is observed beneath the Middle–Lower Yangtze River Metallogenic Belt. Moreover, our tomographic results show that the NingWu and NingZhen ore districts are clearly characterized by the strongest low velocity anomaly in the uppermost mantle at ∼70–200 km depth. The depth extent of the low-velocity zone becomes shallower and the amplitude of low velocity anomaly becomes larger from the southwest JiuRui ore district to northeast NingWu ore districts. The change pattern of the low-velocity zone in the depth extent and the amplitude is consistent with the fact that peak ages of magmatic events along the Middle–Lower Yangtze River Metallogenic Belt progressively become younger and younger from 148 Ma in the southwest to 125 Ma in the northeast. The observed low-velocity zone may represent the cooling hot upper mantle which was partially molten in the past resulting from partial melting of the paleo-Pacific plate or of an enriched mantle source induced by the westward subduction of the paleo-Pacific plate. The upwelling of the mantle-derived magmas may result in the formation of these granitic rocks and coeval ores deposits along the Middle–Lower Yangtze River Metallogenic Belt.

How important are the wetlands in the middle-lower Yangtze River region: An ecosystem service valuation approach

The middle-lower Yangtze River region, with its lake groups and river systems, is one of the important wetland regions in the world. In this study, physical dimension measurement and monetary evaluation were conducted to estimate the value of wetland services in this region. Results revealed that the total value of the wetland ecosystem services in the middle-lower Yangtze River region is US $162.5 billion per year, which reflects the irreplaceable importance of wetlands in this region. The wetland ecosystem service values revealed considerable spatial variability. Poyang Lake, Hong Lake, and Shijiu Lake have the most ecosystem service value. The value of human-made wetlands (2.62×104US$/ha/yr) is 48% lower than that of natural wetlands (5.04×104US$/ha/yr), indicating that the conversion of natural wetlands for aquaculture from the sustainability perspective is not significant. The direct and indirect values of wetland ecosystems are 46.17% and 53.83% of the total values, respectively. Recognizing that the value of wetlands in this region is mainly embodied as indirect use values, conservation of the regulating and supporting services should be prioritized in the design of future wetland ecosystem management plans.

Geochemistry, and zircon U-Pb and molybdenite Re-Os geochronology of Jilongshan Cu-Au deposit, southeastern Hubei Province, China

The Jilongshan skarn Cu–Au deposit is located at the Jiurui ore cluster region in the southwestern part of the Middle–Lower Yangtze River valley metallogenic belt. The region is characterized by NW-, NNW- and EW-trending faults and the mineralization occurs at the contact of lower Triassic carbonate rocks and Jurassic granodiorite porphyry intrusions. The intrusives are characterized by SiO2, K2O, and Na2O concentrations ranging from 61.66 to 67.8 wt.%, 3.29 to 5.65 wt.%, and 2.83 to 3.9 wt.%, respectively. Their A/CNK (A/CNK = n(Al2O3)/[n(CaO) + n(Na2O) + n(K2O)]) ratio, δEu, and δCe vary from 0.77 to 1.17, 0.86 to 1, and 0.88 to 0.96, respectively. The rocks show enrichment in light rare earth elements ((La/Yb)N = 7.61–12.94) and large ion lithophile elements (LILE), and depletion in high field strength elements (HFSE), such as Zr, Ti. They also display a peraluminous, high-K calc-alkaline signature typical of intrusives associated with skarn and porphyry Cu–Au–Mo polymetallic deposits. Laser ablation inductively coupled plasma spectrometry (LA-ICP-MS) zircon U–Pb age indicates that the granodiorite porphyry formed at 151.75 ± 0.70 Ma. A few inherited zircons with older ages (677 ± 10 Ma, 848 ± 11 Ma, 2645 ± 38 Ma, and 3411 ± 36 Ma) suggest the existence of an Archaean basement beneath the Middle–Lower Yangtze River region. The temperature of crystallization of the porphyry estimated from zircon thermometer ranges from 744.3 °C to 751.5 °C, and 634.04 °C to 823.8 °C. Molybdenite Re–Os dating shows that the Jilongshan deposit formed at 150.79 ± 0.82 Ma. The metallogeny and magmatism are correlated to mantle–crust interaction, associated with the subduction of the Pacific Plate from the east. Copyright © 2013 John Wiley & Sons, Ltd.

Statistical tests for a correlation between decadal variation in June precipitation in China and sunspot number

Six different statistical methods (i.e., correlation, difference, prominent period, variance contribution, scale‐averaged spectrum, and cross spectrum) are used to test for regional differences in the relationship between the 11 year sunspot cycle and June precipitation in China during the 20th century. In the Huaihe River basin (HRB) of central China, located at the marginal region of the East Asian summer monsoon (EASM), there exists a reliable positive‐correlation relationship between the 11 year sunspot cycle and June precipitation; whereas, possible negative and very weak positive correlations in the south of the middle–lower Yangtze River Region and the HeTao Basin (HTB), located in the interior of the EASM and the westerlies, respectively. The reasons for these regional differences are investigated, revealing that the marginal region of EASM may be more sensitive to solar forcing than is its interior, which results in the HRB becoming the most susceptible (strongest correlation) region. That is to say, in June during the high sunspot number (SSN) years, the influence of the EASM is significantly greater and more to the north than that in June during the low SSN years, causing the HRB to be mainly influenced by the EASM (westerlies) in June during the high (low) SSN years. The northward expansion of the June EASM probably resulted from enhancement of the low‐level southwesterly monsoon flow over the northern tropical Indian Ocean, combined with an expansion of the western Pacific subtropical high at times of high SSN.

A tectono-genetic model for porphyry–skarn–stratabound Cu–Au–Mo–Fe and magnetite–apatite deposits along the Middle–Lower Yangtze River Valley, Eastern China

The Middle–Lower Yangtze River Valley metallogenic belt (YRB), situated along the northern margin of the Yangtze craton, is characterized by porphyry–skarn–stratabound Cu–Au–Mo–Fe deposits in the areas of uplift and magnetite–apatite deposits in Cretaceous fault basins. Following detailed field investigations and a review of published data, we recognize two episodes of magmatism and mineralization in the YRB: 1) 156–137 Ma high-K calc-alkaline granitoids associated with 148–135 Ma porphyry–skarn–stratabound Cu–Au–Mo–Fe deposits and 2) 135–123 Ma shoshonitic series, associated with 134.9–122.9 Ma magnetite–apatite deposits. A-type granitoids and associated alkaline volcanic have a small age range from 126.5 to 124.8 Ma and are temporally, spatially and genetically associated with the second episode. The geodynamic history of the YRB did not experience the Paleozoic to Mesozoic lithospheric thickening that took place in the North China craton. This process is inferred to be linked to partial melting of the delaminated lower crust at high pressures, resulting in the development of C-type adakitic rocks. The petrochemical and Sr/Nd isotopic data show that both the shoshonitic series and A-type granitoids are quite different from adakites, with only some of the K-calc-alkaline granitoids having adakitic signatures. Previous ore genesis models were established based on an assumed relationship with adakites and a continuous tectono-thermal evolution from 150 to 100 Ma. All data obtained for the Middle–Lower Yangtze River region consistently show that the Tan–Lu regional strike-slip fault zone, initiated at 233 ± 6 to 225 ± 6 Ma from the collision between the North China and Yangtze cratons and was reactivated at ca. 160 Ma. The Tan–Lu fault was caused by the oblique subduction of the Izanagi plate, which along the YRB the low-angle subducted slab and the overlying crust was disrupted or broken due to the disharmonious movement of the two blocks. The high-K calc-alkaline granitoids magmas were derived from melting of the subducted slab, with some input of crustal material. These magmas were emplaced at the intersections between NE- and EW-trending faults and formed porphyry–skarn–stratabound Cu–Au–Mo–Fe deposits between 156 and 137 Ma. After 135 Ma the subducted plate changed its direction of motion to northeast, now running parallel to the Eurasian continental margin, and leading to large-scale continental extension. The shoshonitic series and subsequent A-type granitoids magmatism and the development of magnetite–apatite ores in the YRB, took place in both fault basins and NE-trending rifts between 135 and 124 Ma.

40Ar‐39Ar Dating of Albite and Phlogopite from Porphyry Iron Deposits in the Ningwu Basin in East‐Central China and Its Significance

Abstract 40Ar‐39Ar dating of albite from the Meishan and Taocun iron deposits yields plateau ages of 122.90±0.16 Ma and 124.89±0.30 Ma, and isochron ages of 122.60±0.16 Ma and 124.90±0.29 Ma, respectively. Phlogopite from the Zhongshan‐Gushan ore field has a plateau age of 126.7±0.17 Ma and an isochron age of 127.21±1.63 Ma. Analysis of regional geodynamic evolution of the middle‐lower Yangtze River region suggests that the porphyry iron deposits were formed as a result of large‐scale lithosphere delamination and strong sinistral strike‐slip movement of the Tancheng‐Lujiang fault zone. The copper, molybdenum and gold deposit system in the middle‐lower Yangtze River region was formed during the stress transition period of the eastern China continent.