flow laws for rocks containing two non linear viscous phases a phenomenological approach abstract mylonitic rocks and rock analogue materials reveal two basic types of structure 1 a load bearing framework lbf of strong phase contains isolated pockets of weak phase 2 interconnected layers of weak phase iwl separate boudins and clasts of strong phase aggregates with the lbf microstructure are characterized by nearly uniform strain rate stress is concentrated in the load bearing framework in aggregates with an iwl microstructure strain rate and sometimes also stress are higher in the interconnected weak phase than in the boudins and clasts of strong phase the degree of stress and strain partitioning depends strongly on the viscous strength contrast and on the relative amounts of the constituent mineral phases based on these observations the rheology of two phase rock is modelled with separate functions for lbf and iwl microstructures a new flow law is derived for rock with iwl structure in which two phases undergo dislocation creep the flow law expresses composite creep strength in terms of temperature bulk strain rate and the volume proportions and creep parameters of the minerals in the rock strain rate and stress are averaged in the constituent phases and slip along phase boundaries maintains strain compatibility within the aggregate composite strengths predicted with the iwl flow law fall well within the uniform stress and uniform strain rate bounds and are generally consistent with the viscous strengths of experimentally deformed bimineralic aggregates a hypothesis of viscous strain energy minimization is used to determine the relative stability of the lbf and iwl microstructures during steady state creep the iwl microstructure is predicted to be stable over a broad range of two phase compositions and mineral strength contrasts whereas the lbf microstructure is stable only in rocks with low volume proportions of weak phase and low to moderate mineral strength contrasts the iwl flow law indicates that rheological stratification in the lithosphere depends strongly on rock composition especially in rocks with low volume proportions of a weak phase and high mineral strength contrasts

genesis of the dongguashan skarn cu au deposit in tongling eastern china evidence from fluid inclusions and h o s pb isotopes abstract the dongguashan copper gold deposit is located in the eastern tongling ore district of the middle lower yangtze river valley metallogenic belt mlyrb eastern china the cu au mineralization is associated with the qingshanjiao quartz monzodiorite and consists of various types including stratiform porphyry vein like and skarn there are three deposit models including 1 stratabound skarn type 2 exhalative sedimentary sedex hydrothermal superimposition type and 3 exhalative sedimentary sedex type the ore forming processes can be divided into the prograde skarn alteration stage i retrograde alteration stage ii and quartz carbonate alteration stage iii four types of fluid inclusions fis are recognized at dongguashan vapor rich two phase aqueous type i liquid rich two phase aqueous type ii daughter mineral bearing three phase homogenized to liquid by the disappearance of vapor phase type iii and daughter mineral bearing three phase homogenized to liquid by the disappearance of daughter minerals type iv all four types of fis are present in stage ii stage i does not contain type iv fis and only type ii fis are found in stage iii for stage i type i ii and iii fis homogenized at 379 548 c 319 522 c and 450 512 c respectively with salinities of 10 1 19 6 5 9 19 4 and 36 7 43 3 wt nacl equivalent for stage ii type i ii iii and iv fis homogenized at 286 378 c 235 372 c 265 349 c and 324 350 c respectively with salinities of 1 4 17 0 4 3 16 1 34 7 40 6 and 34 4 41 0 wt nacl equivalent the type i to iii fis in stage i and ii have similar homogenization temperatures but different salinities which indicates the occurrence of fluid immiscibility hydrogen oxygen isotopes of the quartz d 84 0 to 71 5 18oh2o 4 51 to 8 97 and calcite d 70 7 to 60 95 18oh2o 4 41 to 4 91 suggest that the ore forming fluids were principally magmatic derived 34s values of the stratiform orebodies 4 1 to 5 3 vein like orebodies 4 2 to 5 7 skarn orebodies 4 9 porphyry orebodies 5 1 to 5 7 and the qingshanjiao pluton 2 2 to 5 2 are different from those of the wall rocks 29 5 to 4 6 suggesting that wall rocks were unlikely to be a major sulfur source lead isotopes of the sulfides from the different orebody types are similar to those of the plagioclase from the mesozoic intermediate felsic rocks in the mlyrb suggesting that they have had similar pb source sulfur and lead isotopes suggest that the ore forming materials were derived from a deep seated magmatic source the ore forming fluid immiscibility during stage i and ii may have altered the physicochemical conditions of the hydrothermal fluid system leading to the cu au sulfide precipitation based on the ore geological and alteration mineralization features mineral assemblages ore forming material source and fluid evolution we consider that dongguashan is best classified as a porphyry skarn cu au deposit

depletion of light rare earth elements in felsic magmas contrary to simple generalizations about their behavior light rare earth elements lree do not act as incompatible elements in very felsic magmas in fact lree concentrations typically decrease often drastically during differentiation of such magmas the simplest explanation for this depletion involves the separation of minute easily overlooked quantities of an extremely lree rich accessory mineral either monazite or allanite our data indicate that felsic liquids with 50 ppm lree may be saturated in either of these accessories and that the concentration required for saturation decreases in increasingly felsic liquids this accounts for incompatible behavior of lree even at high concentrations in mafic magmas in contrast to compatible behavior at low concentrations in felsic magmas partitioning of lree into solid rather than liquid has important implications for trace element and nd isotope modeling of crustal anatexis as well as for magma differentiation

a review of the intracontinental porphyry deposits in the middle lower yangtze river valley metallogenic belt eastern china abstract the middle lower yangtze river valley metallogenic belt mlyb is one of the most important metallogenic belts in eastern china and contains many important porphyry deposits these deposits include the tongshankou cu mo jiguanzui cu au chengmengshan cu mo wushan cu mo fengshandong cu au dingjiashan cu yangjishan au shaxi cu au dongguashan cu au shujiadian cu and anjishan cu deposits etc in this review we summarize the geological characteristics including the stratigraphy structure ore bearing porphyry types vein characteristics and wall rock alteration metallogenic ages and petro geochemistry of representative porphyry deposits in the mlyb we conclude that porphyritic magmatism and metallogeny have occurred in three stages the early ca 149 135 ma and late ca 123 105 ma stages comprise mainly porphyry skarn mineralization whereas the middle ca 133 125 ma stage comprises porphyry mineralization ore bearing porphyries in the mlyb are the high k calc alkaline to calc alkaline series with the majority possess adakitic geochemical signature the ore bearing porphyries with adakitic signature may have originated from magma mixing produced by the delamination of enriched lithospheric mantle and partial melting of the thickened lower crust the enriched mantle derived mafic melts component are very important for generating fertile magma and the 34s and 18o values suggest that ore forming materials were magma derived compared with porphyry deposits in typical magmatic arc settings porphyry deposits in the mlyb do not contain advanced argillic lithocaps or high to intermediate sulfidation systems and the magmatic and ore forming material sources are also very different

vertical distribution of heat generation in the nissho granitic pluton hokkaido japan vertical distribution of radiogenic heat generation is estimated for the nissho granitic pluton emplaced in the upper crust of the kuril arc the estimated profile shows that heat generation steeply decreases with depth using the exponential model the thickness of the layer with relatively high heat generation is estimated to be 7 2 km this thickness is in the range of those estimated in heat flow provinces on continents it is considered that this upward concentration of heat generation is caused by magmatic processes such as the gravitational differentiation in the magma chamber in the upper crust of evolving arcs where the continental type crust is growing magmatic processes in chambers of granitic magmas could be important for the upward concentration of heat generation

high pressure elastic anisotropy of mgsio3 perovskite and geophysical implications using plane wave pseudopotential method within the local density approximation lda we calculate single crystal elastic constants cij of orthorhombic mgsio3 perovskite generally accepted to be the major component of the lower mantle as a function of pressure up to 150 gpa our results are in excellent agreement with experimental data at zero pressure and compare favorably with other pseudopotential predictions over the pressure regime studied here we use our elastic constants to calculate anisotropy of seismic wave velocities as a function of pressure depth mgsio3 perovskite is shown to be highly anisotropic in all portions of the lower mantle and the nature of anisotropy changes significantly with depth the absence of significant seismic anisotropy in most of the lower mantle suggests that mgsio3 perovskite assumes nearly random orientation in most of this region anisotropy at the topmost lower mantle suggested by some studies can be attributed to the preferred orientation of perovskite however anisotropy in the d layer is difficult to be attributed to preferred orientation of perovskite some other mechanisms including the presence of the aligned melt pockets and or lattice preferred orientation of magnesiowustite are needed

in situ investigations of thermal conductivity heat production and past hydrothermal circulation in the cajon pass scientific drillhole california wireline logs from the cajon pass drillhole provide observations of crustal properties and processes near the san andreas fault mineralogical profiles developed from geochemical logs are combined with a technique for calculating thermal conductivity from the volume fractions of component minerals variations in the equilibrium temperature gradient correlate with conductivity contrasts and thus with lithology rather than with fluid circulation k u and th contents calculated from gamma spectroscopy logs yield heat production values which range from 1 3 to 2 4 w m averaging 1 8 w m in the section from 500 to 1800 m evidence for depletion of u relative to th raises the possibility of extensive fluid circulation in the past however discontinuity of depletion across faults suggests that the fluid regime responsible for u depletion predated san andreas faulting

the probable occurrence of interstitial al in hydrous f bearing and f free aluminosilicate melts experiments carried out on the system sio2 naalsi3o8 kalsi3o8 qz ab or at 1 kbar in the presence of h2o and f show that the quartz alkali feldspar field boundary is progressively displaced towards the feldspar join as f contents increase from 0 to 4 wt f increasing p h 2 o in the absence of f has already been shown to have a similar effect tuttle and bowen 1958 luth jahns and tuttle 1964 the increased size of the quartz field in the f bearing system compared to the hydrous system is believed to be caused by progressive removal of al from the tetrahedral network of the melt by complexing with f the residual network in the melt is thus enriched in si and this stabilizes precipitation of quartz rather than feldspar for certain bulk compositions the common presence of quench cryolite na3alf6 in certain experiments carried out with 4 wt f supports this interpretation and indicates that some al in the melt may be present in six fold coordination with f the effect of h2o in the absence of f may be similar with al being progressively removed from four fold coordination as more h2o is dissolved in the melt although a proportion of al in hydrous melts may occur in six fold coordination dry melts predominantly contain al in four fold coordination this major difference in al complexing may be one of the main causes for differences in the high pressure phase relations of wet and dry albearing silicate systems

petrogenetic modelling of in situ fractional crystallization in the zoned loch doon pluton scotland the late caledonian loch doon granitic intrusion ranges in composition from hypersthene diorite at the margin through quartz diorite granodiorite and granite to cordierite microgranite at its core petrogenetic modelling of trace element variations and least squares analysis of major elements indicate that two distinct magmas are involved each magma controlled by crystallization of plag opx cpx bio late stage rocks related to the second magma include the cordierite microgranites and aplites which are interpreted as the final residue which crystallized rapidly after a build up and loss of volatiles analyses of whole rocks and minerals for ree s and other elements of moderate high ionic potential indicate that these elements are strongly controlled by minor phase crystallization apatite zircon sphene and allanite are dominant at intermediate compositions but other accessory minerals such as monazite and xenotime may also become important at acid compositions it is probable that within each magma the mechanisms of crystal settling and filter pressing operated the former being initially dominant and the latter becoming more important with increasing degree of fractional crystallization

fabric development in mg fe o during large strain shear deformation implications for seismic anisotropy in earth s lower mantle abstract large strain shear deformation experiments were performed on mg 1 x fe x o x 0 25 1 0 one of the important minerals in earth s lower mantle deformation experiments were made on coarse grained 15 20 m grain size hot pressed aggregates at conditions of t t m 0 46 0 65 t temperature t m melting temperature and 0 4 10 3 to 0 9 10 3 differential stress shear modulus up to the shear strain of 7 8 under these conditions deformation occurs by dislocation creep the microstructural development in mg fe o is found to be sluggish and the complete dynamic recrystallization and nearly steady state fabric lattice preferred orientation are achieved only after shear strains of 4 at nearly steady state mg fe o shows strong fabrics characterized by the 1 1 0 axes being parallel to the shear direction and the poles of the 1 0 0 planes and to a lesser extent the poles of the 1 1 1 planes normal to the shear plane the seismic anisotropy corresponding to the deformation fabrics in mg fe o was calculated the nature of anisotropy corresponding to a given flow geometry changes significantly with strain as a result of fabric evolution anisotropy changes also with depth pressure due to the large variation of elastic anisotropy of mg fe o with depth seismic anisotropy caused by the deformation fabric of mg fe o is very weak in the shallow lower mantle v sh v sv anisotropy assuming that mg fe o occupies 20 volume fraction of the lower mantle and little shear wave splitting of vertically travelling waves a result that is consistent with the seismological observations in the d layer of the circum pacific regions thus the deformation fabric of mg fe o is a vital candidate of the cause of seismic anisotropy in these regions anisotropy caused by the lattice preferred orientation of mg fe o has a distinct azimuthal anisotropy with a strong 4 term azimuth the direction of propagation of the fastest slowest sh or p wave is parallel perpendicular to the flow direction and the slowest fastest sh or p wave is at 45 from these two directions

some mineral physics constraints on the rheology and geothermal structure of earth s lower mantle we explore the implications of recent mineral physics measurements of diffusion coefficients and melting temperatures of lower mantle materials on the rheological and geothermal structure of earth s lower mantle we show that mgsio3 perovskite is significantly stronger than mgo periclase and therefore the rheology of the lower mantle depends strongly on the geometry of a weaker phase periclase we calculate viscosities of the lower mantle for two cases 1 where periclase occurs as isolated grains and 2 where periclase occurs as continuous films using mineral physics data and models of two phase rheology we find that the effective viscosity for the former is about 10 1000 times higher than the latter we therefore suggest that the rheology of the lower mantle is structure and hence strain dependent leading to weakening at large strains due to the formation of continuous films of periclase overall depth variation of viscosity depends not only on the pressure dependence of creep but also on the geothermal gradient both mgsio3 perovskite and periclase have relatively small activation energies e g r t m with g 10 14 where r is the gas constant and t m is melting temperature and therefore the depth variation of viscosity is rather small even for a nearly adiabatic temperature gradient however the geothermal gradients consistent with the geodynamical inference of nearly depth independent viscosity are sensitive to the pressure dependence of viscosity which is only poorly understood a superadiabatic gradient of up to 0 6 k km is also consistent with mineral physics and geodynamical observations

constraints from seismic anisotropy on the nature of the lowermost mantle the d layer lies at the bottom of the earth s rocky mantle and separates it from the liquid metal alloy core this region extending from the core mantle boundary to a few hundred kilometres above fig 1 is geodynamically analogous to the more easily studied lithosphere at the top of the mantle the structure of d may reflect the style of lower mantle convection the nature of core mantle interaction and perhaps even the fate of subducting lithosphere1 observations of lithospheric seismic anisotropy have provided valuable insight into the nature of the upper mantle boundary layer but discussion of lower mantle seismic anisotropy has been somewhat contentious2 5 here we present evidence from seismic waves that have traversed the lowermost mantle beneath the caribbean region for a zone of seismic anisotropy below the d discontinuity which in this region lies 250 km above the core mantle boundary the anisotropy is most probably due to horizontal layering or aligned inclusions of a material with differing shear wave velocity if d is a graveyard for subducted lithosphere a plausible explanation of the anisotropy may be the contrast between cold lithospheric mantle and material that formerly constituted the oceanic crust which may have lower shear wave velocity owing to the presence of melt

petrogenesis of dongguashan skarn porphyry cu au deposit related intrusion in the tongling district eastern china geochronological mineralogical geochemical and hf isotopic evidence the dongguashan skarn porphyry cu au deposit located in the tongling district of the middle lower yangtze river valley metallogenic belt mlyb consists of skarn ore bodies in the upper part and porphyry ore bodies in the lower part both of which are hosted in quartz diorite and quartz monzodiorite zircon u pb age and geochemical studies show that the quartz diorite of the dongguashan intrusion formed at 140 3 2 0 ma mswd 0 19 and belongs to the high potassium calc alkaline series it is enriched in large ion lithophile elements lile and light rare earth elements lree depleted in high field strength elements hfse and heavy rare earth elements hree and has a slightly negative eu anomaly 176hf 177hf values of the rims of zircons show a variable range 0 282087 0 282391 corresponding with calculated ehf t values of 10 72 to 21 46 plagioclases in the quartz diorite have unbalanced structure characterized by bright andesine and labradorite an 37 0 65 5 cores with higher contents of fe and sr and are corroded by dark oligoclase an 13 8 27 6 rim major elements trace elements hf isotope and the composition of plagioclases indicate that the parental magma of the dongguashan intrusion was produced by the mixing of underplating mafic magma and felsic magma formed by remelting of paleoproterozoic and neoarchean crustal rocks neoproterozoic crust may also provide some material to the felsic magma mafic magma played a key role and made the parental magma rich in water sulfur metals cu au and gave it a high oxygen fugacity during its magmatic evolution the parental magma underwent fractional crystallization of hornblende apatite sphene and other mafic minerals some quartz diorite and quartz monzodiorite samples that show adakitic signatures may result from injection of mafic magma some inherited zircons of the quartz diorite in the dongguashan intrusion gave ages of 2 40 2 50 ga 1 95 2 05 ga and 0 74 0 81 ga coming from ultramafic mafic and andesitic igneous rocks and this indicates that there may have been three periods 2 4 2 0 and 0 8 ga of magmatic activity in the tongling district

factors controlling the distribution of heat production in selected uk granites the variation of heat production with respect to magma evolution is examined in four uk granites in which fractional crystallization accounts for the range of rock compositions present accessory minerals are the dominant hosts of u and th in these granites and their role in controlling variations of these heat producing elements is assessed melt compositional parameters determine which accessory minerals precipitate solubility control and influence the partitioning of radioelements between early crystallizing fractionating minerals and residual liquid as a result parental magma compositions and the effect of critical properties such as alkalinity aluminosity and volatile contents particularly f complexing on magma evolution are considered important in controlling the primary distribution of radioelements in granites

a scanning electron microscope study of the effects of dynamic recrystallization on lattice preferred orientation in olivine effects of dynamic recrystallization on lattice preferred orientation lpo in olivine were investigated through the combination of two sem based techniques electron backscattered diffraction ebsd technique for crystallographic orientation measurement and backscattered electron imaging bei for dislocation observation samples are experimentally deformed olivine aggregates in simple shear geometry in the sample deformed at t 1473 k and high stresses 480 mpa only incipient dynamic recrystallization is observed along grain boundaries orientations of these small recrystallized grains are more random than that of relict grains suggesting an important role of grain boundary sliding at this stage of recrystallization in the sample deformed at t 1573 k and low stress 160 mpa dynamic recrystallization is nearly complete and the lpo is characterized by two 100 peaks one peak is located at the orientation subparallel to the shear direction and is dominated by grains with high schmid factor the other occurs at high angles to the shear direction and is due to the contribution from grains with low schmid factor grains with high schmid factor tend to have higher dislocation densities than those with low schmid factor based on these observations we identify two mechanisms by which dynamic recrystallization affects lpo 1 enhancement of grain boundary sliding due to grain size reduction leading to the modification of lpo caused by the relaxation of constraint for deformation 2 grain boundary migration by which grains with lower dislocation densities grow at the expense of grains with higher dislocation densities based on the deformation mechanism maps and stress versus recrystallized grain size relation we suggest that the first mechanism always plays an important role whereas the second mechanism has an important effect only under limited conditions

sulfide and oxide inclusions in xenoliths and host rocks of tongling area anhui province this paper presents new petrographic observations and electron microprobe analyses of sulfide and oxide melt inclusions trapped within amphibole and clinopyroxene in xenoliths and host rocks hrs from the late jurassic early cretaceous laomiaojishan xiaotongguanshan and xiaotaojia intrusions in tongling area anhui province the plutons vary in composition from quartz monzonitic diorite to granodiorite and contain mafic clots mfcs hornblende cumulates hcs and microgranular mafic enclaves mmes with gabbroic to dioritic compositions compositions of sulfide inclusions correspond to pyrrhotite chalcopyrite single sulfide solution and pentlandite in mfcs and pyrrhotite and chalcopyrite in mmes and hrs ni and cu content of the sulfide phases except for chalcopyrite in single blebs is averagely 6 91 and 0 44 0 44 and 0 07 and 0 09 and 0 42 in mfcs mmes and hrs respectively compositions of oxide blebs correspond to cr magnetite averagely 4 44 cr2o3 in mfcs and magnetite with an average cr2o3 content of 0 44 in mmes and 0 07 in hrs while compositions of oxide grains are cr magnetite averagely 6 58 cr2o3 in mfcs magnetite and cr magnetite averagely 0 86 cr2o3 in mmes and magnetite averagely 0 34 cr2o3 in hrs paragenetic associations of 1 mono sulfide solution pyrrhotite 2 mono sulfide solution chalcopyrite and 3 pyrrhotite and pentlandite chalcopyrite exist within single blebs in mfcs while paragenetic associations of pyrrhotite chalcopyrite and pyrrhotite magnetite occur within single blebs in mmes and hrs respectively crystallization temperatures of hornblendes in hcs and hornblendes and plagioclases in mmes and hrs are 860 865 714 811 and 614 733 respectively based on al and ti in calcic amphibole and amphibole plagioclase geothermometers the pressures recorded by these phases indicate that they were formed at a depth of 26 27 km 7 16 km and 3 6 km respectively based on al and ti in calcic amphibole and al in hornblende geobarometers the present petrographic observations and microprobe analyses combined with the published geochemical and mineralogical data of the pyroxene cumulates hcs mmes and hrs support an origin of sulfide and oxide melt inclusions in mfcs and hcs mmes and hrs from crystallization products of sulfide and oxide melts immiscibly separated from alkaline basaltic and somewhat evolved underplated alkaline basaltic magmas from the upper mantle to the lower crust the gabbroic to dioritic magmas in the middle to upper crust and the pyroxene or quartz monzodioritic to granodioritic magmas in the upper crust respectively the variations in the oxide and sulfide assemblage and the sulfide and oxide paragenetic association within single blebs presented above correspond to the increase in the amount of the hybridized lower and middle to upper crustal material in the magmas and the decrease in crystallization temperature and depth of the magmas in the formation process of mfcs and hcs mmes and hrs

the role of recrystallization in the preferred orientation of olivine abstract the effects of recrystallization on the preferred orientation in olivine have been studied the recrystallization mechanisms studied include grain growth the deformation induced grain boundary migration digbm and subgrain rotation sgr grain boundary migration is involved in the first two but not in sgr significant preferred orientation was found only in the latter two where dislocations are involved the combined microstructural and fabric preferred orientation observations indicate that the grain boundary migration produces strong preferred orientation when the driving force is the dislocation energy but not when the grain boundary energy is the driving force the nature of preferred orientation due to dislocation related recrystallization digbm or sgr was found to depend on the mechanism of recrystallization the digbm produces preferred orientation in which the low dislocation density grains with unfavourable orientation for easy slip dominate thereby significantly altering the preferred orientation formed by dislocation glide in contrast sgr does not essentially alter the deformation fabric and therefore the fabric associated with sgr recrystallization is related to the geometry of flow the present results demonstrate that the existence of seismic anisotropy in the upper mantle is strong evidence for the dislocation mechanism s of deformation and suggest that care must be exercised in applying the results of laboratory fabric studies made for a particular mechanism of recrystallization to the earth s interior where the dominant mechanism s of dynamic recrystallization can be different

dislocation creep of magnesiowustite mg0 8fe0 2o abstract magnesiowustite is likely the second most abundant and probably weakest lower mantle phase its deformation properties will therefore influence the rheological and dynamic behaviour of this region in this study magnesiowustite aggregates with a composition of mg0 8fe0 2o have been deformed under dry conditions in axial compression at a confining pressure of 300 mpa and temperatures from 1200 to 1400 k 0 41

radioelement distribution in the tertiary lundy granite bristol channel uk the radioelement distribution and content of the lundy granite a coarse grained megacrystic granite of tertiary age has been measured using a portable gamma ray spectrometer in order to assess fractionation and alteration processes in the granite results indicate a systematic variation of k th and u with a few notable exceptions that follows a partially concentric distribution to lower concentrations inland the plateau region of the island particularly the southern half is relatively depleted in all radioelements over the island measurements of k vary from 1 3 4 9 wt th varies from 5 0 20 3 ppm and u varies from 2 0 12 5 ppm a petrographic electron microprobe and autoradiography examination of the granite indicates that the radioelements mainly reside in discrete major and accessory minerals of which k feldspar k biotite k monazite th xenotime u tungsteniferous columbite u and uraninite u are the most important uraninite is rare being preserved only in fresh samples which come mainly from abandoned quarries mass balance modelling indicates that up to 76 6 of uranium could reside in uraninite and where this has been leached by secondary processes such as hydrothermal alteration or weathering then the present radioelement content no longer reflects the original rock composition fission track evidence is presented to show the pathways along which uranium has been mobilized from or within the granite secondary sites of radioelements include fractures cross cutting all major minerals but especially quartz grain boundaries altered cores of plagioclase feldspar and occasionally yellowy brown mixed chlorite smectite replacement product after biotite biotite itself may exhibit secondary tracks along cleavage traces combined effects of crystal fractionation primary variation and secondary alteration best explain the distribution of radioelements with k controlled by fractionation of the major phases k feldspar and biotite th by fractionation of the accessory mineral monazite xenotime and uraninite and u contents by uraninite and tungsteniferous columbite secondary processes have removed much of the uraninite leaving behind indeterminate fe u material along fractures and residual u and th enrichment within altered major minerals there is some evidence to suggest that late radioelement bearing fluids precipitated monazite and uraniferous zircon along fractures during the waning stages of magmatic activity

experimental determination of the solubility of ce monazite in sio2 al2o3 k2o na2o melts at 800 c 2 kbar under h2o saturated conditions the solubility of cerium monazite cepo4 in sio2 al2o3 k2o na2o melts was determined at 800 c 2 kbar under water saturated conditions dissolution experiments using synthetic ce monazite crystals and crystallization experiments using ce and po4 bearing glasses yield results in good agreement microprobe analyses of glasses using a sensitive method detection limit to 130 ppm show that the solubility of monazite is dependent on the melt composition and is especially low for peraluminous compositions application of these data to various geologic occurrences is in good agreement with petrographic and geochemical observations and shows that monazite fractionation is probably a very common phenomenon in two mica granites this provides a good explanation for the light ree and th depletion commonly observed in such rocks