on the significance of aqueous fluid inclusions in gold bearing quartz vein deposits from the southeastern abitibi subprovince quebec canada fluid inclusions have been studied in a quartz epidote actinolite vein within a proterozoic diabase dike crosscutting the donalda 1 gold bearing quartz vein near noranda quebec two types of fluid inclusions were recognized the first type is represented by two phase aqueous fluid inclusions characterized by low eutectic 200dgc temperatures the second type is represented by two or three phase or solid aqueous fluid inclusions characterized by low eutectic 2 o co 2 and co 2 fluid inclusions in archean gold bearing quartz veins of the southeastern abitibi belt and has a chemical composition ca na cl bearing with variable salinity comparable to that of brines and ground waters found in the superior province this study demonstrates that these low t h aqueous fluids showing variable salinity are unrelated to gold deposition but should rather be correlated with younger brines and ground waters which percolated downward in the continental crust in these gold bearing quartz veins only the high t h aqueous fluids may be linked to gold bearing fluids

early proterozoic deformation in the western superior province canadian shield late archean granitic plutons 2700 to 2665 ma u pb zircon of the superior structural province are cut by a variety of brittle discontinuities including joints fractures and faults the latter of which show evidence of cataclasis and meter to tens of meters displacements fluid circulation alteration of wall rocks and neomineralization of epidote actinolite and chlorite occurred under greenschist facies conditions in these structures at the time of their formation the rb sr ages of host rocks are 2650 ma and the fracture zone materials are 2300 ma indicating that most of this activity occurred long after archean plutonism and was concentrated in early proterozoic time the brittle structures formed in response to horizontal compression on a regional scale possibly caused by tectonic processes at margins of the craton the structures are seen as important clues to the tectonic evolution of the superior province

saline minewaters of the keweenaw peninsula northern michigan their nature origin and relation to similar deep waters in precambrian crystalline rocks of the canadian shield

fluid inclusion evidence of basinal brines in archean basement thunder bay pb zn ba district ontario canada fluid inclusions from three quartz galena sphalerite barite calcite veins in the thunder bay district of western ontario contain liquid vapor halite and homogenize by vapor disappearance or halite dissolution at temperatures of 90 200 c cyclically frozen liquid vapor type i inclusions undergo four melting events upon gradual warming initial melting at 55 to 46 c ice disappearance at 30 2 to 25 4 c inversion of hydrohalite to halite at 8 0 to 0 7 c and halite melting at 14 0 to 56 3 c liquid vapor halite type ii inclusions behave similarly but have higher t m ice 27 2 to 21 7 c and t m halite 105 203 c scanning electron microscopy and energy dispersive analysis of fluid inclusion derived decrepitates indicate that the solutes consist of nacl cacl 2 kcl and are consistent with the low temperature phase observations in that they define two distinct populations based on cacl 2 cacl 2 nacl ratios the temperatures and compositional trends defined by the inclusion results are similar to those documented for basinal brines and from fluid inclusions in mississippi valley type ore deposits the thunder bay veins cross the basal unconformity of the middle proterozoic sibley basin and extend into archean basement granites such that the fluid inclusions results provide direct evidence that basinal waters infiltrated basement rock in western ontario the inclusion fluids and associated mineralization are thought to result either from dewatering of the sibley basin during keweenaw age rifting or from the introduction of exotic paleozoic basinal waters when the michigan basin extended over the region

the source of ore fluids and solutes in archaean lode gold deposits of western australia abstract the ore fluids which produced archaean lode gold deposits in sub amphibolite facies rocks of the yilgarn block western australia are characteristically low to moderate salinity h 2 o co 2 ch 4 fluids wall rock alteration and ore deposition were from a generally reducing near neutral fluid at 200 350 c and 1 3 kbar although more oxidising fluids produced some assemblages in the giant golden mile deposit gold was transported as reduced sulphur complexes the ore fluid composition and stable and radiogenic isotope data indicate multiple sources for the fluid and solute deep plumbing systems are invoked with the fluids being either metamorphic fluids that derived solutes from the lower and upper crusts or fluids exsolved from deep seated granitoids formed by anatexis of such crust

synthetic fluid inclusions viii vapor saturated halite solubility in part of the system nacl cacl2 h2o with application to fluid inclusions from oceanic hydrothermal systems abstract halite solubility along part of the vapor saturated liquidus in the system nacl cacl 2 h 2 o has been determined using the synthetic fluid inclusion technique data allow the construction of liquidus isotherms for temperatures up to 500 c and bulk compositions containing 60 wt total salt and as much as 25 wt cacl 2 combined with previous data for the binary system nacl h 2 o and for the ternary system nacl cacl 2 h 2 o in the low salinity low temperature region a preliminary ternary phase diagram can be constructed that remains incomplete only in the cacl 2 rich region results are applied to the interpretation of saline fluid inclusions from quartz veins in oceanic metagabbros and can be applied to many other natural inclusions containing aqueous solutions with nacl and cacl 2 the dominant solutes microthermometric measurements at equilibrium of the melting temperature of ice tm ice and of the dissolution temperature of halite tm halite are sufficient to determine the bulk composition of the nacl cacl 2 h 2 o fluid

gold quartz veins in metamorphic terranes and their bearing on the role of fluids in faulting gold quartz vein fields in metamorphic terranes such as greenstone belts provide evidence for the involvement of large volumes of fluids during faulting and may be products of seismic processes near the base of the seismogenic regime in the val d or district of the abitibi greenstone belt canada quartz tourmaline carbonate veins form a vein field 30 15 km in the hanging wall of a crustal scale fault zone which was the main channelway for upward migration of the deeply generated fluids the veins occur in small high angle reverse faults and in adjacent horizontal extensional fractures extending up to 75 m in intact rocks they have formed incrementally during active reverse faulting in response to crustal shortening at depths corresponding to those at the base of the seismogenic zone in actively deforming crust detailed structural and fluid inclusion studies provide evidence for generally lithostatic but fluctuating fluid pressures p of the order of 200 mpa and for cyclic stress reversals during vein formation and provide good support for the fault valve model a comparison of vein characteristics with standard earthquake rupture parameters suggests that each slip increment along veins in reverse faults was accompanied by a small earthquake 4 m 3 or less the large vein field thus represents both the extent of fluid dispersion in the hanging wall of a crustal scale channelway and the distribution of small earthquakes integrated over the lifetime of the hydrothermal system it is proposed that such small earthquakes along veins in reverse faults are related to large earthquakes m 6 nucleating near the base of the seismogenic regime along the nearby crustal scale fault either as aftershocks or as a precursory smarm

the influence of dikes on auriferous shear zone development within granitoid intrusions the bourlamaque pluton val d or district abitibi greenstone belt shear zone related gold quartz veins in granitoid intrusions are commonly intimately associated with mafic dikes which may have a profound influence on the localization orientation and kinematics of auriferous shear zones the bourlamaque pluton of the val d or district contains several economic auriferous shear zones most of which follow and overprint diorite dikes mineralization in all deposits consists of quartz tourmaline pyrite veins in reverse oblique orientation with a significant range of strike dip and slip direction the geometry and kinematics of shear zone and vein array within the pluton is more complex than the simple conjugate pattern predicted for a deforming homogeneous intrusion the stress tensor determined from the auriferous shear zones within the pluton indicates the same northerly directed compression recorded by similar shear zones outside the pluton this indicates that the complex shear zone and vein pattern within the pluton reflects the influence of diorite dikes which

the collision complex of the north scotia ridge single channel and multichannel seismic reflection profiles of the north scotia ridge trending west east off southernmost south america show the north side to consist of a wedge of deformed sediments resting on a planar layered sequence relative movement of the ridge northward toward the falkland plateau has resulted in deformation and uplift of the near surface sediment layers of the falkland trough to form an accretionary wedge these sediments are 1 to 3 s of two way travel time in thickness and lie above a well defined reflector whose velocity at the northern part of the trough is 3 6 km s the deeper layers extend to depths in places greater than 9 0 s of two way travel time beneath the north slope without any significant deformation the deepest observed reflector is associated with a 5 9 km s basement the deformed pile of sediments or collision zone of the north scotia ridge is similar to that observed at other active compressive plate boundaries

hydrothermal zircon and baddeleyite in val d or archean mesothermal gold deposits characteristics compositions and fluid inclusion properties with implications fortiming of primary gold mineralization zircon and baddeleyite occur within quartz tourmaline veins at four gold deposits in the val d or district of the archean abitibi southern volcanic zone host rocks have experienced intense metasomatic enrichment of zr hf y and rare earth elements the zircons contain primary inclusions of quartz tourmaline pyrite albite k mica scheelite and gold and gold occurs in primary fluid inclusions in zircons magmatic zircons in host rocks do not have this suite of inclusions consequently a wall rock inheritance model for the vein zircons is implausible compositionally the zircons feature pronounced interzone and intergrain variations of hf y yb th and u and sporadic anomalous ce contents of 1100 ppm distinct from magmatic counterparts two principal types of primary fluid inclusion occur in the vein zircons type 1 h2o co2 inclusions have low salinities variable quantities of co2 and homogenization temperatures of 260 380 c and type 2 co2 rich inclusions contain minor h2o and ch4 the vei

landslides in a densely populated county at the footslopes of mount elgon uganda characteristics and causal factors manjiya county on the ugandan slopes of mount elgon is a densely populated mountainous area where landslides have been reported since the beginning of the twentieth century the numerous fatalities and the damage done during the extreme rainfall events of 1997 to 1999 drew attention to this phenomenon in order to better understand the causal factors of these landslides 98 recent landslides in the study area mostly debris slumps were mapped and investigated together they displaced 11 millions m 3 of slope material statistical analysis shows that landslides dominate on steep concave slope segments that are oriented to the dominant rainfall direction northeast and at a relatively large distance from the water divide based on landslide occurrence and impact four different zones can be distinguished within the study area causal factors as well as landslide characteristics differ greatly between the four zones besides the fact that steep slopes high rainfall and typical soil properties and stratification turn manjiya into an inherently unstable area human interference cannot be neglected whereas deforestation has reduced the stability of the shallow soils on the eastern slopes of the study area the excavation of slopes mainly for house building is an important destabilizing factor for the western slopes the growing population density not only increases the risk on damage but hampers the search for solutions for the landslide problem as well d 2005 elsevier b v all rights reserved

sulfate in brines in the crystalline rocks of the canadian shield abstract deep groundwaters in crystalline rocks typically are very saline and are characterized by a rather unique ca na cl dominated chemistry sulfate is present in variable amounts and may be linked to both the geochemical evolution of these fluids as well as to recent processes initiated through mining activities it is possible to distinguish on the basis of isotopic compositions between brine sulfate and secondary sulfate formed by oxidation of sulfides the latter is characterized by 34 s values which reflect the local mineral sulfide precursor and 18 o close to or below 0 smow the isotopic composition of the brine sulfate is characterized by 18 o and 34 s values which resemble marine isotopic compositions at some localities at others they could be explained as being of magmatic hydrothermal origin it is likely that the sulfate participated in the geochemical evolution of these brines thus its isotopic composition reflects geochemical processes rather than a primary origin no evidence for the influence of bacterial reduction was found

dating of archean auriferous quartz vein deposits in the abitibi greenstone belt canada 40 ar 39 ar evidence for a 70 to 100 m y time gap between plutonism metamorphism and mineralization the sigma mine at val d9or quebec in the abitibi belt is typical of vein type gold deposits in archcan greenstone belts although the relative timing of gold mineralization with respect to magmatism metamorphism deformation and hydrothermal events in the mine is well documented precise isotopic age constraints have until recently been lacking this paper presents the results of a 40 ar 39 ar dating study of the sigma mine and of the davidson tisdale deposit in the abitibi belt in the sigma mine dates on metamorphic amphibole indicate that the regional metamorphism which predates the vein formation occurred at ca 2 68 ga muscovite from the gold bearing quartz veins yields a plateau date of 2579 or 9 ma 2sigma whereas biotite from the veins shows disturbed saddle shaped age spectra the mild disturbance of the biotite is attributed to later diabase dike emplacement and a 40 ar 39 ar date on a dike indicates that this event is younger than 2 3 ga thermal effects of the grenville orogeny 1 2 1 0 ga may also be present a muscovite separate from a gold bearing quartz vein at the davidson tisdale deposit yields a 2607 or 10 ma 2sigma plateau date although the amphibole and muscovite dates at the sigma mine bracket the gold mineralization event at between ca 2 68 and 2 58 ga a number of tectonothermal histories are possible for this time interval it is concluded based on all evidence that the muscovite plateau dates are the time of vein and gold formation which thus occurred in the sigma mine ca 100 m y and in the davidson tisdale deposit ca 70 m y after syn to post tectonic magmatism and regional metamorphism

characteristics and chronology of fracture fluid infiltration in the archean eye dashwa lakes pluton superior province evidence from h c o isotopes and fluid inclusions the archean eye dashwa lakes pluton 2672 24 ma has domains of mineralogically fresh isotropic granite domains that have undergone bulk hydrothermal alteration and at least eleven sets of sequential fracture arrays each with distinctive mineral assemblages fresh granite is characterized by whole rock 18o 8 1 to 8 6 and primary magmatic quartz feldspar 1 3 quartz biotite 5 2 to 5 4 and quartz magnetite 9 8 fractionations magmatic fluids had a calculated isotopic composition of 18o 7 9 0 5 and d 80 5 these isotropic volumes of the granite have not experienced significant incursion of external thermal waters pegmatites quartz molybdenite veins and phlogopite muscovite coated fractures are sporadically distributed in the granite and were precipitated from high temperature magmatic fluids where 18o 8 0 to 10 3 and d 80 5

microfracturing and regional stress field a study of the preferred orientations of fluid inclusion planes in a granite from the massif central france abstract a study of the deformation of a granitic massif indicates a relationship between palaeostress fields and the geometry of microfractures as defined by fluid inclusion trails that is healed microfractures a statistical study of the distribution of the trails leads to the following conclusions trails exhibit several distinct preferred orientations on the scale of a grain which may be observed in many samples the orientations of the trails are similar to those of micro and mesoscale fractures in the granite and the dominant trail direction is parallel to the main direction of regional shortening thus fluid inclusion trails are mode i cracks which can be used as excellent markers of palaeostress fields

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

palaeoseismic events recorded in archaean gold quartz vein networks val d or abitibi quebec canada archaean gold quartz vein deposits are commonly hosted in high angle reverse shear zones and are interpreted to have formed in a regime of horizontal compression and high fluid pressure environment this paper presents the results of a combined structural and fluid inclusion study on three gold quartz vein deposits of the val d or area abitibi quebec consisting of subhorizontal extensional veins and e w steeply dipping shear veins crack seal structures tourmaline fibres stretched quartz crystals and open space filling textures indicate that the subhorizontal veins formed by hydraulic fracturing under supralithostatic fluid pressure co2 rich and h2o nacl fluid inclusions interpreted as two coexisting immiscible fluids occur typically in microcracks of different orientations interpreted to have formed in the 1 2 plane horizontal co2 rich fluid inclusion planes are contemporaneous with the opening of these veins 3 vertical vertical h2o nacl fluid inclusion planes as well as some microstructures such as deformed minerals indicate that the same extensional veins have experienced episodic vertical shortening 3 horizontal alternating with the opening events deformation and slip opening also occurred in shear veins in which preferred orientation of fluid inclusion planes is not clear except that the h2o nacl fluid inclusion planes tend to be oriented at high angles to the slip direction the successive opening and collapse events in subhorizontal extensional veins are correlated with deformation and slip opening events in shear veins respectively and are attributed to cyclic fluid pressure fluctuations in the system they are thus consistent with the fault valve model sudden drop in fluid pressure from supralithostatic to lower values induces fluid unmixing and occurs immediately post failure following seismic rupturing along the shear zone sealing of the shear veins allows the fluid pressure to build up again and the subhorizontal extensional veins to form the intermittent change in orientation of 3 in horizontal extensional veins is ascribed to a total shear stress release along the neighbouring shear veins after rupture the complex internal structures of the gold quartz veins provide an excellent record of archaean seismic activity along high angle reverse faults

sm nd and rb sr isotope systematics of scheelites possible implications for the age and genesis of vein hosted gold deposits a positive correlation between present day sup 143 nd sup 144 nd and sup 147 sm sup 144 nd ratios from scheelite samples from the hollinger mcintyre coniaurum gold deposit of ontario canada corresponds to an age of 2403 plus minus 47 ma and may date the age of gold mineralization initial isotope ratios of scheelites suggest that the fluid responsible for the scheelite and gold mineralization was probably of mantle origin and that it subsequently interacted with continental crust

saline ground waters and brines in the canadian shield geochemical and isotopic evidence for a residual evaporite brine component abstract saline ca na cl type groundwaters and brines sampled in deep mines over an extensive area of the canadian precambrian shield have elevated br cl ratios which may indicate that the chlorinity of these waters was derived from the infiltration of residual evaporitic brines remnants of the great marine incursions of the paleozoic era boron concentrations in these waters are generally low i e 11 b 10 b ratios of these waters are significantly greater than the average value for continental crustal rocks with the highest values 4 19 approaching that of present day seawater 4 20 moreover the boron isotopic ratios generally trend to higher values with increasing chlorinity which supports the conclusion from the br cl relationship that most of the chloride in shield brines is of marine origin rather than a product of water rock interactions if this is correct crystalline rocks must then be sufficiently permeable on a regional scale to have allowed the brine to infiltrate to depths of several kilometers where it now resides

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