Stages Of Mineralization Research Articles

Geneses of multi-stage carbonate minerals and their control on reservoir physical properties of dolomitic shales

The formation and distribution of carbonate minerals have important influences on reservoir development. The dissolution-precipitation effect plays an important role in controlling the reformation of reservoir physical properties. High-quality source rocks with abundant reserves exist in the Lower Permian Fengcheng Formation, Junggar Basin, China, and the basin reservoir contains a large amount of carbonate minerals. Multi-stage cementation and dissolution of these carbonate minerals have important influences on diagenesis-porosity evolution of the reservoirs. Because of the coupled influences of deep fluid transformation and volcanic activity in the diagenetic evolution of the Fengcheng Formation, it has experienced a complex evolution of carbonate minerals. In this study, through core observation, thin section, X-ray diffraction mineral composition, carbon and oxygen isotope, fluid inclusion homogenization temperature, and laser Raman and cathodoluminescence analysis, the material sources, development period, dissolution-precipitation reactions, and transformation mechanisms of carbonate minerals in the diagenetic evolution of the Fengcheng Formation reservoir were evaluated in detail. Finally, the controlling effect of multi-stage cementation of carbonate minerals on the reservoir physical properties was determined. The results showed that there are three stages of carbonate minerals in the Fengcheng Formation. The material source of the early carbonate was mainly terrigenous debris, and the formation temperature range was 30–70 °C. The material source of middle-late carbonate minerals was mainly decarboxylation of organic acid, and the formation temperature was 60–110 °C. In addition, some were generated through hydrothermal metasomatism at high ambient temperatures, up to 120 °C. In areas where early carbonate minerals are well developed, a large number of microcracks was more likely to form under the influence of tectonic movements, resulting in high-quality reservoirs. The formation of late carbonate minerals, which is the main reason for reservoir densification in the later stage of diagenesis, resulted in poor reservoir physical properties. This study provides information useful for predicting the distribution areas of favorable reservoirs in the Fengcheng Formation, and a theoretical basis and guidance for improving the accuracy of shale oil exploration and development.

Geology, geochemistry and genesis of the Suolong gold deposit in the West Qinling Orogen, Gansu Province, China

The Suolong gold deposit is in the eastern part of the Min‐Li metallogenic belt within the West Qinling Orogen. It is hosted in Lower Permian sandstone and siltstone. The gold mineralization is fault‐ and joint‐controlled. Four hydrothermal stages of mineralization, including the sulphide‐quartz stage, the arsenian pyrite‐quartz stage, the polymetallic sulphide‐quartz‐carbonate stage and the sulphide‐carbonate stage, were identified. Here we report results from fluid inclusion studies and C‐H‐O‐S‐Pb isotopes to get insight into the characteristics of mineralization and ore genesis. Fluid inclusion results indicate that the ore‐forming temperatures and salinities were in the range from 135 to 419°C and 0.18 to 15.27 wt.%, respectively. The δ34S values of pyrite, arsenopyrite and pyrrhotite varied in the 5.3‰–11.4‰ range, suggesting that sulphur originated from stratum sulphur. Lead isotopic compositions of sulphide (206Pb/204Pb = 18.344–18.418, 207Pb/204Pb = 15.628–15.701, 208Pb/204Pb = 38.508–38.743) indicate an upper crust source for Pb. The δ18OH2O‐SMOW and δDSMOW values range from 1.01‰ to 10.31‰ and −116.0‰ to −29.2‰, respectively, indicating that metamorphic water was the source of ore‐forming fluids. The δ13CPDB values (−11.4 to −2.1‰) show that the carbon in the ore‐forming fluids originated predominantly from a deep source. Our data suggest that the Suolong gold deposit is an orogenic gold deposit related to the subduction of an oceanic plate along the Mianlue belt.

Two stages of porphyry Cu mineralization at Jiru in the Tibetan collisional orogen: Insights from zircon, apatite, and magmatic sulfides

Continental collision−related porphyry copper (Cu) deposits provide significant global copper resources, but their genesis remains controversial because it is not clear whether remelting of remnant arc-derived lower-crustal Cu-rich cumulates is critical to their formation. We investigated zircon and apatite compositions of the Jiru porphyry Cu deposit in the Gangdese belt of southern Tibet, which is characterized by weaker early Eocene mineralization and more pronounced Miocene mineralization. Our data demonstrate that apatite hosted in zircon can record the volatile compositions of magma before fluid exsolution. Zircon-hosted apatites from the early Eocene granite that have low XF/XCl ratios (≤3) and are interpreted to have crystallized from volatile-undersaturated magma have Cl contents of 0.96−2.14 wt% (1.86 ± 0.38 wt%; n = 15) and SO3 contents of 0.01−0.14 wt% (0.08 ± 0.04 wt%; n = 15). In contrast, zircon-hosted apatites from the Miocene porphyry that have low XF/XCl ratios (≤10) and are interpreted to have crystallized from volatile-undersaturated magma have Cl contents of 0.40−0.56 wt% (0.47 ± 0.06 wt%; n = 11) and SO3 contents of 0.20−0.92 wt% (0.59 ± 0.29 wt%; n = 11). In addition, the early Eocene magma was relatively reduced (ΔFMQ = 0.86 ± 0.55, where FMQ is fayalite-magnetite-quartz) compared with the oxidized Miocene magma (ΔFMQ = 2.04 ± 0.43). The contrasting magmatic oxidation states and apatite/melt S contents were likely critical in controlling the different scales of Cu mineralization during the early Eocene and Miocene, as more highly oxidized magma can dissolve much larger amounts of sulfur and metals (e.g., Cu). Melt Cl content may not play a critical role in magma fertility, since the Jiru early Eocene granite had higher melt Cl contents than the Miocene porphyry. Magmatic sulfides (pyrrhotite, chalcopyrite, and pyrite) were not recognized in the Miocene zircons but did occur in the early Eocene zircons, and these sulfides were demonstrated to have crystallized before fluid exsolution in the shallow magma reservoir. The Jiru early Eocene magmatic sulfide saturation might not have enhanced the amount of copper available to hydrothermal fluids during the early Eocene. Late-stage sulfide saturation in the previous arc magmas might reduce the potential for collision-related porphyry Cu mineralization that is associated with remelting of the previous arc lower crust.

Magnetite‐fluorapatite geochemistry and monazite U–Pb geochronology of the Mohuldih uranium deposit, Singhbhum Shear Zone, eastern India

In this study, textural relations coupled with mineral chemistry of hydrothermal magnetite, fluorapatite, monazite and allanite from the Mohuldih uranium deposit in the Singhbhum Shear Zone (SSZ) is used to characterize the nature of the fluid during various events of alteration and uranium precipitation. These minerals have two distinct textural types, the earlier of which are coeval with the uraninite mineralization. The later type formed during subsequent hydrothermal overprint as a result of coupled dissolution‐reprecipitation of earlier fluorapatite and mobilization of light rare earth elements. Uranium‐lead dating of texturally‐constrained hydrothermal monazite grains yields two major concordant age clusters at 1855 ± 7 Ma and 963 ± 10 Ma and several discordant analyses. Two spot analyses furnish concordant ages of 1656 ± 33 Ma and 1438 ± 35 Ma that are identical within error of the 207Pb/206Pb ages (1628–1643 Ma and ca. 1392 Ma) of several discordant data points. Similar ages have been reported by other studies from the rocks of the SSZ and are therefore considered to be geologically meaningful. The oldest age of ca. 1855 Ma obtained from the texturally early core regions of monazite corresponds to the earliest stage of uraninite mineralization. The two main alteration types can be interpreted based on the known metamorphic events in the SSZ. A combination of high‐temperature calcic iron ± sodic and high‐temperature potassic iron alteration accompanied the M1 metamorphic event and the low‐temperature silicification/K‐Al alteration during the M2 metamorphic event. A comparative study between our data on magnetite and fluorapatite compositions with those from global iron oxide‐Cu‐gold (IOCG) and iron oxide‐apatite deposits classifies Mohuldih as an IOCG‐type deposit.

Зміни розрахункових індексів біохімічних показників сироватки крові щурів різного віку після заповнення дефекту в метафізі стегнової кістки алогенними кістковими імплантатами, насиченими мезенхімальними стовбуровими клітинами

The purpose of the study was based on the analysis of calculated biochemical parameters of mineralization in the blood serum of laboratory rats to evaluate the course of metabolic processes in bone tissue after filling a defect of critical size in the metaphysis of the femur with allogeneic bone implants saturated with mesenchymal stem cells. Materials and methods. Indicators of mineralization of bone tissue in the blood serum of white rats were studied (the content of total protein, calcium, alkaline and acid phosphatase activity), the ratio of alkaline to acid phosphatase activity, as well as the degree of mineralization, were calculated. Results and discussion. In 3-month-old rats with alloimplants without mesenchymal stem cells on the 90th day, a decrease in the degree of mineralization was observed, which reflects the final stages of bone tissue remodeling by 1.13 times compared to the level of this in animals of a similar age and conditions of filling the defect on the 14th day (р = 0.008) and 1.12 times compared to the data on the 28th day of the experiment (р = 0.008). In 3-month-old rats with alloimplants saturated with mesenchymal stem cells, a decrease in the degree of mineralization on the 90th day was determined compared to that in experimental rats of a similar age and defect filling conditions on the 14th day by 1.13 times (p = 0.008), and compared with the data of the similar group on the 28th day – 1.14 times (p = 0.008), which reflects the delay in the course of the full stage of bone tissue remodeling due to the use of mesenchymal stem cells. The ratio of serum alkaline to acid phosphatase activity in 3-month-old rats with alloimplants saturated with mesenchymal stem cells was 1.32 times lower on the 14th day compared to the data of a group of the same age with alloimplants without mesenchymal stem cells (p = 0.008), and on the 90th day – by 1.12 times (p = 0.008), which also indicates a delay in the early stages of bone tissue mineralization due to the use of mesenchymal stem cells as part of alloimplants. In 12-month-old rats without the use of mesenchymal stem cells, on the 90th day, there was a decrease in the degree of mineralization by 1.10 times, in accordance with the level of this in a group of rats of a similar age and conditions of defect filling on the 14th day (р = 0.008) and by 1.09 times compared to that on the 28th day (p = 0.008), from which we can conclude about a progressive decrease in the activity of the final stages of bone tissue remodeling. The ratio of the activity of alkaline and acid phosphatase in 12-month-old rats with alloimplants without mesenchymal stem cells on the 90th day was significantly inferior to that in the corresponding 3-month-old animals by 1.12 times (p = 0.008), which indicates a lower activity of the initial stages of bone tissue mineralization in the late stages of defect healing. This indicator progressively decreased during the experiment. Thus, on the 28th day, it was 1.12 times smaller than on the 14th day, and on the 90th day – by 1.53 times less, in accordance with the data on the 14th day (p = 0.008) and by 1.36 times compared to that on the 28th day (p = 0.008). Conclusion. Treatment of experimental rats with a critical size defect in the femoral metaphysis with alloimplants saturated with mesenchymal stem cells, especially in the early stages, leads to a slowing down of bone tissue remodeling processes

Fluid evolution and metallogenic mechanism of the Xianghualing skarn-type Sn deposit, South China: Evidence from petrography, fluid inclusions and trace-element composition of cassiterite

The Xianghualing Sn-polymetallic deposit is a large skarn-type Sn deposit located in the Nanling polymetallic metallogenic belt, South China. The ore bodies are controlled by NE-trending faults and mainly hosted in the contact of Middle Devonian carbonate rock and granite. The Xianghualing deposit is divided into four mineralization stages, and two stages of Sn mineralization are identified. The mineralization stages from early to late include stage I (prograde stage), stage II (retrograde stage), stage III (cassiterite-magnetite-arsenopyrite-topaz-quartz stage), stage IV (sphalerite-galena-pyrite-chalcopyrite-quartz-calcite stage). Stage II is the initial stage of Sn mineralization where only minor cassiterite precipitates, and stage III is the main Sn mineralization stage where abundant cassiterite precipitates. On this basis, fluid inclusion microthermometry and Raman spectroscopy analyses were carried out for ore and/or gangue minerals at different stages. In addition, trace element composition analysis was also conducted on cassiterite. These data can contribute to reveal the fluid properties, evolution and formation mechanism of Xianghualing deposit. Three types of fluid inclusions were identified in different mineralization stages, including halite-bearing multi-phase inclusions (Type B), liquid-rich two-phase inclusions (Type L) and vapor-rich two-phase inclusions (Type V). Garnet (stage I) contains Type B inclusions and Type V inclusions, with homogenization temperatures and salinities of 511–549 °C, 37.6–48.9 wt% NaCl equiv. and 551–559 °C, 4.0–5.1 wt% NaCl equiv., respectively. Topaz (stage II) contains Type L inclusions with homogenization temperatures of 408–445 °C and salinities of 9.5–12.4 wt% NaCl equiv. Cassiterite (stage III) contains Type L inclusions with homogenization temperatures of 368–417 °C and salinities of 8.7–11.5 wt% NaCl equiv. Quartz (stage IV) contains Type L inclusions with homogenization temperatures of 162–227 °C and salinities of 2.6–5.0 wt% NaCl equiv. The temperature and salinity of the fluid from stage I to stage II decreased significantly, recording intense meteoric water mixing. The temperature of the fluid decreased from stage II to stage III, while the salinity changed little, indicating that, except for minor meteoric water mixing, cooling of fluid is predominant. The temperature and salinity of the fluid from stage III to stage IV continued to decrease, recording the further mixing of meteoric water. From stage II to stage III, the evolution temperature of the fluid is basically consistent with the temperature indicated by trace elements (Nb, Ta, Ti) of cassiterite in the two stages. Fluid mixing may be the predominant mechanism for the minor Sn mineralization occurred in stage II. Fluid cooling may be the predominant mechanism for the abundant cassiterite precipitation in stage III, which is accompanied by redox reactions of Sn (II)-Cl complexes with As (III) and/or CO2 as potential oxidants, and acid neutralization of carbonate rocks. Combined with the cassiterite composition, it is indicated that the ore forming fluid of the Xianghualing deposit mainly derived from the highly evolved granitic magma in the region, and the genesis of cassiterite is consistent with that of typical skarn-type Sn deposits.

Mechanisms of ore formation in Silurian (Caledonian) scheelite deposits of the Nanling Range, South China: A case study from the Pingtan W deposit

The Pingtan scheelite deposit is a newly-discovered Caledonian W deposit situated in the northwestern portion of the Miao’ershan granitic batholith in the Nanling Range. The W mineralization can be divided into three stages, the altered granite-scheelite stage (I), the quartz-scheelite stage (II) and the quartz-sulfide stage (III). This contribution characterizes the mechanisms of ore formation of the deposit using fluid inclusion microthermometry, H-O isotopes, and in situ S isotopes. Fluid inclusion microthermometry demonstrates that the scheelite mainly formed at moderate to high temperatures (∼260–380 °C for stage I and ∼ 240–300 °C for stage II). The inclusions were trapped at maximum pressures of ∼ 140 MPa, which corresponds to a maximum depth of ∼ 5.3 km. Homogenization temperatures of the inclusions decrease slightly from stage I to stage II mineralization, and more drastically from stage II to stage III, whereas their salinity decreases gradually during the entire mineralization process. Raman spectroscopy indicates that fluid inclusions in stages I and II contain CO2, CH4, and N2, whereas those in stage III mainly contain H2O. The presence of native bismuth, pyrrhotite, and marcasite, and the presence of CH4-bearing fluid inclusions suggest reduced ore-forming conditions during Stages I and II. The δ34SCDT value (+0.8 to + 5.3 ‰, average 3.2 ‰) of sulfides and the δ18Ovsmow value of ore-bearing quartz, which decreases from Stage I (δ18Ovsmow = +5.1 to + 6.3 ‰) to Stage III (δ18Ovsmow = − 1.5 ‰ to + 0.6 ‰), as well as the presence of abundant fluid inclusions with daughter minerals in the first two stages, supports a magmatic origin for the ore-forming material, with exogenic fluid input after the tungsten mineralization stage. Based on the results of this contribution, boiling may be the dominant mechanism for the formation of W deposits in the Nanling Range.

Fluid evolution and origin of the Tamazert fluorite deposits, Moroccan High Atlas

This study focuses on the origin of fluorite ore deposits that are associated with the Eocene alkaline igneous suite of the Tamazert complex in the Moroccan High Atlas. Based on field observations and mineralogy, two major ore styles were identified: 1) a disseminated purple fluorite in aegirine-rich nepheline syenites (stage 1) and 2) a banded purple-white fluorite ore in karstic cavities and veins hosted in the Jurassic carbonate (stage 2). Both fluorite mineralization stages are commonly accompanied by calcite. The distribution of fluorite deposits at the peripheries of syenite and the surrounding Jurassic carbonates suggests the development of long-lived hydrologic systems around the shallow intrusion. Based on fluid inclusion, Rare Earth Elements and Yttrium (REY), and C–O isotopic constraints, this study reveals that different fluid systems were responsible for the deposition of fluorite ores in and around the Tamazert alkaline igneous complex. The disseminated interstitial fluorite precipitated from a F-rich magmatic-hydrothermal fluid, which exsolved from the highly evolved alkaline-silicate melt and was subsequently altered by Na–Ca metasomatic brines. Vein-type fluorite deposits hosted in the Jurassic carbonates precipitated from low salinity (1.6–8.5 wt% NaCl equiv.) and heated (Th = 118–157 °C) meteoric fluids, which migrated in response to the heat flow around the shallow intrusion. Fluid cooling, fluid interaction with Jurassic carbonates, and pressure fluctuations were the most important fluorite deposition mechanisms. The evolved melt provided F and REY for the interstitial fluorites, whereas meteoric fluids leached F− from syenites and other F-bearing igneous rocks. Based on the fractionation pattern, the REY inventory of the vein fluorites was acquired by interaction of meteoric fluids with Jurassic carbonates.

Thermal history of Carlin-type gold deposits in Yukon (Canada) as revealed by organic matter geothermometry, clumped isotope data, fluid inclusion microthermometry, and apatite fission-track analyses

Sediment-hosted gold deposits in central Yukon have most of the diagnostic characteristics of Carlin-type gold deposits in Nevada. This study combines organic matter geothermometry with fluid inclusion microthermometry, clumped isotope data (Δ47) for late ore-stage hydrothermal calcite, and apatite fission-track analyses to constrain the thermal evolution of Carlin-type gold zones in central Yukon. The Tmax parameter derived from pyrolysis analyses indicates that organic matter is overmature and records regional temperatures of > 150 °C. Calcite and fluorite associated with the waning stage of mineralization at ca. 74 Ma have mean fluid inclusion homogenization temperatures of 123–173 °C, with an average salinity of 4.8 wt.% NaCl equiv. These temperatures overlap values of 91–162 °C determined from calcite clumped isotope measurements and are similar to data from Carlin-type deposits in Nevada. Fluid mixing is suggested by a variation of the isotopic composition of the fluid in equilibrium with calcite, with the higher temperature end-member having higher δ18OH2O values. In thermal models based on Tmax, fluid inclusion microthermometry, clumped isotope measurements, and apatite fission-track data, a higher temperature event at approximately 220 °C is consistent with pyrobitumen reflectance measurements. This event is either related to maximum tectonic burial prior to mineralization or to the flow of acidic hydrothermal fluids early in the main ore-stage. Each analytical technique used in this study is independent of the others and records part of the thermal and chemical evolution of the Yukon Carlin-type gold deposits and their host rocks.

Textural and LA-ICP-MS trace element analyses reveal co-enriched Au-Sb-W metallogeny in the Woxi deposit, west Jiangnan Orogen, South China

It is well-known that tungsten and antimony are commonly enriched in the gold deposit and occur as Au-Sb or Au-W deposits. However, the Woxi deposit, located in the West Jiangnan Orogen of South China, is remarkably co-enriched in the Au-Sb-W elemental association. This deposit is characterized by multistage Au mineralization and reactivation of structures developed in the Neoproterozoic metamorphic rocks, but the detailed mechanism of its co-enriched Au-Sb-W metallogeny is still unclear. Here, we perform detailed petrographic observations and ore mineral textural and pyrite compositional analyses by using SEM and LA-ICP-MS to constrain ore-forming physiochemical conditions and to decipher the Au-Sb-W metallogenic mechanism in the Woxi deposit. The Woxi deposit consists of nine auriferous quartz lodes in the shape of stratiform, tabular, and lenticular, which are surrounded by alteration halos in the Neoproterozoic slate. These orebodies are distributed along the bedding-parallel fracture zones of the EW-striking and N-dipping in the purplish red slate of the Madiyi Formation, below the regional EW-striking Woxi fault. Four stages of hydrothermal mineralization and alteration processes could be recognized in the Woxi. Stage 1 occurs in bleached slate, and consists of euhedral, porous, and coarse auriferous pyrite (Py1), with slight arsenopyrite, siderite, and rutile. Stage 2 mainly consists of subhedral to euhedral and compositional zoning auriferous pyrite (Py2) and scheelite (Sch1), with slight wolframite and apatite hosted in quartz veinlets and native gold enclaved in Sch1. Stage 3 is characterized by scheelite (Sch2) and stibnite, with slight native gold and dendritic-shaped anhedral auriferous pyrite (Py3) hosted in quartz veins. Stage 4 features a quartz-calcite-barite-chlorite mineral assemblage that occurred as veinlets, or in the pressure shadows of Py1. Gold is mainly incorporated in the three stages (S1 to S3) of arsenian pyrite (Py1to Py3) as invisible gold and, to a lesser extent, formed visible native gold at late S2 and S3, tungsten mineralization occurs mainly as scheelite (Sch1) and wolframite at S2, with a minor amount of scheelite (Sch2) at S3, and antimony mineralization is mainly occurred as stibnite at S3. Furthermore, invisible gold most likely occurs as nanoscale particles of Au-Bi-Pb-bearing tellurides in Py1, and may be hosted in the structurally bounded lattice of Py2 and Py3.The SEM study presents highly developed dissolution-reprecipitation microstructures in hydrothermal minerals, such as pyrite, arsenopyrite, wolframite, scheelite, and apatite. Mineral paragenesis and pyrite trace element signatures suggest the ore fluid is characterized by elevated fO2, low pH and high temperature in S1, decreased fO2, medium pH and medium temperature in S2, and elevated fO2, high pH and low temperature in S3. The evolution of the physicochemical condition may be induced by penetration of multipulse ore-forming fluids and the transition of the ore-forming mechanism from fluid-rock interaction in S1 and early S2 to phase separation in late S2 and S3, as suggested by textural and LA-ICP-MS analyses. This study highlighted that coupled dissolution-reprecipitation reactions might facilitate the association of the Au-Sb-W elemental that successively mineralized and co-enriched in the Woxi deposit.

Mineral Characteristics and the Mineralization of Leptynite-Type Nb–Ta Ore Deposit in the Western Qilian Orogenic Belt

A large Nb–Ta ore deposit was found in the Yushishan leptynite in the west Qilian Orogenic Belt (QOB). Based on a field geological survey and using a Mineral Liberation Analyser (MLA, including scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS)) methods, eight Nb minerals (fergusonite, polycrase, columbite, Nb-rutile, aeschynite, pyrochlore, microlite, and ilmenorutile) were found to occur in the leptynite. This accounted for approximately 69% of Nb, with fergusonite, polycrase, and columbite being the dominant phases. The other 17.90% Nb as a minor element was dispersed in titanium magnetite–maghemite, and another 13.00% Nb was dispersed in gangue minerals. Nb minerals are formed mainly by two metallogenesis stages. The first stage is magmatic genesis to form four Nb minerals, euhedral-subhedral fergusonite, polycrase, pyrochlore, and microlite, which are crystallized within or between primary minerals, such as quartz and feldspar. Late alteration phenomena are locally observed. The second stage is the hydrothermal genesis of columbite, anhedral fergusonite, Nb-rutile, and aeschynite, which are dispersed in the fissures of the wall rocks as irregular veins and lump assemblages. Meanwhile, they are closely associated with metasomatic chlorite, albite, and secondary quartz. Furthermore, direct metasomatism among different Nb minerals is also found at the local scale. The Nb percentage of these two Nb mineral mineralization types is approximately equal, which reflects two main mineralizing periods. The first stage of mineralization occurred in the Neoproterozoic Era (834–790 Ma). Magmatism of this period produced early niobium and formed fergusonite, polycrase, pyrochlore, microlite, and zircon. The initial enrichment of Nb, Ta, and other rare metals occurred during this stage. The second stage of mineralization occurred in the Caledonian period (490–455 Ma). Large-scale and intense tectonic–magmatic thermal events occurred in the western part of the QOB due to the plate subduction and convergence (510–450 Ma). Hydrothermal activity in this period formed columbite, fergusonite, Nb-rutile, and aeschynite. Moreover, rare metal elements in the Nb-bearing rocks activated and migrated at short distances, forming in situ Nb–Ta-rich ore deposits.

Proximal to distal geochemical variations of the Ruwai polymetallic skarn deposit, Central Borneo, Indonesia: Insights from sulfides chemistry and implications to exploration

The Ruwai deposit is the largest polymetallic skarn deposit in Borneo and is located within the Schwaner Mountains Complex. The mineralization is hosted by metalimestone of the Jurassic Ketapang Complex and the causative intrusions belong to the Cretaceous Sukadana Granitoids. Despite its large resources, the geochemical characteristics of the Ruwai skarn are still not well known. Thus, this study provides the whole-rock geochemistry of the skarn, metalimestone and intrusions, as well as the chemical compositions of sulfides (i.e., pyrite, sphalerite, galena, and chalcopyrite). The occurrence of skarn mineralization can be divided into proximal (Gojo-Karim) and distal (Central Gossan-Southwest Gossan) zones. Furthermore, the mineralization stage can be divided into prograde, retrograde and supergene stages. The whole-rock geochemical analyses clearly show that the skarn is enriched in several metals such as Ag, Nb, Co, La, Cu, V, Zr and Ti, which are higher in intrusions compared to metalimestone, which implies that these metals are mostly derived from magma. On the other hand, the skarn is also enriched in As, Pb, and Se, elements that are higher in metalimestone than in the intrusions. Thus, it can be inferred that metalimestone provided significant amounts of these metals to the mineralizing fluid. The pyrite analyses show that Cu, Zn, Bi and Ag increase towards the distal zone, while Fe, Mn and Bi in sphalerite also increase towards the distal zones Copper and Sb in galena and Ag in chalcopyrite collected from the distal zone increase from Central Gossan to Southwest Gossan zones while Bi in both minerals decrease. These trends of trace metal contents in sulfides can be utilized as a vectoring tool to delineate the center of the hydrothermal system.

Metallogeny and exploration strategy for volcanic rocks hosting world class Be-U-F mineralization at Spor Mountain, Utah, U.S.A.

We report new geochemical data (major-elements, trace-elements, and Nd-Pb isotopes) for the Spor Mountain Formation (SMF), a volcanic sequence that hosts the largest deposit of beryllium in the world. Understanding the genesis of the deposit is critical for improved recognition of regional exploration targets containing additional volcanic-hosted beryllium resources. The deposit occurs in an area of extensive alkalic rhyolitic ash flow tuffs and calderas underlain by Paleozoic and older limestone, dolomite, shale, and quartzite. The lower fluorite and bertrandite-rich tuff and upper topaz-rich rhyolite of the SMF have overlapping zircon crystallization ages (25.59 + 0.29/−0.45 Ma). Enrichment of Be, U, and F is a key attribute of the SMF inherited from melting heterogeneous source materials and magma hybridization in the continental lithosphere. Two mineralization stages are implicated: magmatic, and hydrothermal/metasomatic. The magmatic stage occurred early, as indicated by the high beryllium content in early-crystallizing zircon. The post-magmatic/hydrothermal stage involved F-rich fluids that reacted with glass and carbonate nodules in the tuff to form bertrandite (and U-rich fluorite and opal) and high-grade mineralization. The rhyolite best displays the magmatic stage of enrichment. The SMF is alkaline. Chondrite-normalized REE patterns for tuff and rhyolite are regular, stacked subparallel, and imply a shared source derivation and evolution. The tuff and rhyolite plot along a sub-vertical array for Pb isotopes and suggest they are cogenetic; both have negative values of εNd. Pb isotopic ratios for SMF do not match the slopes, initial isotopic values, or estimated basement ages of precious and base metal mining districts in Utah; thus, they do not share a source region or evolution. Crustal ages from Nd isotopes (average TDM ~ 2.29 Ga) are older than basement ages obtained by Pb isotopes. The deposit occurs in a transitional area of thinned crust near the boundary between two basement domains, the eastern Great Basin and Colorado Plateau, which have contrasting ages. Many geochemical attributes are shared between SMF and the Ermakovka deposit in Russia: they represent the world's major commercial Be deposits. Rare-metal indices of granite-related mineralization show that SMF resembles other global beryllium-bearing granitic deposits. Despite this coincidence, none of these examples matches the mineralogy, geologic setting, or type of rare metal mineralization at Spor Mountain.

Bioglass obtained via one-pot synthesis as osseointegrative drug delivery system

Osseointegration is a fundamental process during which implantable biomaterial integrates with host bone tissue. The surgical procedure of biomaterial implantation is highly associated with the risk of bacterial infection. Thus, the research continues for biodegradable bone void fillers which are able to stimulate the bone tissue regeneration and locally deliver the antibacterial agent. Herein, we obtained bifunctional bioglass (BG) using novel, preoptimized, rapid one-pot synthesis. Following the ISO Standards, the influence of the obtained BG on osteoblast-mediated phenomena, such as osteoconduction and osteoinduction was assessed and compared to two commercial materials: bioactive glass powder 45S and bioactive glass powder 85S. Direct-contact tests revealed osteoblast adhesion to BG particles; whereas, tests on extracts confirmed high viability of cells incubated with BG extract. Analyses of gene expression, alkaline phosphatase activity, and calcium phosphates deposition confirmed the stimulation of early and late stages of osteoblast differentiation and mineralization. Additionally, an extended evaluation of intracellular calcium fluctuations revealed a possible correlation between osteoblast calcium uptake and extracellular matrix mineralization. Moreover, proposed bioglass exhibited satisfactory doxycycline adsorption capacity and release profile. The obtained results confirmed the bifunctionality of the proposed BG and indicated its potential as osseointegrative bone drug delivery system.

Contribution of Triassic Tectonomagmatic Activity to the Mineralization of Liziyuan Orogenic Gold Deposits, West Qinling Orogenic Belt, China

The Western Qinling orogenic belt (WQOB) is one of the most important prospective gold districts in China, with widely distributed Indosinian intermediate–acidic intrusions. The Liziyuan Au deposit is a representative orogenic deposit in the northern WQOB, hosting several sections spatially associated with igneous rocks. The Au deposit is hosted by meta-sedimentary volcanic rocks of the Cambrian–Ordovician Liziyuan Group and the Tianzishan monzogranite. Two periods, including five stages of mineralization, are recognized in this area: an early metamorphic mineralization period (PI), including quartz–pyrite (Stage I) and banded quartz–polymetallic sulfide (Stage II) veins, and a later magmatic mineralization period (PII) including quartz–K-feldspar–pyrite–molybdenite veins (Stage III), quartz–polymetallic sulfide–chlorite ± calcite veinlets and stockwork (Stage IV), and late calcite–quartz veinlets (Stage V). Geochronological studies indicate a SHRIMP zircon U-Pb age of 236.1 Ma for the Tianzishan monzogranite, and our published ages of ore-bearing diorite porphyrite of the Suishizi section and granite porphyry of the Jiancaowan section being 213 and 212 Ma, respectively. Pyrites formed in association with PI and PII mineralization have well-defined Rb–Sr ages of 220 ± 7.5, 205.8 ± 8.7, and 199 ± 15 Ma, with close temporospatial coupling between mineralization and magmatism. The δ18O and δD values of fluid inclusions in Stage IV auriferous quartz veins range from −0.03‰ to +5.24‰ and −93‰ to −75‰, respectively, suggesting that mineralizing fluid was likely of magmatic origin. Three distinct ranges of δ34S values are identified in the studied sections (i.e., 7.04‰–9.12‰, −4.95‰ to −2.44‰, and 0.10‰–3.08‰), indicating a source containing multiple sulfur isotopes derived from magmatic and metamorphic fluids. The Liziyuan Au deposit is thus likely an orogenic deposit closely related to magmatism. Geochemical characteristics indicate that Tianzishan monzogranite is adakitic and was derived from thickened lower crust during Triassic orogenesis. The ore-bearing diorite porphyrite and granite porphyry formed in a post-collision extensional setting. Together with previous geological and geochemical data, our results indicate that the Liziyuan orogenic Au deposit was formed by early collisional–compressional metamorphism and late post-collision extensional magmatic fluids related to the evolution of the WQOB.

Metallogeny of the Yi’nan Tongjing Au–Cu skarn deposit, Luxi district, North China Craton: Perspective from in-suit trace elements, sulfur and lead isotopes of sulfides

Gold–Cu skarn deposits are characterized by a diverse mineral assemblage, whose in-situ major/trace elements and isotope compositions can provide key constraints to the migration and enrichment of Au during hydrothermal processes. The Yi’nan Tongjing Au–Cu deposit is located in the central part of the Luxi district, and both skarn and Au–Cu ore bodies occur at the contact between the Early Cretaceous diorite porphyry and the Neoproterozoic to Cambrian carbonate rocks. Five stages of mineralization were identified: 1) early skarn (garnet–diopside–wollastonite); 2) late skarn (magnetite–epidote–actinolite±tremolite); 3) oxide (specularite–hematite); 4) sulfide (pyrite–chalcopyrite–sphalerite–quartz–chlorite); and 5) late quartz–calcite. The mineralization process in the Tongjing Au-Cu deposit was revealed by detailed scanning electron microscope-backscattered electron imaging, electron probe microanalysis, in-situ trace element, sulfur and lead isotope analysis. Magnetite is enriched in chalcophile elements (Cu, Zn, Pb), Co and Ni, probably due to hydrothermal overprint. The substitution of As and other elements in the formation of pyrite is conducive to the entry of Au into pyrite. The increase of Se and As contents in pyrite from stage IVa to IVb indicates that the temperature, salinity and oxygen fugacity of the ore-forming fluid decrease while the pH rises, resulting in the unloading of Au. The temperature of Au mineralization based on the Se content in pyrite does not exceed 300°C. Furthermore, V positively correlated with Ti and Ni/Cr ratios ≥1 in magnetite and most Co/Ni ratios in pyrite >10 all confirm their hydrothermal origins. The restricted sulfur (δ34SV-CDT = −0.5–1.2‰; mean = 0.4‰) and lead (206Pb/204Pb = 17.323–17.383; 207Pb/204Pb = 15.424–15.452; 208Pb/204Pb = 37.367–37.454) isotopic compositions suggest that the deep magma provided the primary mineralized material, accompanied by a relatively small amount of shallow crustal material. The Yi’nan Tongjing Au–Cu skarn deposit was formed in the Early Cretaceous, which is an important metallogenic response to the strong decratonization of the North China Craton induced by the paleo-Pacific Plate roll-back. This study shows that there is a large potential of Early Cretaceous skarn mineralization in the Luxi district.

Conditions of formation and stages of mineralization of the Pyazbashi gold-sulfide-quartz deposits (Leser Caucasus, Azerbaijan)


 
 
 We analyzed the conditions of the formation and stages of mineralization of the Pyazbashi gold-sulfide-quartz deposits. The deposits were determined to contain three structural-morphologic types of ore bodies: gold-quartz-sulfide – veinular, gold-bearing veins and the strip of gold-bearing metasomatites. We determined that in the deposits, quartz-pytire, quartz-carbonate and carbonate veins with gold and polymetal mineralization are confined to the volcanic-tectonic structures. Those volcanic-tectonic structures have various fracture systems, are complicated and have been inherited by later changes that occurred after the formation of the Lower and Middle Eocene volcanogenic complexes, and some of them have been embedded again. We de- termined that gold ore mineralization in the deposits is related to various hydrothermal-metasomatic formations and has developed in complex multy-stage process. Interaction of various veins and minerals that comprise them allow us to assume the following pattern in the sequence of the mineralization stages (from early stage to later stages): 1-quartz-sericite; 2-quartz-pyrite-molybdenum; 3-quartz- pyrite-gold ore; 4-quartz-polymetal; 5-carbonate. Gold-ore bodies are mainly complicated by aggregates of quartz-pyrite-gold ore stage of mineralization, which is the productive stage. We present the results of chemical analysis of native pyrite and chalcopyrite. We determined that native gold occurs as small, regular-shaped bodies in pyrite grains. In the veinlets of chalcopyrite, it is usually confined to marginal parts.
 
 

Fluid mineralization of the Dongtongyu gold deposit in the southern margin of North China craton: Evidence from microthermometry and composition of fluid inclusions

In this study, petrographic, microthermometric, and synchrotron radiation X-ray fluorescence (SRXRF) analyses of fluid inclusions were conducted to shed light on the mineralization mechanism of the Dongtongyu deposit and provide some evidence of the relationship among CO2, Au, and other ore elements (e.g., Cu, Fe, Zn, and Pb) in ore-forming fluids. The ore-forming fluid is characterized as the H2O–CO2–NaCl system with medium–high temperatures and low salinities. Four structural mineralization stages are distinguished: Pyrite-quartz (Stage 1), gold-quartz-pyrite (Stage 2), gold-quartz-polymetallic sulfide (Stage 3), and quartz-calcite (Stage 4). Fluid inclusions in Stages 1–3 are dominated by the H2O–CO2 type, and most of them contain liquid H2O and liquid CO2 at room temperature. The melting temperatures (Tm-CO2 = −82.1°C to −57.5°C) of solid CO2 in Stage 1 are relatively low. The values of Tm-CO2 in Stages 2–3 are quite close, with ranges of −60.5°C to −56.5°C and −59.2°C to −58.6°C, respectively. The melting temperatures of clathrate in Stages 1–3 are −2.7°C to +7.8°C, −5.5°C to +7.8°C, and +3.7°C to +7.2°C. The homogenization temperatures of the CO2 phase in the H2O–CO2 inclusions of the three stages are measured as −7.5°C to +31.7°C, −7.5°C to +29.3°C, and 7.1°C to +24.1°C. The total homogenization temperatures in Stages 1–3 are 180°C–394°C, 202°C–305°C, and 224°C–271°C, with salinities of 4.3 wt.%–18.2 wt% NaCl, 4.3 wt.%–20.0 wt% NaCl, and 5.3 wt.%–11.0 wt% NaCl, respectively. The laser Raman spectroscopy results show that the CO2–H2O inclusions in the quartz veins contain abundant CO2 and CH4. The SRXFR results show that most of the elements, especially As, Te, and Cu, are more enriched in liquid CO2 than in liquid H2O. The elements of Au, Fe, Ni, Cu, and Pb have higher concentrations in H2O–CO2-type fluid inclusions in Stage 2 than other fluid inclusions in Stages 1–2, suggesting that gold mineralization is closely related to CO2-rich fluids. During the fluid evolution process, fluid immiscibility is an important mineralization mechanism of gold. The increase in CO2 and CH4 and the decrease in the fluid temperature might promote fluid immiscibility.

Tin-bearing magnetite with nanoscale Mg-Si defects: Evidence for the early stages of mineralization in a skarn system

Tin-bearing magnetite is reported from several types of magmatic-hydrothermal ore deposits. The question of whether tin is incorporated within solid solution, as Sn4+, or as nanoinclusions remains open, however. We report a micron- to nanoscale investigation of Sn (Mg, Si)-bearing magnetite from serpentinite in the Dulong Zn-Sn-In skarn, South China, with the dual aims of understanding the mechanisms involved in accommodating Sn and associated elements into the Fe-oxide, and the inferences that this carries for constraining the early stages of skarn formation. Magnetite preserves a range of textures that record the evolution of metasomatism during prograde growth of grain cores and retrograde rim replacement. Observations reveal the presence of chondrodite and sellaite (MgF2) as nanoscale inclusions preserved in magnetite. This implies initiation of the Dulong mineralizing system during a humite-bearing, magnesium skarn stage. Magnesium-Si defects, forming along (110) planes prior to Sn-enrichment, are recognized for the first time. Release of high volatile, F-rich fluids is interpreted to lead to precipitation of cassiterite inclusions along <111*> directions in magnetite.

Nature and conditions of gold mineralization at the Tau deposit, Mupane mine, Tati Greenstone Belt, Botswana: Evidence from fluid inclusion and arsenopyrite geothermometer

AbstractThe gold mineralization at the Tau deposit in northeastern Botswana can be distinguished into two stages. The first stage of mineralization consists of invisible gold associated with early, sulfur‐rich arsenopyrite (Apy1). The second stage is characterized by native gold associated with late, sulfur‐poor arsenopyrite (Apy2). This study aims to constrain the nature of the ore‐forming fluid at the Tau deposit on the basis of fluid inclusion microthermometry and arsenopyrite geothermometry. Quartz crystals closely associated with gold‐bearing sulfides (Apy1) from the host rock host three types of fluid inclusions occurring in the same assemblages: Type I, two‐phase aqueous fluid inclusions, Type II three‐phase aqueous‐carbonic fluid inclusions and Type III one‐ or two‐phase CO2‐rich fluid inclusions. Microthermometric and Raman spectroscopic studies revealed the dominance of coexisting H2O+NaCl (Type I) and CO2N2CH4 (Type III) fluid inclusions. The coexisting Type I and Type III fluid inclusions could represent products of the immiscibility of a homogenous H2OCO2NaClN2CH4 primary ore fluid. The salinity of Type I (calculated from melting temperature of ice) and Type II (calculated from dissolution temperature of clathrate) fluid inclusions vary from 3.4 to 9.2 wt% NaCl equiv. and 5.8 to 9.8 wt% NaCl equiv., respectively. The overall fluid inclusion salinity range (<10 wt% NaCl equiv.) and gas compositions of fluids suggest that the primary ore‐forming fluid at the Tau deposit was of low salinity and H2OCO2N2CH4NaCl composition. Integration of fluid inclusion microthermometry and arsenopyrite geothermometer results suggest that the first stage and second stages of gold mineralization and the associated alteration at the Tau deposit occurred at pressure and temperature conditions of 75–145 MPa and 290–370°C and 85–160 MPa and 330–370°C, respectively. These results suggest that there was an increase in temperature from the first stage to the second stage of mineralization, resulting in the recrystallization of invisible gold‐bearing arsenopyrite in the first stage to form native gold‐bearing arsenopyrite in the second stage. Fluid composition and the estimated physico‐chemical conditions at the Tau deposit confirm that gold was transported as reduced bisulfide complexes and initial gold deposition was likely caused by a reduction in sulfur contents as a result of sulfidation reactions and pressure‐induced phase separation (fluid immiscibility).