reassessing the evidence for the earliest traces of life the isotopic composition of graphite is commonly used as a biomarker in the oldest 3 5 gyr ago highly metamorphosed terrestrial rocks earlier studies on isotopic characteristics of graphite occurring in rocks of the approximately 3 8 gyr old isua supracrustal belt isb in southern west greenland have suggested the presence of a vast microbial ecosystem in the early archean this interpretation however has to be approached with extreme care here we show that graphite occurs abundantly in secondary carbonate veins in the isb that are formed at depth in the crust by injection of hot fluids reacting with older crustal rocks metasomatism during these reactions graphite forms from the disproportionation of fe ii bearing carbonates at high temperature these metasomatic rocks which clearly lack biological relevance were earlier thought to be of sedimentary origin and their graphite association provided the basis for inferences about early life the new observations thus call for a reassessment of previously presented evidence for ancient traces of life in the highly metamorphosed early archaean rock record

reintensification and eyewall formation in strong shear a case study of typhoon noul 2015 abstractstrong vertical wind shear produces asymmetries in the eyewall structure of a tropical cyclone tc and is generally a hostile environment for tc intensification typhoon noul 2015 howev

methane rich fluids in the oceanic crust analyses of fluid inclusions in plutonic rocks recovered from the slow spreading southwest indian ridge swir record ch4 concentrations of 15 40 times those of hydrothermal vent fluids and of basalt hosted volcanic gases and provide the first direct sampling of co2 ch4 h2o h2 c bearing fluids in the oceanic crust compositional thermal and spatial analyses of these fluids are used to model the evolution of volatiles during the crystallization and cooling of mid ocean ridge magma chambers and to assess the potential importance of carbon bearing fluids in geochemical processes in the lower crustal component of hydrothermal systems results from these analyses show that the earliest fluids to be exsolved from the melts are dominated by co2 rich vapors which with progressive fractionation evolved to more h2o rich compositions these later fluids were most likely exsolved under immiscible conditions and involved the development of co2 h2o rich vapors and co2 h2o nacl brines that were trapped during mineral growth as well as during later high temperature fracturing events co2 ch4 h2o rich fluids in olivine and plagioclase minerals that contain up to 30 50 mol co2 and 33 mol ch4 may reflect respeciation of magmatic co2 during cooling and attendant graphite precipitation phase equilibria suggest that these fluids reequilibrated at 500 600 c and at fo2 s 3 log units below to close to qfm conditions alternatively the inclusions may record respeciation of magmatic fluids attendant with the inward diffusion of h2 into the inclusions and reduction of entrapped co2 during degassing and cooling of the gabbros throughout the subsolidus regime subsequent seawater reaction at minimum temperatures of 400 c with mafic rich layers within the gabbroic rocks or with ultramafic material that underlies the plutonic sequence resulted in the formation of ch4 h2o fluids that contain up to 40 mol ch4 molecular h2 and graphite daughter minerals these data provide strong evidence that the ch4 h2o rich fluids produced during serpentinization reactions were trapped under equilibrium conditions in the presence of graphite at very near to qfm conditions the ubiquitous occurrence of ch4 rich fluids in oceanic crustal layer 3 rocks from the swir indicates that these fluids may be a significant and previously unrecognized source for these volatile species in some hydrothermal systems venting on the seafloor and that the deep seated fluids most likely play an important role in the transfer of carbon from the lithosphere to the hydrosphere

a 3 800 million year isotopic record of life from carbon in sedimentary rocks an increased ratio of 12c to 13c an indicator of the principal carbon fixing reaction of photosynthesis is found in sedimentary organic matter dating back to almost four thousand million years ago a sign of prolific microbial life not long after the earth s formation partial biological control of the terrestrial carbon cycle must have been established very early and was in full operation when the oldest sediments were formed

metasomatic origin of quartz pyroxene rock akilia greenland and implications for earth s earliest life a quartz pyroxene rock interpreted as a banded iron formation bif from the island of akilia southwest greenland contains 13 c depleted graphite that has been claimed as evidence for the oldest 3850 million years ago life on earth field relationships on akilia document multiple intense deformation events that have resulted in parallel transposition of early archean rocks and significant boudinage the tails of which commonly form the banding in the quartz pyroxene rock geochemical data possess distinct characteristics consistent with an ultramafic igneous not bif protolith for this lithology and the adjacent schists later metasomatic silica and iron introduction have merely resulted in a rock that superficially resembles a bif an ultramafic igneous origin invalidates claims that the carbon isotopic composition of graphite inclusions represents evidence for life at the time of crystallization

fluid regimes during late stages of a continental collision physical chemical and stable isotope measurements of fluid inclusions in fissure quartz from a geotraverse through the central alps switzerland fluid evolution during neo alpine metamorphism during late stages of the continental collision between europe and africa was studied by analyzing fluid inclusions in alpine fissure quartz collected in forty nine localities along a geotraverse through the central alps switzerland the methods employed include microthermometry micro raman spectroscopy k na thermometry and stable isotope analysis early fluid inclusions provide evidence of close to peak metamorphic temperatures of the late tertiary or neo alpine metamorphic event fluid composition evolved along the geotraverse from north to south as follows higher hydrocarbons were dominant in the low and medium grade diagenetic zones methane was the main volatile in the high grade diagenetic and low grade anchizone water dominated in the highgrade anchizone and low grade epizone with co2 10 mol in the high grade epizone and in the mesozone higher hydrocarbons and ch4 were the products of kerogen maturation and cracking of preexisting petroleum large water supplies originated from the dehydration of cooler metasedimentary rocks that were overthrust by crystalline basements of the lepontines aar and gotthard massifs carbon isotope analyses suggest that the co2 component was derived from oxidation of graphitic matter especially in the vicinity of sulfate bearing metasediments and from decarbonation reactions in the aar and gotthard massifs as well as in the helvetic axen nappe and its underlying north helvetic flysch high fluid pressures prevailed and favored nappe transport by contrast in the southern lepontine area very low early fluid pressures were probably related to dry rocks and scarce metasediments and to high geothermal gradients that resulted from intense uplift and erosion between 26 and 18 ma retrograde fluid evolution was recorded by a succession of fluid inclusion populations in each alpine fissure it was controlled by uplift and cooling and characterized by decreasing contents of volatiles and an increase in 18o of host quartz tectonic activity led to episodic pressure drops of at least 0 5 to 2 kbar and promoted fluid unmixing channelized flow and rapid growth of skeletal quartz channelized rather than pervasive fluid migration at temperatures 450 c and under conditions of brittle deformation is documented by episodic increases in salinity and by fluid flushing through the massifs there is stable isotope evidence for involvement of meteoric water only in late crystallizing quartz formation of alpine fissures and fissure minerals was the result of a unique coincidence of late continental collision 450 c fluid expulsion from overthrust metasediments uplift and erosion

exogenous carbonaceous microstructures in early archaean cherts and bifs from the isua greenstone belt implications for the search for life in ancient rocks abstract the microstructure of hf etched samples of early archaean banded iron formations bifs and cherts from the 3 7 b y old isua greenstone belt southwestern greenland was investigated using high resolution scanning electron microscopy equipped with an electron diffraction system capable of analysing light elements the rocks contain both endogenous of internal origin and exogenous of external origin carbonaceous microstructures the former consist of inclusions of graphite and possibly small amorphous carbonaceous particles both embedded in metacherts however further in situ tem studies are needed to verify the endogeneity of the amorphous particles moreover these rocks also contain endolithic microorganisms i e inhabiting cracks in rocks as well as undifferentiated carbonaceous matter that occur in fractures and cracks between grains the microorganisms include cyanobacteria filamentous microorganisms such as fungal hyphae and possibly bacteria as well as large unidentified cells or spores most of the microorganisms appear to have been fossilised the endoliths are evidently younger than the host rock but must have infiltrated at different periods most likely after the inland ice retreated 8000 years ago the presence of endolithic carbonaceous matter in cracks and microfissures in these rocks will affect any analyses of bulk samples such as carbon isotopes and chemical biomarkers as well as analyses of acid macerated residues thus previous isotope measurements made on bifs and cherts from isua may reflect younger contamination rather than an endogenous original signal likewise some of the previously described isuan microorganisms probably represent recent endolithic contamination

application of stable carbon isotopes to early biochemical evolution on earth the emergence and early evolution of life on earth have long been intriguing subjects for scientific inquiry and a continuous source of intel lectual excitement current work at this frontier proceeds along a number of different avenues and comprises a variety of disciplinary approaches that together strongly suggest that the earth was inhabited by life as early as almost 4 gyr ago the present state of the field as inferred from the results of a broad interdisciplinary approach has recently been summarized by j w schopf and coworkers cf schopf 1 983 it is with the advantage of such a synoptic view that the present review addresses a single facet of the theme namely the potential isotopic infer ences of the presence of co2 fixing autotrophic organisms for the carbon cycle of the early earth with biologically derived organic carbon as well as carbonates limestone dolomite etc abundantly preserved in sediments relevant isotopic evidence should have been encoded in the geologic record from its onset about 3 8 gyr ago it has been known since the pioneering studies by nier gulbransen 1939 murphey nier 1941 and rankama 1948 that the trans formation of inorganic carbon into living matter entails a marked bias in favor of the light isotope c2c with the heavy species l3c retained in the inorganic reservoir subsequent work performed by many investigators e g craig 1953 park epstein 1960 has confirmed that all common

metamorphism in archaean greenstone belts calculated fluid compositions and implications for gold mineralization an inescapable consequence of the metamorphism of greenstone belt sequences is the release of a large volume of metamorphic fluid of low salinity with chemical characteristics controlled by the mineral assemblages involved in the devolatilization reactions for mafic and ultramafic sequences the composition of fluids released at upper greenschist to lower amphibolite facies conditions for the necessary relatively hot geotherm corresponds to those inferred for greenstone gold deposits xco2 0 2 0 3 this result follows from the calculation of mineral equilibria in the model system cao mgo feo al2o3 sio2 h2o co2 using a new expanded internally consistent dataset greenstone metamorphism cannot have involved much crustal over thickening because very shallow levels of greenstone belts are preserved such orogeny can be accounted for if compressive deformation of the crust is accompanied by thinning of the mantle lithosphere in this case the observed metamorphism which was contemporaneous with deformation is of the low p high t type for this type of metamorphism the metamorphic peak should have occurred earlier at deeper levels in the crust i e the piezothermal array should be of the deeper earlier type however at shallow crustal levels the piezothermal array is likely to have been of deeper later type as a consequence of erosion thus while the lower crust reached maximum temperatures and partially melted to produce the observed granites mid crustal levels were releasing fluids prograde into shallow crustal levels that were already retrograde we propose that these fluids are responsible for the gold mineralization thus the contemporaneity of igneous activity and gold mineralization is a natural consequence of the thermal evolution and does not mean that the mineralization has to be a consequence of igneous processes upward migration of metamorphic fluid via appropriate structurally controlled pathways will bring the fluid into contact with mineral assemblages that have equilibrated with a fluid with significantly lower xco2 these assemblages are therefore grossly out of equilibrium with the fluid in the case of infiltrated metabasic rocks intense carbonation and sulphidation is predicted if as seems reasonable gold is mobilized by the fluid generated by devolatilization then the combination of processes proposed most of which are an inevitable consequence of the metamorphism leads to the formation of greenstone gold deposits predominantly from metamorphic fluids

remnants of early archaean hydrothermal methane and brines in pillow breccia from the isua greenstone belt west greenland abstract fluid inclusions containing high density methane and saline waters brines associated with carbonates have been found in undeformed annealed quartz bearing vesicles from pillow breccia at isua west greenland massive quartz veins cementing the pillow fragments contain the same type of carbonate bearing saline aqueous inclusions as the pillows but different gaseous inclusions either trails of low density methane close to the boundary of the pillow fragment or isolated high density co2 rich inclusions in the centre of the veins high density methane and carbonate bearing aqueous inclusions brines are presumed to represent remnants of a sea floor type hydrothermal alteration system subsequently re equilibrated in terms of fluid density during the metamorphic evolution low density methane has been expelled from pillow fragments during post metamorphic uplift whereas high density co2 probably represents remnants of the peak metamorphic fluids some present day sea floor hydrothermal systems notably the off axis hydrothermal vent field near the mid atlantic ridge at 30 n appear to be quite comparable with this hypothetical early archaean fluid this setting represents a highly favourable environment for the development of life on earth

hydrothermal vents near a mantle hot spot the lucky strike vent field at 37 n on the mid atlantic ridge the lucky strike hydrothermal field occurs in the summit basin of a large seamount that forms the shallow center of a 65 km long ridge segment near 37 n on the mid atlantic ridge the depth and chemistry of the ridge segment are influenced by the azores hot spot and this hydrothermal field is the first atlantic site found on crust that is dominated by a hot spot signature multiple hydrothermal vents occur over an area of at least 300 m by 700 m vent morphologies range from flanges and chimneys with temperatures of 200 212 c to black smoker chimneys with temperatures up to 333 c cooler fluids from northern vents have higher chlorinities and lower gas volumes while hotter southern fluids have chlorinities 20 below seawater with higher gas volumes suggesting phase separation has influenced their compositions all gas volumes in fluids are higher than those at tag and snake pit hydrothermal fields black smokers exhibit their typical mineralogy except that barite is a major mineral particularly at lower temperature sites which contrasts with previously investigated atlantic sites the fluid chemistry distribution of the relict sulfide deposits on the seamount summit in the areas investigated using dsv alvin and contact relationships between active vent sites and surrounding basaltic and sulfide substrate suggest that the hydrothermal system has a long history and may have recently been rejuvenated fauna at the lucky strike vent sites are dominated by a new species of mussel and include the first reported sea urchins the lucky strike biological community differs considerably from other vent fauna at the species level and appears to be a new biogeographic province the lucky strike field helps to constrain how variations in the basaltic substrate influence the composition of hydrothermal fluids and solids because basalt compositions at lucky strike are 10 30 times enriched in incompatible elements compared to other atlantic hydrothermal sites such as tag snake pit and broken spur the incompatible element

fluids in metamorphic rocks abstract basic principles for the study of fluid inclusions in metamorphic rocks are reviewed and illustrated a major problem relates to the number of inclusions possibly formed on a wide range of p t conditions having also suffered in most cases extensive changes after initial trapping the interpretation of fluid inclusion data can only be done by comparison with independent p t estimates derived from coexisting minerals but this requires a precise knowledge of the chronology of inclusion formation in respect to their mineral host the three essential steps in any fluid inclusion investigation are described observation measurements and interpretation observation with a conventional petrographic microscope leads to the identification and relative chronology of a limited number of fluid types same overall composition eventually changes in fluid density for the chronology the notion of gis group of synchronous inclusions is introduced it should serve as a systematic basis for the rest of the study microthermometry measurements completed by nondestructive analyses mostly micro raman specify the composition and density of the different fluid types the major problem of density variability can be significantly reduced by simple considerations of the shape of density histograms allowing elimination of a great number of inclusions having suffered late perturbations finally the interpretation is based on the comparison between few isochores representative of the whole inclusion population and p t mineral data essential is a clear perception of the relative chronology between the different isochores when this is possible as illustrated by the complicated case of the granulites from central kola peninsula a good interpretation of the fluid inclusion data can be done if not fluid inclusions will not tell much about the metamorphic evolution of the rocks in which they occur

volatile lines of descent in submarine plutonic environments insights from stable isotope and fluid inclusion analyses microthermometric and isotopic analyses of fluid inclusions in primitive olivine gabbros oxide gabbros and evolved granitic material recovered from ocean drilling program hole 735b at the southwest indian ridge provide new insights into the evolution of c o h nacl fluids in the plutonic foundation of the oceanic crust the variably altered and deformed plutonic rocks span a crustal section of over 1500 m and record a remarkably complex magma hydrothermal history magmatic fluids within this suite followed two chemically distinct paths during cooling through the subsolidus regime the first path included formation of co21ch41h2o1c fluids with up to 43 mole ch 4 the second path produced hypersaline brines that contain up to 50 nacl equivalent salinities subsequent to devolatilization respeciation of magmatic co2 attendant graphite precipitation and cooling from 800 c to 500 c promoted formation of ch 4 enriched fluids these fluids are characterized by average d 13 c ch4 values of 227 1 6 4 3 n5 45 with associated d 13 c co2 compositions ranging from 224 9 to 21 9 n539 and average dd values of exsolved vapor of 241 6 12 n523 in pods veins and lenses of highly fractionated residual material hypersaline brines formed during condensation and by direct exsolution in the absence of a conjugate vapor phase entrapped co21ch41h2o rich fluids within many oxide bearing rocks and felsic zones are significantly depleted in 13 c with d 13 c co2 values down to about 225 and contain co 2 concentrations higher than those predicted by equilibrium devolatilization models we hypothesize that lower effective pressures in high temperature shear zones promoted infiltration of highly fractionated melts and compositionally evolved volatiles into focused zones of deformation significantly weakening the rock strength in felsic rich zones volatile build up may have driven hydraulic fracturing of gabbroic wall rocks resulting in the formation of magmatic breccias comparison of isotopic compositions of fluids in plutonic rocks from 735b the mark area of the mid atlantic ridge and the mid cayman rise indicate 1 that the carbon isotope composition of the lower oceanic crust may be far more heterogeneous than previously believed and 2 that carbon bearing species in the oceanic crust and their distribution at depth are highly variable copyright 2001 elsevier science ltd

metamorphic history suggested by garnet growth chronologies in the isua greenstone belt west greenland abstract compositional maps for garnets from the five tectonic domains of the isua greenstone belt in west greenland are used to identify episodes of garnet growth during the metamorphism of the greenstone belt three distinct episodes of garnet growth are recorded in domains iii v two in domain ii and one in domain i a wide variety of garnet textures are observed including growth zoning post growth homogenisation replacement rim resorption and oscillatory zoning there is no simple correlation of garnet growth events among domains indicating that at least some events are related to localised metasomatic processes in the greenstone belt however the relative growth chronology combined with the available geochronology indicates that the observed metamorphic processes span both the early and late archaean

invited review paper neogene to quaternary tectonics of the coastal cordillera northern chile abstract the extreme aridity of the northern chilean coastal cordillera enables the complete preservation of permanent deformation related to the coupling between nazca and south america the region between antofagasta and arica is characterized by four types of late cenozoic structures ew striking reverse faults ns striking normal faults sparse wnw and nnw striking right lateral strike slip faults and unimodal and bimodal populations of surface cracks the ew reverse faults occur only between 19 and 21 40 s latitude and have been active since at least 6 ma to present a march 2007 earthquake demonstrates that this deformation can occur during the interseismic phase of the plate boundary seismic cycle the ns normal faults are most abundant near antofagasta and mejillones and diminish in significance northward several of these faults in both the antofagasta and the salar grande area have been reactivated as reverse faults causing minor topographic inversion we suggest that normal faults move during both interseismic and coseismic deformation and are fundamentally very weak surface cracks are ubiquitous throughout the region and form by both non tectonic and tectonic mechanisms a significant proportion forms during coseismic deformation and thus may be used to identify long lived rupture segments on the plate boundary overall forearc deformation is very slow with permanent strain rates of 1 5 nstrain year and fault slip rates less than 0 5 mm year

recognizable primary volcanic and sedimentary features in a low strain domain of the highly deformed oldest known 3 7 3 8 gyr greenstone belt isua west greenland a low strain domain has been identified in the metamorphosed mostly highly deformed volcanic and sedimentary rocks of the early archaean isua supracrustal belt this domain contains well preserved volcanic and sedimentary features including basaltic pillow lavas pillow breccia heterogeneous volcanic breccia amygdules in metabasalt and polymict conglomerate dominated by recrystallized chert and volcanic clasts the low strain domain is bounded by highly deformed rocks mostly derived from basalt chert and banded iron formation these discoveries demonstrate that some primary features have escaped the pervasive metasomatism dominant in other parts of the belt and furthermore strengthen the characterization of the isua supracrustals as a typical greenstone belt

graphite ch4 h2o co2 equilibria at low grade metamorphic conditions equilibrium calculations and published phase equilibria are used to show that at temperatures below 400 c and pressures above 300 bar the fluids coexisting with graphite in the c o h system consist either of co2 h2o mixtures or ch4 h2o mixtures bulk fluid compositions consisting of ch4 h2o will unmix to methane rich fluid and h2o rich liquid at temperatures below about 325 c compositions on the co2 h2o join will unmix only at temperatures below about 275 c oxygen fugacity in the ch4 h2o graphite three phase region is fixed at constant p and t and approximately equal to that of the quartz magnetite fayalite assemblage in the co2 h2o graphite three phase region oxygen fugacity is about three orders of magnitude greater from the end stages of diagenesis to temperatures of 300 c and possibly 400 c in salt rich systems many metamorphic rocks may contain ch4 h2o fluids rather than co2 h2o mixtures thus metamorphic reactions involving carbonate minerals would involve ch4 graphite and h2o rather than co2 the immiscibility between ch4 and h2o could result in the common occurrence of methane natural gas in low grade metamorphic terrains

salinity of oceanic hydrothermal fluids a fluid inclusion study abstract an extensive microthermometric study of quartz epidote plagioclase anhydrite and sphalerite hosted fluid inclusions from ophiolitic semail oman and trinity california ophiolites and oceanic east pacific rise hydrothermal vents gorringe bank odp leg 111 hole 504b crust has been carried out in order to constrain a model accounting for wide salinity variations measured in the oceanic hydrothermal fluids recorded salinities in fluid inclusions vary between 0 3 and 52 wt nacl eq however more than 60 of the mean standard deviation salinities of the samples are within the range 3 2 0 3wt nacl eq microthermometric error and the mean salinity of all fluid inclusions without the brines is 4 0 wt nacl eq with a standard deviation of 1 6 wt nacl eq whereas most samples display slightly higher salinities than seawater several samples exhibit very high salinities more than two times that of seawater these high salinities are restricted to the plagiogranites semail and trinity ophiolites which mark the top of the fossil magma chamber in the transition zone between the plutonic sequence and the sheeted dyke complex the fluid inclusion population studied in the plagiogranites is characterized by the occurrence of four major fluid inclusion families 1 low to medium salinity liquid vapor fluid inclusions which homogenize into the liquid phase 2 low salinity liquid vapor fluid inclusions with pseudocritical homogenization 3 low to medium salinity liquid vapor fluid inclusions which homogenize into the vapor phase and 4 high salinity liquid vapor halite fluid inclusions which homogenize into the liquid phase by halite dissolution and exhibit salinities as high as 52 wt nacl eq these fluid inclusion families are interpreted as resulting from phase separation occurring in hydrothermal or magmatic fluids within the transition zone between the hydrothermal system and the magma chamber at temperatures higher than 500 c very low salinities less than half that of seawater have been found only in one dioritic sample from the gorringe bank mineralogical and petrological data from the semail ophiolite shows the absence of cl rich minerals furthermore hydration of the crust although very important cannot account for the large salinity variations thus the large salinity variations measured are interpreted as resulting from phase separation and generation of brine rich fluids at the top of the magma chamber this phase separation and subsequent phase segregation and brine accumulation may result in a double diffusive convection of the fluids in the hydrothermal system

a mechanism for preferential h 2 o leakage from fluid inclusions in quartz based on tem observations preferential leakage of h2o from fluid inclusions containing multiple gas components has been suspected in natural metamorphic rocks and has been demonstrated experimentally for synthetic h2o co2 rich inclusions in natural quartz knowledge of the physical and chemical characteristics of the leakage mechanism which may be very complex increases the value of natural fluid inclusions to metamorphic geology it is proposed that crystal defects play a major role in nondecrepitative preferential h2o leakage through quartz and remain effective during metamorphism inclusions with either an internal overpressure or underpressure produce strain in the adjacent quartz crystal via the nucleation of many dislocations and planar defects like dauphine twin boundaries these defects allow preferential loss of h2o from h2o co2 rich inclusions at supercritical conditions the transport capacity of this leakage mechanism is enhanced by nucleation of small bubbles on defect structures the nucleation of these bubbles seems to be a recovery process in strained crystals solubility gradients of quartz in water in a crystal with internally underpressurized inclusions may result in optical visible implosion halos in a three dimensional spatial arrangement caused by the growth of small bubbles at the expense of the larger original fluid inclusion natural fluid inclusions from naxos greece are always associated with numerous interlinked dislocations these dislocations may have been produced by plastic derormation or by crystal growth related processes e g crack healing the presence of small bubbles on these dislocations indicates that a similar leakage mechanism for h2o must have occurred in these rocks

fluid controlled quartz recovery in granulite as revealed by cathodoluminescence and trace element analysis bamble sector norway dispersed quartz veinlets in proterozoic enderbitic charnockite from tromoy bamble sector southern norway with ti concentrations of mostly 80 180 ppm produce bright blue cathodoluminescence cl against contrasting micro textures of secondary pure quartz with low cl intensity the textures comprise grain boundary alteration healed micro fractures patches of secondary quartz and euhedral quartz nuclei the secondary quartz locally makes up 50 of the total quartz trace element analysis has been done by electron probe micro analysis epma laser induced coupled plasma mass spectrometry la icpms and additional electron paramagnetic resonance epr spectroscopy these studies testify systematic trace element reduction and extensive quartz recovery during retrograde metamorphism we assume healing of a part of the aqueous fluid inclusions during a late thermal event possible correlated with paleozoic magmatic activity in the oslo rift during final cooling aqueous fluids were largely retrapped in patches of secondary quartz associated with healed fractures whereas carbonic inclusions without secondary quartz may have survived retrograde metamorphism the variable but generally high salinity of fluid inclusions is assumed to be in part the result of quartz recovery by which ion concentrations were increased in the percentage range

textural evolution of synthetic fluid inclusions in quartz during reequilibration with applications to tectonic reconstruction experimental reequilibration of synthetic 10 wt nacl h2o inclusions in natural quartz reveals that reequilibration textures show distinct differences depending upon the p t path followed by the inclusion after formation these differences combined with other geological information may be used to determine whether the sample rock followed a dominantly isothermal or isobaricp t path following entrapment the intensity and style of inclusion reequilibration features is related to the direction and magnitude of the departure of thep t path from the original isochore for the inclusion thus fluid inclusion reequilibration textures not only permit inclusionists to determine whether the rocks followed an isothermal or isobaric retrogradep t path but also the magnitude of departure of this path from one that is isochoric