Fluid Inclusion Homogenization Research Articles

Жильный кварц из рудопроявлений золота в рифейских отложениях Авзянского рудного района (Южный Урал): минералогические и термокриометрические особенности

Quartz reefs from the gold-sulfide-quartz deposit Gorny Priisk and gold-quartz sulfide bearing ore occurrences Ulyuk-Bar and Vostochno-Aktashskoe have the similar temperatures of homogenization of primary fluid inclusions (228-382 ° C) and salt composition, in which magnesium and potassium chloride predominate. Salinity varies in the range of 5,4-15,8 wt. % NaCl equiv. Generation of gold- bearing quartz reefs was caused by the migration of magmatogene fluids connected with the tectono-thermal stage between the Middle and Late Riphean. Barren vein quartz from the host Riphean rocks is characterized by lower temperatures of homogenization (128-238 ° C), predominance of the iron chlorides in salt composition and higher salinity (12,9-22,8 wt% NaCl equiv.). The generation of quartz in the gold-sulphide ore occurrence Bogryashka, which have temperatures of homogenization of 152-292 ° C and the predominance of calcium and magnesium chlorides in the salts, is associated with the pre-ore process of magnesian-ferruginous metasomatism.

The crystallization temperature of vein quartz estimated from the concentration of the titanium paramagnetic center in quartz: A case study of the Peschanka porphyry copper–molybdenum–gold deposit, Western Chukchi Peninsula, Russia

The concentration of the Al and Ti paramagnetic impurity centers in pre-ore and ore-stage quartz at the Peschanka porphyry copper–molybdenum–gold deposit in the Western Chukchi Peninsula, Russia were determined using electron paramagnetic resonance spectroscopy (EPR). The [AlO 4 - /h+]0 concentration in pre-ore and ore-stage quartz varies from 29 to 124 and from 13 to 101 at. ppm, respectively. The contents of the [TiO 4 - /Li+]0 and [TiO 4 - /H+]0 centers reach 20 and 6.3 at. ppm, respectively. Pre-ore quartz associated with the formation of biotite–potassium feldspar–quartz alteration and ore-stage quartz associated with the formation of quartz–sericite rocks followed by the ore deposition differ considerably in the Ti center content, especially the [TiO 4 - /H+]0 center. The [TiO 4 - /H+]0 concentration is much higher in the pre-ore quartz (>2 at. ppm) than that in the ore-stage quartz related to copper mineralization (<2 at. ppm). The [TiO 4 - /Li+]0 concentration also decreases from pre-ore to ore-stage quartz. Taking the data we obtained into account, the formation temperature of pre-ore and ore-stage quartz estimated from a titaniumin-quartz geothermometer is 590–470°C (weighted average 520°C) and 510–310°C (weighted average 430°C), respectively. The obtained temperature range of 590 to 310°C is similar to that determined from homogenization of fluid inclusions in quartz.

Crystallization temperature of vein quartz at Peschanka porphyry Cu-Mo-Au deposit, Western Chukchi Peninsula, Russia: Estimation from content of paramagnetic titanium centers in quartz

The Al and Ti paramagnetic impurity center concentrations in pre-ore and ore-bearing quartz at the Peschanka porphyry copper-molybdenum-gold deposit in the Western Chukchi Peninsula, Russia were determined using electron paramagnetic resonance (EPR). The [AlO4-/ h+]0 concentration in pre-ore and ore-bearing quartz varies from 29 to 124 and from 13 to- + 0- + 0101 at. ppm, respectively. The contents of [TiO4 /Li ] - and [TiO4 /H ] -centers reach 20 and6,3 at. ppm, respectively. Pre-ore stage quartz associated with the formation of biotite-potassiumfeldspar-quartz alteration and quartz of the ore stage associated with the formation of quartz-sericite rocks followed by the ore deposition are substantially in content of the titanium centers,- + 0- + 0especially [TiO4 /H ] -centers: the [TiO4 /H ]concentration is much higher in the pre-orestage quartz (>2 at. ppm) than that in quartz related to copper mineralization (<2 at. ppm).+ 0The [TiO4-/Li ]concentration also decreases from pre-ore to ore-bearing quartz. Taking intoaccount the data obtained, the formation temperature of pre-ore and ore-bearing quartz estimatedfrom a titanium-in-quartz geothermometer is 590-470 °C (average 520 °C) and 510-310 °C (average 430 °C), respectively. The obtained temperature range of 590 to 310 °C is similar to that determined from homogenization of fluid inclusions in pre-ore and ore-bearing.

Unusual acid melts in the area of the unique Rosia Montana gold deposit, Apuseni Mountains, Romania: Evidence from inclusions in quartz

Crystalline and melt inclusions were studied in large (up to 2 cm across) dipyramidal quartz phenocrysts from Miocene dacites in the area of the Rosia Montana Au-Ag deposit in Romania. Data were obtained on the homogenization of fluid inclusions and the composition of crystalline inclusions and glasses in more than 40 melt inclusions, which were analyzed on a electron microprobe. The minerals identified in the crystalline inclusions are plagioclase (An 51–62), orthoclase, micas (biotite and phengite), zircon, magnetite (TiO2 = 2.8 wt %), and Fe sulfide. Two types of the melts were distinguished when studying the glasses of the melt inclusions. Type 1 of the melts is unusual in composition. The average composition of 20 inclusions is as follows (wt %): 76.1 SiO2, 0.39 TiO2, 6.23 Al2O3, 4.61 FeO, 0.09 MnO, 1.64 MgO, 3.04 CaO, 2.79 Na2O, 3.79 K2O (Na2O/K2O = 0.74), 0.07 P2O5, 0.02 Cl. The composition of type 2 of the melts is typical of acid magmas. The average of 23 inclusion analyses is (wt %) 79.3 SiO2, 0.16 TiO2, 10.27 Al2O3, 0.63 FeO, 0.08 MnO, 0.29 MgO, 1.83 CaO, 3.56 Na2O, 2.79 K2O (Na2O/K2O = 1.28), 0.08 P2O5, 0.05 Cl. The compositions of these melts significantly differ in concentrations of Ti, Al, Fe, Mg, Ca, Na, and K. The high analytical totals of the analyses (close to 100 wt %, more specifically 98.9 and 99.0 wt %, respectively) testify that the melts were generally poor in water. Two inclusions of type 1 and two inclusions of type 2 were analyzed on an ion probe, and their analyses show remarkable differences in the concentrations of certain trace elements. These concentrations (in ppm) are for the melts of types 1 and 2, respectively, as follows: 10.0 and 0.69 for Be, 29.3 and 5.7 for B, 6.4 and 1.4 for Cr, 146 and 6.9 for V, 74 and 18 for Cu, 92 and 29 for Rb, 45 and 15 for Zr, 1.7 and 0.6 for Hf, 10.3 and 2.3 for Pb, and 52 and 1.3 for U. The Th/U ratio of these two melt types are also notably different: 0.04 and 0.19 for type 1 and 2.0 and 2.9 for type 2. These data led us to conclude that the magmatic melts were derived from two different sources. Our data on the melts of type 1 testify that the magmatic chamber was contaminated with compositionally unusual crustal rocks (perhaps, sedimentary, metamorphic, or hydrothermal rocks enriched in Si, Fe, Mg, U, and some other components). This can explain the ore-forming specifics of magmatic chambers in the area.

Fluid inclusion analysis for constraining the hydrocarbon accumulation periods of the Permian reservoirs in Northeast Ordos Basin

Geochronology of hydrocarbon accumulation and reconstruction is an important and challenging subject of petroleum geology in multi-cycle superimposed basin. By fluid inclusion (FI) analysis combined with the apatite fission track (AFT) modeling thermal path of the FI host rock, a case study of constraining the hydrocarbon accumulation and reconstruction periods of the Permian reservoirs in Northeast Ordos Basin (OB) has been conducted. The FI homogenization temperatures of the oil-gas-bearing sandstone core-samples from the Lower to Upper Permian reservoirs statistically present two groups with a low and a high temperature peaks in ranges of 90–78 and 125–118 °C, r ° espectively, corresponding to 2-stage primary hydrocarbon accumulations of the Early-Middle Mesozoic. Besides, there exists another group with a medium-high peak temperature of 98 °C in the Upper Permian reservoirs, corresponding to the hydrocarbon reconstruction and destruction of the Late Mesozoic to Cenozoic. According to the projected ages of the FI peak temperatures on the AFT thermal path of the FI host rocks, it is further induced that there experienced 3-stage hydrocarbon accumulations in the Permian reservoirs during the Mesozoic to Cenozoic. These are: (1) all the various primary hydrocarbon Permian reservoirs together developed 2-stage accumulations of 162–153 and 140–128 Ma in agreement with the multi-cycle subsidence burial heating process of the basin; (2) the Upper Permian reservoirs further experienced 1-stage secondary hydrocarbon accumulation and reconstruction at ca. 30 Ma in coincidence with a critical tectonic conversion of the slow to rapid uplifting process from the Late Cretaceous to Neogene.

Molybdenum mineralization in the ores of the Tigriny tin deposit (Primorye, Russia)

The molybdenum mineralization at the Tigriny tin deposit is considered for the first time in the light of possible recovery of Mo as a by-product of selective mining. It is established that Mo has a positive correlation with Bi and does not show a correlation with Sn, W, or Zn. The highest Mo grade (>0.1%) in the ore stockwork is related to hornfels near the exposed granite porphyry stock and decreases downward by an order of magnitude. At the level of adit 5, the most numerous quartz-molybdenite veinlets develop at a distance of 50–100 m from the granite porphyry stock. The molybdenite-quartz, pegmatoid, and autogreisen generations of molybdenum mineralization are related to different substages of the first ore stage. All these generations predated crystallization of wolframite, cassiterite, and other ore minerals. The formation temperature for each molybdenite generation was determined by homogenization of fluid inclusions in quartz and decrepitation of samples characterizing each molybdenite-bearing assemblage. These data allowed us not only to estimate the crystallization temperature of each molybdenite generation but also to establish that the molybdenite crystallized from a pneumatolytic-hydrothermal melt-solution at the early stage of the deposit formation. The molybdenum mineralization is genetically related to the granite porphyry stock. The structure of the quartz-molybdenum stockwork was studied to determine the clusters of quartz-molybdenite veinlets and establish their orientation. Molybdenite 1 occurs in variably oriented veinlets that make up a stockwork around the apical portion of the porphyry stock. Disseminations and pockets of molybdenites 2 and 3 are hosted in pegmatoid rocks, greisen, and greisenized granite porphyry. The density of the Tigriny stockwork varies from 0 to 40–50 quartz-molybdenite veinlets per 5 m. Their orientation and spatial distribution were studied in quantitative terms. The most promising targets for selective mining of molybdenite from the Tigriny deposit are the framework of the Minor porphyry stock and the apical portion of the Main stock. The Tigriny deposit demonstrates a clear relationship between ore formation and granitic magmatism.

Fluid Temperature and Salinity Characteristics of the Matagami Volcanogenic Massive Sulfide District, Quebec

Fluid inclusions hosted within various lithologic units of the >40 million metric ton (Mt) Matagami district, Abitibi greenstone belt, preserve samples of Archean volcanogenic massive sulfide (VMS) and postvolcanogenic massive sulfide hydrothermal fluid. Microthermometric measurements on ore-hosted primary two-phase liquid-vapor inclusions from Matagami’s south limb deposits indicate that the VMS hydrothermal fluid was highly saline (16.2 ± 4.7 wt % NaCl-CaCl2 equiv, 1σ, n = 230) and of moderate temperature (trapping temperature, Tt = 208° ± 32°C, 1σ, n = 230). A fluid with these characteristics is capable of transporting ~5 × 10−4 m (30 ppm) Zn as ZnCl3 − and ZnCl4 2− chloride complexes. However, the low temperature of this fluid precluded efficient Cu transport (≤ 3 ppm), which may in part explain the relatively Cu poor nature of the Matagami deposits. Calculated densities of this ore fluid as high as 1.10 g/cm3 are consistent with a bottom-hugging brine model. However, a subset of the data indicate a fluid less dense than ambient seawater, suggesting that buoyant hydrothermal plumes were also present. A microthermometrically determined high CaCl2 content (XNaCl <0.55, molar Na/Ca = 2.3/1) for the VMS ore-hosted primary fluid is consistent with an Archean hydrothermal fluid more Ca-rich than modern-day seawater. Quartz-epidote veins located in the hydrothermal cracking zone of the Bell River Complex host primary liquid-vapor-halite inclusions. These inclusions are interpreted to be samples of the deep-seated equivalent to the VMS ore-hosted hydrothermal fluid described above. Microthermometry indicates that these inclusions trapped a high-temperature brine (Tt = 373° ± 44°C, 1σ , n = 92; 38.2 ± 1.9 wt % NaCl equiv, 1σ , n = 92). We interpret this brine to be a phase-separated product of (modified) model seawater (3.2 wt % NaCl), an exsolved magmatic fluid, or a combination thereof, deep within the hydrothermal system at 650° to 670°C and a near-lithostatic pressure of 90 MPa. Phase separation and subsequent convection lowered the temperature of the brine prior to its entrapment within the hydrothermal cracking zone. The occurrence of high-temperature brine overlain by lower temperature/salinity fluid suggests a two-cell convection model, consistent with metal mass-balance calculations for the south limb. The high salinity of the ore-hosted fluid inclusions indicates two possibilities: (1) a significant amount of brine was incorporated into the upper cell and mixed with heated seawater during convection; (2) Archean seawater itself was very saline and of variable salinity. With the cooling of the Bell River Complex, lower temperature fluids, dominantly of seawater origin, circulated deep within the hydrothermal system. Modified by water-rock interaction, yet not phase separated, these fluids sealed off the remnant permeability of the fracture network of the hydrothermal cracking zone and were locally trapped as secondary liquid-vapor fluid inclusions (homogenization temperature, Th = 242° ± 17°C; 9.1 ± 1.6 wt % NaCl equiv, 1σ , n = 14) hosted within the Bell River Complex quartz-epidote vein material. Post- and/or waning-stage VMS hydrothermal activity is evident from the presence of quartz-epidote veins crosscutting Wabassee Group hanging-wall rocks. Microthermometry on quartz-hosted primary liquid-vapor fluid inclusions suggests that this activity occurred at relatively low temperatures (Th = 76°–177°C, n = 212), over a wide range of salinity (6.0–32.4 wt % NaCl-CaCl2 equiv, n = 212), and with a high apparent CaCl2 content (XNaCl <0.06). These fluid inclusion data illustrate the importance of subsea-floor chemical and physical processes directly related to metal transport and deposition in VMS systems. In particular, phase separation deep within the hydrothermal system is interpreted as a key process for generating saline brines capable of forming significant ore deposits.

Iron-Rich and Iron-Poor Mississippi Valley-Type Mineralization, Metaline District, Washington

Two texturally and mineralogically distinct types of Mississippi Valley-type mineralization are hosted by the upper Cambrian Metaline Formation in northeastern Washington. Josephine-type mineralization is iron poor and coarse grained, whereas Yellowhead-type mineralization is iron rich, fine grained, and commonly botryoidal. Josephine mineralization is found largely in the Josephine lithofacies, a fragmental unit near the contact between dolomites of the Metaline Formation and shales of the overlying Ledbetter Formation. Yellowhead mineralization forms several planar zones several hundred meters below, largely in the light-gray bedded dolostone lithofacies of the Metaline Formation. About 12.7 million tonnes (Mt) of Josephine-type ore (1.3% Pb, 3.0% Zn) and 730,000 t of Yellowhead-type ore (4.5% Zn, 0.5% Pb) were produced from the district before 1977, and about 5.5 Mt of ore (7.2% Zn, 1.3% Pb) remain, largely in the Yellowhead zone. Ore textures in both types of mineralization indicate a complete lack of equilibrium among adjacent minerals, and this is confirmed by geochemical measurements. Although fluid inclusion homogenization and freezing temperatures are similar for both types of ore, fluid inclusion leachate and gas analyses differ for each mineral. Compositions for Josephine minerals appear to form a cluster that differs from compositions for Yellowhead minerals, suggesting that ore minerals were deposited from two parent brines that changed composition slightly to deposit each mineral. Isotopic analyses indicate that sulfur in both types of mineralization was probably derived from the same source whereas lead definitely came from two distinct sources. These observations indicate that ore formed when two parent metal-rich brines mixed with the same source of sulfur. Abundant pyrite that retains the form of marcasite suggests that the original brine in at least the Yellowhead ores was moderately acid. Geochemical speciation calculations indicate that relatively high temperatures are needed to dissolve enough iron to make iron-rich Mississippi Valley-type deposits. Furthermore, moderately acid brines with relatively low sulfur contents are enriched in iron whereas those with high sulfur contents lack iron, suggesting that the variations in iron content of these deposits reflect variations in the dissolved sulfur content of the parent brines.

Geochemical Variation of Dolomite Cement Within the Cambrian Bonneterre Formation, Missouri: Evidence for Fluid Mixing

ABSTRACT Compositionally zoned dolomite in the Cambrian Bonneterre Formation of Missouri precipitated from warm, basin-derived brine, as evidenced by its fluid inclusion homogenization and freezing temperatures and radiogenic 87Sr/86Sr composition. Preexisting host carbonates played a major role in governing parent fluid composition during precipitation of the dolomite cement. This is indicated by significant overlap in the isotopic and minor and trace element composition of the cement and host. There is a decrease in 13C and 18O with succeeding dolomite cement zones, suggesting that isotopically lighter cement armored the host rock, progre sively isolating the fluids from preexisting dolomite. 87Sr/86Sr values for a single cement zone (zone 4) vary from 0.7086 to 0.7201. The more radiogenic values reflect a contribution of 87Sr to the brine primarily through silicate reactions prior to entering the Bonneterre Formation. The lower values overlap with preexisting replacement dolomite and limestone within the Bonneterre, again indicating the importance of host-rock buffering. Possible mechanisms governing the apparent control on cement composition by preexisting replacement dolomite were evaluated using computer models which simulate fluid and cement composition in: 1) a system in which a single fluid progressively interacts with host carbonate, and 2) a system in which there is mixing of fluids having undergone different degrees of fluid-rock interaction. The predicted covariation of geochemical parameters using the mixing model matches the actual data from zone 4 cement better than that offer progressive fluid-rock interaction in most cases. The contrast between the predicted mixing and fluid-rock interaction curves is greatest for cross plots involving Mn, Fe, and 13C which are effectivel buffered by host rock during progressive fluid-rock interaction. The mixing model works best for zone 4 cement data subdivided according to stratigraphic subunit and area, suggesting a great deal of spatial variation in end-member fluids. Equilibrium modelling with the speciation-reaction modelling program PHRQPITZ suggests that dolomite supersaturation occurs when a relatively hot dolomite-saturated fluid mixes with a cooler dolomite-saturated fluid having similar PCO2 values. This is consistent with geochemical data from zone 4 cement, which indicates mixing of a relatively unbuffered fluid with fluids buffered by local host rocks.

Chemical and thermodynamic constraints on the hydrothermal transport and deposition of tin; II, Interpretation of phase relations in the Southeast Asian tin belt

Correlation of laboratory and field observations of mineral assemblages in quartz-cassiterite veins and adjacent greisen alteration zones in the Southeast Asian tin belt with equilibrium constraints generated from thermodynamic calculations can be used to assess the composition of the hydrothermal solutions responsible for the transport and deposition of tin. The hydrothermal mineral assemblage in the Southeast Asian tin deposits consists of quartz, cassiterite, muscovite, K-feldspar, topaz, magnetite, and rarely, hematite, fluorite, tourmaline, and zinnwaldite. Depth estimates and fluid inclusion homogenization and freezing temperatures indicate that this assemblage formed at approximately 350 degrees C and approximately 500 bars in the presence of an electrolyte solution containing approximately 1 molal (m) total chloride. Thermodynamic calculations indicate that the solution pH, fugacity of oxygen, fugacity of H 2 S, activity of K (super +) , activity of Ca (super +2) , and the total molality of F (super -) were approximately 4.5, approximately 10 (super -31) , < or =10 (super -1) , approximately 0.1, approximately 10 (super -3) , and approximately 10 (super -2.1) , respectively, during the mineralizing process. Tin was apparently transported in solution primarily as stannous chloride and hydroxide complexes. The presence of topaz precludes significant transport of tin as fluoride complexes. Solubility calculations indicate a minimum total tin concentration in solution on the order of 10 ppm. The intimate association of cassiterite and the greisenized wall rock adjoining the veins suggests that tin mineralization occurred in response to increasing solution pH accompanying hydrothermal alteration of the host rock.

Hydrothermal and Uplift Histories of Northern Appalachian Basin: ABSTRACT

Geochemical and structural analysis techniques were integrated in an investigation of epigenetic mineralization on fault zones to develop an evolutionary model for the post-Paleozoic history of the northern Appalachian basin. Analysis of faults in outcrop, excavations, and oriented drill cores revealed the occurrence of strike-slip and dip-slip faults which are representative of a fabric which is persistent in style, orientation, and magnitude across New York State. The elements of this fabric do not decrease in frequency with distance from the Allegheny structural front nor do they fan around the centers of deformation as do the Allegheny structures. Indeed the west-northwest trends of the normal faults and the acute bisectrix of the conjugate strike-slip faults are para lel with the short axis of the Appalachian basin. Their formation is attributed to the stresses produced during the asymmetric uplift of the basin in post-Paleozoic time. Mississippi Valley-type epigenetic mineralization was deposited along these fault zones where they served as the dominant channels for circulating fluids within the well-cemented sandstones. Homogenization of fluid inclusions in vein minerals revealed an intermittent range of depositional temperatures from that typical of the peak of diagenesis in deep sediments, 170°C, to as low as 70°C. The higher temperatures may reflect waning of an elevated heat-flow regime produced by dehydration during diagenesis. The temperatures between 112 and 70°C are attributed to cooling during uplift. Strike-slip faulting was initiated at temperatures near 170°C as indicated by syntectonic deposition of high-temperature calcite. Normal faulting did not occur until the hydrothermal brines had cooled to 112°C. Minor deformation and entrapment of secondary fluid inclusions continued to 70°C. The timing of tectonic events can be estimated by several techniques which generally indicate a late Paleozoic to early Mesozoic age for strike-slip faulting and a late Mesozoic to Cenozoic age for normal faulting. End_of_Article - Last_Page 1589------------