syndeformational fluid trapping in quartz determining the pressure temperature conditions of deformation from fluid inclusions and the formation of pure co2fluid inclusions during grain boundary migration observations and microthermometric data on fluid inclusions from a terrane that underwent deformation following peak metamorphic conditions show that grain boundary migration recrystallization favours the entrapment of carbonic inclusions whereas microfracturing during brittle deformation favours the infiltration and eventual entrapment of aqueous fluids our results imply that pure co2 fluid inclusions in metamorphic rocks are likely to be the residue of deformation recrystallization process rather than representing a primary metamorphic fluid where the temperature of deformation can be deduced by other means the densities of fluid inclusions trapped during recrystallization which we call recrystallization primary fluid inclusions can be used to constrain the ambient pressure during deformation using these constraints the data imply that the post metamorphic hercynian exhumation in sardinia brought rocks at 300 c to within 3km of the surface this conclusion is similar to that described for the rapidly uplifted southern alps in new zealand

understanding the emplacement of martian volcanic rocks using petrofabrics of the nakhlite meteorites in order to validate calculated ages of the martian crust we require precise radiometric dates from igneous rocks where their provenance on the martian surface is known martian meteorites have been dated precisely and quantitatively but the launch sites are currently unknown inferring the formation environment of a correlated suite of martian meteorites can constrain the nature and complexity of the volcanic system they formed from the nakhlite meteorites are such a suite of augite rich rocks that sample the basaltic crust of mars and as such can provide unique insights into its volcanic processes using electron backscatter diffraction we have determined the shape preferred and crystallographic preferred orientation petrofabrics of four nakhlites governador valadares lafayette miller range 03346 and nakhla in order to understand the conditions under which their parent rocks formed in all samples there is a clear link between the shape preferred orientation spo and crystallographic preferred orientation cpo of augite phenocrysts this relationship reveals the three dimensional shape of the augite crystals using cpo as a proxy for 3d spo and also enables a quantitative 3 dimensional petrofabric analysis all four nakhlites exhibit a foliation defined by the cpo of the augite axis in a plane although individual meteorites show subtle textural variations nakhla and governador valadares display a weak cpo lineation within their axis foliation that is interpreted to have developed in a combined pure shear simple shear flow regime indicative of emplacement of their parent rock as a subaerial hyperbolic lava flow by contrast the foliation dominated cpo petrofabrics of lafayette and miller range 03346 suggest formation in a pure shear dominated regime with little influence of hyperbolic flow these cpo petrofabrics are indicative of crystal settling in the stagnant portion of cooling magma bodies or the flattening area of spreading lava flows the cpo foliation of lafayette s is substantially weaker than miller range 03346 probably due to its higher phenocryst density causing grain grain interactions that hindered fabric development the cpo petrofabrics identified can also be used to determine the approximate plane of the martian surface and the line of magma flow to within 20 our results suggest that the nakhlite launch crater sampled a complex volcanic edifice that was supplied by at least three distinct magmatic systems limiting the possible locations these rocks could have originated from on mars

grain boundary migration of water and carbon dioxide during uplift of garnet zone alpine schist new zealand deformed quartz veins in garnet zone schist adjacent to the active alpine fault new zealand have fluid inclusions trapped along quartz grain boundaries textures suggest that the inclusions formed in their present shapes during annealing of the deformed veins many of the inclusions are empty but some contain carbon dioxide with densities that range from 0 16 to 0 80 g cm 3 no water nitrogen or methane was detected the inclusions are considerably more co2 rich than either the primary metamorphic fluid 5 co2 or fluids trapped in fracture related situations in the same or related rocks 50 co2 enrichment of co2 is inferred to have resulted from selective migration wicking of saline water from the inclusions along water wet grain boundaries after cooling induced immiscibility of a water co2 mixture inclusion volumes changed after loss of water non wetting co2 remained trapped in the inclusions until further percolation progressively removed co2 in solution this mechanism of fluid migration dominated in ductile quartz rich rocks near but below the brittle ductile transition at deeper levels hydraulic fracturing is also an important mechanism for fluid migration whereas at shallower levels advection through open fractures dominates the fluid flow regime

origin and evolution of hydrothermal fluids in the taochong iron deposit middle lower yangtze valley eastern china evidence from microthermometric and stable isotope analyses of fluid inclusions abstract the middle lower yangtze river valley is one of the most important metallogenic belts in china hosting numerous cu fe au mo deposits the taochong deposit is located in the northern part of the fanchang iron ore district of the middle lower yangtze river metallogenic belt the fe orebody is hosted by middle carboniferous to lower permian limestones skarns and fe orebodies occur as tabular bodies along interlayer gliding faults at some distance from the inferred granitic intrusions field evidence and petrographic observations indicate that the three stages of hydrothermal activity the skarn iron oxide main mineralization stage and carbonate stages all contributed to the formation of the taochong iron deposit the skarn stage is characterized by the formation of garnet and pyroxene with high temperature hypersaline hydrothermal fluids with isotopic compositions similar to those of typical magmatic fluids these fluids were probably generated by the separation of brine from a silicate melt instead of the product of aqueous fluid immiscibility the iron oxide stage coincides with the replacement of garnet and pyroxene by actinolite chlorite quartz calcite and hematite the hydrothermal fluids at this stage are represented by saline fluid inclusions that coexist with vapor rich inclusions with anomalously low d values 66 to 94 the decrease in ore fluid 18 o water with time and decreasing depth is consistent with the decreases in fluid salinity and temperature the fluid d values also show a decreasing trend with decreasing depth both fluid inclusion and stable isotopic data suggest that the ore fluid during the main period of mineralization was evolved by the boiling of various mixtures of magmatic brine and meteoric water this process was probably induced by a drop in pressure from lithostatic to hydrostatic the carbonate stage is represented by calcite veins that cut across the skarn and orebody locally producing a dense stockwork this observation indicates the veins formed during the waning stages of hydrothermal activity the fluids from this stage are mainly represented by a variety of low salinity fluid inclusions as well as fewer high salinity inclusions these particular fluids have the lowest 18 o water values 2 2 to 0 4 and a wide of range of d values 40 to 81 which indicate that they were originated from a mixture of residual fluids from the oxide stage various amounts of meteoric water and possibly condensed vapor low temperature boiling probably occurred during this stage we also discuss the reasons behind the anomalously low d values in fluid inclusion water extracted by thermal decrepitation from quartz at high temperatures and suggest that calcite data provide a possible benchmark for adjusting low d values found in quartz intergrown with calcite

thin skinned thrust mineralization in the brasilia fold belt the example of the old luziânia gold deposit the luzi nia gold deposits in southern goias lie within the late proterozoic brasilia fold belt the rocks that host the gold mineralization are a monotonous series of hydrothermally altered phyllites that have been subject to low grade regional metamorphism the major controls on the gold mineralization are northeast trending and gently northwest dipping ductile brittle dextral reverse shear zones associated with regional thin skinned thrusting of the canastra group from a preliminary fluid inclusion study it is deduced that low salinity 7 eq wt nacl moderately dense h2o co2 ch4 ore fluids deposited gold at temperatures of 300 75 c and pressures of 1 5 to 3 kb in the filling stage of the vein formation post filling stage gold deposition probably occured by mixing of fluids at higher crustal levels 1 5 2 kb during thrusting prograde metamorphism released pore water which penetrated along thrust planes that acted as high permeability zones for the ponding and release by hydraulic fracturing of overpressured fluids later in the tectonic evolution and at shallower crustal levels there was likely an incursion of near suface water into the fault zone

fluid inclusion characteristics of hematite bearing quartz vein from the daenam mine republic of korea abstract the daenam mine which produced over 9250 tons of iron oxide ore from 1958 to 1962 is situated in the early cretaceous yeongyang subbasin of the gyeongsang basin it consists of two lens shaped hematite bearing quartz veins that occur along faults in cretaceous leucocratic granite the hematite bearing quartz veins are mainly composed of massive and euhedral quartz and hematite with minor amounts of pyrite pyrrhotite mica feldspar and chlorite fluid inclusions in quartz can be divided into three main types co2 rich co2 h2o and h2o rich hydrothermal fluids related to the formation of hematite are composed of either h2o co2 nacl ch4 homogenization temperature 262 455 c salinity

iron transport and deposition mechanisms in the taochong iron rich skarn deposit middle lower yangtze valley eastern china abstract the taochong skarn iron deposit is one of 38 iron prospects in the fanchang iron ore district of the middle lower yangtze river valley one of the most important economic mineral districts in china orebodies are hosted mainly within the middle upper carboniferous huanglong dolomitic limestone in this deposit two types of ore types 1 and 2 are recognized based on the mineral assemblage the type 1 ore is dominant throughout the deposit and consists mainly of hematite magnetite quartz and calcite this ore is characterized by euhedral and skeletal textures and massive brecciated comb like and vein structures the type 2 ore is composed of hematite garnet pyroxene actinolite chlorite quartz and calcite and has a relict metasomatic texture and disseminated structure field evidence and petrographic observations indicate that three stages of hydrothermal activity i e the skarn iron oxide and carbonate stages contributed to the formation of the taochong iron deposit the iron oxide stage can be further divided into early and late oxide stages which saw the formation of the type 2 and type 1 ores respectively fluid inclusion and stable isotope data indicate that the skarn formed at depths of 2 km under lithostatic pressure of 500 bars from high temperature 500 c acidic saline up to 50 wt nacl equiv and iron rich fluids that had chemical and isotopic compositions 18owater 4 5 11 7 similar to those of magmatic fluid replacing a certain amount of the huanglong dolomitic limestone the iron ores formed under hydrostatic conditions after fracturing of the early skarn fluid inclusions within quartz in equilibrium with hematite in the type 2 ores yields homogenization temperatures of 372 390 c and salinities of 31 39 wt nacl equiv whereas fluid inclusions within quartz in equilibrium with hematite in the type 1 ores has lower homogenization temperatures 280 320 c and variable salinities 0 40 wt nacl equiv during the formation of the type 1 ores fluids contained moderate concentrations of ions variable 13c values 5 3 to 5 8 and relatively convergent 18o values 1 7 4 5 the temporal decrease in the concentration of ions and 18o values in the fluid inclusions is matched by marked decreases in fluid salinity and temperature suggesting that the fluids of the oxide stage were mixtures of magmatic brine and meteoric water the coexistence of saline and vapor rich fluid inclusions as internal trails or clusters within individual quartz grains of the late oxide stage with contrasting homogenization characteristics for the liquid and vapor at similar temperatures strongly suggests that fluid boiling occurred during the late oxide stage our estimates of the physico chemical conditions during ore formation together with fluid inclusion data and the results of previous experimental studies indicate that iron in the taochong deposit was transported mainly as fecl4 along with minor amounts of other chloride complexes e g fecl2 and fecl2 h2o 4 the precipitation of hematite followed the breakdown of the iron chloride complexes probably induced by a decrease in temperature and ligand chloride ion activity and an increase in ph based on the results we infer that deposition of the type 2 ore was caused by the replacement of garnet and pyroxene by a retrograde alteration assemblage which was likely induced by fluid rock interaction and the mixing of magmatic brine and meteoric water the type 1 ore was deposited in open spaces probably induced by fluid boiling

origin of co2 rich fluid inclusions in synorogenic veins from the eastern mount isa fold belt nw queensland and their implications for mineralization synorogenic veins from the proterozoic eastern mount isa fold belt contain three different types of fluid inclusions co2 rich aqueous two phase and rare multiphase inclusions of co2 without a visible h2o phase are particularly common the close association of co2 rich inclusions with aqueous two phase and possibly multiphase inclusions suggests that phase separation of low to moderate salinity co2 rich hydrothermal fluids led to the selective entrapment of the co2 microthermometric results indicate that co2 rich inclusions homogenize between 15 5 and 29 9 c which corresponds to densities of 0 99 to 0 60 g cm 3 the homogenization temperatures of the associated aqueous two phase inclusions are 127 397 c with salinities of 0 5 to 18 1 wt nacl equivalent the rarely observed multiphase inclusions homogenize between 250 and 350 c and have salinities ranging from 34 6 to 41 5 wt nacl equivalent evidence used to support the presence of fluid immiscibility in this study is mainly derived from observations of coexisting h2o rich and co2 rich inclusions in groups and along the same trail in addition these two presumably unmixed fluids are also found on adjacent fractures where monophase co2 rich inclusions are closely related to h2o rich inclusions similar co2 rich inclusions are widespread in mineral deposits in this region which are simply metal enriched synorogenic veins therefore we argue that fluid immiscibility caused volatile species such as co2 and h2s to be lost from liquid thus triggering ore deposition by increasing the fluid ph and decreasing the availability of complexing ligands

p t x conditions of hydrothermal fluids and precipitation mechanism of stibnite gold mineralization at the wiluna lode gold deposits western australia conventional and infrared microthermometric constraints the wiluna lode gold deposits are located in the archean wiluna greenstone belt in the northern sector of the norseman wiluna belt in the yilgarn craton of western australia they are hosted in subgreenschist facies meta basalts and controlled by the wiluna strike slip fault system and associated shear veins and breccias the 13 individual lode gold deposits have produced around 115 t au from 1901 to 1946 and 1986 to today historically they also produced 38 3 t as and 3 5 t sb gold formed in two stages stage 1 gold pyrite arsenopyrite is finely disseminated in the wallrock and breccia fragments whereas stage 2 gold stibnite is located in massive shear veins and breccia matrix as fracture fill and in banded colloform textured veins stibnite gold orebodies only occur in some of the deposits e g moonlight and northern part of the west lode and also display a restricted vertical extent being preserved only in the uppermost 200 m of stibnite bearing lodes petrographic conventional and infrared microthermometric and laser raman analysis on stibnite bearing quartz veins and breccias reveal that the antimony and gold rich hydrothermal fluid was of mixed h2o nacl co2 ch4 type microthermometric measurements reveal maximum homogenization temperatures of 340 c average 290 25 c and a wide range of salinities between 0 2 and 23 eq wt nacl aqueous carbonic fluid inclusions contain variable xco2 ch4 0 03 to 0 82 with the carbonic phase containing a maximum xch4 of 0 21 combined petrographic and microthermometric evidence suggests that the fluid inclusion properties reflect fluid immiscibility of a low salinity medium xco2 ch4 homogeneous parent fluid at about 290 c and pressures between 700 and 1 700 bar fluid immiscibility was triggered by cyclic pressure release during fault zone movement the decompression adiabatic cooling of the hydrothermal fluids shifted the ore fluid to lower temperatures significantly reduced the degree of stibnite undersaturation and caused stibnite to precipitate the deposition of stibnite reduced the ore fluid h2s concentration thereby destabilized gold bisulfide complexes in solution and caused gold precipitation locally this mechanism explains the intimate spatial association of stibnite and gold in quartz veins and breccias in the stibnite gold orebodies at wiluna

genesis of high grade hematite orebodies of the hamersley province western australia a reply sir we are very thankful for the constructive comments provided by kneeshaw and kepert unfortunately the competitive ownership structure of the iron ore mining industry in the hamersley province limits our personal knowledge of the mount whaleback deposit to occasional mine visits and to the available literature published and unpublished we do however have access to the data on the smaller giles mini and lido deposits 50 and 10 km west of mount whaleback respectively and to extensive exploration mapping in the ophthalmia ranges to the north direct proof for rotation of the orebody as it is preserved at paraburdoo in the approximately 50 dip of the overlying proterozoic hematite conglomerates of the mount mcgrath formation is not preserved at mount whaleback however we believe that there is sufficient information available in the literature to think that a rotational model for a large part of the deposit is perfectly plausible first and above all as stated in taylor et al 2001 f2 folds are more upright with axial planes dipping about 50 s in the southern and western part of the deposit away from the whaleback fault e g as shown on section no 315120e fig 4 in powell et al 1999 interestingly the ore controlling faults are also more upright in this part of the deposit which suggests an intimate link between the dip of these fault planes and dip of the axial planes of f2 folds secondly

fluid immiscibility in natural processes use and misuse of fluid inclusion data ii interpretation of fluid inclusion data in terms of immiscibility abstract phase equilibrium analysis of the relevant systems together with the application of the principles of chemical equilibrium put severe constraints on the interpretation of fluid inclusion data in terms of immiscibility in part i following from that point the major limits on the accuracy and even the validity of fluid inclusion quantitative data and their interpretation in terms of fluid composition and density are briefly discussed the practical implications of the general constraints temperature pressure topology of the fluid systems are envisaged emphasis is laid on some important consequences such as the use of isochore intercepts and the possible resulting interpretation of fluid mixing rather than unmixing the case of highly saline inclusions the identification and interpretation of heterogeneous trapping the composition and density constraints on coexisting fluids are presented and illustrated by natural examples taking into account all the measurable parameters in fluid inclusions volume temperature and nature of phase transitions more or less complete individual spectroscopic analyses all the available experimental data and all the theoretical constraints may be long and difficult however it is most generally very informative and productive although part of these data is often sufficient to deny unmixing nevertheless a final example on metamorphic fluids demonstrates how such an approach can prove and also characterize a fluid unmixing during a geologic process

the bronzewing lode gold deposit western australia p t x evidence for fluid immiscibility caused by cyclic decompression in gold bearing quartz veins abstract the bronzewing lode gold deposit is located in the yandal greenstone belt in the yilgarn craton of western australia gold mineralization is hosted in tholeiitic basalt that is metamorphosed to greenschist facies individual ore bodies are controlled by a complex gold bearing quartz vein system that comprises shear and extension veins formed during a progressive d2 deformation event gold is localized in quartz along fractures and deformed grain boundaries and is interpreted to have formed late in the formation of the veins detailed petrography and microthermometry on primary pseudosecondary and secondary fluid inclusions trapped in gold bearing shear and extension veins revealed five types of fluid inclusions 1 co2 ch4 h2o nacl inclusions of variable salinity 0 1 to 17 5 eq wt nacl containing between 10 and 99 mol co2 and molar volumes that range from 22 to 76 cm3 2 h2o nacl inclusions of variable salinity 0 4 to 22 1 eq wt nacl 3 co2 ch4 inclusions with up to 58 mol ch4 and molar volumes between 54 and 73 cm3 4 ch4 h2o inclusions with ch4 ranging from 80 to 90 mol and 5 ch4 inclusions with low molar volumes of 19 to 23 cm3 types 1 2 and 3 constitute a fluid inclusion assemblage that occurs consistently in primary pseudosecondary and secondary trails and clusters within the gold bearing quartz vein system these co existing fluids are interpreted to have formed by fluid immiscibility of a low salinity homogeneous parent fluid at about 300 c and 1500 bars locally type 2 fluid inclusions exhibit total homogenization temperatures that are on average 100 c less than the co genetically trapped type 1 aqueous carbonic inclusions this discrepancy is interpreted to have involved co2 effervescence in response to fluid pressure fluctuations types 4 and 5 fluid inclusions are rare and are only present locally in secondary trails and clusters in extension veins significant pressure fluctuations but relatively constant homogenization temperatures for types 1 2 and 3 fluid inclusions suggest that cyclic decompression of the hydrothermal fluids due to seismic activity along the shear zones that host the gold bearing veins triggered fluid immiscibility the process of fluid immiscibility and subsequent lowering of gold solubility is interpreted to be the most efficient precipitation mechanism for gold in the d2 shear zone hosted vein system at bronzewing

fluid characteristics of granitoid hosted gold deposits in the birimian terrane of ghana a fluid inclusion microthermometric and raman spectroscopic study fluid inclusions in vein quartz from 10 granitoid hosted gold deposits and prospects in the birimian terrane of ghana as well as from the sansu mine ashanti shear zone type and quartz veins in the nonmineralized princess town granodiorite were studied by microthermometry and raman microspectrometry fluid inclusions from the granitoid hosted gold deposits are dominated by aqueous h2o co2 nacl type 1 and liquid co2 n2 ch4 type 2 with minor 10 aqueous h2o nacl type 3 type 1 inclusions show large variations in co2 phase volume proportions 10 90 at 25 c and have salinities commonly between 0 and 6 wt percent nacl equiv their bulk densities fall in a major range from 0 62 to 1 11 g cm3 type 2 inclusions show no visible h2o phase at room temperature and have bulk densities between 0 30 and 0 92 g cm3 type 3 inclusions containing 10 to 20 vol percent h2o vapor have salinities of 1 to 8 wt percent nacl equiv and bulk densities of 0 77 to 1 03 g cm3 in most cases the three types of fluid inclusions coexist as groups in individual quartz grains of the samples studied these fluid inclusions are interpreted to be trapped during phase separation of an originally homogeneous h2o co2 fluid with low salinity 6 wt nacl equiv and moderate to high density 0 65 0 95 g cm3 the type 1 fluid inclusions are suggested to be heterogeneous mixtures of the two end members of type 2 and 3 inclusions fluid immiscibility is documented by petrographic characteristics and microthermometric results of the three types of inclusions trapping temperatures and pressures estimated from microthermometry of type 3 inclusions equation of state and the p t x nature of the h2o co2 nacl system are mainly between 200 and 350 cand 1 and 3 kbars for the gold deposits by contrast fluid inclusions in the sansu mine at ashanti mostly comprise the liquid co2 n2 ch4 type 2 the inclusions are considered to represent postentrapment modifications of trapped fluids in addition fluid inclusions in barren vein quartz from the princess town granodiorite comprise the low salinity commonly 6 wt nacl equiv h2o nacl type 3 raman microspectrometry shows that gaseous compositions of fluid inclusions from both granitoid and shear zone hosted gold deposits are mainly composed of co2 80 95 mol with significant amounts of n2 2 20 mol and ch4 0 10 mol the distinct low salinity h2o co2 rich fluids from the granitoid hosted gold deposits are comparable in composition to those from the major ashanti and tarkwaian types of gold deposits in the birimian terrane of ghana these fluids are most likely to be metamorphic in origin and associated with the waning stages of the regional birimian orogeny gold deposition within the birimian granitoids was related to fluid phase separation and sulfidization of host rocks during hydrothermal alteration and mineralization the present study together with previous publications suggests that fluid inclusions are characterized by h2o co2 nacl and or co2 n2 ch4 types in mineralized areas whereas h2o nacl fluid compositions dominate in barren areas fluid inclusion characteristics may therefore be a useful tool for regional gold exploration in the birimian terrane of ghana

hydrothermal origin for the 2 billion year old mount tom price giant iron ore deposit hamersley province western australia giant iron ore deposits such as those in the hamersley province of northwestern australia may contain more than a billion tonnes of almost pure iron oxides and are the world s major source of iron it is generally accepted that these deposits result from supergene oxidation of host banded iron formation bif accompanied by leaching of silicate and carbonate minerals new textural evidence however shows that formation of iron ore at one of those deposits mount tom price involved initial high temperature crystallisation of magnetite siderite iron silicate assemblages this was followed by development of hematite and ferroan dolomite bearing assemblages with subsequent oxidation of magnetite leaching of carbonates and silicates and crystallisation of further hematite preliminary fluid inclusion studies indicate both low and high salinity aqueous fluids as well as complex salt rich inclusions with the range of fluid types most likely reflecting interaction of hydrothermal brines with descending meteoric fluids initial hematite crystallisation occurred at about 250 c and high fluid pressures and continued as temperatures decreased although the largely hydrothermal origin for mineralisation at mount tom price is in conflict with previously proposed supergene models it remains consistent with interpretations that the biosphere contained significant oxygen at the time of mineralisation

crustal structure from deep seismic soundings along the koyna ii kelsi loni profile in the deccan trap area india abstract the crustal depth section obtained from deep seismic soundings along the koyna ii kelsi loni profile which lies near latitude 18 n roughly in the east west direction in that part of the deccan trap maharashtra state india shows a number of reflection segments below the deccan traps down to the moho discontinuity a deep fault below the deccan traps 13 km east of mahad divides the entire cross section including the moho boundary into two crustal blocks the reflection segments show updip towards the west coast in the western block the moho discontinuity which is at a depth of 39 km near the deep fault starts rising towards the coast reaching a depth of 31 5 km at the west coast the eastern block is thrown up by 1 5 km with respect to the western block along the deep fault a structural contour map of the moho discontinuity for the koyna reservoir area has been prepared from the present results and the crustal information obtained along the koyna i profile kaila et al 1979a shows that the deep fault in the koyna area is aligned in the nnw sse direction refraction seismic data analysis by the wave front method reveals that the thickness of the deccan trap increases towards the west coast the deccan trap is 600 700 m thick in the eastern region between nira sp 130 and loni sp 200 and attains a thickness of 1500 m at 10 km east of the west coast the longitudinal wave velocity in the deccan traps along the profile varies from 4 8 to 5 0 km sec and in the crystalline basement from 6 0 to 6 15 km sec a tentative isopach contour map of the deccan traps and a tentative structural contour map of the pre deccan trap contact have been prepared for the koyna reservoir area from the results along the koyna ii and koyna i profiles a flexure aligned in a nnw sse direction in the pre deccan trap contact which is an expression of the deep fault into the basement has been clearly brought out the flexure coincides in general with the orientation of the deccan volcanic scarp in this area

enrichment of co2 in fluid inclusions in quartz by removal of h2o during crystal plastic deformation abstract ductile strain induced leakage of h 2 o from mixed co 2 h 2 o fluid inclusions in quartz is proposed as a mechanism for producing occurrences of pure co 2 fluid inclusions in metamorphic rocks the h 2 o needed for hydrolytic weakening of quartz under stress may be provided by the h 2 o in fluid inclusions with dislocation creep as dislocations nucleate on the walls of fluid inclusions or intersect them h 2 o can be transported with the dislocations from the inclusion to the grain boundaries the process should continue so long as there is stress on the host quartz and the inclusion contains h 2 o the h 2 o taken to the grain boundaries would due to its wetting properties be wicked out along the grain boundaries if the h 2 o is totally removed from an inclusion by a flux of dislocations through the quartz during the crystal plastic flow then a residual inclusion bearing components other than water should remain a mixed co 2 h 2 o inclusion would as a consequence of the process become a pure co 2 fluid inclusion during dynamic recrystallization the co 2 would collect at grain boundary triple junctions and following grain boundary migration would become incorporated into the recrystallized quartz as fluid inclusions this mechanism of generating pure co 2 inclusions could result in co 2 fluid inclusions having densities appropriate for the pressure temperature conditions during deformation using estimates of temperature of deformation the total confining pressure during deformation could be determined from the density of the co 2 fluid in these inclusions

mesozoic episodic magmatism in south korea and its tectonic implication 1 ne trending granitoid batholiths in south korea are part of the huge phanerozoic granitoid belt in east asia the crystallization ages of granitoid plutons show three episodes of mesozoic magmatism in south korea triassic 248 210 ma jurassic 197 158 ma and late cretaceous early tertiary 110 50 ma with a late jurassic early cretaceous 50 m y hiatus the granitoid ages and kinematic analyses of the mesozoic structures in south korea suggest that the middle jurassic 180 170 ma dextral strike slip ductile shear zones formed by the northwest orthogonal subduction of the izanagi plate whereas the cretaceous sinistral faults formed by the northward oblique subduction of the same plate which generally agree with proposed reconstruction of plate motions albeit uncertain around east asia among the models proposed to explain magmatic lull in a continental arc shallow angle subduction associated with high convergence rate and subduction of oceanic plateaus might be the probable cause for the magmatic hiatus in south korea and japan the huge width 500 km of the east asian granitoid belt may be explained by oceanward retreat of subduction zone in the cretaceous in association with change in the movement direction of the subducting plate

veins and hydrothermal fluid flow in the mt whaleback iron ore district eastern hamersley province western australia abstract with the advent of recent hydrothermal models for genesis of giant microplaty hematite ore deposits of the hamersley province we have undertaken regional scale analysis of veins and rocks surrounding the mt whaleback deposit with an aim to characterize the nature of fluid flow before during and after ore formation at least five groups of veins formed in the brockman iron formation in deformational events associated with the paleoproterozoic interaction between the yilgarn and pilbara cratons in a 600 km 2 area around the mt whaleback microplaty hematite orebody the five main veining events most likely correspond to the collisional d 2 and extensional collapse d 3 phases of the ca 2300 2200 ma ophthalmian orogeny with one or two later phases probably associated with the waning stages of the ca 1700 1650 ma capricorn orogeny d 4 and or later proterozoic events the abundance of veins associated with d 2 contraction and d 3 extensional fabrics and the composition up to 15 wt nacl equivalent and pressure corrected homogenisation temperatures of primary fluid inclusions 200 400 c indicate that the temperature salinity and likely volume of fluid reached a peak during the last stages of the ophthalmian orogeny and the first stages of post ophthalmian extension paragenesis of veins relative to the deformation history and localization of highest vein densities in the dales gorge member provides circumstantial evidence that the peak of hydrothermal activity in the district was synchronous with the main phase of microplaty hematite ore formation at mt whaleback we propose that the veins record part of the fluid flow system related to the genesis of this giant ore deposit

fluid inclusion petrography abstract a procedure of fluid inclusion studies is proposed with emphasis on the criteria of selecting fluid inclusions for detailed microthermometry and spectroscopic analysis an overview of descriptive and genetic classifications of fluid inclusions in single crystals and in massive rocks is given with the intention of further differentiating the commonly used terms primary and secondary fluid inclusions some principles of fluid inclusion modification are explained cathodoluminescence cl studies of quartz with the optical high power cl microscope and the electron microprobe provided with a cl detector are an important help in fluid petrography cl textures are subdivided in primary growth textures and a wide variety of secondary microtextures which are in part induced by fluid inclusions the latter is grouped in textures indicative of local lower crystal order increasing defect structures and microtextures indicative of local quartz healing reduction of the defect structures microtextures showing the genetic relationship between fluid inclusions and the host mineral provide information about the possible post entrapment changes of fluid inclusions and therewith testify their geological relevance

determining phase volumes of mixed co 2 h 2 o inclusions using microthermometric measurements a new graphical technique has been developed which permits the composition and volumetric properties of mixed co2 h2o inclusions to be determined using microthermometric measurements if the values of only two of the four variables 1 density of the co2 phase derived from the temperature and mode of partial homogenization 2 temperature and mode of total homogenization 3 volume fraction of the co2 phase at 40 c and 4 molar fraction of co2 of a mixed co2 h2o inclusion are known the values of the other two variables can be taken from a diagram depicting the relationships between all four variables the diagram can be used to derive the volume fraction of the co2 phase from measurements of the partial and total homogenization temperature it can also be employed in the opposite sense for determining the theoretical homogenization temperature of an inclusion which decrepitates before reaching total homogenization provided a good visual phase volume estimate is available the graphical technique can also be applied to mixed co2 h2o inclusions which contain 6 wt nacl

ore forming fluids in archean gold bearing quartz veins at the sigma mine abitibi greenstone belt quebec canada archean gold bearing quartz veins at the sigma mine occur in deformed metavolcanics intruded by two generations of preore porphyries the veins were emplaced during a late compressional tectonic event and they consist primarily of quartz tourmaline carbonates pyrite and scheelite vein minerals have been deformed and are also cut by abundant healed fractures outlined by fluid inclusions in the veins gold typically occurs in late fractures and in recrystallized quartz microthermometric sem eda leachate analysis and gas chromatographic techniques were used to study fluid inclusions in quartz most fluid inclusions at sigma occur in late fractures and are secondary the fluid inclusions are commonly found in fractures parallel to or less commonly within gold bearing fractures and are genetically related to the gold three types of fluid inclusions are identified 1 high salinity na ca cl aqueous inclusions 25 34 wt salt with small amounts of co 2 some containing halite calcite and nahcolite as daughter minerals 2 co 2 rich inclusions containing small amounts of h 2 o and ch 4 and 3 low salinity h 2 o co 2 inclusions 10 equiv wt nacl with co 2 contents which are variable but commonly in the range of 15 to 30 mole percent co 2 leachate analyses show that in addition to na and ca the aqueous fluids contain minor amounts of k fe mg and li homogenization temperatures of h 2 o co 2 inclusions with constant phase ratios range from 285 degrees to 395 degrees c those of aqueous inclusions range from 60 degrees to 295 degrees c the aqueous and co 2 rich inclusions are interpreted to have trapped two coexisting fluids resulting from the unmixing of a homogeneous h 2 o co 2 parent fluid itself occasionally trapped in late fractures the ore bearing fluid is interpreted to be a low salinity 10 equiv wt nacl fluid containing 15 to 30 mole percent co 2 at minimum temperatures in the range of 285 degrees to 395 degrees c the relatively low homogenization temperatures of aqueous inclusions are interpreted to be the result of co 2 effervescence from a co 2 saturated aqueous fluid due to pressure fluctuations at the time of entrapment it is also proposed that the onset of gold deposition is related to the onset of fluid unmixing

interpretation of post entrapment fluid inclusion re equilibration at the three mile hill marvel loch and griffins find high temperature lode gold deposits yilgarn craton western australia abstract fluid inclusions that are interpreted to be related to vein filling of quartz veins at the three mile hill and marvel loch gold deposits in amphibolite facies rocks and the griffins find deposits in granulite facies rocks in the yilgarn craton of western australia are dominantly low salinity h 2 o co 2 ch 4 mixtures or co 2 ch 4 fluids at each deposit inclusions have a wide range of compositions with respect to both the aqueous carbonic ratio and the co 2 ch 4 ratio of the carbonic phase and most fluids could not have been in equilibrium with the mineral assemblage in the vein and adjacent rock inclusion densities suggest a range of p t conditions of entrapment and are in general not consistent with the conditions of vein formation indicated by vein assemblages diffusional addition of h 2 into inclusions diffusional loss of h 2 o and reduction of inclusion volume are possible during cooling and uplift along the inferred p t path the inclusion populations could have been derived from an originally uniform population of low salinity aqueous dominated h 2 o co 2 inclusions by a combination of these processes inclusion modification as the cause of the complex inclusion populations is supported by relations of molar volume to composition and to an extent by variations in fluid salinity if inclusion re equilibration is the cause of inclusion variability it was of variable intensity within a single vein system and within individual clusters of inclusions in some samples and is suggested to have been a function of the local petrological and textural environment

macflincor and its application to fluids in archean lode gold deposits abstract macflincor was developed to process laboratory data gathered on fluid inclusions and to calculate isochores for geologically important fluids composed of h2o c02 ch4 nacl and n2 within the program interactive diagrams are available to describe those chemical systems which cannot be adequately constrained numerically the user can choose from various published equations of state describing fluid behavior and can easily compare the results obtained by using different equations the program once the basic fluid parameters have been established allows the data to be used to determine the p t trapping conditions to evaluate possible pressure corrections and to compare different depths of formation based on the pressure calculations and given geothermal gradients for illustrative purposes macflincor has been utilized here to constrain different physical chemical parameters of fluid inclusions trapped in ore related quartz veins and breccias of archean lode gold deposits in western australia inferred pressures from individual deposits show a wide range of values which may be due to post entrapment modifications and or observational uncertainties including estimation of liquid vapor ratios

provenance of the hayang group early cretaceous in the yeongyang subbasin se korea and its bearing on the cretaceous palaeogeography of sw japan abstract the lower cretaceous hayang group in the yeongyang subbasin se korea was deposited in a forearc basin formed by the subduction of the palaeo pacific izanagi plate underneath the east asian continent it is characterized by an alternating sequence of reddish sandstones and mudstones deposited in fluvial plain environments sandstone compositions upsequence reveal that the tectonic regimes of source terrains evolved successively from basement uplift to recycled orogen to magmatic arc and back to recycled orogen characteristically sandstones contain abundant plagioclases but rare k feldspars except for sandstones derived from basement sources sandstones derived from recycled orogens are rich in sedimentary rock fragments especially chert fragments which contain radiolarian faunas similar to those of the jurassic accretionary complex located in southwest japan minor continental arc volcanism contributed volcanic materials to the basin during the middle stage of the basin filling during the deposition of the hayang group strike slip fault movements were active due to the oblique subduction of the izanagi plate and caused strong pulsed uplift of the trench slope break areas resulting in supply of accretionary complex derived sediments considering a direct drainage connection between the uplifted accretionary complex in southwest japan and the yeongyang subbasin current cretaceous palaeogeographic reconstructions of the east asian continental margin need to be reconsidered and it is suggested that the collage of tectonic blocks in southwest japan assembled in post early cretaceous time

melting behavior of fluid inclusions in laboratory grown halite crystals in the systems naclh2o naclkclh2o naclmgcl2h2o and naclcacl2h2o abstract the chemical composition of aqueous fluid inclusions in crystals of halite can be accurately determined from observed melting behaviors of ice hydrohalite and sylvite some fluid inclusion melting behaviors observed in laboratory grown halite crystals systems nacl h 2 o nacl kcl h 2 o nacl mgcl 2 h 2 o and nacl cacl 2 h 2 o differ from predicted stable equilibrium relations in the nacl h 2 o and nacl kcl h 2 o systems observed first melt temperatures are up to 15 c below the equilibrium eutectic temperatures of 21 2 and 22 9 c respectively the final melting temperature of ice in the presence of hydrohalite and the final melting temperature of hydrohalite are reproducible and match predicted melting temperatures the limit of detection of sylvite daughter crystals in the nacl kcl h 2 o system is approximately 5 wt 1 molal kcl final melting temperatures of sylvite match published equilibrium data to within 0 3 c in the nacl kcl h 2 o system at halite saturation m kcl can be determined from the final sylvite dissolution temperature or from the final melting temperature of hydrohalite fluid inclusions in the nacl mgcl 2 h 2 o and nacl cacl 2 h 2 o systems that form stable salt hydrates mgcl 2 12h 2 o and cacl 2 6h 2 o during freezing first melt within 3 c of predicted eutectic temperatures 37 and 52 c however fluid inclusions with mgcl 2 or cacl 2 may also start melting at temperatures as low as 80 c such low first melt temperatures indicate the presence of metastable salt hydrates presumably mgcl 2 8h 2 o mgcl 2 6h 2 o or cacl 2 4h 2 o the formation of metastable phases during freezing of fluid inclusions can lead to misinterpretation of the chemical composition of fluid inclusions in natural samples this is especially true for fluid inclusions with first melt temperatures below 37 c which may be erroneously interpreted as being rich in cacl 2 the final melting of ice in the presence of hydrohalite may vary by more than 15 c in fluid inclusions of different size but identical bulk composition and occurs at lower temperatures than predicted in fluid inclusions from the nacl mgcl 2 h 2 o and nacl cacl 2 h 2 o systems however the final melting temperature of ice in inclusions which fail to nucleate hydrohalite and the final melting temperature of hydrohalite are reproducible to within 0 1 c and can be used to determine mgcl 2 and cacl 2 molalities

the p v t x f o2 evolution of h2o co2 ch4 bearing fluid in a wolframite vein reconstruction from fluid inclusion studies aqueous carbonaceous and later pure aqueous fluid inclusions in quartz from a ferberite fe 95mn 05 wo4 vein within the low grade metamorphic aureole of the borne granite french massif central have been studied by microthermometry and raman spectrometry the bulk v x properties of the aqueous carbonaceous inclusions have been derived using the equation of state of heyenet al 1982 for the low temperature co2 ch4 system a p t path has been proposed for their trapping using the equations of state of jacobs and kerrick 1981a for the h2o co2 ch4 system two main episodes were reconstructed for the history of the aqueous carbonaceous fluid 1 primary h2o co2 ch4 vapourrich inclusions in quartz indicated the early circulation of a low density fluid 65 mole h2o 34 mole co2 1 mole ch4 and traces of n2 d 0 35 gcm 3 at around 550 50 c and 700 100 bar fluid cooled approximately isobarically to 450 400 c and was progressively diluted by h2o with a concomitant increase in density the fo2 of the h2oco2 ch4 fluid estimated from the equilibrium co2 2h2o ch4 2o2 first ranged from 10 22 to 10 27 bar close to the q f m buffer within analytical errors these values were consistent with the presence of graphite in equilibrium with the fluid 2 a drop in pco2 and therefore a drop in fo2 was recorded by the secondary liquid rich inclusions in quartz the inclusions formed at and below 400 c were composed of h2o and ch4 only and fo2 at that stage was below that fixed by the graphite fluid equilibrium this second episode in the fluid rock system could be explained by the drop of temperature below the blocking temperature of the graphite fluid equilibrium according to this interpretation the blocking of the graphite fluid equilibrium occurred at t 370 c and probably at 400 c on account of the pressure correction mass spectrometric data show that ferberite contains h2o co2 and ch4 in fluid inclusions which lie in the gap of the v x properties of the aqueouscarbonaceous fluid in quartz deposition of ferberite probably occurred at around 400 c the previously inferred blocking temperature resulting from either the drop in pco2 the drop fo2 and or the related ph increase it is concluded that the existence of a blocking temperature for the graphite fluid chemical equilibrium may be a critical factor for maintaining a stable fluid pressure gradient in geothermal systems occurring under greenschist facies conditions in graphite bearing rocks

early archaean hydrothermal fluids a study of inclusions from the 3 4 ga buck ridge chert barberton greenstone belt south africa abstract fluid inclusions have been studied from cavities and breccias in one of the oldest well preserved relatively low grade metamorphosed sedimentary sequences on earth the fluid inclusion bearing samples are from the uppermost part of the early archaean 3 4 ga buck ridge volcano sedimentary complex in the barberton greenstone belt south africa which was affected by hydrothermal alteration during and immediately after its deposition in banded silicified sandy sediments this alteration is characterised among other features by quartz cemented hydrothermal breccias layer bound stockworks of cm size quartz veins and quartz filled cavities below stacked pebbles quartz grains in these hydrothermal deposits contain numerous fluid inclusions filled with either two phase aqueous or mixed h 2 o co 2 fluid the aqueous inclusions are divided into three different groups based on their microthermometric characteristics type h a relatively high salinity type m a intermediate salinity and type l a relatively low salinity optical and microthermometric characteristics of the fourth type of inclusions the mixed h 2 o co 2 fluid type c indicate that it was homogeneous at the time of trapping with only some minor changes occurring after trapping type h a and type c fluids appear as immiscible fluids in their host crystal most probably resulting from unmixing of the hydrothermal fluid phase relations in the co 2 h 2 o system show that the unmixing must have occurred at a relatively low pressure of 100 bars this conclusion is in line with the geological context of the samples which indicates a shallow environment of deposition for the sediments almost contemporaneous hydrothermal activity and a very low metamorphic grade however it is contrary to the first impression given by the homogeneous character of type c inclusions which suggests much higher p t conditions at the time of trapping the aqueous component of type c fluids may have progressively mixed with high salinity aqueous fluids type h a resulting in a dilution trend from h a to m a to l a fluids the hydrothermal fluids from the buck ridge chert in the barberton greenstone belt are strikingly similar to those encountered in present day systems they show minor differences with older ca 3 8 ga fluids preserved in hydrothermally altered rocks from the isua greenstone belt in greenland

a new concept on tectonic correlation between korea china and japan histories from the late proterozoic to cretaceous abstract the dabie sulu collision belt in china extends to the hongseong odesan belt in korea while the okcheon metamorphic belt in korea is considered as an extension of the nanhua rift within the south china block the hongseong odesan belt divides korea s gyeonggi massif into northern and southern portions the southern gyeonggi massif and the yeongnam massif are correlated with china s yangtze and cathaysia blocks respectively while the northern gyeonggi massif is part of the southern margin of the north china block the southern and northern gyeonggi massifs rifted from the rodinia supercontinent during the neoproterozoic to form the borders of the south china and north china blocks respectively subduction commenced along the southern and eastern borders of the north china block in the ordovician and continued until a triassic collision between the north china and south china blocks while subduction was occurring on the margin of the north china block high p t metamorphic belts and accretionary complexes developed along the inner zone of southwest japan from the ordovician to the permian during the subduction the hida belt in japan grew as a continental margin or continental arc collision between the north and south china blocks began in korea during the permian 290 260 ma and propagated westwards until the late triassic 230 210 ma creating the sinistral tanlu fault in china and the dextral fault in the hida and hida marginal belt in japan phanerozoic subduction and collision along the southern and western borders of the north china block led to formation of the qinling dabie sulu hongseong hida yanji belt

fluid inclusion evidence for p v t x evolution of hydrothermal solutions in late alpine gold quartz veins at brusson val d ayas northwest italian alps