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Meteoric Water (meteoric + water)

Distribution by Scientific Domains

Earth and Environmental Science	83%

Distribution within Earth and Environmental Science

Geology & Geophysics	44%
Economic & Applied Geology	34%

Terms modified by Meteoric Water

meteoric water line

Selected Abstracts

Syntectonic infiltration by meteoric waters along the Sevier thrust front, southwest Montana

GEOFLUIDS (ELECTRONIC), Issue 4 2006
A. C. RYGEL
Abstract Structural, petrographic, and isotopic data for calcite veins and carbonate host-rocks from the Sevier thrust front of SW Montana record syntectonic infiltration by H2O-rich fluids with meteoric oxygen isotope compositions. Multiple generations of calcite veins record protracted fluid flow associated with regional Cretaceous contraction and subsequent Eocene extension. Vein mineralization occurred during single and multiple mineralization events, at times under elevated fluid pressures. Low salinity (Tm = ,0.6°C to +3.6°C, as NaCl equivalent salinities) and low temperature (estimated 50,80°C for Cretaceous veins, 60,80°C for Eocene veins) fluids interacted with wall-rock carbonates at shallow depths (3,4 km in the Cretaceous, 2,3 km in the Eocene) during deformation. Shear and extensional veins of all ages show significant intra- and inter-vein variation in ,18O and ,13C. Carbonate host-rocks have a mean ,18OV-SMOW value of +22.2 ± 3, (1,), and both the Cretaceous veins and Eocene veins have ,18O ranging from values similar to those of the host-rocks to as low as +5 to +6,. The variation in vein ,13CV-PDB of ,1 to approximately +6, is attributed to original stratigraphic variation and C isotope exchange with hydrocarbons. Using the estimated temperature ranges for vein formation, fluid (as H2O) ,18O calculated from Cretaceous vein compositions for the Tendoy and Four Eyes Canyon thrust sheets are ,18.5 to ,12.5,. For the Eocene veins within the Four Eyes Canyon thrust sheet, calculated H2O ,18O values are ,16.3 to ,13.5,. Fluid,rock exchange was localized along fractures and was likely coincident with hydrocarbon migration. Paleotemperature determinations and stable isotope data for veins are consistent with the infiltration of the foreland thrust sheets by meteoric waters, throughout both Sevier orogenesis and subsequent orogenic collapse. The cessation of the Sevier orogeny was coincident with an evolving paleogeographic landscape associated with the retreat of the Western Interior Seaway and the emergence of the thrust front and foreland basin. Meteoric waters penetrated the foreland carbonate thrust sheets of the Sevier orogeny utilizing an evolving mesoscopic fracture network, which was kinematically related to regional thrust structures. The uncertainty in the temperature estimates for the Cretaceous and Eocene vein formation prevents a more detailed assessment of the temporal evolution in meteoric water ,18O related to changing paleogeography. Meteoric water-influenced ,18O values calculated here for Cretaceous to Eocene vein-forming fluids are similar to those previously proposed for surface waters in the Eocene, and those observed for modern-day precipitation, in this part of the Idaho-Montana thrust belt. [source]

Contrasting paleofluid systems in the continental basement: a fluid inclusion and stable isotope study of hydrothermal vein mineralization, Schwarzwald district, Germany

GEOFLUIDS (ELECTRONIC), Issue 2 2007
B. BAATARTSOGT
Abstract An integrated fluid inclusion and stable isotope study was carried out on hydrothermal veins (Sb-bearing quartz veins, metal-bearing fluorite,barite,quartz veins) from the Schwarzwald district, Germany. A total number of 106 Variscan (quartz veins related to Variscan orogenic processes) and post-Variscan deposits were studied by microthermometry, Raman spectroscopy, and stable isotope analysis. The fluid inclusions in Variscan quartz veins are of the H2O,NaCl,(KCl) type, have low salinities (0,10 wt.% eqv. NaCl) and high Th values (150,350°C). Oxygen isotope data for quartz range from +2.8, to +12.2, and calculated ,18OH2O values of the fluid are between ,12.5, and +4.4,. The ,D values of water extracted from fluid inclusions vary between ,49, and +4,. The geological framework, fluid inclusion and stable isotope characteristics of the Variscan veins suggest an origin from regional metamorphic devolatilization processes. By contrast, the fluid inclusions in post-Variscan fluorite, calcite, barite, quartz, and sphalerite belong to the H2O,NaCl,CaCl2 type, have high salinities (22,25 wt.% eqv. NaCl) and lower Th values of 90,200°C. A low-salinity fluid (0,15 wt.% eqv. NaCl) was observed in late-stage fluorite, calcite, and quartz, which was trapped at similar temperatures. The ,18O values of quartz range between +11.1, and +20.9,, which translates into calculated ,18OH2O values between ,11.0, and +4.4,. This range is consistent with ,18OH2O values of fluid inclusion water extracted from fluorite (,11.6, to +1.1,). The ,D values of directly measured fluid inclusion water range between ,29, and ,1,, ,26, and ,15,, and ,63, and +9, for fluorite, quartz, and calcite, respectively. Calculations using the fluid inclusion and isotope data point to formation of the fluorite,barite,quartz veins under near-hydrostatic conditions. The ,18OH2O and ,D data, particularly the observed wide range in ,D, indicate that the mineralization formed through large-scale mixing of a basement-derived saline NaCl,CaCl2 brine with meteoric water. Our comprehensive study provides evidence for two fundamentally different fluid systems in the crystalline basement. The Variscan fluid regime is dominated by fluids generated through metamorphic devolatilization and fluid expulsion driven by compressional nappe tectonics. The onset of post-Variscan extensional tectonics resulted in replacement of the orogenic fluid regime by fluids which have distinct compositional characteristics and are related to a change in the principal fluid sources and the general fluid flow patterns. This younger system shows remarkably persistent geochemical and isotopic features over a prolonged period of more than 100 Ma. [source]

Syntectonic infiltration by meteoric waters along the Sevier thrust front, southwest Montana

K-feldspar alteration to gel material and crystallization of glauconitic peloids with berthierine in Cretaceous marine sediments,sedimentary implications (Prebetic Zone, Betic Cordillera, SE Spain)

GEOLOGICAL JOURNAL, Issue 1 2008
Juan Jiménez-Millán
Abstract Glauconitic peloids from a Hauterivian condensed level in a hemipelagic unit of the Internal Prebetic (Los Villares Formation, eastern Betic Cordillera) have been studied by X-ray diffraction (XRD), optical microscopy, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) and analytical electron microscopy (AEM). The sediments forming the condensed level are characterized by abundant spherical to ovoid green glauconite peloids with radial cracks. Quartz, feldspar and muscovite are also abundant, whereas calcium phosphate is rarely detected. XRD analysis of the peloids reveals glauconite and small amounts of berthierine. SEM and HRTEM data show feldspar dissolution features, a Si,Al-rich gel-like substance filling K-feldspar micropores and interlayering of well-crystallized glauconite and berthierine packets. The last stage of the glauconitization process resulted in conversion of the smectitic precursor. Sedimentary and mineralogical features indicate an autochthonous origin for the glauconite. The depositional environment was a distal, hemipelagic ramp on the Southern Iberian Continental Palaeomargin. Low sedimentation rates lead to sediment condensation in a general transgressive context. The margin was affected by extensional tectonics, creating tilted blocks, resulting in lateral facies changes. The dissolution of K-feldspars probably occurred after their deposition in the marine environment but predating the glauconitization. An influx of meteoric water is therefore required, probably related to subsurface fluxes from adjacent emergent areas (the higher parts of tilted blocks). Copyright © 2007 John Wiley & Sons, Ltd. [source]

Origin and geochemistry of Miocene marine evaporites associated with red beds: Great Kavir Basin, Central Iran

GEOLOGICAL JOURNAL, Issue 1 2007
Hossain Rahimpour-Bonab
Abstract During the Cenozoic numerous shallow epicontinental evaporite basins formed due to tectonic movements in the Northern Province of the Central Iran Tectonic Zone (the Great Kavir Basin). During the Miocene, due to sea-level fluctuations, thick sequences of evaporites and carbonates accumulated in these basins that subsequently were overlain by continental red beds. Development of halite evaporites with substantial thickness in this area implies inflow of seawater along the narrow continental rift axis. The early ocean basin development was initiated in Early Eocene time and continued up to the Middle Miocene in the isolated failed rift arms. Competition between marine and non-marine environments, at the edge of the encroaching sea, produced several sequences of both abrupt and gradual transition from continental wadi sediments to marginal marine evaporites in the studied area. These evaporites show well-preserved textures indicative of relatively shallow-brine pools. The high Br content of these evaporites indicates marine-derived parent brines that were under the sporadic influence of freshening by meteoric water or replenishing seawater. However, the association of hopper and cornet textures denotes stratified brine that filled a relatively large pool and prevented rapid variations in the Br profile. Unstable basin conditions that triggered modification of parent brine chemistry prevailed in this basin and caused variable distribution patterns for different elements in the chloride units. The presence of sylvite and the absence of Mg-sulphate/chlorides in the paragenetic sequence indicate SO4,depleted parent brine in the studied sequence. Petrographic examinations along with geochemical analyses on these potash-bearing halites reveal parental brines which were a mixture of seawater and CaCl2 -rich brines. The source of CaCl2 -rich brines is ascribed to the presence of local rift systems in the Great Kavir Basin up to the end of the Early Miocene. Copyright © 2007 John Wiley & Sons, Ltd. [source]

In situ hydraulic tests in the active fault survey tunnel, Kamioka Mine, excavated through the active Mozumi-Sukenobu Fault zone and their hydrogeological significance

ISLAND ARC, Issue 4 2006
Tsuyoshi Nohara
Abstract The spatial hydrogeological and structural character of the active Mozumi-Sukenobu Fault (MSF) was investigated along a survey tunnel excavated through the MSF in the Kamioka Mine, central Japan. Major groundwater conduits on both sides of the MSF are recognized. One is considered to be a subvertical conduit between the tunnel and the surface, and the other is estimated to be a major reservoir of old meteoric water alongside the MSF. Our studies indicate that part of the MSF is a sub-vertical continuous barrier that obstructs younger meteoric water observed in the south-eastern part of the Active Fault Survey Tunnel (AFST) and water recharge to the rock mass intersected by the north-western part of the AFST. The MSF might be a continuous barrier resulting in the storage of a large quantity of older groundwater to the northwest. The observations and results of in situ hydraulic tests indicate that the major reservoir is not the fault breccia associated with the northeast,southwest trending faults of the MSF, but the zone in which blocks of fractured rocks occur beside high angle faults corresponding to X shears whose tectonic stress field coincides with the present regional stress field and antithetic Riedel shears of the MSF. The results from borehole investigations in the AFST indicate that secondary porosity is developed in the major reservoir due to the destruction of filling minerals and fracture development beside these shears. The increase in hydraulic conductivity is not directly related to increased density of fractures around the MSF. Development of secondary porosity could cause the increase in hydraulic conductivity around the MSF. Our results suggest that minor conduits of the fracture network are sporadically distributed in the sedimentary rocks around the MSF in the AFST. [source]

Study of mineral water resources from the Eastern Carpathians using stable isotopes,

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2009
Dana A. Magdas
The Eastern Carpathians contain many mineral water springs that feed famous Romanian health resorts such as Borsec, Biborteni and Vatra Dornei. These waters have been used for their different therapeutic effects. In this work, mineral and spring waters from these Romanian regions were investigated by means of chemical and isotopic (,D and ,18O) analyses in order to understand the recharge mechanisms and also to determine their origins. Most of the investigated springs are of meteoric origin, having the average deuterium content of the local meteoric water. The higher 18O content with respect to the Meteoric Water Line (MWL) indicated an exchange reaction with crystalline igneous rocks at depth and with other rocks that the water encounters on its journey back to the surface. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Oxygen isotopes in nitrate: new reference materials for 18O:17O:16O measurements and observations on nitrate-water equilibration,,

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2003
J. K. Böhlke
Despite a rapidly growing literature on analytical methods and field applications of O isotope-ratio measurements of NO3, in environmental studies, there is evidence that the reported data may not be comparable because reference materials with widely varying ,18O values have not been readily available. To address this problem, we prepared large quantities of two nitrate salts with contrasting O isotopic compositions for distribution as reference materials for O isotope-ratio measurements: USGS34 (KNO3) with low ,18O and USGS35 (NaNO3) with high ,18O and ,mass-independent' ,17O. The procedure used to produce USGS34 involved equilibration of HNO3 with 18O-depleted meteoric water. Nitric acid equilibration is proposed as a simple method for producing laboratory NO3, reference materials with a range of ,18O values and normal (mass-dependent) 18O:17O:16O variation. Preliminary data indicate that the equilibrium O isotope-fractionation factor (,) between [NO3,] and H2O decreases with increasing temperature from 1.0215 at 22°C to 1.0131 at 100°C. USGS35 was purified from the nitrate ore deposits of the Atacama Desert in Chile and has a high 17O:18O ratio owing to its atmospheric origin. These new reference materials, combined with previously distributed NO3, isotopic reference materials IAEA-N3 (=IAEA-NO-3) and USGS32, can be used to calibrate local laboratory reference materials for determining offset values, scale factors, and mass-independent effects on N and O isotope-ratio measurements in a wide variety of environmental NO3, samples. Preliminary analyses yield the following results (normalized with respect to VSMOW and SLAP, with reproducibilities of ±0.2,0.3,, 1,): IAEA-N3 has ,18O,=,+25.6, and ,17O,=,+13.2,; USGS32 has ,18O,=,+25.7,; USGS34 has ,18O,=,,27.9, and ,17O,=,,14.8,; and USGS35 has ,18O,=,+57.5, and ,17O,=,+51.5,. Published in 2003 by John Wiley & Sons, Ltd. [source]

Hydrothermal Alteration and Cu-Au Mineralization at Nena High Sulfidation-type Deposit, Frieda River, Papua New Guinea

RESOURCE GEOLOGY, Issue 4 2002
Joseph Onglo Espi
Abstract. The Nena Cu-Au deposit, located in the Frieda River mineral district of northwestern mainland Papua New Guinea, is a composite structurally-lithologically controlled high sulfidation (HS) system. Its hydrothermal alteration and Cu-Au mineralization are presented in this paper. Initially propylitized andesitic volcanics veined by epithermal quartz were pervasively superimposed by zoned HS alteration. The zonation grades from vuggy silica core to sulfur-rich, pyritic silica-alunite halo followed by pyrophyllite-dickite-kaolinite interval and finally to thin illite-smectite margin, suggesting progressive decrease in temperature and increase in pH. This zonation is enveloped by chlorite-epidote-calcite-gypsum alteration. The acid altered rocks were then invaded by multiple phases of pyrite, subsequently crosscut by quartz, vein alunite and barite. Then sequential deposition of bladed covellite, enargite, luzonite and stibioluzonite occurred from the NW to the SE portions of the deposit, forming a zonation suggestive of progressive decrease in temperature, sulfur fugacity and sulfidation stage. Most ore mineralization occurs in the vuggy silica core. Gold mineralization commenced from the transition of enargite to luzonite and continued throughout the stibioluzonite stage. Associated with gold deposition are Au-rich pyrite, tennantite-tetrahedrite, chalcopyrite-bornite, native tellurium, electrum, calaverite, bismuthinite and galena. Native sulfur occupied the remaining cavities and represents the waning stage of the hydrothermal system. Fluid inclusions studies distinguished magmatic (>300,350d,C, 9,15 wt% NaCl equiv.) and meteoric (<150,200d,C, 1,2 wt% NaCl equiv.) fluids (Holzberger et al., 1996). Temperatures and salinities of fluid inclusions from barite associated with Cu sulfides show a general decrease from NW (330d,C, 9,15 wt% NaCl equiv.) to SE (172d,C, 10 wt% NaCl equiv.) parts of the deposit, indicating gradual entrainment of ground water (Hitchman and Espi, 1997). Interaction of magmatic fluids with meteoric water accompanied by changes in temperature, salinity, acidity and oxidation state of the resultant fluids is interpreted to have been the main cause of metal precipitation. Finally, supergene processes generated Au zone with an underlying chalcocite-covellite-digenite blanket over the primary sulfides at depth. Gold occurs as lattice constituent in scorodite, limonite-goethite and jarosite. Chalcocite is more abundant and widespread than other Cu sulfides. Acidic fluids deposited powdery alunite and kaolinite, vein alunite and amorphous silica. Weakly secondary biotite-quartz altered porphyry located below the known HS Cu-Au deposit contains chalcopyrite-bornite and is overprinted by quartz-alunite-pyro-phyllite-pyrite assemblage. This feature indicates close temporal, spatial and genetic relation between the two deposit types. [source]

Mineralogy, Geochemistry, and Age Constraints on the Beni Bou Ifrour Skarn Type Magnetite Deposit, Northeastern Morocco

RESOURCE GEOLOGY, Issue 1 2002
Mohammed EL RHAZI
Abstract: The Beni Bou Ifrour deposit of northeastern Morocco is a skarn type magnetite deposit. K-Ar age determination suggests that the mineralization occurred at 7.040.47 Ma. The spatial relationship between skarn and dikes of microgran-odiorite derived from the batholith of Wiksane Granodiorite, and the similarity of age (8.020.22 Ma), confirms that the Wiksane Granodiorite is the igneous rock most probably related to mineralization. The skarn is distributed asymmetrically in the limestone, and magnetite ore was developed just below the calc-silicate skarn as two parallel beds separated by 100 m of barren limestone and schist. The mineralization can be divided into three stages. The early stage is characterized by the formation of calc-silicate minerals, mainly clinopyroxene (80,70 % diopside) and garnet (early almost pure andradite to the late 60 % andradite). The main stage is characterized by the formation of a large amount of magnetite. Epidote and quartz formed simultaneously with magnetite. Fluid temperatures exceeded 500 C during the early to main stages. Fluid with very high salinity (50,75 wt% NaCl equiv.) was responsible for the formation of the magnetite ore. The oxygen isotope composition, together with the fluid inclusion data, suggests that magmatic fluid was significant for the formation of calc-silicate skarn minerals and magnetite. Low temperature (-230C) and low salinity (-10 % NaCl equiv.) hydrothermal fluids dominated by meteoric water were responsible for the late stage quartz and calcite formation. [source]

Hydrothermal Fluid Evolution Associated with Gold Mineralization at the Wenyu Mine, Xiaoqinling District, China

RESOURCE GEOLOGY, Issue 2 2000
Neng JIANG
Abstract: The Wenyu mesothermal gold deposit is located in the Xiaoqinling district about 1000 km southwest of Beijing in central China. It occurs in the Late Archean to Early Proterozoic metamorphosed volcanic and sedimentary rocks. Three distinct stages of veins have been identified: (I) gold-poor quartz,pyrite veins, (II) gold-rich sulfide,quartz veins, and (III) gold-poor carbonate,quartz veins. Stage II can be subdivided into IIa and IIb. Gold typically occurs as fracture-fillings associated with chalcopyrite and galena. Fluid inclusions were examined in quartz samples from veins of both stage I and II. Three types of fluid inclusions are identified: CO2,H2O, CO2,rich, and aqueous inclusions. The first two types are of primary in origin. The last type occurs in two ways: coexisting with CO2,H2O and CO2,rich inclusions and thus primary in origin; and occurring along late healed fractures and hence secondary in origin. CO2,H2O inclusions display progressively decreasing Th and increasing Thco2, from the highest Th (311,408C) and lowest Thco2 (average 18C) in stage I quartz through middle Th (284,358C) and ThCO2(average 25C) in stage IIa quartz to the lowest Th (275,314C) and highest ThCO2 (average 28C) in stage IIb quartz, indicating an evolving H2O,CO2,NaCl fluid system. CO2,rich and primary aqueous inclusions show consistent ThCO2 or Th with their coexistent CO2,H2O inclusions. Whereas the secondary aqueous inclusions in stage I and IIa quartz have almost the same Th and salinity as the primary aqueous inclusions in stage IIb quartz. Comparing with CO2,H2O inclusions, these non,CO2, low salinity aqueous inclusions may come from different origin, most probably meteoric water. Unlike in both stage I and IIa quartz, fluid inclusions in stage IIb do not show evidence of fluid immiscibility. The fact that most of gold is associated with stage IIa and IIb veins and not with veins of stage I which is the main stage of vein formation suggests that gold deposition occurs at the later stage of fluid immiscibility. The continuing phase separation led to the deposition of large amounts of gold at the Wenyu mine. [source]

Stable Isotope Study of the Langshan Polymetallic Mineral District, Inner Mongolia, China

RESOURCE GEOLOGY, Issue 1 2000
Ping DING
The lead isotope study shows that these deposits were probably formed from 2. 0 to 1. 5 Ga, and were deformed and metamorphosed 1. 45 Ga. Ore lead could be a mixture of mantle lead and crustal lead. The C and S isotope results indicate that these deposits were precipitated in closed or semi-closed rift basins, and the source of sulfur might be Proterozoic ocean sulfate. The H and O isotope results indicate that the ,D and ,18O values of rocks were changed by water-rock interaction during metamorphism and hydrothermal alteration. The scale of ,D and ,18O shift of rocks reflects the grade of metamorphism and alteration as well as the water-rock ratios. However, the water-rock ratios in the metamorphic processes of Langshan mineral district were relatively low, and the source of water during metamorphism is suggested to be ancient meteoric water. Based on isotopic results and the geological background, it is concluded that these deposits may belong to Proterozoic sedimentary exhalative (SEDEX) type. [source]

Origin of Paleofluids in Dabashan Foreland Thrust Belt: Geochemical Evidence of 13C, 18O and 87Sr/86Sr in Veins and Host Rocks

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 5 2010
ZENG Jianhui
Abstract: In the last ten years, with important discoveries from oil and gas exploration in the Dabashan foreland depression belt in the borderland between Shanxi and Sichuan provinces, the relationship between the formation and evolution of, and hydrocarbon accumulation in, this foreland thrust belt from the viewpoint of basin and oil and gas exploration has been studied. At the same time, there has been little research on the origin of fluids within the belt. Based on geochemical system analysis including Z values denoting salinity and research on ,13C, ,18O and 87Sr/86Sr isotopes in the host rocks and veins, the origin of paleofluids in the foreland thrust belt is considered. There are four principal kinds of paleofluid, including deep mantle-derived, sedimentary, mixed and meteoric. For the deep mantle-derived fluid, the ,13C is generally less than ,5.0,PDB, ,18O less than ,10.0,PDB, Z value less than 110 and 87Sr/86Sr less than 0.70600; the sedimentary fluid is mainly marine carbonate-derived, with the ,13C generally more than ,2.0,PDB, ,18O less than ,10.0,PDB, Z value more than 120 and 87Sr/86Sr ranging from 0.70800 to 0.71000; the mixed fluid consists mainly of marine carbonate fluid (including possibly a little mantle-derived fluid or meteoric water), with the ,13C generally ranging from ,2.0, to ,8.0,PDB, ,18O from ,10.0, to ,18.0, PDB, Z value from 105 to 120 and 87Sr/86Sr from 0.70800 to 0.71000; the atmospheric fluid consists mainly of meteoric water, with the ,13C generally ranging from 0.0, to ,10.0,PDB, ,18O less than ,8.0%cPDB, Z value less than 110 and 87Sr/86Sr more than 0.71000. The Chengkou fault belt encompasses the most complex origins, including all four types of paleofluid; the Zhenba and Pingba fault belts and stable areas contain a simple paleofluid mainly of sedimentary type; the Jimingsi fault belt contains mainly sedimentary and mixed fluids, both consisting of sedimentary fluid and meteoric water. Jurassic rocks of the foreland depression belt contain mainly meteoric fluid. [source]

Distribution of the Ordovician Fluid in the Tahe Oilfield and Dynamic Response of Cave System S48 to Exploitation

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2008
LOU Zhanghua
Abstract: The Tahe Oilfield is a complex petroleum reservoir of Ordovician carbonate formation and made up of spatially overlapping fracture-cavity units. The oilfield is controlled by a cave system resulting from structure-karst cyclic sedimentation. Due to significant heterogeneity of the reservoir, the distribution of oil and water is complicated. Horizontally, a fresh water zone due to meteoric water can be found in the north part of the Akekule uplift. A marginal freshening zone caused by water released from mudstone compaction is found at the bottom of the southern slope. Located in a cross-formational flow discharge zone caused by centripetal and the centrifugal flows, the main part of the Tahe Oilfield, featuring high salinity and concentrations of Cl, and K++Na+, is favorable for accumulation of hydrocarbon. Three types of formation water in the Tahe Ordovician reservoir are identified: (1) residual water at the bottom of the cave after oil and gas displacement, (2) residual water in fractures/pores around the cave after oil and gas displacement, and (3) interlayer water below reservoirs. The cave system is the main reservoir space, which consists of the main cave, branch caves and depressions between caves. Taking Cave System S48 in the Ordovician reservoir as an example, the paper analyzes the fluid distribution and exploitation performance in the cave system. Owing to evaporation of groundwater during cross-formational flow, the central part of the main cave, where oil layers are thick and there is a high degree of displacement, is characterized by high salinity and Br, concentration. With high potential and a long stable production period, most wells in the central part of the main cave have a long water-free oil production period. Even after water breakthrough, the water content has a slow or stepwise increase and the hydrochemistral characteristics of the produced water in the central part of the main cave are uniform. From the center to the edge of the main cave, displacement and enrichment of oil/gas become weaker, residual water increases, and the salinity and concentration of Br, decrease. At the edge of the main cave, although the wells have a high deliverability at the beginning with a short stable production period and water-free production period. After water breakthrough, the pressure and deliverability drop quickly, and the water content rises quickly. The hydrochemistral characteristics of the produced water are relatively uniform. Wells in the branch caves have a relatively low deliverability at the beginning, with a short stable production period. Water breakthrough appears quickly and then the pressure and deliverability drop quickly. The salinity and concentrations of Cl, and K++Na+ are usually fluctuant or descend slowly in the produced water. Wells in low areas of ancient karst have a low deliverability and a short stable production period. The yield drops quickly and the water content is high, while the characteristics of the produced water may vary significantly well to well. The salinity and concentrations of Cl, and K++Na+ in the produced water are usually fluctuant with a precipitous decline. [source]

Mineralogical and Geochemical Constraints on Arsenic Mobility in a Philippine Geothermal Field

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 2 2006
Chelo PASCUA
Abstract, Arsenic is usually associated with sulphide minerals formed in the geothermal environment. However, sulphide minerals are prone to dissolution after contact with meteoric water under surface oxidizing conditions. Secondary precipitates that form from the dissolution of the primary sulfides exert a greater influence on arsenic mobility in the geothermal environment. Fe-hydroxides have very good affinity with dissolved arsenate and are stable under most surface oxidizing conditions. Both amorphous silica directly precipitated from geothermal fluids and possibly a kaolinite alteration can host a small significant amount of arsenic. These silicates are also more stable under a wide range of pH and redox conditions. [source]

Uranium Provinces in China

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2000
CHEN Zhaobo
Abstract, Three uranium provinces are recognized in China, the Southeast China uranium province, the Northeast China-Inner Mongolia uranium province and the Northwest China (Xinjiang) uranium province. The latter two promise good potential for uranium resources and are major exploration target areas in recent years. There are two major types of uranium deposits: the Phanerozoic hydrothermal type (vein type) and the Meso-Cenozoic sandstone type in different proportions in the three uranium provinces. The most important reason or prerequisite for the formation of these uranium provinces is that Precambrian uranium-enriched old basement or its broken parts (median massifs) exists or once existed in these regions, and underwent strong tectonomagmatic activation during Phanerozoic time. Uranium was mobilized from the old basement and migrated upwards to the upper structural level together with the acidic magma originating from anatexis and the primary fluids, which were then mixed with meteoric water and resulted in the formation of Phanerozoic hydrothermal uranium deposits under extensional tectonic environments. Erosion of uraniferous rocks and pre-existing uranium deposits during the Meso-Cenozoic brought about the removal of uranium into young sedimentary basins. When those basins were uplifted and slightly deformed by later tectonic activity, roll-type uranium deposits were formed as a result of redox in permeable sandstone strata. [source]

Syntectonic infiltration by meteoric waters along the Sevier thrust front, southwest Montana

Origin of quartz geodes from Laño and Tubilla del Agua sections (middle,upper Campanian, Basque-Cantabrian Basin, northern Spain): isotopic differences during diagenetic processes

GEOLOGICAL JOURNAL, Issue 2 2002
Juan J. Gómez-Alday
Abstract Quartz geodes and nodular chert have been found within middle,upper Campanian carbonate sediments from the Laño and Tubilla del Agua sections of the Basque-Cantabrian Basin, northern Spain. The morphology of geodes together with the presence of anhydrite laths included in megaquartz crystals and spherulitic fibrous quartz (quartzine-lutecite), suggest an origin from previous anhydrite nodules. The anhydrite nodules at Laño were produced by the percolation of marine brines, during a period corresponding to a sedimentary gap, with ,34S and ,18O mean values of 18.8, and 13.6, respectively, consistent with Upper Cretaceous seawater sulphate values. Higher ,34S and ,18O mean values of 21.2, and 21.8, recorded in the Tubilla del Agua section are interpreted as being due to a partial bacterial sulphate reduction process in a more restricted marine environment. The idea that sulphates may have originated from the leaching of previously deposited Keuper sulphate evaporites with subsequent precipitation as anhydrite, is rejected because the ,34S, ,18O and 87Sr/86Sr values of anhydrite laths observed at both the Tubilla del Agua and Laño sections suggest an origin from younger marine brines. Later calcite replacement and precipitation of geode-filling calcite is recorded in both sections, with ,13C and ,18O values indicating the participation of meteoric waters. Synsedimentary activity of the Peñacerrada diapir, which lies close to the Laño section, played a significant role in the local shallowing of the basin and the formation of quartz geodes. In contrast, eustatic shallowing of the inner marine series of the Tubilla del Agua section led to the generation of morphologically similar quartz geodes. Copyright © 2002 John Wiley & Sons, Ltd. [source]

,Distribution of oxygen-18 and deuterium in river waters across the United States

HYDROLOGICAL PROCESSES, Issue 7 2001
Carol Kendall
Abstract Reconstruction of continental palaeoclimate and palaeohydrology is currently hampered by limited information about isotopic patterns in the modern hydrologic cycle. To remedy this situation and to provide baseline data for other isotope hydrology studies, more than 4800, depth- and width-integrated, stream samples from 391 selected sites within the USGS National Stream Quality Accounting Network (NASQAN) and Hydrologic Benchmark Network (HBN) were analysed for ,18O and ,2H (http://water.usgs.gov/pubs/ofr/ofr00-160/pdf/ofr00-160.pdf). Each site was sampled bimonthly or quarterly for 2·5 to 3 years between 1984 and 1987. The ability of this dataset to serve as a proxy for the isotopic composition of modern precipitation in the USA is supported by the excellent agreement between the river dataset and the isotopic compositions of adjacent precipitation monitoring sites, the strong spatial coherence of the distributions of ,18O and ,2H, the good correlations of the isotopic compositions with climatic parameters, and the good agreement between the ,national' meteoric water line (MWL) generated from unweighted analyses of samples from the 48 contiguous states of ,2H=8·11,18O+8·99 (r2=0·98) and the unweighted global MWL of sites from the Global Network for Isotopes in Precipitation (GNIP) of the International Atomic Energy Agency and the World Meteorological Organization (WMO) of ,2H=8·17,18O+10·35. The national MWL is composed of water samples that arise in diverse local conditions where the local meteoric water lines (LMWLs) usually have much lower slopes. Adjacent sites often have similar LMWLs, allowing the datasets to be combined into regional MWLs. The slopes of regional MWLs probably reflect the humidity of the local air mass, which imparts a distinctive evaporative isotopic signature to rainfall and hence to stream samples. Deuterium excess values range from 6 to 15, in the eastern half of the USA, along the northwest coast and on the Colorado Plateau. In the rest of the USA, these values range from ,2 to 6,, with strong spatial correlations with regional aridity. The river samples have successfully integrated the spatial variability in the meteorological cycle and provide the best available dataset on the spatial distributions of ,18O and ,2H values of meteoric waters in the USA. Published in 2001 by John Wiley & Sons, Ltd. [source]

DOLOMITIZATION OF THE EARLY EOCENE JIRANI DOLOMITE FORMATION, GABES-TRIPOLI BASIN, WESTERN OFFSHORE, LIBYA

JOURNAL OF PETROLEUM GEOLOGY, Issue 4 2000
I. Y. Mriheel
Dolomitization in the early Eocene Jirani Formation in the Gabes-Tripoli Basin (offshore western Libya) occurred in two stages. Stage I dolomites are composed of two types, one associated with anhydrite (Type I) the other anhydrite free (Type II,). The stratigraphic and sedimentological settings together with petrographic and geochemical criteria suggest that dolomitization was effected by refluxed evaporative seawater. Stable isotope and trace element analyses suggest dolomitization of both Types from a fluid of near-surface seawater composition under oxidising conditions modified by evaporation. Non-luminescence and lack ofzonation of all the dolomite indicate that the dolomitizing fluids maintained a relatively constant composition. The geologic setting during the early Eocene, interpreted as hypersaline lagoon, supports an evaporative reflux origin for the anhydritic dolomite Type I. Type II developed under less saline conditions in the transition zone between lagoon and open marine shelf. Stage II dolomitization is recorded by negative isotope values in both Types I and II indicating their dissolution and recrystallization (neomorphism) by dilute solutions. A period of exposure of the overlying Jdeir Formation following a relative sea-level fall allowed ingress of meteoric waters into both the Jdeir and the underlying Jirani Formations. Flushing by meteoric waters also resulted in development of excellent secondaly porosity and caused major dissolution of anhydrite to form the anhydritic-free dolomite facies typical of Type II. Following, and possibly during, both Stages I and II, low temperature dolomites (Type IIIa) precipitated in pore spaces from residual jluids at shallow burial depths, partially occluding porosity. In the late stage of basin evolution, medium clystalline, pore-filling saddle dolomite precipitated, causing some filling of mouldic and vuggy porosity (Type IIIb). Very light oxygen isotopic signatures confirm that it developed from high temperature fluids during deep burial diagenesis. Calculation of temperatures and timings of the dolomitization and cement phases show that the main dolomitization phases and Type IIIa cements occurred in the early Eocene, and that the saddle dolomite precipitated in the Miocene; these results are consistent with age relationships established from stratigraphic, petrographic and geochemical signatures. The most common porosity includes intercrystal, vuggy and mouldic types. Porosity is both pre-dolomitization and syn-dolomitization in origin, but the latter is the most dominant. Hence, reservoir quality is largely controlled by fluid dynamics. [source]

Multielement (H, C, N, O, S) stable isotope characteristics of lamb meat from different Italian regions,

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2009
Matteo Perini
The study focuses on the 2H/H, 13C/12C, 15N/14N, 18O/16O and 34S/32S values of defatted dry matter (DFDM) and on the 2H/H, 13C/12C and 18O/16O values of the fat fraction of meat samples from various lamb types reared in seven Italian regions, following different feeding regimes (forage, concentrate, milk). The 13C/12C (r,=,0.922), 2H/H (r,=,0.577) and 18O/16O (r,=,0.449) values of fat and DFDM are significantly correlated, the fat values being significantly lower for C and H and higher for O than for DFDM values and the differences between the two fractions not being constant for different lamb types. The feeding regime significantly affected the 13C/12C, 15N/14N, 18O/16O and 2H/H of fat. The DFDM 2H/H, and 18O/16O values, excluding an outlier, are significantly correlated with the corresponding values in meteoric waters, thus allowing us to trace the variability of geoclimatic factors. 15N/14N is influenced by pedoclimatic conditions, whereas 34S/32S is influenced by the sea spray effect and the surface geology of the provenance area. By applying stepwise linear discriminant analysis only the 2H/H of fat was found not to be significant and 97.7% of the samples were correctly assigned to the lamb type and more than 90% cross-validated. With the feeding regime, 97.7% of the samples were both correctly assigned and cross-validated using a predictive model including 13C/12C, 15N/14N, 18O/16O, 34S/32S of DFDM and 18O/16O of fat. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Fluid Evolution and Metallogenic Dynamics during Tectonic Regime Transition: Example from the Jiapigou Gold Belt in Northeast China

RESOURCE GEOLOGY, Issue 2 2009
Jun Deng
Abstract The Jiapigou gold belt, one of the most important gold-producing districts in China, is located in the northern margin of the North China Craton (NCC). The tectonic evolution of the gold belt is closely related to the Siberian Plate (SP) in the north, Yangtze Craton (YC) in the south and Pacific Plate in the east. In order to investigate the nature of the tectono-fluid-metallogenic system, the authors investigated the relationships among the tectonic regimes, fluid evolution and metallogenesis. This paper examined the corresponding spatial,temporal relationship between the ore-controlling tectonic regime and hydrothermal fluid evolution in the Jiapigou gold belt. There are two types of gold mineralization: disseminated ores that are distributed within the NW-trending main ductile shear zone and gold-bearing quartz veins and minor disseminated ores that are distant to the ductile shear zone. The fluid inclusions in quartz contain a large amount of CO2. Metamorphic fluids of middle to high temperatures and pressures and meteoric waters of low temperatures and pressures mixed together during mineralization. A proposed ore-forming model is as follows: in the pre-ore phase, the collision of SP and NCC resulted in the NS-trending compression of the ore belt. This formed the NE-trending and NW-trending shear faults and EW-trending folds. During the ore-forming phase, the collision of YC and NCC resulted in dextral shearing of the NW-trending Jiapigou fault and the NE-trending Green faults. High-pressure fluids caused by the compression flowed into the dilatant zone. This may have caused both phase separation of CO2 -bearing fluids and the mixing of meteoric waters, metamorphic waters and magmatic source fluids and finally resulted in the disequilibrium of the ore fluids and precipitation of ore minerals. [source]

Geology, Wall-rock Alteration and Vein Paragenesis of the Bilimoia Gold Deposit, Kainantu Metallogenic Region, Papua New Guinea

RESOURCE GEOLOGY, Issue 3 2007
Joseph Onglo Espi
Abstract The Bilimoia deposit (2.23 Mt, 24 g/t Au), located in the eastern Central Mobile Belt of mainland Papua New Guinea, is composed of fault-hosted, NW,NNW-trending Irumafimpa,Kora and Judd,Upper Kora Au-quartz veins hosted by Middle,Late Triassic basement that was metamorphosed to medium-grade greenschist facies between Middle,Late Triassic and Early,Middle Jurassic. Mineralizing fluids were introduced during crustal thickening, rapid uplift, change of plate motions from oblique to orthogonal compression, active faulting and S3 and S4 events in an S1,S4 deformation sequence. The Bilimoia deposit is spatially and temporally related to I-type, early intermediate to felsic and late mafic intrusions emplaced in Late Miocene (9,7 Ma). Hydrothermal alteration and associated mineralization is divided into 10 main paragenetic stages: (1) chlorite,epidote-selvaged quartz,calcite,specularite vein; (2) local quartz,illite,pyrite alteration; (3) quartz,sericite,mariposite,fuchsite,pyrite wall-rock alteration that delimits the bounding shears; (4) finely banded, colloform-, crustiform- and cockade-textured and drusy quartz ± early wolframite ± late adularia; (5) hematite; (6) pyrite; (7) quartz ± amethyst-base metal sulfides; (8) quartz,chalcopyrite,bornite,Sn and Cu sulfides,Au tellurides and Te ± Bi ± Ag ± Cu ± Pb phases; (9) Fe ± Mn carbonates; and (10) supergene overprint. Fluid inclusions in stage 4 are characterized by low salinity (0.9,5.4 wt% NaCl equivalent), aqueous,carbonic fluids with total homogenization temperatures ranging from 210 to 330°C. Some of the inclusions that homogenized between 285 and 330°C host coexisting liquid- and vapor-rich (including carbonic) phases, suggesting phase separation. Fluid inclusions in quartz intergrown with wolframite have low salinity (0.9,1.2 wt% NaCl equivalent), aqueous,carbonic fluids at 240,260°C, defining the latter's depositional conditions. The ore fluids were derived from oxidized magmatic source initially contaminated by reduced basement rocks. Wall-rock alteration and involvement of circulating meteoric waters were dominant during the first three stages and early part of stage 4. Stage 5 hematite was deposited as a result of stage 4 phase separation or entrainment of oxygenated groundwater. Gold is associated with Te- and Bi-bearing minerals and mostly precipitated as gold-tellurides during stage 8. Gold deposition occurred below 350°C due to a change in the sulfidation and oxidation state of the fluids, depressurization and decreasing temperature and activities of sulfur and tellurium. Bisulfides are considered to be the main Au-transporting complexes. The Bilimoia deposit has affinities that are similar to many gold systems termed epizonal orogenic and intrusion-related. The current data allow us to classify the Bilimoia deposit as a fault-controlled, metamorphic-hosted, intrusion-related mesothermal to low sulfidation epithermal quartz,Au,Te,Bi vein system. [source]