modelling garnet fluid partitioning in h2o bearing systems a preliminary statistical attempt to extend the crystal lattice strain theory to hydrous systems accurate geochemical models of magmatic processes require an understanding of crystal melt partitioning of trace elements many major igneous processes at different tectonic environments in earth occur in the presence of garnet as a residual phase since the pioneering crystal lattice strain model several attempts have been made to quantify garnet melt partitioning coefficients over a wide range of conditions however high pressure high temperature experimental data demonstrate distinct differences in partitioning determined at anhydrous conditions and partitioning determined in the presence of h2o in this study we present for the first time a constraint on the partitioning of ree y and sc between garnet and hydrous fluids as a function of the water content in the fluid phase we analysed published hydrous experimental partitioning data using different statistical methods and modelled key parameters in the crystal lattice strain model r0 d0 and e we show a robust correlation between r0 temperature and garnet fluid partitioning of mg we further show that d0 can be predicted using the garnet fluid partitioning of fe and that e can be predicted using various parameters describing the fluid phase we validate and illustrate the ability to predict partitioning of ree in h2o bearing systems using major element analysis of garnet and fluid only consequently our statistical model paves the way to integrate thermodynamic models based on major element chemical equilibria with trace element studies on hydrous magmatic systems allowing a description of the transfer of key trace elements in more realistic conditions

the source region and melting mineralogy of high titanium and low titanium lunar basalts deduced from lu hf isotope data five high ti basalts from the apollo 11 and 17 landing sites have been analyzed for their hafnium isotope composition these data serve to better constrain the hafnium isotope variation of the moon s mantle variations in initial hf and nd values of low and high ti basalts imply that the source region mineral assemblages of these lunar magma types are distinct low ti basalts have higher initial hf values at a given nd value than high ti basalts the differences in the hafnium and neodymium isotopic composition of low and high ti basalts reflect the fact that the source of low ti basalts had a lu hf n ratio approximately four times greater than its sm nd n ratio in contrast the high ti source region had subequal lu hf n and sm nd n ratios if it is assumed that mare basalts are partial melts of the moon s cumulate mantle the differences between low and high ti basalts can only be explained by these mare magma types being generated from melting sources with distinctly different mineral assemblages the large lu hf fractionations relative to sm nd fractionations of low ti basalts can best be produced by an assemblage of olivine and orthopyroxene with trace amount of clinopyroxene that crystallized early in the history of the lunar magma ocean lmo the subequal lu hf n and sm nd n fractionations of high ti basalts can be produced from a variety of ilmenite bearing mineral assemblages low and high ti basalts have similar lu hf ratios approximately 0 6 times chondrite the low lu hf ratios measured for these mare magmas contrast sharply with the high lu hf ratios greater than chondritic calculated for their sources from initial hf values and an assumed chondritic bulk moon initial hf value the difference between the measured lu hf of a lava vs the calculated lu hf of its source implies that during partial melting lu was preferentially retained in the residual source relative to hf in order to explain the extreme fractionation of measured lu hf ratios we suggest mare basalts can best be explained using a polybaric melting model initial melting of a garnet bearing source followed by continued melting in the spinel stability field can produce the required lu hf fractionations and produce a liquid that last equilibrated with a residuum of olivine and orthopyroxene

conductive structures in southwestern canada a regional magnetometer array study an array of 33 three component recording magnetometers was operated in june and july 1980 in alberta and british columbia south of the edmonton prince rupert highway this very large array with its stations dispersed through 550 000 km2 and on average 150 km apart had limited resolution and was designed to confirm known conductive structures discover new ones and locate them sufficiently for suitable placement of further arrays with closer spaced stations and therefore higher resolution magnetograms and three sets of fourier transform anomaly maps are presented they show the general attenuation of the vertical component of variation fields west of the rocky mountain belt known from previous work and generally attributed to a conductive layer in the lower crust or upper mantle two prominent local anomalies are shown by variation fields of periods 15 30 min the first indicates induced currents near tete jaune cache west of jasper the highly conductive structure carrying the induced currents ma

lithoprobe seismic reflection structure of the southeastern canadian cordillera initial results nearly 270 km of crustal seismic reflection data obtained by lithoprobe in the southern canadian cordillera provide a geometric link between the rocky mountain foreland thrust and fold belt the purcell anticlinorium and the extensional regime superimposed on the crystalline core zone autochthonous north american basement and its overlying deformed and transported cover can be traced from the thrust and fold belt beneath the rocky mountain trench to 20 km depth beneath the central part of the purcell anticlinorium the purcell anticlinorium is cored by foreshortened proterozoic supracrustal rocks that were carried northeastward on a series of west dipping imbricate thrust faults these faults crop out within and east of the anticlinorium and converge downward with subhorizontal detachments above the autochthonous north american basement beneath the western purcell anticlinorium and kootenay arc reflections associated with the purcell stratigraphy and its underlying crystalline basement terminate at about 20 km depth and may be truncated against the east dipping eocene slocan lake fault zone the slocan lake fault zone is clearly imaged from the surface to about 12 km depth and can probably be followed discontinuously to about 25 km depth a west dipping high amplitude reflection from beneath the valhalla gneiss complex outlines the domal geometry of the complex and is probably related to an east verging compressional shear zone

experimental study of trace element partitioning between lunar orthopyroxene and anhydrous silicate melt effects of lithium and iron abstract orthopyroxene opx was present during a significant portion of crystallisation of the lunar magma ocean but its influence on co existing melt trace element contents is not well quantified we performed high pressure p 1 1 to 3 2 gpa high temperature t 1400 to 1600 c experiments on synthetic fe rich compositions at reducing conditions relevant to the lunar mantle to constrain trace element partitioning between opx and anhydrous silicate melts opx melt partition coefficients d opx melt for a wide range of trace elements lile li ba ree la ce nd sm dy eu er tm y yb lu hfse zr nb hf ta th u and transition metals sc v mn co mo show only very minor variations across the considered p t range ree partition coefficients increase from d la opx melt 0 0014 0 0008 to d lu opx melt 0 051 0 007 d values for highly charged elements vary from d th opx melt 0 0013 0 0008 through d nb opx melt 0 0018 0 0006 and d u opx melt 0 0015 0 0006 to d ti opx melt 0 068 0 0010 d lu opx melt d hf opx melt values of 6 3 2 4 are at the high end of reported values for minerals that played a role during crystallisation of the lunar magma ocean and higher than previously reported for opx under identical oxygen fugacity conditions implying opx rich cumulates in the lunar mantle have highly superchondritic lu hf ratios lattice strain modelling of our ree partitioning data suggests that varying the concentration of divalent fe in opx very slightly decreases the ideal cation radius for m 3 elements entering the m2 site r 0 m2 whereas the partitioning of m 3 elements entering the m1 site is unaffected a subtle increase in the maximum partition coefficient for m 3 elements entering both the m1 and m2 sites with decreasing t is identified when experiments carried out at similar reducing oxygen fugacities are considered the presence of li at concentrations of up to 350 ppm does not have a measureable effect on the opx melt partitioning behaviour of ree or any other element showing that charge balancing of m 3 m 4 and m 5 elements in opx is likely dominated by a vacancy mechanism

quantifying garnet melt trace element partitioning using lattice strain theory assessment of statistically significant controls and a new predictive model as a complement to our efforts to update and revise the thermodynamic basis for predicting garnet melt trace element partitioning using lattice strain theory van westrenen and draper in contrib mineral petrol this issue we have performed detailed statistical evaluations of possible correlations between intensive and extensive variables and experimentally determined garnet melt partitioning values for trivalent cations rare earth elements y and sc entering the dodecahedral garnet x site we applied these evaluations to a database containing over 300 partition coefficient determinations compiled both from literature values and from our own work designed in part to expand that database available data include partitioning measurements in ultramafic to basaltic to intermediate bulk compositions and recent studies in fe rich systems relevant to extraterrestrial petrogenesis at pressures sufficiently high such that a significant component of majorite the high pressure form of garnet is present through the application of lattice strain theory we obtained best fit values for the ideal ionic radius of the dodecahedral garnet x site r0 3 its apparent young s modulus e 3 and the strain free partition coefficient d0 3 for a fictive ree element j of ionic radius r0 3 resulting values of e d0 and r0 were used in multiple linear regressions involving sixteen variables that reflect the possible influence of garnet composition and stoichiometry melt composition and structure major element partitioning pressure and temperature we find no statistically significant correlations between fitted r0 and e values and any combination of variables however a highly robust correlation between fitted d0 and garnet melt fe mg exchange and dmg is identified the identification of more explicit melt compositional influence is a first for this type of predictive modeling we combine this statistically derived expression for predicting d0 with the new expressions for predicting e and r0 outlined in the first of our pair of companion papers into an updated set of formulae that use easy to measure quantities e g garnet composition pressure temperature to predict variations in e r0 and d0 these values are used in turn to calculate d values for those garnets the updated model substantially improves upon a previous model van westrenen et al in contrib mineral petrol 142 219 234 2001 and accounts well for trivalent cation partitioning in nominally anhydrous systems up to at least 15 gpa including for eclogitic bulk compositions and for fe rich systems appropriate to magmagenesis on the moon and mars the new model is slightly less successful in predicting partitioning with strongly majoritic garnets although the mismatch is much less than with the original 2001 model although it also improves upon the 2001 model in predicting partitioning in hydrous systems the mismatch between model and observation is still unacceptably large the same statistical tools were applied in an attempt to predict tetravalent partitioning as well because lattice strain based techniques are not applicable to such partitioning however no statistically significant predictive relationships emerged from that effort our analyses show that future efforts should focus on filling the gap in partitioning data between 10 and 25 gpa to evaluate more closely the gradual transition of garnet to majorite and on systematically expanding the hydrous partitioning database to allow extension of our model to water bearing systems

conductive structures under the canadian rocky mountains the paper reports results from an array of 33 three component magnetometers that recorded time varying fields in 1981 over an area of some 56 000 km2 in the canadian cordillera the array was centr

crustal structures from mt soundings in the canadian cordillera abstract magnetotelluric soundings have been made across the intermontane and omineca tectonic belts of the canadian cordillera between latitudes 51 5 and 53 5 n the frequency range 0 016 to 130 hz gives penetration into the middle crust in this part of the cordillera the upper crust has very low resistivities ranging from 3 to 300 ohm m compared with continental shields and stable platforms the most resistive rocks 100 300 ohm m rise to the surface as the coast plutonic complex is approached and we identify them with confidence as granodiorites and similar plutonic rocks hereafter plutonics phase pseudosections and resistivity depth sections are used to infer that these plutonics continue northeastward from the coast plutonic complex across more than half of the width of the intermontane belt with a sharp edge well located in the phase pseudosections the miocene basalts have extremely low resistivities 3 30 ohm m and form a sheet 0 2 km thick covering the plutonics the very low resistivities in all rocks are probably caused by saline hot water in connected spaces with low fracture density giving relatively high resistivities in the plutonic rocks and much greater fracture densities giving extremely low resistivities in the volcanics this is consistent with the lower mechanical strength of basalt as against granodiorite the volcanics may have accommodated most of the post miocene extension of the upper crust off the edge of the plutonic rocks beneath the basalts very low resistivities extend at least into the middle crust this deep extension of the highly conductive rock may mark the feeder channel of the miocene basalt to the surface three resistivity depth sections show a fall of resistivity with depth to values of 10 ohm m or even less at a depth of only 8 km heat flow is high in the region and the temperature at 8 km may be as high as 350 c the increase in conductivity may be due in part to the temperature effect on nacl solutions and in part to release of water from hydrated minerals all crustal features disclosed in this work support the hypothesis advanced earlier that the interior canadian cordillera lie above an elongated upflow in the mantle inland from the currently active subduction

electrical resistivity structure of the flathead basin in southeastern british columbia canada in june 1985 wide band magnetotelluric data were acquired at 12 equally spaced sites along a 30 km profile crossing the flathead kishenehn basin in southeastern british columbia canada these d

electromagnetic images of crustal structures in southern and central canadian cordillera data from more than 400 magnetotelluric soundings made since the early 1980 s in the canadian cordillera over a 300 000 km2 area between 49 and 53 5 n are used to image qualitatively regional three dimensional crustal variation in electrical conductivity by means of phase maps phase frequency sections and maps of resistivity at depth two hundred of the soundings were acquired as part of lithoprobe southern canadian cordillera transect activities and their locations were coordinated with the seismic reflection and refraction experiments the lower crust has a generally pervasive low resistivity 1 100 m throughout the cordillera west of the foreland belt within this canadian cordilleran regional conductor the magnetotelluric data reveal both two dimensional structures with highest conductivities along the coast belt and omineca belt and three dimensional variation along geological strike this conductor mapped over a volume in excess of 106 km3 is most probably caused by fluids saline wat

magnetotelluric soundings in the canadian rocky mountains summary magnetotelluric soundings have been made at 25 stations in the rocky mountain trench rmt and main ranges near 53 n close to the centre of a major conductivity anomaly which had been mapped in a magnetovariation array study most stations covered the frequency range 0 01 500 hz and three stations 0 0002 500 hz the resistivity tensor shows low to moderate anisotropy in the rmt but is strongly 2 d or 3 d in the rocky mountains apparent resistivities as a function of frequency are displayed in pseudosections along the trench and along a transverse profile across the rmt and into the main ranges in preparation for 2 d modelling 1 d inversions have been used to construct resistivity depth sections satisfying both magnitudes and phases of the mt responses these show very low resistivities in the range 1 10s2m in the upper crust under the rmt and even lower values under the main ranges the latter values give strong confirmation of the northern rockies conductor reported by bingham gough ingham and are in agreement with models of the conductors fitted to long period magnetovariation fields by ingham gough parkinson the mt results here reported add some essential depth and resistivity information it is suggested that the conductors beneath the rocky mountains main ranges and trench constitute a thickening at the edge of the canadian cordilleran regional ccr conductor gough has argued that a wide variety of geophysical and geological parameters indicate high temperatures and partial melting in the mantle under the ccr conductor at the upper crustal depths penetrated in this magnetotelluric study it is considered more probable that the high conductivity is caused by hot saline water of mantle origin rather than silicate melt the ccr in general may have two layers of fluid producing its high conductivity silicate melt below and saline hot water above

electromagnetic exploration for fluids in the earth s crust abstract electromagnetic geophysical techniques yield information on the spatial distribution of electrical conductivity a parameter sensitive to fluids in the rocks the paper describes electromagnetic techniques of use through the earth s crust including magnetovariation mv arrays magnetotelluric mt sounding and dc resistivity sounding field studies using these techniques lead to a discussion of various causes of high crustal conductivity including aqueous fluids silicate partial melt and films of graphite or magnetite on grain surfaces water in the crust is proposed as the preferred cause of high conductivity in the juvenile crust of tectonically active regions in particular where the anomalous conductivity is correlated with high heat flow and other geophysical and geological parameters

interpreting granulite facies events through rare earth element partitioning arrays the use of rare earth element ree partition coefficients is an increasingly common tool in metamorphic studies linking the growth or modification of accessory mineral geochronometers to the bulk silicate mineral assemblage the most commonly used mineral pair for the study of high grade metamorphic rocks is zircon and garnet the link from u pb ages provided by zircon to the p t information recorded by garnet can be interpreted in relation to experimental data the simplistic approach of taking the average ree abundances for zircon and garnet and comparing them directly to experimentally derived partition coefficients is imperfect in that it cannot represent the complexity of a natural rock system this study describes a method that uses all the zircon analyses from a sample and compares them to different garnet compositions in the same rock using the most important ree values it is possible to define zircon garnet equilibrium using an array rather than an average the array plot describes partitioning between zircon and garnet using dyb and dyb dgd as the defining features of the relationship this approach provides far more sensitivity to mineral reactions and diffusional processes enabling a more detailed interpretation of metamorphic history of the sample this article is protected by copyright all rights reserved

trace element partitioning between ilmenite armalcolite and anhydrous silicate melt implications for the formation of lunar high ti mare basalts abstract we performed a series of experiments at high pressures and temperatures to determine the partitioning of a wide range of trace elements between ilmenite ilm armalcolite arm and anhydrous lunar silicate melt to constrain geochemical models of the formation of titanium rich melts in the moon experiments were performed in graphite lined platinum capsules at pressures and temperatures ranging from 1 1 to 2 3 gpa and 1300 1400 c using a synthetic ti enriched apollo black glass composition in the cao feo mgo al2o3 tio2 sio2 system ilmenite melt and armalcolite melt partition coefficients d show highly incompatible values for the rare earth elements ree with the light ree more incompatible compared to the heavy ree d la ilm melt 0 0020 0 0010 to d lu ilm melt 0 069 0 010 for ilmenite d la arm melt 0 0048 0 0023 to d lu arm melt 0 041 0 008 for armalcolite d values for the high field strength elements vary from highly incompatible for th u and to a lesser extent w for ilmenite d th ilm melt 0 0013 0 0008 d u ilm melt 0 0035 0 0015 and d w ilm melt 0 039 0 005 and for armalcolite d th arm melt 0 008 0 003 d u arm melt 0 0048 0 0022 and d w arm melt 0 062 0 03 to mildly incompatible for nb ta zr and hf e g d hf ilm melt 0 28 0 05 and d hf arm melt 0 76 0 07 both minerals fractionate the high field strength elements with dta dnb and dhf dzr between 1 3 and 1 6 for ilmenite and 1 3 and 1 4 for armalcolite armalcolite is slightly more efficient at fractionating hf from w during lunar magma ocean crystallisation with dhf dw 12 13 compared to 6 7 7 5 for ilmenite the transition metals vary from mildly incompatible to compatible with the highest compatibilities for cr in ilmenite d 7 5 and v in armalcolite d 8 1 d values show no clear variation with pressure in the small range covered crystal lattice strain modelling of d values for di tri and tetravalent trace elements shows that in ilmenite divalent elements prefer to substitute for fe while armalcolite data suggest ree replacing mg tetravalent cations appear to preferentially substitute for ti in both minerals with the exception of th and u that likely substitute for the larger fe or mg cations crystal lattice strain modelling is also used to identify and correct for very small 0 3 wt melt contamination of trace element concentration determinations in crystals our results are used to model the lu hf ti concentrations of lunar high ti mare basalts the combination of their subchondritic lu hf ratios and high tio2 contents requires preferential dissolution of ilmenite or armalcolite from late stage lunar magma ocean cumulates into low ti partial melts of deeper pyroxene rich cumulates

models of conductive structure under the canadian cordillera summary extensive 2 d forward modelling has been used to study conductive structures beneath the cordillera the rocky mountains and the rocky mountain trench of western canada both large scale geology and magnetovariation anomalies indicate generally 2 d structure eleven stations close to a profile transverse to strike were chosen from two magnetovariation arrays the response parameter modelled at these stations is the real part of z h for a linearly polarized uniform horizontal primary field along the profile and transverse to the structures calculated from single station transfer functions at periods of 600 and 1500 s induction arrows indicate that the quadrature phase response is related mainly to currents induced in sedimentary rocks in another conductor very large real z h at stations in the main ranges and small values 50 km sw of these in the rocky mountain trench can be modelled by currents induced in highly conductive rocks rising to within a few kilometres of the surface beneath the main ranges this conductive ridge is well constrained in position and depth it is joined to the canadian cordilleran regional conductive layer and is essentially a thickening of the ccr conductor along its edge the best purely inductive model places the top of the ccr conductor within 5 km of the surface but it can be modelled at greater depth if the entire conductive structure carries a small amount of channelled current in addition to the induced currents available magnetotelluric soundings indicate a midcrustal depth to the ccr conductor sw of revelstoke but depths of 5 km or less under the rocky mountains and trench in good agreement with our models fitted to long period magnetovariation fields the nature of the ccr conductor has been considered elsewhere its high conductivity may be due to silicate partial melt in interconnected pores at upper mantle depths with saline hot water in interconnected pores and fractures at crustal depths

a 1 d enthalpy model of sea ice we present a 1 d enthalpy based model of sea ice that allows for quantitative studies of sea ice and its interaction with radiative processes melt ponds oceanic heat and salt fluxes internal density changes and surface heat fluxes on a single computational domain the model provides new insight into the interior structure and the salinity evolution of sea ice we compare our model results with measurements from laboratory experiments and show for example that no salt is lost from sea ice by brine expulsion

seismic reflection geometry of the columbia river fault zone and east margin of the shuswap metamorphic complex in the canadian cordillera vibroseis conoco incorporated seismic reflection data recorded near the transition between the cordilleran fold and thrust belt and the east margin of the shuswap metamorphic complex of the southern canadian cordillera outline an east tapering wedge geometry in the upper crust the wedge comprises part of the shuswap metamorphic complex and may be the result of either a foreland dipping duplex or tectonic wedging the geometric wedge separates the overlying miogeoclinal rocks of the selkirk fan structure from the crystalline basement rocks below and delineates the eastern limit of the monashee complex brittle motion on the columbia river fault zone produced an east dipping listric normal fault which may have offset the upper portion of the monashee complex the columbia river fault zone is imaged over the entire 15 km of the profile and can be traced to a depth of at least 10 km reflections from the lower crust are generally subhorizontal and discontinuous and they may be a manifestation of crustal extension the crust mantle transition is probably represented as reflections with travel times of 11 0 12 0 s

magnetometer array studies earth structure and tectonic processes this review presents results from magnetovariation fields recorded by two dimensional arrays of magnetometers the emphasis is on the conductive structures mapped and studied and their tectonic implications eleven arrays were operated in north america between 1967 and 1985 a region of highly conductive uppermost mantle and or lower crust extending at least from 33 n to 54 n has been shown to extend beneath much of the continent west of the rocky mountains two recent investigations are discussed in more detail those of conductive structures under the canadian rockies and emslab electromagnetic sounding of the lithosphere and beyond array results for washington and oregon including a conductive strip beneath the cascades volcanoes correlations with high heat flow and seismic parameters make it reasonable to attribute these regional conductors to partial melting and or hot saline water within the craton the north american central plains conductor is discussed this narrow crustal feature is associated with a major fracture zone and age boundary which may be a plate boundary of proterozoic time an array beneath the auroral electrojet for study of the external currents is noted results from four array studies in southern africa are considered two of these relate to the southern cape conductive belt which correlates not with high heat flow but with a large static magnetic anomaly the magnetovariation magnetic and gravity anomalies and geological data can be accounted for if an accumulation of ophiolitic rocks including serpentine is present in the lower crust such an accumulation may have formed at a subduction in proterozoic time two other arrays delineated a conductive belt associated with the southwestern end of the african rift system in namibia subsequent resistivity soundings located a conductor of resistivity 10 ohm m at less than 4 km depth two array studies in india follow one in the north and one in the south the array in the himalayan foothills and indo gangetic plain mapped a conductor transverse to the regional strike this may be a fracture zone produced in the interplate collision with a rise of asthenospheric material such as fluids into the fractures the southern indian array reveals crustal conductors under the indo sri lankan graben and another under the comorin ridge southwest of the tip of the subcontinent array studies in central and southeastern australia and in fennoscandia in regions without large local conductivity anomalies have been used to study conductivity variation with depth a note on the carpathian crustal anomaly is included as an example of combination of response parameters secured at different times to form a virtual array

inversion of magnetovariation event to causative current iii test of channelled current model sabc conductor inverted as chennelled currents and structure evaluation abstract algorithms developed in an earlier paper for the inversion of fields of channelled currents are tested with models the deepening effect of the inverted model expected from the spreading of current is found to be slight the same algorithms are then applied to 1983 magnetometer array data which appear to be dominated by current channelling the model space is explored with different models and constraints on models and with inversion from different data sets some features are consistent with all best fitting 3 d line and sheet current models inverted these are a the conductor plunges east of the canadian rocky mountains and b it makes a sharp bend towards the east with the plunge the inversion results are compatible with other geophysical data from the same area the conductive structure is located crossing the rocky mountains in the depth range 30 120 km it is either in the upper mantle or in the lower crust and may be related to a seismic low velocity zone

experimental determination of ree partition coefficients between zircon garnet and melt a key to understanding high t crustal processes the partitioning of rare earth elements ree between zircon garnet and silicate melt was determined using synthetic compositions designed to represent partial melts formed in the lower crust during anatexis the experiments performed using internally heated gas pressure vessels at 7 kbar and 900 1000 c represent equilibrium partitioning of the middle to heavy ree between zircon and garnet during high grade metamorphism in the mid to lower crust the dree zircon garnet values show a clear partitioning signature close to unity from gd to lu because the light ree have low concentrations in both minerals values are calculated from strain modelling of the middle to heavy ree experimental data these results show that zircon is favoured over garnet by up to two orders of magnitude the resulting general concave up shape to the partitioning pattern across the ree reflects the preferential incorporation of middle ree into garnet with dgd zircon garnet ranging from 0 7 to 1 1 dho zircon garnet from 0 4 to 0 7 and dlu zircon garnet from 0 6 to 1 3 there is no significant temperature dependence in the zircon garnet ree partitioning at 7 kbar and 900 1000 c suggesting that these values can be applied to the interpretation of zircon garnet equilibrium and timing relationships in the ultrahigh t metamorphism of low ca pelitic and aluminous granulites

high pressure phase equilibria and element partitioning experiments on apollo 15 green c picritic glass implications for the role of garnet in the deep lunar interior abstract we report results of nominally anhydrous near liquidus experiments on a synthetic analog to very low titanium apollo 15 green c lunar picritic glass from 2 to 5 gpa apollo 15 green c glass a15c is saturated with garnet and pyroxene on the liquidus at 3 gpa however such an assemblage is unlikely to represent the lunar mantle source region for this glass and instead an olivine orthopyroxene dominated source is favored in accord with earlier lower pressure experiments on a15c near liquidus garnet has a slight but significant majorite component at 5 gpa in this iron rich bulk composition as expected from our previous work in ordinary chondritic bulk compositions ion microprobe measurements of partitioning of sr ba sc nd sm dy yb y zr hf and th between garnet and coexisting melt in these experiments are the first garnet partition coefficients d values available that are directly relevant to lunar compositions d values for these garnets differ significantly compared to d values for garnets grown in more magnesian terrestrial bulk compositions which until now are all that have been available in modeling the possible role of garnet in the lunar interior for example d values for heavy rare earth elements are lower than are those from terrestrial basaltic systems these partitioning values are well described by the lattice strain partitioning model but predictive relationships for garnet partitioning using that model fail to match the measured values as was the case in our earlier work on chondritic compositions using our new d values in place of the terrestrial values in a variety of models of lunar petrogenesis we suggest that garnet is unlikely to be present in the source regions for very titanium poor lunar liquids despite its appearance on the liquidus of a15c

garnet fractionation in a hydrous magma ocean and the origin of al depleted komatiites melting experiments of hydrous pyrolite with rees at high pressure abstract melting experiments of a representative mantle composition doped with some key trace elements were conducted under hydrous conditions at pressures to 20 gpa the results demonstrate that only 5 25 of garnet fractionation and relatively low pressures 3 5 ga in the solidifying hydrous magma ocean this suggests that the archean mantle was much cooler than so far believed from the origin of the komatiites based on anhydrous experiments

late cenozoic volcanic rocks of the clearwater wells gray area british columbia the clearwater wells gray area of east central british columbia includes a succession of late cenozoic alkali olivine basalt flows that lie east of the extensive chilcotin lavas and define the eastern end of the anahim volcanic belt the rocks are petrographically similar to but less altered than the chilcotin basalts the volcanic activity spanned at least two episodes of glacial advance and produced both subaerial flows and a subaqueous facies comprising pillow lava pillow breccia and tuff breccia locally intercalated with fluvial gravels and sand four morphological assemblages have been recognized an early glacial assemblage characterized by tuyalike forms gives k ar dates of 0 27 3 5 ma these circular features are surrounded by a deeply dissected valley filling assemblage of subaerial and minor subaqueous flows and tuff breccia that rest locally on lag gravel and till subaerial flows in this assemblage give k ar dates of 0 15 0 56 ma whitehorse bluffs a volcanic centre composed o