Platinum-Group Element Geochemistry of the Escondida Igneous Suites, Northern Chile: Implications for Ore Formation

Platinum-group element (PGE) geochemistry may be used to constrain the timing of sulfide saturation in magmas, which influences the Cu and Au fertility of evolving magmatic systems. We report new geochronological and geochemical data, with emphasis on PGE geochemistry, for a suite of regional porphyritic hornblende–diorite intrusions and ore-bearing porphyries from the super-giant Escondida and smaller Zaldivar Cu deposits of Northern Chile. The regional dioritic intrusions have zircon U–Pb ages between 39·6 to 37·1 Ma, which overlap with the ages of the ore-bearing Escondida and Zaldivar porphyries (38·1 to 35·0 Ma). Whole-rock major and trace element, and Sr–Nd–Pb and zircon O–Hf isotope geochemistry indicate that the regional diorites and ore-bearing porphyries are co-magmatic and originated from the same mantle-derived magma by fractional crystallization, with minor contamination by Paleozoic crust (∼10%). The low concentrations of PGE in the regional diorites show that they reached sulfide saturation before the MgO content of the melt fell to 4·7 wt %, the MgO content of the most primitive sample analysed. The fraction of sulfide melt which separated from the melts that formed the regional diorites is estimated to be ∼0·12 wt %; this resulted in the partitioning of highly chalcophile elements (Au and PGE) into a sulfide phase that was retained in cumulus rocks at depth. However, the fraction of sulfide melt was too low to have a significant effect on the Cu content of the fractionating melt. As a consequence, when the evolving melt eventually reached volatile saturation, it contained enough Cu (40 ± 10 ppm) to form a super-giant Cu deposit. In contrast, Au was largely stripped from the melt by sulfide precipitation, with the result that the mineralization at Escondida is Cu dominant, with only minor Au. The Zaldivar deposit, on the other hand, contains even less Au, which is attributed to a longer fractionation interval between sulfide and volatile saturation. This study provides evidence to support previously proposed models which suggest that the timing of sulfide saturation, the amount of sulfide melt produced, the water content and oxidation state of the melt, and the magma volume are critical factors in determining the potential to form a porphyry Cu deposit. Plots of Pd/MgO against Y can be used as empirical indicators of magma fertility for porphyry mineralization, and to discriminate between Cu–Au and Cu-dominated systems, but cannot predict the size of the deposit. The super-giant status of the Escondida deposit is attributed to it being underlain by a large batholith with a calculated minimum mass of 1012 tonnes (∼400 km3).This work was supported by the Australian Research Council [DP170103140]

Constructing a Tough Shield around the Wellbore by Stabilizing the Multi-Scale Structure of Granular Plugging Zone in Deep Fractured Reservoirs

Fracture plugging zone with low strength is one of the key reasons for plugging failure in deep fractured reservoirs. Forming a high-strength plugging zone is a key engineering problem to be solved in wellbore strengthening. In this chapter, wellbore strengthening mechanisms of plugging zone for wellbore strengthening in deep fractured reservoirs are revealed from a relationship between mechanical structure and strength standpoint. Physical granular bridging materials dislocation and crushing under pressure fluctuation induce the strong force chains network failure, which leads to macroscale friction or shear failure of plugging zone. The main methods to improve microscale materials stability are to increase friction resistance, exert embedding effect, and strengthen bonding effect. Factors, which strengthen the meso-structure stability, include increasing shear strength and proportion of strong force chains. Key measures to strengthen the macrostructure stability of plugging zone are by improving its compactness, controlling its length, and ensuring the stability timeliness

Laparoscopic distal gastrectomy demonstrates acceptable outcomes regarding complications compared to open surgery for gastric cancer patients with pylorus outlet obstruction

BackgroundFor gastric cancer (GC) patients with pylorus outlet obstruction (POO), whether laparoscopic surgery has advantages over open surgery remains unclear. This study aims to investigate the differences between patients with and without POO in open and laparoscopic groups and to determine the differences between laparoscopic distal gastrectomy (LDG) and open distal gastrectomy (ODG) in GC patients with POO.MethodsA total of 241 GC patients with POO who underwent distal gastrectomy at the Department of Gastric Surgery of the First Affiliated Hospital of Nanjing Medical University between 2016 and 2021 were included in this study. A total of 1,121 non-POO patients who underwent laparoscopic surgery and 948 non-POO patients who underwent open surgery from 2016 to 2021 were also enrolled in the study. We compared complication rates and hospital stays between open and laparoscopic groups.ResultsThere was no significant difference for LDG between GC patients with and without POO regarding the overall complication rates (P = 0.063), the Grade III–V complication rate (P = 0.673), and the anastomotic complication rate (P = 0.497) from 2016 to 2021. The patients with POO had longer preoperative hospital stay (P = 0.001) and postoperative hospital stay (P=0.007) compared to patients without POO. No significant difference was observed for open patients between POO and non-POO patients regarding the overall complication rate (P = 0.357), grade III–V complication rate (P = 1.000), and anastomosis-related complication rate (P = 0.766). Compared with open surgery in GC patients with POO (n = 111), the total complication rate of the LDG group was 16.2%, which was significantly lower than that of the open group (26.1%, P = 0.041). No significant differences in the Grade III–V complication rate (P = 0.574) and anastomotic complication rate (P = 0.587) were observed between laparoscopic and open groups. Patients receiving laparoscopic surgery had shorter postoperative hospital stay than open surgery (P = 0.001). More resected lymph nodes (LNs) were also observed in the laparoscopic group (P = 0.0145).ConclusionThe comorbidity of GC with POO does not increase the complication rate after laparoscopic or open distal gastrectomy. In GC patients with POO, laparoscopic surgery shows advantages over open surgery with a lower overall complication rate, shorter postoperative hospital stay, and more harvested lymph nodes. Laparoscopic surgery is a safe, feasible, and effective treatment for GC with POO

Using precious metal probes to quantify mid-ocean ridge magmatic processes

Basalts from the East Pacific Rise (EPR), Siqueiros transform zone and Mid-Atlantic Ridge (MAR) area have been analyzed for the platinum-group elements (PGE) and a wide range of incompatible elements. The low PGE content of the most primitive mid-ocean ridge basalts (MORB) suggests that they leave the mantle sulfide-saturated but become sulfide under-saturated, as a consequence of decompression, during their ascent from the mantle to the MOR magma chamber. Because the pressure drop is small, the ascending magma enters the magma chamber slightly sulfide under-saturated and requires only a small amount of fractional crystallization to return it to sulfide-saturation. Sulfide-saturation is marked by the Pd content of the melt falling by over an order of magnitude at ca. 9.5 wt.% MgO. However, once the magma has become sulfide-saturated, it shows no evidence of a further decline in Pd with decreasing MgO as the system evolves. This must result from regular replenishment of the underlying axial magma chamber by fresh batches of primitive magma. Most replenishments occur when the MgO content of the resident melt in the magma chamber is between ∼9 to 6.5 wt.% MgO. We combine the tight constraints imposed by highly compatible Pd abundances, with those imposed by strongly incompatible elements, to produce the first model that successfully accounts for the variations of both classes of elements in open system mid-ocean ridges magma chambers for normal-type MORB (N-MORB). We show that the lack of decline in the Pd content of sulfide-saturated mid-ocean ridge basalts, with decreasing MgO, requires frequent small replenishments (between 1% and 4%) of similar magnitude, rather than large initial inputs that systematically decline from near 100% to near zero during the life of an individual ridge system. Assuming the spreading rate of ∼110 mm/yr for the EPR at 9°N, and 14 yr between the 1991–1992 and 2005–2006 eruptions, the calculated volume of erupted and intruded magma is 2.3 × 103 m3/m of ridge length. If the expelled melt represents 0.5% of the accessible magma in the chamber, as suggested by the Pd modeling, the volume of the magma accessible during tapping is 4.6 × 105 m3/m of ridge length.This study is supported by Korea Research Fellowship Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (2019H1D3A1A01102977) to Hongda Hao and Special Analytical funding from ANZIC IODP (LG01_Campbell15) to Ian Campbell and Richard Arculus. We would like to thank Jeff Chen and Hua Chen for assistance with the electronic microprobe and X-Ray fluorescence (XRF) spectrometry analyses, respectively, and Jung-Woo Park for some helpful sug- gestions. Hongda Hao acknowledges the China Scholarship Council (CSC) and RSES scholarship for supporting his study in the ANU. Field work, sample collection and initial geochemical analyses of samples from the EPR and the Siqueiros Transform were funded by NSF grants (OCE-0138088, OCE-0819469, OCE-825265, OCE- 638406, OCE-527077 and OCE-535532) to Michael Perfit. We thank two anonymous reviewers for their helpful and constructive com- ments and Rajdeep Dasgupta for his editorial handling

Role of magma differentiation depth in controlling the Au grade of giant porphyry deposits

Porphyry deposits are the world's most important source of Cu and a major source of Au. It has been recognized that low Au grades generally characterize porphyry deposits in thick continental arcs, like the Andes, where the magmas are likely to differentiate at depth. In contrast, Au-rich porphyries are mainly found in thin island arcs, for example, those of the southwest Pacific, or associated with short extensional periods in continental arcs, where the magmas are likely to experience relatively shallow differentiation. However, the key factors that control this difference remain debated. This study shows that the Au grade of giant porphyry deposits and La/Yb ratios of the ore-associated suites are negatively correlated (r =& SIM; 0.7, p = 10-7). We attribute the negative correlation to be mainly due to varying sulfide saturation histories, modulated by the depth of magma differentiation. Magmas differentiating in deep crustal reservoirs are likely to reach sulfide saturation early due to high pressure and early depletion of FeO (calc-alkaline trend). Early sulfide saturation causes most Au to be held in cumulus sulfides, making it unavailable to enter ore-forming fluid released in the upper crust, resulting in Au-poor porphyry systems. In contrast, magmas evolving in shallow reservoirs are likely to experience late sulfide saturation because of the high sulfur solubility induced by low pressure and the high FeO content of the melts (tholeiitic trend). Late sulfide saturation enhances the potential of a magmatic system to form Au-rich porphyry deposits due to the high Au content of the magma at voluminous fluid saturation and efficient Au transfer from melt to the ore-forming fluids via sulfide fluid interaction. The link between average magma differentiation depth and Au content is supported by platinum-group element geochemistry of the porphyry ore-forming suites, which shows that the magmas differentiating at shallower depths (lower La/Yb) reach sulfide saturation later and therefore have higher Au concentrations than those that differentiate at deeper levels (higher La/Yb). Numerical models for ore-associated magmas with different sulfide saturation histories indicate that variations in the Au grades of giant porphyry deposits can be explained by the variations in the timing of sulfide saturation. Based on the results, we propose that Au concentration in the magma, modulated by average magma differentiation depth and sulfide saturation history, is one of the critical factors controlling the Au grade of giant porphyry Cu deposits.(c) 2022 Elsevier B.V. All rights reserved.N

Nd-Hf isotopic systematics of the arc mantle and their implication for continental crust growth

The 143Nd/144Nd and 176Hf/177Hf values of depleted mid-ocean ridge basalt (MORB) mantle have long been used to calculate the Nd and Hf model ages and constrain the growth rate of the continental crust. However, because continental crust forms principally at subduction zones, the appropriate 143Nd/144Nd and 176Hf/177Hf for use in model age calculations are those of the mantle wedge that underlies the juvenile magmatic arcs. In this study, we compile the Nd and Hf isotopic compositions of the modern island arc volcanic rocks. The average 143Nd/144Nd value obtained for the arc mantle is 0.512959 (eNd = +6.3), with upper and lower 95% confidence uncertainties of 0.513115 (eNd = +9.3) and 0.512613 (eNd = -0.5), respectively. The average obtained for 176Hf/177Hf is 0.283144 (eHf = +13.2) with upper and lower limits of 0.283272 (eHf = +17.7) and 0.282927 (eHf = +5.5), respectively, at the 95% confidence level. The Nd and Hf isotopic compositions of the modern island arc volcanic rocks can be divided into three populations, the high, transitional and low e arc mantle populations, that reflect a combination of mantle heterogeneity and additions of different slab-derived components to the mantle wedge. The high e arc mantle (HAM) population (eNd +5.7 and eHf +10) were metasomatized by the transfer of unradiogenic Nd and Hf from pelagic sediments, and Fe-Mn crusts and nodules, to the mantle wedge, the HAM by fluid dominate process and the TAM by a combination of sediment melts and fluids. In contrast, melts derived from subducted sediments, particularly zircon-rich turbidites, play a more important role in the low e arc mantle population (LAM, eNd < +5.7 and eHf < +10). The average of both Nd and Hf isotopic data for the arc mantle, together with the 95% confidence limits, are used to define the arc mantle growth curves and their uncertainties. We suggest that these arc mantle growth curves should be used to calculate Nd and Hf model ages and constrain the growth rate of the continental crust.N

Two-Dimensional Black Phosphorus: Preparation, Passivation and Lithium-Ion Battery Applications

As a new type of single element direct-bandgap semiconductor, black phosphorus (BP) shows many excellent characteristics due to its unique two-dimensional (2D) structure, which has great potential in the fields of optoelectronics, biology, sensing, information, and so on. In recent years, a series of physical and chemical methods have been developed to modify the surface of 2D BP to inhibit its contact with water and oxygen and improve the stability and physical properties of 2D BP. By doping and coating other materials, the stability of BP applied in the anode of a lithium-ion battery was improved. In this work, the preparation, passivation, and lithium-ion battery applications of two-dimensional black phosphorus are summarized and reviewed. Firstly, a variety of BP preparation methods are summarized. Secondly, starting from the environmental instability of BP, different passivation technologies are compared. Thirdly, the applications of BP in energy storage are introduced, especially the application of BP-based materials in lithium-ion batteries. Finally, based on preparation, surface functionalization, and lithium-ion battery of 2D BP, the current research status and possible future development direction are put forward

Platinum-group element geochemistry used to determine Cu and Au fertility in the Northparkes igneous suites, New South Wales, Australia

Recent studies have shown that platinum-group elements (PGE) can be used to constrain the timing of sulfide saturation in evolving felsic systems. In this study, we report trace-element, PGE, Re and Au data for the barren and ore-associated suites of intermediate to felsic rocks from the Northparkes Cu-Au porphyry region, emphasizing the timing of sulfide saturation and its influence on the tenor of the associated hydrothermal mineralization. Two barren suites, the Goonumbla and Wombin Volcanics and associate intrusive rocks, are found in the region. Geochemical modelling shows that the barren suites are dominated by plagioclase-pyroxene fractionation, whereas the ore-associated Northparkes Cu-Au porphyry suite is characterized by plagioclase-amphibole fractionation, which requires the ore-bearing suite to have crystallized from a wetter magma than barren suites. The concentrations of PGE, Re and Au in the barren suites decrease continuously during fractional crystallization. This is attributed to early sulfide saturation with the fraction of immiscible sulfide precipitation required to produce the observed trend, being 0.13 and 0.16. wt.% for the Goonumbla and Wombin suites, respectively. The calculated partition coefficients for Au and Pd required to model the observed change in these elements with MgO are well below published values, indicating that R, the mass ratio of silicate to sulfide melt, played a significant role in controlling the rate of decline of these elements with fractionation. Palladium in the ore-associated suite, in contrast, first increases with fractionation then decreases abruptly at 1.2. wt.% MgO. The sharp decrease is attributed to the onset of sulfide precipitation. Platinum on the other hand shows a moderate decrease, starting from the highest MgO sample analysed, but then decreasing strongly from 1.2. wt.% MgO. The initial Pt decrease is attributed to precipitation of a platinum-group mineral (PGM), probably a Pt-Fe alloy, and the sharp decrease of both Pt and Pd at 1.2. wt.% MgO to sulfide saturation. We suggest that the Goonumbla and Wombin suites are barren because early sulfide saturation locked most of the Cu and Au in a sulfide phase in the cumulus pile of a deep parental magma chamber, well before volatile saturation, so that when the magma reached volatile saturation, it did not have access to the Cu and Au. This contrasts with the relatively late sulfide saturation in the ore-associated suite, which was followed shortly afterwards by volatile saturation. Rayleigh fractionation concentrated incompatible Cu and Au by at least a factor of five before volatile saturation. The short crystallization interval between immiscible sulfide and volatile saturation allowed some Au and Cu to be stripped from the evolving magma. Gold, with its higher partition coefficient into immiscible sulfide melts, was more affected than Cu. The result is a Cu-Au deposit. Our study also suggests that Rayleigh fractionation is as at least as important as the initial concentration of chalcophile elements in the parent magma in determining the fertility of felsic magma suites.This work was supported by the Australian Research Council [DP170103140]. We would like to thank the Rock Library and Geological Museum of the University of Tasmania and the Londonderry Drillcore Library, NSW Resource and Energy for providing us the samples used in this study. Hongda Hao acknowledges the China Scholarship Council (CSC) for supporting his study in the ANU

Influence of Organic Loading Rate on Methane Production from Brewery Wastewater in Bioelectrochemical Anaerobic Digestion

The effect of bioelectrochemical anaerobic digestion (BEAD) on the methanogenic performance of brewery wastewater at different organic loading rates (OLRs) was investigated and compared to conventional anaerobic digestion. A continuous BEAD reactor was used to treat brewery wastewater at different OLRs of 2, 4, 8, 16, and 20 g COD/L.d. The experimental results showed that the methane production was gradually increased from 0.48 L/L.d at an OLR of 2 g COD/L.d to 5.64 L/L.d at an OLR of 20 g COD/L.d. The methane production of the BEAD system was significantly higher than that of the conventional anaerobic reactor, indicating that BEAD has a better treatment effect for brewery wastewater. The performance of the conventional anaerobic reactor was significantly reduced especially at an OLR of 16 g COD/L.d, while the BEAD system could withstand a higher OLR. Bioelectrochemical systems provide a completely new platform for the anaerobic treatment of brewery wastewater and greatly improve the operation of anaerobic processes