Fluid Source Research Articles

Magmatic fluids responsible for lode gold mineralization in the giant Linglong deposit at Jiaodong, North China Craton: Constraints from Li[sbnd]O isotopes

The Jiaodong Peninsula, located in the eastern margin of the North China Craton, contains numerous world-class lode gold deposits that combined have a proven gold reserve of >5000 t. Despite a large amount of research, the source and evolution of hydrothermal fluids responsible for the gold mineralization in this region remains highly debated. The Linglong gold deposit is one of the largest deposits in the Jiaodong Peninsula. Gold lodes at Linglong are predominantly hosted within the Late Jurassic Linglong granite and structurally controlled by NE-trending faults. They are closely associated with large-scale hydrothermal alteration, which is paragenetically characterized by hydrothermal K-feldspar in pre-ore stage I, and sericite-quartz-pyrite in syn-ore stages II and III. The syn-ore alteration mineral assemblage is distributed within and around the gold lodes, whereas the K-feldspar alteration remains mainly distal to the gold lodes. From the unaltered to progressively intensifying K-feldspar-altered Linglong granites, there are decreasing trends for both whole-rock Li concentrations and δ7Li values, which are attributed to Rayleigh fractionation. The two values increase covariantly within the sericite-quartz-pyrite alteration zone towards the mineralization center, suggesting that further fluid-rock interaction and buffering of the ore fluid accounts for the observed Li elemental and isotopic variations. Fluid inclusion assemblages in quartz of stages I-III have homogenization temperatures of 349°-312 °C, 318°-272 °C, and 307°-246 °C, respectively. In-situ oxygen isotopic analysis on stage I quartz reveals δ18OQ values of 10.9–14.7 ‰, corresponding to δ18OW values of 4.3–9.2 ‰ for the equilibrated fluid. The δ18OW values of the equilibrated fluids of stages II and III are 5.6–8.9 ‰ and 5.2–8.8 ‰, respectively. The oxygen isotopic compositions indicate that magmatic fluid is prevailing for the K-feldspar and sericite-quartz-pyrite alterations. A binary mixing model using Li concentrations and δ7Li values further implies that the hydrothermal fluid was mainly sourced from coeval mafic magmas derived from the metasomatized lithospheric mantle. Our study highlights that lithium and in-situ oxygen isotopes can be used effectively to fingerprint the source of hydrothermal fluids and fluid-rock interactions.

Stability of the static-fluid cylindrical regular spacetime

In this paper, we study the mechanical stability of a static cylindrically symmetric regular solution to Einstein’s field equations that is supported by a static uniform perfect fluid with the equation of state p=−13ɛ in which p and ɛ are the pressure and the energy density of the uniform and isotropic perfect fluid. With the line-element ds2=−dt2+sech2ξρdρ2+dz2+1ξ2sinh2ξρdϕ2, this spacetime contains only one parameter, namely, ξ=8πɛ3 such that for small ρ or ξ→0 limit, the spacetime becomes flat. This solution belongs to a class of solutions found long ago by Bronnikov in the context of a static cylindrically symmetric perfect fluid, however, its interesting properties have not been noticed previously. Particularly, we show that this special cylindrically symmetric solution to the Einstein equations describes a regular distribution of gas of disordered cosmic strings. Moreover, with detailed calculations, we prove that the spacetime is unstable against a radial linear perturbation of its perfect fluid source.

Geochronology and ore-forming fluid source of the Buzhu orogenic gold deposit in southern Tibet

The Buzhu gold deposit is a newly discovered and representative gold deposit in the Indus-Yarlung Zangbo suture zone. At Buzhu, auriferous quartz veins with paragenetic sequences of quartz-pyrite-sericite hosted by Early Jurassic greenschist facies rocks, and gold occurs mainly as invisible lattice gold in pyrite as well as minor as visible micrograins inside (arseno)pyrite fractures. We have recognized two auriferous pyrite generations formed in the syn-ore stage (Py2a and Py2b). Py2a is euhedral-subhedral granular with cavities, whilst Py2b mainly grew colloidally around Py2a, indicating that pre-existing pyrite may have been dissolved to form the porous Py2a and Py2b rim. Py2a and Py2b have similar δ34SV-CDT values of 6.98‰ to 7.54‰ and 6.18‰ to 6.85‰, respectively, which are also similar to those of the ore-hosting sediments (6.08‰ to 7.08‰). In-situ trace element analysis shows that Py2b (avg. 1.63% Au) contains more gold than Py2a (avg. 0.42% Au). Combined with petrological and geochemical data, we hypothesized that the gold was derived from the metamorphic devolatilization of the sedimentary wallrocks, and pyrite dissolution-reprecipitation has driven the gold enrichment from Py2a to Py2b. The sericite Ar-Ar date of 19.60 ± 0.66 Ma likely represents the gold mineralization age, as the dated sericite coexists with the auriferous pyrite. This age is much younger than most orogenic gold mineralization (ca. 60–41 Ma) in southern Tibet and indicates an orogenic gold mineralization event (ca. 20–15 Ma) related to extensional tectonics during the late-stage India-Asia continental collision.

Geology, fluid inclusions, and isotope signatures reveal hydrothermal evolution and genesis of the Aqishan Pb-Zn deposit in Eastern Tianshan and implications for exploration of skarn mineralization

The Aqishan deposit (1.97 Mt at 1.05 % Pb + Zn) is located in the Aqishan-Yamansu arc, on the southwest section of the Eastern Tianshan, Northwest China. Pb-Zn mineralization is mainly hosted by garnet skarn and the volcaniclastic rocks of the Yamansu Formation. To decipher the evolution of ore fluids and source(s) of ore-forming components, and constrain the ore genesis, a combination of geological work, fluid inclusions, and C-O-S-Pb isotope systematics is presented. Detailed field and microscopic observations reveal that the skarn alteration and ore formation at Aqishan could be divided into four hydrothermal stages, consisting of prograde skarn (I), retrograde skarn (II), quartz–sulfides (III), and carbonate stage (IV). Sphalerite and galena are the dominant ore minerals generally occurring as disseminations and veins with locally laminated ores in stage III. Fluid inclusion data show that the fluids responsible for prograde skarn are high-temperature (342–518 °C) and high-salinity (7.3–44.2 wt% NaCl equiv.), and recorded fluid phase separation from an intermediate-salinity supercritical fluid, which was exsolved from crystallizing granitic magma. Microthermobarometry results limit the retrograde alteration within the temperature range of 313 to 388 °C and trapping pressures of 98 to 241 bars (1.0–2.5 km), with pressure dropping from lithostatic to hydrostatic regimes associated with a phase separation event. The boiling fluid inclusions in ore stage quartz show that the Pb-Zn mineralization formed at 205–357 °C, with a decrease in temperature facilitating the precipitation of ore-forming metals from hydrothermal system. Carbon and oxygen isotope compositions of calcite indicate a predominantly magmatic source for ore fluids at Aqishan with later meteoric water involved. Bulk and in situ sulfur values of sulfides range from −6.4 to −0.7 ‰, consistent with a dominantly magmatic origin. Sulfides together with the granite porphyry and tuff, show relatively homogeneous Pb isotope compositions, indicating that abundant ore-forming metals were sourced from a magmatic reservoir with contribution from country rocks. Fluid inclusion study and available calcite C-O isotopes suggest that significant decrease in temperature and fluid-rock interactions remarkably contributed to the metal deposition at Aqishan. The skarn alteration with typical alteration assemblages of garnet–diopside is proposed as an effective mineral exploration target of skarn(–like) ores in Eastern Tianshan.

Genesis of the Hatu gold deposit: Constrained by in situ S[sbnd]Pb isotope geochemistry of pyrite

As the largest gold deposit in west Junggar, the Hatu gold deposit is located between the Anqi and Hatu faults in the Hatu-Sartohay district. The orebodies, composed of gold-bearing quartz veins and auriferous altered wall-rocks, are controlled by NE-, NW-, and EW-trending faults in Early Carboniferous volcano-sedimentary rocks. In this study, integrated textural, in situ sulfur and lead isotope analyses of pyrite grains in the host rocks and ores reveal new information on the sources of the ore-forming fluids and metal, as well as the mechanism of gold deposition. Framboidal pyrite in tuffaceous siltstone has a large δ34S range of −26.7 to +54.0 ‰, which is attributed to sulfur-reducing bacterial (SRB) activity during sedimentary-diagenetic process. Fine-grained subhedral pyrite in meta-basalt shows negative δ34S values from −26.7 to −12.1 ‰, which may be generated by reduction of seawater sulfate by ferrous iron bearing minerals during metamorphism. The δ34S values of four generations of hydrothermal pyrite (Py1–Py4) in the orebodies vary in a narrow range from +1.4 to −1.9 ‰. The sulfur isotopic characteristics of the hydrothermal pyrite are similar to most magmatic hydrothermal deposits, but differ from the metamorphic pyrite in meta-basalt and the framboidal pyrite in tuffaceous siltstone. In addition, the uniform in situ lead isotope ratios of hydrothermal pyrite resemble the lead isotopic compositions of the granitic plutons in the west Junggar, but differ from those of pyrite in meta-basalt. The progressive decrease of δ34S values from early-stage pyrite (+0.7 ‰ to +1.4 ‰) to late-stage pyrite (−1.9 ‰ to +0.4 ‰) corresponds to the major gold precipitation processes, which can be explained by gradual decrease of oxygen fugacity and increase of pH with decrease of temperature of a gold-bearing magmatic-hydrothermal system. A relatively stable environment for Au precipitation probably is a key factor controlling the scale of gold deposit, as the ore-forming fluid has enough time to form large gold deposit such the Hatu gold deposit.

Genesis and Formation of the Tuwaishan Gold Deposit in Hainan Island, South China: Implications from H-O-S Isotopes

The Tuwaishan gold deposit is located at the northeastern end of the Gezhen shear zone in the western part of Hainan Island, South China. It is one of a series of similar gold deposits hosted in the Mesoproterozoic basement rocks and structurally controlled by the Gezhen shear zone. The hydrothermal ore-forming period can be divided into quartz-pyrite-arsenopyrite stage, quartz-pyrite-base metal sulfides stage and quartz-carbonate stage. Eleven gold-bearing quartz vein samples yield δDV-SMOW and δ18OV-SMOW values of −75.9‰ to −54.4‰ and +8.1‰ to +13.7‰, respectively, and the corresponding δ18Owater values range from +3.1‰ to +8.7‰. In addition, the pyrite separates from 14 ore samples yield δ34S values of +4.5‰ to +7.9‰. The H-O-S isotopic data, along with fluid properties of the Tuwaishan and other gold deposits along the Gezhen shear zone, suggest that the ore-forming fluid and materials are of metamorphic rather than magmatic origin. Hence, we propose that the Tuwaishan gold deposit is best classified as orogenic gold deposit that resulted from regional metamorphism. Considering that the Mesoproterozoic basement rocks have experienced amphibolite facies metamorphism prior to the gold mineralization, the metamorphic devolatilization of the Ordovician-Silurian rocks at depth would provide a realistic source of fluid, gold and sulfur for the Tuwaishan and other gold deposits of the Gezhen gold belt.

Intermittent Exposure to a Single Bottle of Ethanol Modulates Stress Sensitivity: Impact of Age at Exposure Initiation.

Alcohol use during adolescence is a serious public health problem, with binge drinking and high-intensity drinking being particularly harmful to the developing adolescent brain. To investigate the adverse consequences of binge drinking and high-intensity adolescent drinking, adolescent rodents were intermittently exposed to ethanol through intragastric gavage, intraperitoneal injection, or vapor inhalation. These models revealed the long-lasting behavioral and neural consequences of adolescent intermittent ethanol (AIE) exposure. The present study was designed to characterize a different AIE model, namely, intermittent exposure to a single bottle of 10% ethanol as the only source of fluids on a 2 days on/2 days off (water days) schedule, and to determine whether this AIE exposure model would produce changes in hormonal and neuroimmune responsiveness to challenges of differing modalities. Assessments of ethanol intake as well as blood and brain ethanol concentrations (BECs and BrECs, respectively) in adult male and female rats (Experiment 1) revealed that BECs and BrECs peaked following access to ethanol for a 2 h period when assessed 1 h into the dark cycle. Experiment 2 revealed age differences in ethanol intake, BECs, and BrECs following a 2 h access to ethanol (1 h into the dark cycle), with adolescents ingesting more ethanol and reaching higher BECs as well as BrECs than adults. In Experiment 3, intermittent exposure to a single bottle of 10% ethanol for 10 cycles of 2 days on/2 days off was initiated either in early or late adolescence, followed by an acute systemic immune challenge with lipopolysaccharide (LPS) in adulthood. LPS increased corticosterone and progesterone levels regardless of sex and prior ethanol history, whereas an LPS-induced increase in cytokine gene expression in the hippocampus was evident only in ethanol-exposed males and females, with females who underwent early exposure to ethanol being more affected than their later-exposed counterparts. In Experiment 4, intermittent ethanol exposure in females was initiated either in adolescence or adulthood and lasted for 12 ethanol exposure cycles. Then, behavioral (freezing behavior), hormonal (corticosterone and progesterone levels), and neuroimmune (cytokine gene expression in the PVN, amygdala, and hippocampus) responses to novel environments (mild stressors) and shock (intense stressors) were assessed. More pronounced behavioral and hormonal changes, as well as changes in cytokine gene expression, were evident in the shock condition than following placement in the novel environment, with prior history of ethanol exposure not playing a substantial role. Interleukin (IL)-1β gene expression was enhanced by shock in the PVN, whereas shock-induced increases in IL-6 gene expression were evident in the hippocampus. Together, these findings demonstrate that our intermittent adolescent exposure model enhances responsiveness to immune but not stress challenges, with females being more vulnerable to this AIE effect than males.

Formation of Cu–Au porphyry deposits: hydraulic quartz veins, magmatic processes and constraints from chlorine

Copper–gold porphyry deposits are the world’s main source of copper and a significant source of gold. They consist of vein networks and their surrounding alteration zones. Commonly the deposits are centred on narrow intrusions (stocks), but calling these deposits ‘porphyries’ is unjustified because the name carries little descriptive or genetic value. Extensional veins were formed by hydraulic fracturing of the stocks, at depths where open spaces could not be maintained and where fluid pressure approaches lithostatic pressure. The post-crystallisation timing of the veins is important because it indicates that the host stocks could not have been the direct sources of either metals or ore-forming fluids. In the traditional magmatic model, precursor batholiths, lying at depth, are inferred to be the sources of the Cu and Au in the overlying host stocks. In this model, the batholiths are assumed to have crystallised and produced the mineralising aqueous fluids, Cu and Au. However, in many porphyry deposits, the concept of metal and fluid supply from deeper batholiths is problematic. Neither Cu nor Au is strongly enriched during the crystallisation of silicate magmas, and although hypersaline fluids are a characteristic of Cu–Au porphyry deposits globally, the source of the Cl remains unconstrained. There is little evidence that silicate magmas can release such Cl-rich fluids, and it remains unexplained how elevated levels of Cl may be achieved in a silicate magma. Therefore, the starting assumption that these deposits formed predominantly from magmatic sources and processes is questioned. This study has selectively focused on the roles of rheology, rock mechanics, vein control, metal-enrichment processes and the sources of Cl. Non-magmatic processes may be enough to facilitate strong partitioning of Cu and Au into high-temperature, oxidising, high-salinity, hydrothermal fluids to form Cu–Au porphyry deposits.

Geochemical diversity and tectonic relationships in monogenetic volcanic fields: A case study of the Sredinny Range, Kamchatka

We report, here, the composition and KAr ages of a representative collection of volcanic rocks that erupted within three monogenetic volcanic fields in the active fault zone of the Sredinny Range of Kamchatka: Tigilsky Dol, Mount Oxi massif and Anaunsky Dol. The studied rocks display a wide range of compositions (medium-K, moderate-Mg, high-K, high-Ti and high-Mg basalts, and high-LREE picrobasalts); the high-Mg varieties are confined to faults. Five main periods of volcanic activity were investigated, 4.3–3, 2, 1.5, 1 Ma and from 0.3 to <0.05 Ma. Primitive lavas first emerged on the surface at 3.5 Ma. There was a massive outpouring of high-Mg lavas at 1.5–1 and 0.3 Ma, which could have been related to the formation of the fault zone. This is the first report of rocks in Kamchatka with a high-LREE picrobasaltic composition (1.5 Ma). The Fo content of the olivine phenocrysts reaches 93.2 mol%, which is the highest value known for Quaternary Kamchatka basalts. A very heterogeneous source, even for individual eruptions is indicated by the minor element contents in the olivine (Ni, Mn and Ca); Cr-spinel – olivine paragenesis show that all the rocks studied crystallized in the same temperature range (1111–1292 °C), whereas the oxygen fugacity for the different samples varied from ΔQFM +0.7 to +2.0 log. units. A melt inclusion study showed that the Mg basalts of the Mt. Oxi massif and the high-LREE picrobasalts of Tigilsky Dol had different fluid sources that were enriched and depleted in water and Cl, respectively. We argue that the fluid source for the Mt. Oxi massif was likely the remains of the Pacific slab under the Sredinny Range, whereas, for the high-LREE picrobasalts of Tigilsky Dol, it was the lithospheric lithologies. The low content of S and high content of Cu in the oxidized high-LREE basalts provide additional evidence that they originated from the re-melting of sulfur-poor lithospheric lithologies. Both the fault zone and the lithosphere re-activation in the region are likely linked to the regional stress field.

Timing and origin of skarn-, greisen-, and vein-hosted tin mineralization at Geyer, Erzgebirge (Germany)

AbstractThis contribution presents new insights into the origin and age relationships of the Geyer tin deposit in the Erzgebirge, Germany. Tin mineralization occurs in skarns, greisen, and in cassiterite-bearing fluorite-quartz veins. Skarn alteration replaces marble layers of the Cambrian Jáchymov Group and occurs in two clearly distinct stages. The first skarn stage forms skarnoid textured assemblages of clinopyroxene, garnet, and wollastonite with no tin phases recognized. Garnet U-Pb ages of this skarn stage (~322 Ma) relate the earlier skarn stage to the emplacement of the Ehrenfriedersdorf granite (~324 to 317 Ma). The second stage of skarn alteration is marked by the occurrence of malayaite and cassiterite associated with garnet recording ages of 307 to 301 Ma. Greisen- and skarn-hosted cassiterite-bearing veins provide U-Pb ages in the range of 308 to 305 Ma, relating greisenization and vein formation to the same magmatic-hydrothermal event as the second skarn stage. This suggests that tin mineralization at Geyer is related to a distinctly younger magmatic-hydrothermal event, clearly postdating the Ehrenfriedersdorf granite, which was previously assumed as the source of the tin-rich fluids. Fluid inclusions show salinities in the range of 1.0 to 31.5 % eq. w(NaCl±CaCl2) and homogenization temperatures between 255 and 340 °C. Cassiterite-associated fluid inclusions show indications for heterogeneous entrapment and dilution of hydrothermal with meteoric fluids. Dilution of high-salinity fluids with low-salinity fluids and cooling of the system was probably a decisive process in the precipitation of cassiterite in the Geyer Sn system.

Bulges at vortical outflows

This paper constructs steady solutions of the two-dimensional Euler equations corresponding to a line source of vortical fluid on the impermeable boundary of a quiescent flow. The nonlinear, free-boundary problem is solved by mapping the flow domain to the hodograph plane. A vortex dipole or, equivalently, a source–sink doublet is superposed on the source leading to flow patterns that model the ballooning outflows observed where rivers and straits discharge into the open ocean and in the rotating flow experiments and numerical simulations designed to reflect these observations.

Mineralization process of the Mazhala Au–Sb deposit, South Tibet: Constraints from fluid inclusions, H-O-S isotopes, and trace elements

The Mazhala deposit is a typical Au-Sb deposit in the northern Himalayan orogenic belt that has increasingly attracted worldwide attentions. However, debates remain regarding the source of ore–forming fluid and its evolutionary process. Herein, we investigate the genetic and compositional evolutionary characteristics of different types of pyrite grains in order to better constrain the ore–forming fluid source and ore–forming processes by means of Using in-situ trace and sulfur isotope data of pyrite and inclusion temperature and H-O isotope data of quartz. Based on the occurrence and morphological features of pyrite, four types of pyrite (Py0, Py1, Py2, and Py3) have been identified. The framboids of pyrite Py0 have high contents of Au, Ag, Cu, Pb, and Sb, with Co/Ni < l, and their δ34S values range from −34.0‰ to −19.3‰, indicating a sedimentary-diagenetic origin. Py1 pyrite exhibits stark core-rim structure. The contents of Sn, Ti, Be and W in Py1c are higher, with Co/Ni > 1. The δ34S of Py1c ranges from 0.30 to 3.9‰ (mean = 1.7‰), indicating a magmatic hydrothermal transformation origin. Py1r, Py2, and Py3 differ greatly in pyrite morphology and trace element contents, with Co/Ni < 1, indicating as hydrothermal sedimentary transformation origin. The δ34S values of Py1r, Py2, and Py3 vary from 1.4 to 6.50‰, interpreted as the presence of metamorphic sulfur sources. The δ34S values of Py1-Py2-Py3 firstly increases and then decreases, indicatinga fluid mixing process. The Mazhala ore–forming fluid is typical of low temperature (270–291 °C), low salinity (1.1–5.0 wt%NaCl equiv) and CO2-enrichment, with H-O isotopic compositions of quartz resembling magmatic and/or metamorphic water, which makes us to infer a mixture of magmatic and/or metamorphic water source for the Mazhala ore-forming fluid. The early pyrite grains were dissolved and reprecipitated under the action of fluid. In the process of multistage hydrothermal interaction, Au and other trace elements were released from the primary pyrite lattice into the fluid, forming the gold–bearing ore–forming fluid. Separation of fluid phase coupled with significant change in the pH value of fluid prompted the co-precipitation of Au and Sb to form the Mazhala Au-Sb deposit.

Hydrothermal circulation at 1.8 Ga in the Kiruna area, northern Sweden, as revealed by apatite geochemical systematics

The Kiruna area in northern Sweden hosts the classic Kiruna iron-oxide-apatite (IOA) deposit. The area has experienced complex tectonic processes, including basin formation, inversion, and hydraulic fracturing events from ∼1.9 Ga and possibly down to ∼1.5 Ga. However, the nature, timing and links of hydrothermal events related to this tectono-thermal evolution are unclear, impairing our full understanding of IOA formation processes. Here, we use multiple analytical methods to study apatite from the Kiirunavaara orebody. Electron microscopy, cathodoluminescence images, and rare earth element contents of the studied apatite indicate alteration by hydrothermal fluids. U-Pb Tera-Wasserburg lower intercept age of the altered apatite is 1800 ± 36 Ma, indicating a contemporaneous hydrothermal event in the central Kiruna area during coeval basin inversion. Sr isotopes obtained in these altered apatites, ranging from 0.709 to 0.713, may represent intermediate Sr isotope values between primary apatite and secondary fluid resetting. The relatively high but scattered 87Sr/86Sr ratios suggest that country rocks of the IOA deposits and other regional intermediate-felsic igneous rocks with old or enriched components are most likely the source of the fluids. Previous studies have revealed two hydrothermal events in the IOA ores at roughly 1.73 Ga and 1.63 Ga. Thus, fluids sourced from the host rocks of the regional IOA deposits and regional granitoids have circulated episodically at 1.80 Ga, 1.73 Ga, 1.63 Ga and possibly 1.5 Ga in the Kiruna area and have partly redistributed rare earth elements formed during the primary 1.88 Ga IOA formation event.

Iron, boron, and sulfur isotope constraints on the ore-forming process of subseafloor replacement-style volcanogenic massive sulfide systems

The well-preserved Ashele subseafloor replacement-style volcanogenic massive sulfide (VMS) deposit in the Central Asian Orogenic Belt comprises two stages of Cu mineralization, i.e., early massive sulfides dominated by colloform and euhedral pyrite intergrown with chalcopyrite and sphalerite, which were replaced by late vein-dominated chlorite-chalcopyrite assemblages. In this study, a combined systematic Fe, B, and S isotope investigation was first applied to investigate the sulfide precipitation processes and the relative proportion of fluid sources in different alteration and mineralization stages of the Ashele deposit. Boron isotopes of Mg-rich tourmaline (δ11B from −5.57‰ to −2.73‰, average (avg.) −4.23‰) indicate significant seawater (∼19%) participated during the formation of massive sulfides. A two-component mixing model is used to estimate the contribution of seawater and igneous sulfur to the total sulfur budget, and the results show the increasing contribution of magmatic sulfur from the early (35%) to late (76%) stages. In addition, δ56Fe values of pyrite gradually increase from the massive ore (−0.46‰ to −0.02‰, avg. −0.24‰), quartz-pyrite (−0.09‰ to 0.07‰, avg. −0.01‰), chlorite-chalcopyrite-quartz-pyrite (0‰ to 0.21‰, avg. 0.08‰) to the quartz-sericite zone (−0.02‰ to 0.29‰, avg. 0.14‰), which is likely related to the different extent of isotopic exchange and formation temperature, and could be used in the exploration of VMS systems. The new two-stage ore-forming model shows that in the early stage, rapid mixing of hydrothermal fluid from underlying magma chamber with abundant cold seawater led to rapid deposition of pyrite and associated Cu mineralization under relatively oxidized condition, and long-term hydrothermal activities in relatively closed systems would promote the formation of upper massive ores, which resulted in an equilibrium system between pyrite, chalcopyrite, and associated fluid with wide ranges of δ56Fe in pyrite (−0.46‰ to −0.02‰) and chalcopyrite (−1.56‰ to −0.49‰). The late hydrothermal activities in relatively open system would contribute to stringer sulfides or stockworks underlying the massive ore in relatively reduced conditions with heavier Fe isotope compositions in pyrite (−0.09‰ to 0.29‰) and chalcopyrite (−0.60‰ to −0.04‰). Overall, our study demonstrates that the coupling of B, Fe, and S isotopes could be a useful tool to indicate long-term subseafloor infilling and replacement processes for subseafloor replacement-type VMS deposits, which are the prerequisite to form large-tonnage VMS deposits.

The magmatic-hydrothermal transition in P-rich pegmatitic melts: Crystal-melt-fluid interactions recorded by phosphate minerals

Rare-element pegmatites are the crystallization product of melts strongly enriched in incompatible elements. Some of these elements, e.g., Li, B, P, F, and H2O, function as melt structure modifiers, allowing such melts to reach unusually low crystallization temperatures and regulating the saturation of aqueous-carbonic fluids from the melt. However, the timing of fluid saturation is highly debated, and the processes that mark the magmatic-hydrothermal transition in rare-element pegmatites are still elusive. The crystallization sequence of phosphate minerals can be used to assess the timing and nature of fluid-related processes in pegmatitic systems. In the Buranga pegmatite, western Rwanda, magmatic phosphates are replaced by (hydrous) alkali-rich phosphates and later by strongly hydrated phosphates as the dike cools. This reaction series indicates a disequilibrium in the crystal-melt-fluid system and records complex fluid-rock interactions during dike consolidation. This contribution compares these interactions with the fluid record preserved in fluid inclusions in the main phosphates of the crystallization sequence. Three major fluid inclusion types are observed, aqueous-carbonic (mostly-two-phase, L-V), carbonic-aqueous (two-phase, V-L, or three-phase, L-L-V), and crystal-rich inclusions (multiphase, L-V-Solids). Crystal-rich fluid inclusions in trolleite [Al4(PO4)3(OH)3], the last primary phosphate to precipitate from the melt, show a paragenesis of solid phases similar to the secondary phosphates observed in the dike. LA-ICPMS analyses of individual fluid inclusions show high concentrations of Na and K, with some content of Li, Rb, Cs, B, Fe, and Mn in the fluid. A similar composition is present in all inclusion types within the same mineral. Crystal-rich fluid inclusions demonstrate that during the magmatic-hydrothermal transition, primary phosphates react with the fluid in the presence of melt to generate secondary phosphates. No evidence of external fluid sources has been observed during the magmatic-hydrothermal transition. The fluid inclusion record shows that the fluid salinity is kept constant due to fluid-mineral interactions and corroborates the hypothesis that fluid-soluble elements are internally remobilized in the melt-crystal-fluid system during the magmatic-hydrothermal stage. These interpretations have implications for the general evolution of P-rich pegmatitic melts and the mineralization of Nb and Ta in these systems.

Role of aspirin, beta-blocker, statins, and heparin therapy in septic patients under mechanical ventilation: a narrative review.

Sepsis is the main cause of death among patients admitted to intensive care units. Management of sepsis includes fluid resuscitation, vasopressors, intravenous antimicrobials, source control, mechanical ventilation, and others. New insights into the potential benefits of non-antimicrobial drugs in sepsis have evolved based on the pathophysiology of the disease and the mechanism of action of some drugs, but the findings are still controversial. In this study, we aimed to evaluate the effect of beta-blockers, aspirin, statins, and heparin as adjunctive treatments in septic patients under mechanical ventilation with non-cardiovascular diseases and their effect on mortality. We searched PubMed with relevant keywords (beta-blockers, aspirin, statins, or heparin, and critically ill or sepsis) for the last 10 years and some personal collection of relevant articles, and then we assessed studies according to prespecified inclusion and exclusion criteria. Our results show that beta-blockers, aspirin, and heparin may have promising feedback on reducing mortality. However, new well-controlled, randomized, multicenter studies are needed to confirm that, and multiple issues regarding their usage need to be addressed. On the other hand, the feedback regarding the effectiveness of statins was not as strong as that of the other drugs studied, and we suggest that further research is needed to confirm these results.

The B isotopic signature of serpentine from obducted ophiolites: Mixing of fluids and tectonic implications

Obducted ophiolites expose oceanic lithosphere slivers in suture zones. The few previous studies focusing specifically on the serpentinization of the ultramafic part of ophiolites mostly concluded that serpentinization was driven by seawater. Recent developments in B isotope geochemistry have enabled the tracking of fluid source(s) in serpentinites, suggesting δ11B values above +10‰ mostly reflect seawater hydration and δ11B values below +10‰ mostly reflect hydration by subducted crust-derived metamorphic fluids. In this study, we further investigate the fluid sources recorded by ophiolitic serpentinites by presenting B isotopic geochemistry for seventeen samples from well-characterized ophiolites in Guatemala, Iran, and Brazil. The samples from Guatemala and Iran are from fossil Supra Subduction Zones (SSZ), while samples from Brazil represent a fossil Ocean-Continent Transition (OCT). Most of the samples display the pseudomorphic mesh matrix and bastite microtexture typical of serpentinites. Nine of the samples are either totally (both microtextures) or partially (one microtexture only) out of isotopic equilibrium, with δ11B variations of up to 18‰ within individual samples/textures. Among the samples with a narrow δ11B range (i.e., at isotopic equilibrium), those from a fossil OCT ophiolite have δ11B ranging from +3.8 to +23.2‰, which is broadly consistent with serpentinization by seawater. In contrast, serpentinites from fossil SSZ ophiolite have δ11B straddling 0‰, ranging from −7.7 to +13.5‰. These data indicate that seawater alone cannot be responsible for serpentinization of these ultramafic rocks, but rather either subducted crust-derived metamorphic fluids, or a mixture of seawater and subducted crust-derived metamorphic fluids. This interpretation agrees with the recent suggestions that SSZ ophiolites possibly represent fossil forearc lithosphere.

Soft computing-based predictive modeling of flexible electrohydrodynamic pumps

Flexible electrohydrodynamic (EHD) pumps have been developed and applied in many fields due to no transmission structure, no wear, easy manipulation, and no noise. Physical simulation is often used to predict the output performance of flexible EHD pumps. However, this method neglects fluid–solid interaction and energy loss caused by flexible materials, which are both difficult to calculate when the flexible pumps deform. Therefore, this study proposes a flexible pump output performance prediction using machine learning algorithms. We used three different types of machine learning: random forest regression, ridge regression, and neural network to predict the critical parameters (pressure, flow rate, and power) of the flexible EHD pump. Voltage, angle, gap, overlap, and channel height are selected as five input data of the neural network. In addition, we optimized essential parameters in the three networks. Finally, we adopt the best predictive model and evaluate the significance of five input parameters to the output performance of the flexible EHD pumps. Among the three methods, the MLP model has exceptionally high accuracy in predicting pressure and flow. Our work is beneficial for the design process of fluid sources in flexible soft actuators and soft hydraulic sources in microfluidic chips.

Discovery of the large-scale Eocene Xiwu Pb–Zn–Ag deposit in the Tethyan Himalaya: Geochronology, geochemistry, and C–H–O–S–Pb–Sr–Nd isotopes

The known Pb–Zn–Sb–Au polymetallic deposits in the Himalaya mainly formed during the main-collisional convergence (65–41 Ma) and post-collisional crustal extension (25–0 Ma) tectonic settings. Here, we report the discovery and genesis of the large-scale Eocene Xiwu Pb–Zn–Ag deposit that formed during the late-collisional tectonic transition stage (40–26 Ma) in the eastern Himalaya. The surrounding ore-hosting rocks are mainly low-grade metamorphosed Jurassic clastic rocks and Early Cretaceous diabase. The most important ore-controlling structures are NE–SW thrust faults. The ore minerals include large amounts of galena, sphalerite, tetrahedrite and siderite, with minor chalcopyrite, pyrite, arsenopyrite, calcite and quartz. In this contribution, we analyzed the S–Pb isotopes of sulfides, fluid inclusions and the C–H–O–Pb–Sr–Nd isotopes of nonmetallic minerals. The results indicate that the ore-forming materials originated from deeper metamorphic rocks of the Greater Himalayan Crystalline Complex. This study infer that the source of ore-forming fluids was mainly metamorphic fluids with moderate temperatures and salinities, and S and C were mainly derived from microbial sulfate reduction and the decarboxylation of organic matter, respectively. The main ore-forming mechanism is fluid mixing between the deep ore-bearing metamorphic fluids and shallow formation waters. The Sm–Nd isotopic age of siderite is 37.4 ± 1.1 Ma, which is slightly younger than the zircon U–Pb age of the Zhunba leucogranite (38.9 ± 0.4 Ma) but is consistent with the main epoch of early prograde metamorphism (43–36 Ma) in the Himalaya. We propose a new metallogenic model for Himalayan Pb–Zn–Ag deposits that can greatly promote ore prospecting. The genetic type of the Xiwu deposit is a clastic-dominated subtype of sediment-hosted Pb–Zn deposits.

Fluid evolution and metallogenesis of the Zhangjiapingzi gold deposit in mianning, Sichuan province: constraints from fluid inclusion studies

Introduction: The Zhangjiapingzi gold deposit, located at the western margin of the Yangtze Craton and controlled by the Jinhe-Chenghai deep fault, is a newly discovered super-large gold deposit in the Danba-Mianning metallogenic belt. The gold ore bodies are hosted in the Middle Triassic (T2) altered dolomite (Dm), and have two types of mineralization: altered rock type and quartz vein type. Previous studies on this deposit are rare, especially on the ore-fluid characteristics, which limit the understanding on the ore genesis.Methods: This study focused on fluid inclusions in quartz from altered rocks, and used microthermometry and laser Raman spectroscopy to investigate the properties and sources of ore-forming fluids, and to determine the ore genetic type.Results and discussion: The results show that the fluid inclusions are mainly CO2-H2O-NaCl inclusions, with medium temperature (220–300°C), low salinity (&amp;lt;10%), medium-low density (0.79–1.01 g/cm3) and high contents of CO2 and CH4, resembling typical orogenic gold ore fluids. We suggest that the Zhangjiapingzi is best classified as orogenic type, and our findings provide new insights into the fluid origin and metallogenesis of orogenic gold deposits in the Danba-Mianning metallogenic belt.