permian rifting related fayalite syenite in the panxi region sw china abstract within the panxi rift of the permian emeishan large igneous province elip sw china a 20 km 2 quartz bearing fayalite syenitic pluton intrudes the 260 ma baima igneous complex bic the fayalite syenite is dated using shrimp zircon u pb techniques at 252 2 5 ma the panxi fayalite syenite is mainly composed of alkali feldspar ferroan augite fayalite quartz and fe ti oxides and contains 61 8 63 7 wt sio 2 5 0 7 3 wt fe 2 o 3 t and 9 9 12 1 wt total alkalis belonging to an a type variety of ferroan alkalic metaluminous granitoids the fayalite syenite displays positive eu anomalies eu eu 0 9 8 9 and is enriched in lree la yb n 6 6 11 5 the nd values and 87 sr 86 sr initial ratios of the fayalite syenite range from 1 3 to 1 9 and from 0 7035 to 0 7068 respectively the fayalite syenite and the bic had the same mantle source however the 8 myr age gap between them suggests the fayalite syenite formed by remelting of underplated mafic magmas injected into the crust during elip magmatism the ages of the fayalite syenite and bic are coincident with two permian mass extinction events and suggest that elip may have influenced both

two magma series and associated ore deposit types in the permian emeishan large igneous province sw china the late middle permian 260 ma emeishan large igneous province in sw china contains two magmatic series one comprising high ti basalts and fe rich gabbroic and syenitic intrusions the other low ti basalts and mafic ultramafic intrusions the fe rich gabbros are spatially and temporally associated with syenites each series is associated with a distinctive type of mineralization the first with giant fe ti v oxide ore deposits such as panzhihua and baima the second with ni cu pge sulfide deposits such as jinbaoshan limahe and zhubu new shrimp zircon u pb isotopic data yielded 263 3 ma for the limahe intrusion 261 2 ma for the zhubu intrusion and 262 2 ma for a syenitic intrusion these new age dates together with previously reported shrimp zircon u pb ages suggest that all these intrusions are contemporaneous with the emeishan flood basalts and formed during a major igneous event at ca 260 ma the oxide bearing intrusions have higher al2o3 feo as total iron and total alkalis na2o k2o but lower mgo than the sulfide bearing intrusions all intrusions are variably enriched in lree relative to hree the oxide bearing intrusions display positive nb and ti anomalies and in certain cases negative zr hf anomalies whereas the sulfide bearing intrusions have obvious negative nb and ti anomalies a feature of crustal contamination individual intrusions have relatively small ranges of nd t values all the intrusions however have nd t values ranging from 3 9 to 4 6 and initial 87sr 86sr ratios from 0 7039 to 0 7105 the syenites have very low mgo 2 wt but highly variable fe2o3 2 5 to 13 wt with initial 87sr 86sr ratios ranging from 0 7039 to 0 7089 magmas from both series could have derived by melting of a heterogeneous mantle plume the high ti series from a fe rich more fertile source and the low ti series from a fe poor more refractory source in addition the low ti series underwent significant crustal contamination the two magma series evolved along different paths that led to distinct mineralization styles

multiple cold trap pyrolysis gas chromatography a new technique for modeling hydrocarbon generation abstract the newly developed multiple cold trap pyrolysis gas chromatography mctp gc technique allows us to calculate activation energies for the generation of individual hydrocarbons from source rocks this improves our ability to predict the timing of oil generation and the compositional changes of oil at the different stages of kerogen conversion the activation energies for n c 12 and n c 24 for a type ii kerogen toarcian shale are 57 5 0 8 kcal mol and 51 2 2 2 kcal mol with frequency factors of 8 71 10 16 min and 1 15 10 15 min respectively the relative rates of alkane generation are n c 24 n c 18 n c 12 n c 2 c 5 by comparing the rates of generation from kerogen and asphaltenes for monterey source rocks we conclude that normal alkanes can be generated directly without going through an asphaltene intermediate

spodosol alfisol intergrades bisequal soils in ne michigan usa abstract twenty three well drained boralfs most of which exhibit bisequal soil morphology were described and sampled in ne lower michigan where they occur on landscapes shaped by greatlakean ice ca 12 ka bisequal soils in michigan are intergrades between orthods and udalfs with a spodic like upper sequum a e bs overlying a sequence of e bt c horizons thus they frequently occupy a pedogenic ecotone the purpose of the study was to characterize these soils which have been little studied and to determine if parent material homogeneity and texture are correlated with various aspects of their morphology the soils have formed in coarse loamy and fine loamy materials often with a distinct lithologic discontinuity between the two sequa the lower material interpreted as glacial till is strongly calcareous and slightly coarser textured with considerably more dolomitic gravel than the upper material water flowing through the material above may hang at the discontinuity and deposit illuvial clay bt horizons are found at or immediately below the discontinuity statistical correlations indicate that bisequal sola and their eluvial horizons are thicker when developed in coarser textured materials finer textured pedons contain more extractable fe and al in the spodic sequum but have thinner eluvial zones which have not been as completely stripped of metal cations in the finest textured pedons the e horizon may be completely lacking

apatite chemical composition determined by electron microprobe and laser ablation inductively coupled plasma mass spectrometry as a probe into granite petrogenesis abstract major minor and trace element abundances in apatites from various i and s type igneous and sedimentary granites of the lachlan fold belt have been determined using electron microprobe and laser ablation inductively coupled plasma mass spectrometer the results show that apatite can accommodate many minor and trace elements whose concentrations and ratios are relatively sensitive to factors controlling many of the fundamental differences between i and s type granites apatites from s type granites generally have higher f but lower cl contents than those from i type granites which is ascribed mainly to the loss of cl during the weathering processes forming the source rocks of s type granites although fractional crystallisation can cause significant enrichment in f as well high mn and fe contents in apatites from s type granites and high s and as abundances in apatites from mafic i type granites result from different oxygen fugacities and degrees of al saturation or aluminosity between metaluminous mafic i type magmas and peraluminous s type and felsic i type magmas there are systematic and distinctive differences in absolute rare earth element ree abundances ree distribution patterns and element ratios e g la y sm nd etc between apatites from different types of granite the strong eu depletion that characterises apatites from s and felsic i type granites is interpreted here to be a result of the uniqueness of crystal chemistry of apatite and high eu2 eu3 ratios in s type and felsic i type magmas which are more reduced and peraluminous than mafic i type magmas strong ree la to eu and th enrichment in apatites from mafic i type granites and marked nd depletion in apatites from most s type and felsic i type granites are caused by the precipitation and fractionation of monazite in the parental magmas of the latter rocks substitution mechanisms are responsible for high na in apatites from s type and felsic i type granites and for high si in apatites from mafic i type granites and may also have important effects on ree partitioning between apatite and melt thus apatite chemistry can be used as an excellent indicator of granite petrogenesis the results have important implications for identifying different types of granite and are potentially significant for determining the provenance of sedimentary rocks

use of numerical estimators and multivariate analysis to characterize the genesis and pedogenic evolution of xeralfs from southern spain abstract eight xeralfs from the province of jae n in the region of andalusia southern spain were studied the micromorphology and mineralogy of the clay and sand fractions from the bt horizon among other characteristics were investigated and indices of pedogenic evolution including relative redness index relative development index of color and the relative development index of color structure clay illuviation index anisotropy index for clay content iron release index and kaolinite smectite ratio were calculated these findings were supported by the results of factorial analysis r mode and correlation between variables we found micromorphological evidence of clay illuviation even in calcareous soils alterations leading to clay formation argillopedoturbation coating disruption by carbonates and polycyclicity the clay fraction was essentially illitic with smaller amounts of kaolinite smectite and interstratified phases alterations were therefore moderate numerical estimators of evolution were informative of some specific pedogenic processes and confirmed the influence of certain soil formation factors and the relative degree of evolution of different soils the soil system comprising the xeralfs can be defined in terms of four factors that grouped the soil variables and accounted for more than 90 of the variance factor 1 pedological development of the bt horizon factor 2 a mineralogical factor factor 3 clay translocation in the profile and factor 4 a mineralogenetic feature of the bt horizon

investigations of the stillwater complex part v apatites as indicators of evolving fluid composition variations in the f cl and oh contents of apatite are not constrained by crystal chemical factors in contrast to micas and amphiboles and thus changes in the abundance of these components provide an indicator of halogen fugacity variations and insights into the degassing history of igneous rocks microprobe analysis of intercumulus apatites from the stillwater complex reveal that cl rich apatites typically containing 6 0 wt cl occur throughout the lower 1 3 of the complex excluding the basal series a change from cl rich to more f rich apatite occurs within olivine bearing zone i ob i of the banded series the host zone of the platiniferous j m reef although apatite compositions are somewhat variable above the j m reef more f rich apatites predominante and typically contain 1 2 wt f and 3 0 wt cl the most f rich apatites occur in the uppermost exposed cumulates pristine apatites from coeval sills and dikes from below the complex and from the basal series are similarly f rich in all apatites the cl and f contents are lower in rocks affected by later metamorphic fluids rare earth element ree concentrations in chlorapatites show a marked peak in the olivine rich rocks of the j m reef and contain up to 2 wt ce2o3 la2o3 the trend of first increasing then decreasing cl f ratios with stratigraphic height is modeled by a vapor driven zone refining process occurring within the cumulate pile causing cl enrichment in the interstitial melt accompanied by degassing at the top of the magma chamber causing overall loss of cl from the magma as crystallization proceeded the abrupt change from cl rich to more f rich apatites within ob i is interpreted as the result of a breakdown of the cl rich zone refining front and mixing with cl poor supernatant melt any high temperature fluids that exsolved and circulated through the lower 1 3 of the complex must have been enriched in cl and could have transported ree and trace metals

timing of ti magnetite crystallisation and silicate disequilibrium in the panzhihua mafic layered intrusion implications for ore forming processes abstract the 260 ma panzhihua mafic layered intrusion is one of a suite of intrusions related to the emeishan large igneous province elip sw china the panzhihua intrusion hosts a large 60 m thick fe ti oxide ore body at the base of the intrusion this study provides new constraints on the genesis of fe ti oxide ore layers at the panzhihua intrusion using geochemistry petrography and modeling of parent magma crystallisation with variation in f o 2 and h 2 o content whole rock major element geochemical trends are controlled by the modal abundance of fe ti oxides ti magnetite and ilmenite the lower 270 m of the intrusion is clearly dominated by a ti magnetite accumulation trend whereas above this level the geochemical variation is consistent with a ti magnetite and ilmenite accumulation trend this suggests that the lower 270 m of the intrusion crystallised at higher f o 2 conditions relative to that above 270 m detailed petrographic analysis of exsolution microtextures of the ti magnetite from within ore layers and gabbroic host rocks also indicates a relative increase in f o 2 within the ore rocks modeling of panzhihua parent magma shows that ti magnetite crystallises late for dry 1 5 wt h 2 o compositions this corresponds to a distinct variation in plagioclase crystallisation temperature which decreases with increasing h 2 o content of the parent magma the initial plagioclase composition varies from an 55 for a dry magma up to an 73 for a magma containing 3 wt h 2 o the average plagioclase composition for the panzhihua intrusion is an 58 indicating an initial magma with low h 2 o content textures within the fe ti oxide ore rocks clearly indicate that ti magnetite crystallised after the silicate phases plag cpx and disequilibrium textures indicate that the fe ti oxide ores were not in equilibrium with the enclosed silicates we present a model for fe ti oxide ore formation in an open system by multiple replenishments of magma with variable h 2 o contents ti magnetite crystal load and volume intruding h 2 o and crystal rich magmas effectively thermo chemically erode previously formed gabbroic cumulates forming the footwall and incorporates previously crystallised silicate grains these grains are consumed by the magma due to the high h 2 o content and higher temperature resulting in the association of consumed silicate primocrysts enclosed in fe ti oxide ore layers

multivariate analysis in the quantitative evaluation of soils for reforestation in the sierra nevada southern spain soil characteristics that most strongly influence the outcome of the evaluation of soils for reforestation were determined with multivariate analysis r mode factor analysis was used to relate results of the soil survey with those of the soil evaluation we studied the area of the sierra nevada mountains in southern spain soil variables were measured in 163 soil profiles collected in a survey of the two soil environments of the sierra nevada the calcareous and silicic zones four factor analyses showed that sand clay gravel and organic carbon content and ph were the most useful soil characteristics in evaluating site keys that affect tree and shrub growth nutrient availability rooting space and soil water availability in the calcareous zone hue value and chroma color and ph were easily determined soil characteristics that established and classified the suitability of forest sites in the silicic zone hue value and chroma and altitude were the characteristics found most useful in evaluating forest sites

trace element compositions of apatite from the middle zone of the panzhihua layered intrusion sw china insights into the differentiation of a p and si rich melt abstract the panzhihua layered intrusion in the 260 ma emeishan large igneous province is composed of melagabbro and fe ti oxide ore bodies in the lower zone lz and the lower part of the middle zone mza and fe ti oxide poor leucogabbro in the upper part of the middle zone mzb and upper zone uz cumulus apatite grains occur in the 500 to 600 m thick mzb which makes up 25 30 of the 2 km thick intrusion apatite grains from the mzb show two compositional reversals in the composition of sr which divide the mzb into three sub units from the base upwards mzb1 mzb2 and mzb3 there is 1 3 vol apatite in the mzb1 and mzb2 and 2 5 vol apatite in the mzb3 both apatite and plagioclase have an overall trend of decreasing sr in each sub unit most apatite grains from the mzb1 and mzb2 have negative eu anomalies eu eu 0 70 0 98 on chondrite normalized ree plots and some at the top of the mzb2 have positive eu anomalies eu eu 1 09 1 18 whereas all grains from the mzb3 have positive eu anomalies eu eu 1 11 1 25 we consider that the panzhihua intrusion formed due to immiscibility of ferrobasaltic magmas in a large convection cell at high temperatures the immiscible fe rich melt tended to move towards the base of the chamber whereas the si rich melt moved upwards due to density differences crystallization of fe ti oxides from the fe rich melt at high temperatures may result in the enrichment of p in the residual magmas the upward moving residual p rich magmas may have mixed with si rich melt to form a p and si rich melt in the upper part of the chamber from which the mzb formed double diffusive convection circulated in the p and si rich melt to form stratified magma layers magma mixing between the stratified magma layers resulted in the compositional reversals of apatite along the boundaries negative eu anomaly of apatite in the mzb1 and mzb2 is attributed to prior crystallization of plagioclase whereas replenishment of a syenitic magma to the mzb3 may result in the positive eu anomaly of apatite in the mzb3 the immiscibility model can explain why the apatite rich mzb is above the major fe ti oxide layers in the panzhihua intrusion

thermal cracking of kerogen in open and closed systems determination of kinetic parameters and stoichiometric coefficients for oil and gas generation abstract the purpose of the study is to compare artificial maturation of kerogens representative of the main types of organic matter kerogen types i ii ii s and iii in open and anhydrous closed pyrolysis systems the generated compounds are fractionated according to their thermal stability into six chemical classes c 1 c 2 c 5 c 6 c 14 c 15 saturates c 15 aromatics and nsos which include resins and asphaltenes in both systems primary cracking of kerogen can be described by two main reactions oil generation together with early gas generation followed by late gas production mass balances obtained in the two pyrolysis systems are reasonably similar although some secondary cracking of the nsos and underestimation of methane potential due to incomplete pyrolysis may occur in the open system kinetic parameters of thermal cracking are derived from experiments in the open system using an optimization procedure which determines a unique frequency factor and a weight distribution of chemical classes for a discrete series of activation energies the resultant frequency factors are checked with those obtained for specific molecular tracers such as n c 12 and n c 24 alkanes generated from kerogens in open and closed systems under isothermal conditions the results show that using a unique frequency factor as determined by optimization is correct for type i ii and ii s kerogens this factor is more questionable however when the distribution of activation energies is very broad such as for type iii coals based on this study a strategy for determination of kinetic parameters on any new source rock sample is proposed

comparison of rate constants for some molecular tracers generated during artificial maturation of kerogens influence of kerogen type abstract the purpose of this work is to carry out artificial maturation of various kerogens under isothermal conditions in open and closed systems and to derive kinetic parameters for specific molecular tracers such as n c 12 and n c 24 alkanes results show that individual normal alkane generation from type i and type ii kerogens follows first order kinetics in both open and closed pyrolysis systems however the normal alkanes generated from type iii samples do not follow a first order mechanism for type i and type ii kerogens slightly different rate constants are obtained for n c 12 and n c 24 generation whereas for the two type iii kerogens n c 24 is produced much faster than n c 12 combining the rate constants derived from open and closed system pyrolysis arrhenius plots were obtained for the four samples under study from which accurate sets of kinetic parameters were calculated

formation of thick stratiform fe ti oxide layers in layered intrusion and frequent replenishment of fractionated mafic magma evidence from the panzhihua intrusion sw china 1 the panzhihua intrusion is one of the largest layered intrusions that hosts huge stratiform fe ti oxide layers in the central part of the emeishan large igneous province sw china up to 60 m thick stratiform massive fe ti oxide layers containing 85 modal of magnetite and ilmenite and overlying magnetite gabbro compose cyclic units of the lower zone of the intrusion the cyclic units of the middle zone consist of magnetite gabbro and overlying gabbro in these cyclic units contents of fe2o3 t tio2 and cr and fe3 ti4 ratio of the rocks decrease upward cr content of magnetite and forsterite percentage of olivine decrease as well the upper zone consists of apatite gabbro characterized by enrichment of incompatible elements e g 12 18 ppm la 20 28 ppm y and increasing of fe3 ti4 ratio from 1 3 to 2 3 upward these features indicate that the panzhihua intrusion was repeatedly recharged by more primitive magma and evolved magmas had been extracted calculations using melts indicate that extensive fractionation of olivine and clinopyroxene in deep level resulted in increasing fe and ti contents in the magma when these fe ti enriched magmas were emplaced along the base of the panzhihua intrusion fe ti oxides became an early crystallization phase leading to a residual magma of lower density we propose that the unusually thick stratiform fe ti oxide layers resulted from coupling of gravity settling and sorting of the crystallized fe ti oxides from fe ti enriched magmas and frequent magma replenishment along the floor of the magma chamber

geochronology of layered mafic intrusions from the pan xi area in the emeishan large igneous province sw china the panzhihua xichang pan xi area hosts mafic ultramafic intrusions which are part of the permian emeishan large igneous province some of these intrusions host giant fe ti v deposits and minor ni cu pge mineralization in the present study zircon u pb ages of 259 3 1 3 and 260 7 0 8 ma have been obtained from the giant fe ti v ore bearing hongge and the unmineralized binggu intrusions respectively by isotope dilution thermal ionization mass spectrometry method in combination with the ages of other ore bearing intrusions this age shows that these mafic ultramafic intrusions were emplaced at ca 260 ma the hongge and binggu intrusions cut the lower part of the rapidly deposited emeishan flood basalt sequence but no further into the upper volcanic sequence in the pan xi area thus emplacement and mineralization of the mafic ultramafic intrusions were almost contemporaneous with the eruption of the emeishan flood basalts during a relatively short time span

abundant fe ti oxide inclusions in olivine from the panzhihua and hongge layered intrusions sw china evidence for early saturation of fe ti oxides in ferrobasaltic magma abundant fe ti oxide inclusions in cumulus olivine fo77 81 from the panzhihua and hongge intrusions emeishan large igneous province sw china document the first evidence for early crystallization of fe ti oxides in ferrobasaltic systems in nature the intrusions also contain significant stratiform fe ti v oxide ores the oxide inclusions are sub rounded or irregular range from 5 to 50 m in diameter and are dominated by either titanomagnetite or ilmenite the fact that the inclusions are either titanomagnetite or ilmenite dominant suggests that they are trapped crystals instead of immiscible oxide melt formed during growth of the host olivine the absence of other silicate phases in the inclusion bearing olivine is difficult to reconcile with a possible xenocrystic origin of the oxide inclusions these oxide inclusions are thus interpreted to be cumulus minerals crystallized together and trapped in olivine from the same parental magma in addition to fe ti oxides some inclusions contain amphibole biotite fluorapatite that might have formed by reaction of trapped hydrous liquid with the host olivine numerical modeling of high ti emeishan basalts using the melts program successfully simulates early crystallization of olivine fo81 and fe ti spinel in the presence of a moderate amount of h2o 1 5 wt under pressure and fo2 conditions generally pertinent to the panzhihua and hongge intrusions the modal mineralogy of the oxide inclusions is in good agreement with the bulk compositions of the ore as inferred from whole rock data in a given intrusion this is consistent with the interpretation that the stratiform oxide ores in the intrusions formed by accumulation of fe ti oxide crystals that appeared on the liquidus with olivine and clinopyroxene

parental magmas of the nain plutonic suite anorthosites and mafic cumulates a trace element modelling approach equilibrium melt trace element contents are calculated from proterozoic nain plutonic suite nps mafic and anorthositic cumulates and from plagioclase and orthopyroxene megacrysts assumed trapped melt fractions tmf 20 generally eliminate all minor phases in most mafic cumulate rocks reducing them to mixtures of feldspar pyroxene and olivine which would represent the high temperature cumulus assemblage in anorthosites tmf 15 generally reduce the mode to a feldspar only assemblage all model melts have trace element profiles enriched in highly incompatible elements relative to normal mid ocean ridge basalt nmorb commonly with negative nb and th anomalies most mafic cumulates yield similar profiles with constant incompatible element ratios and can be linked through fractional crystallization high k la subtypes probably represent crust contaminated facies mafic cumulates are inferred to belong to a tholeiitic differentiation series variably contaminated by upper and lower crustal components and probably related to coeval tholeiitic basaltic dyke swarms and lavas in labrador model melts from anorthosites and megacrysts have normalized trace element profiles with steeper slopes than those calculated from mafic cumulates indicating that mafic cumulates and anorthosites did not crystallize from the same melts orthopyroxene megacrysts yield model melts that are more enriched than typical anorthositic model melts precluding an origin from parental melts jotunites have lower k rb ba y yb and higher la ce than model residues from fractionation of anorthositic model melts suggesting they are not cosanguineous with them but provide reasonable fits to evolved mafic cumulate model melts incompatible element profiles of anorthositic model melts closely resemble those of crustal melts such as tonalites with steep y yb lu segments that suggest residual garnet in the source inversion models yield protoliths similar to depleted lower crustal granulite xenoliths with aluminous compositions suggesting that the incompatible trace element budget of the anorthosites are derived from remobilization of the lower crust the similarity of the highly incompatible trace elements and lile between anorthositic and mafic cumulate model melts suggests that the basalts parental to the mafic cumulates locally assimilated considerable quantities of the same crust that yielded the anorthosites the reaction between underplating basalt and aluminous lower crust would have forced crystallization of abundant plagioclase and remobilization of these hybrid plagioclase rich mushes then produced the anorthosite massifs

zircon u pb and hf isotope constraints on crustal melting associated with the emeishan mantle plume abstract shrimp zircon u pb dates combined with in situ hf isotopic data provide new constraints on the petrogenesis and protolith of peralkaline metaluminous and peraluminous intrusions and rhyolitic tuffs in the emeishan large igneous province with significant bearing on crustal melting associated with mantle plumes syenite and a type granitic intrusions from huili miyi and taihe in the center of this large igneous province yield u pb dates at 260 ma consistent with the ages obtained for mafic layered intrusions in the same province zircon from these rocks exhibits a wide range of initial hf isotope ratios ehf t 1 4 to 13 4 with corresponding tdm1 of 400 900 ma the highest ehf t value is only marginally lower than that of depleted mantle reservoir at 260 ma suggesting that their source is primarily juvenile crust added during emeishan volcanism with incorporation of variable amounts of neoproterozoic crust the trigger of crustal melting is most likely related to advective heating associated with magmatic underplating in contrast the 255 251 ma peraluminous granites from ailanghe and 238 ma rhyolitic tuff from binchuan have negative initial ehf values of 1 3 to 4 4 and of 7 7 to 14 respectively hf isotopic model ages and presence of inherited zircons indicate their derivation from mesoproterozoic and paleoproterozoic crust respectively given the time lag relative to the plume impact 260 ma and insignificant mantle contribution to 255 238 ma magmatism conductive heating is suggested as the trigger of crustal melting that resulted in formation of delayed felsic magmas the involvement of older crust in younger felsic magmas is consistent with upward heat transfer to the lithosphere during plume impregnation if the age of crust is inversely stratified i e changes from paleoproterozoic to mesoproterozoic to neoproterozoic to permian with increasing depth such crust may have resulted from episodic downward crustal growth during the evolution of the western yangtze craton

east west extension and holocene normal fault scarps in the hellenic arc examination of surface fault traces with spot images and in the field corroborates the inference that the active tectonics of southern peloponnesus and crete are dominated by approximately north south normal faulting and approximately east west extension the heights of holocene normal fault scarps yield first order regional estimates of fault slip rates between 0 1 and 2 3 mm yr most of the surface scarps probably ruptured during past earthquakes such as that which destroyed sparta in 464 b c on the sparta fault the holocene average slip rate and the recurrence time of large earthquakes may be 1 mm yr and 3000 yr respectively the regional pattern of quaternary faulting suggests that the east west extension near the hellenic subduction zone is fast about 5 10 m y the change from north south to east west extension in the late pliocene 2 4 ma implies that the aegean is starting to collide with the northern margin of africa

new textural and mineralogical constraints on the origin of the hongge fe ti v oxide deposit sw china the hongge magmatic fe ti v oxide deposit in the panxi region sw china is hosted in a layered mafic ultramafic intrusion this 2 7 km thick lopolith like intrusion consists of the lower middle and upper zones which are composed of olivine clinopyroxenite clinopyroxenite and gabbro respectively abundant fe ti oxide layers mainly occur in the middle zone and the lower part of the upper zone fe ti oxides include cr rich and cr poor titanomagnetite and granular ilmenite cr rich titanomagnetite is commonly disseminated in the olivine clinopyroxenite of the lower parts of the lower and middle zones and contains 1 89 to 14 9 wt cr2o3 and 3 20 to 16 2 wt tio2 whereas cr poor titanomagnetite typically occurs as net textured and massive ores in the upper middle and upper zones and contains much lower cr2o3 0 4 wt but more variable tio2 0 11 to 18 2 wt disseminated cr rich titanomagnetite in the ultramafic rocks is commonly enclosed in either olivine or clinopyroxene whereas cr poor titanomangetite of the net textured and massive ores is mainly interstitial to clinopyroxene and plagioclase the lithology of the hongge intrusion is consistent with multiple injections of magmas the lower zone being derived from a single pulse of less differentiated ferrobasaltic magma and the middle and upper zones from multiple pulses of more differentiated magmas cr rich titanomagnetite in the disseminated ores of the lower and middle zones is interpreted to represent an early crystallization phase whereas clusters of cr poor titanomagnetite granular ilmenite and apatite in the net textured ores of the middle and upper zones are thought to have formed from an fe ti p rich melt segregated from a differentiated ferrobasaltic magma as a result of liquid immiscibility the dense fe ti p rich melt percolated downward through the underlying silicate crystal mush to form net textured and massive fe ti oxide ores whereas the coexisting si rich melt formed the overlying plagioclase rich rocks in the intrusion

the sept iles anorthosite complex field relationships geochronology and petrology the sept iles anorthosite complex is located in the grenville structural province of the canadian shield geochronological studies of both the basic and acidic portions of the complex show that i

mineral compositional constraints on petrogenesis and oxide ore genesis of the late permian panzhihua layered gabbroic intrusion sw china a systematic study of mineral compositions has been carried out on stratigraphic sections through the panzhihua intrusion a layered gabbroic sill of late permian age that hosts significant magmatic fe ti v oxide deposits in the emeishan large igneous province sw china the intrusion which is 19 km long and 2 km thick is divided into a marginal zone mgz lower zone lz middle zone sub zones mza and mzb and upper zone uz from the base upwards compositions of the most primitive cumulus olivine fo81 and plagioclase an73 found in the intrusion suggest that the parental magma was similar to the mg rich end member of the coeval high ti basalts in the region two reversals in terms of mineral compositions are found in the intrusion one in the lower mza and the other at the transition between the mzb and the uz the first reversal is marked by a gradual increase in the an content of plagioclase an60 to an70 over a 100 m vertical interval the other is characterized by abrupt changes in the compositions of olivine fo28 to fo70 clinopyroxene mg 51 to 75 and plagioclase an24 to an51 over a 20 m vertical interval these suggest that the panzhihua intrusion opened at least twice for recharge of more primitive magmas strong depletion of incompatible trace elements such as zr in the cumulate sequence without corresponding enrichment in any border series is suggested to be evidence for significant loss of residual liquid at a late stage during solidification of the intrusion compared to other well studied layered intrusions the panzhihua intrusion contains fe ti oxides crystallized at a high temperature consistent with evidence obtained in earlier studies early appearance of liquidus fe ti oxides in the panzhihua magma is most likely a combined effect of a rather high degree of initial oxidation and elevated volatile fugacity

petrogenesis of apatite rich rocks nelsonites and oxide apatite gabbronorites associated with massif anorthosites we report field petrographic mineralogical and geochemical data for two p rich rock types of the anorthosite suite fe ti oxide apatite rock or nelsonite and fe ti oxide apatite gabbronorite or oxide apatite gabbronorite these rocks are take from the ch teau richer labrieville and st urbain massifs in quebec from the roseland massif in virginia and from the carthage massif in new york our data set includes x ray fluorescence xrf and instrumental neutron activation ina analyses of whole rock samples as well as electron microprobe emp and ina analyses of separated apatites at st urbain and labrieville nelsonite forms a small capping on massive hemoilmenite deposits fully contained within anorthosite whereas at roseland nelsonite occurs as dikelike bodies within country rock all three nelsonite occurrences consist almost entirely of ilmenite apatite but do not have a 2 1 oxide apatite ratio with only trace amounts of other minerals all oxide apatite gabbronorites form sill like layers within or near the margins of anorthosite massifs and contain ilmenite magnetite apatite orthopyroxene clinopyroxene and plagioclase all apatites are f rich and cl poor consistent with high temperature magmatic crystallization concentrations of apatite rare earth elements ree are highly variable e g lan 700 2 000 chondrites but patterns show a consistent fractionation e g lan lun 10 20 with small to moderate negative eu anomalies interestingly the labrieville nelsonite and its apatite lack an eu anomaly consistent with crystallization in a highly oxidizing environment apatites in both rock types are enriched in ree relative to whole rock samples by factors of 3 to 10 but ree patterns of apatites and whole rocks are parallel in each case mass balance calculations indicate that for nelsonite 100 percent of the ree is contained in apatite for oxide apatite gabbronorites 100 percent of the light ree 90 percent of the middle to heavy ree and 75 percent of eu are in apatite these results can be explained satisfactorily by assuming that the rocks are cumulate in origin if on the other hand nelsonites and oxide apatite gabbronorites represent liquids apatite dree values must vary by more than a factor of 3 our field mineralogical and geochemical observations indicate that most nelsonites and oxide apatite gabbronorites are not related directly indeed apatites from oxide apatite gabbronorites contain lower sr and mgo but higher ree than those in nelsonites indicating that nelsonites are the more primitive rock type nelsonites probably formed as cumulates primarily within larger deposits of fe ti oxide locally mobilized as dikelike bodies oxide apatite gabbronorites also represent cumulates but these are related spatially and genetically to associated jotunites and mangerites and appear to form at several stages in the evolution of a particular anorthosite complex

whole rock and mineral composition constraints on the genesis of the giant hongge fe ti v oxide deposit in the emeishan large igneous province southwest china the hongge giant fe ti v oxide ore deposit is hosted by a layered intrusion located in the central part of the emeishan large igneous province sw china the intrusion is relatively small in comparison with other typical oxide bearing intrusions worldwide it consists of a lower olivine clinopyroxenite zone a middle clinopyroxenite zone and an upper gabbro zone herein referred to as the lower middle and upper zones most of the economic fe ti v oxide ore layers occur within the middle zone the hongge oxide ores are depleted in ree and enriched in zr hf nb and ta as compared to the associated clinopyroxenites this enrichment of elements that are compatible in titanomagnetite is consistent with the interpretation that the ores formed by accumulation of magnetite and ilmenite as in the nearby coeval panzhihua fe ti v oxide deposit described previously by others mafic silicates in the hongge deposit have much higher mgo contents than those in other oxide deposits associated with large layered intrusions in the world this highlights the importance of relatively primitive parental magma becoming saturated in titanomagnetite at an early stage in the genesis of the giant fe ti v oxide deposits in the emeishan large igneous province phase equilibrium constraints suggest that the parental magma of the hongge deposit is similar to that of some of the most primitive high ti basalts in the emeishan large igneous province the ferrobasaltic parental magma and the ferropicritic primary magma of the hongge intrusion are similar in major and trace element composition to the ferropicritic ferrobasaltic magma in the pechenga belt kola peninsula russia depletion of incompatible trace elements in the oxide ores and associated rocks in the hongge intrusion as compared to the coeval high ti basalts suggest that not all the magma involved in the development of the hongge intrusion has been retained in the intrusion the occurrence of multiple fe ti oxide layers alternating with fe ti oxide bearing silicate layers within a single zone and the repetitive appearance of sulfides olivine and cr rich layers suggest that multiple pulses of magma were involved in the formation of the hongge intrusion and related fe ti v oxide deposit we propose that the middle zone of the hongge intrusion was a magma stepwise flow through system and that some of the liquid was lost to the peripheral lavas to form the basalt

variations of trace element concentration of magnetite and ilmenite from the taihe layered intrusion emeishan large igneous province sw china implications for magmatic fractionation and origin of fe ti v oxide ore deposits abstract in situ la icp ms trace elemental analysis has been applied to magnetite and ilmenite of the taihe layered intrusion emeishan large igneous province sw china in order to understand better fractionation processes of magma and origin of fe ti v oxide ore deposits the periodic reversals in mg ti mn in magnetite and mg sc in ilmenite are found in the middle zone of the intrusion and agree with fractionation trends as recorded by olivine fo plagioclase an and clinopyroxene mg compositions these suggest the taihe intrusion formed from open magma chamber processes in a magma conduit with multiple replenishments of more primitive magmas the v and cr of magnetite are well correlated with v and cr of clinopyroxene indicating that they became liquidus phases almost simultaneously at an early stage of magma evolution ilmenite from the middle and upper zones shows variable cr ni v mg nb ta and sc contents indicating that ilmenite at some stratigraphic levels crystallized slightly earlier than magnetite and clinopyroxene the early crystallization of magnetite and ilmenite is the result of the high feot and tio2 contents in the parental magma the ilmenite crystallization before magnetite in the middle and upper zones can be attributed to higher tio2 content of the magma due to the remelting of pre existing ilmenite in a middle level magma chamber compared to the coeval high ti basalts the relatively low zr hf nb and ta contents in both magnetite and ilmenite throughout the taihe intrusion indicate that they crystallized from fe ti p rich silicate magmas positive correlations of ti with mg mn sc and zr of magnetite and zr with sc hf and nb of ilmenite also suggest that magnetite and ilmenite crystallized continuously from the homogeneous silicate magma rather than an immiscible fe rich melt therefore frequent replenishments of fe ti p rich silicate magma and gravitational sorting and settling are crucial for the formation the massive and apatite rich disseminated ores in the lower and middle zones of the taihe intrusion

holocene soil chronofunctions southern alps new zealand abstract field and laboratory data for two soil chronosequences from the high country of the south island of new zealand suggest rapid soil formation rates the areas studied are the ben ohau range and the mt cook area where mean annual precipitation is about 1 and 4 m respectively most soil ages are estimated from the thicknesses of rock weathering rinds soil chronofunctions are derived for indices that depict field profile and color development and a modified index of profile anisotropy for laboratory data out of a possible 21 chronofunctions 16 are statistically significant at the 0 05 level and 8 are from each area most 13 of the chronofunctions best fit a power model and the remaining ones are split between linear 2 and exponential 1 models although problems exist in the purity of the chronosequences because other soil forming factors are not constant duration of pedogenesis seems to be the most significant factor in explaining the trends despite the large differences in mean annual precipitation between the two areas many of the derived curves for property vs time are quite similar

comparison of generative capacities for bitumen and gas between carboniferous coals from donets basin ukraine and a cretaceous coal from sabinas piedras negras basin mexico during artificial maturation in confined pyrolysis system abstract the goal of this work is to study the ability of two immature carboniferous coals from donets basin ukraine to act as source for oil heating experiments in confined medium were performed to compare the thermal behavior of these coals 1l1 dim r r 0 55 h c at 0 79 and 2c10yd r r 0 65 h c at 0 80 relative to a mature cretaceous coal from sabinas basin olmos r r 0 92 h c at 0 77 macerals analysis carried out on starting materials showed that olmos is exhausted in liptinite contrary to 2c10yd 20 vol and 1l1dim 6 vol the vitrinite content is lower for 2c10yd 59 vol than for olmos 84 vol and 1l1dim 80 vol solid bitumen occurs often dispersed in the raw coals both petrographic and geochemical analyses on starting materials revealed that the selected carboniferous donets coals have better potentialities for bitumen generation than the cretaceous sabinas coal the presence of long chain n alkanes n c 8 in the pyrolysis gc chromatograms indicates that the two raw carboniferous coals from donets basin can yield non volatile hydrocarbons under further thermal maturation it is speculated that some vitrinite macerals present in hydrogen rich carboniferous coals from donets basin can act as source rocks for oil as a matter of fact results showed that the oil window occurs between 1 0 r r and 2 0 r r for both cretaceous sabinas and carboniferous donets coals during confined pyrolysis as expected from geochemical and petrographic analyses of starting samples the carboniferous donets coals yielded more bitumen and hydrocarbons than cretaceous sabinas coal during artificial maturation low proportions of solid bitumen r r and 1 5 r r during confined pyrolysis of coals two solid bitumen groups have been identified which correspond to distinct phases of neo formation the drop in the solid bitumen content at higher ranks indicates that it contributes to generation of gas during experimental simulation moreover their morphology and porosity change with the level of maturity the porosity of the vitrinite matrix increases as well as the pore size with increasing maturity a relationship has been observed between the porosity and the weight loss the higher pore content of carboniferous donets coals is correlated with a higher generation of gas compared to cretaceous sabinas coal

apatite liquid partition coefficients for the rare earth elements and strontium abstract sixteen sets of apatite liquid partition coefficients dap liq for the rare earth elements ree la sm dy lu and six values for sr were experimentally determined in natural systems ranging from basanite to granite the apatite melt glass assemblages were obtained from starting glasses artificially enriched in ree sr and fluorapatite components these were run under dry and hydrous conditions of 7 5 20 kbar and 950 1120 c in a solid media piston cylinder apparatus an sem equipped electron microprobe was used for subsequent measurement of ree and sr concentrations in coexisting apatites and quenched glasses the resulting partition coefficient patterns resemble previously determined apatite phenocryst groundmass concentration ratios in the following respects 1 the rare earth patterns are uniformly concave downward i e the middle ree are more compatible in apatite than the light and heavy ree 2 dreeap liq is much higher for silicic melts than for basic ones and 3 strontium and therefore eu2 is less concentrated by apatite than are the trivalent ree the effects of both temperature and melt composition on dreeap liq are systematic and pronounced at 950 c for example a change in melt sio2 content from 50 to 68 wt causes the average ree partition coefficient to increase from 7 to 30 a 130 c increase in temperature on the other hand results in a two fold decrease in dreeap liq partitioning of sr is insenstitive to changes in melt composition and temperature and neither the sr nor the ree partition coefficients appear to be affected by variations in pressure or h2o content of the melt the experimentally determined partition coefficients can be used not only in trace element modelling but also to distinguish apatite phenocrysts from xenocrysts in rocks reported apatite megacryst host basalt ree concentration ratios 12 for example are considerably higher than the equilibrium partition coefficients which suggest that in this particular case the apatite is actually xenocrystic a reversal experiment incorporated in our study yielded diffusion profiles of ree in apatite from which we extracted a ree ca interdiffusion coefficient of 2 4 10 14 cm2 s at 1120 c extrapolated downward to crustal temperatures this low value suggests that complete ree equilibrium between felsic partial melts and residual apatite is rarely established

apatite geochemistry of the taihe layered intrusion sw china implications for the magmatic differentiation and the origin of apatite rich fe ti oxide ores abstract the taihe intrusion is one of the layered intrusions situated in the central zone of the emeishan large igneous province elip sw china the cyclic units in the middle zone of the intrusion are composed of apatite magnetite clinopyroxenite at the base and gabbro at the top the apatite rich oxide ores contain 6 12 modal apatite and 20 50 modal fe ti oxides evidently distinguished from the coeval intrusions in which apatite rich rocks are poor in fe ti oxides most of apatites of the taihe middle and upper zones are fluorapatite although four samples show slightly high cl content in apatite suggesting that they crystallize from a hydrous parental magma compared to the apatite from the gabbro of the panzhihua intrusion situated 100 km to the south of the taihe intrusion the apatite of the taihe rocks is richer in sr and depleted in hree relative to lree the calculated magma in equilibrium with apatite of the taihe middle and upper zones also shows weakly negative sr anomalies in primitive mantle normalized trace element diagrams these features indicate that the apatite of the taihe middle and upper zones crystallizes after clinopyroxene and before plagioclase the apatite of the taihe middle and upper zones shows weakly negative eu anomalies suggesting a high oxygen fugacity condition the high iron and titanium contents in the oxidizing magma result in crystallization of fe ti oxides crystallization of abundant fe ti oxides and clinopyroxenes lowers the solubility of phosphorus and elevates sio2 concentration in the magma triggering the saturation of apatite the positive correlations of sr v total ree contents and ce yb ratio in apatite with cumulus clinopyroxene demonstrate approximately compositional equilibrium between these phases suggesting they crystallized from the same ferrobasaltic magma early crystallization and accumulation of fe ti oxide together with apatite produced the apatite rich oxide ores at the base of the cyclic units of the taihe middle zone

key factors controlling the accumulation of the fe ti oxides in the hongge layered intrusion in the emeishan large igneous province sw china abstract the hongge layered intrusion hosts the largest fe ti v oxide ore deposit in the central part of the emeishan large igneous province sw china it is divided into lower zone lz middle zone mz and upper zone uz from the bottom to the top for the lz relatively higher cr 250 3000 ppm and ni 50 200 ppm contents of clinopyroxene lower end259ma and higher 87sr 86sr 259ma values 2 82 to 0 07 and 0 7057 0 7076 respectively and plenty of hornblende demonstrate a more primitive parental hydrous magma in contrast relatively low cr

the partitioning of trace elements between ilmenite ulvospinel armalcolite and silicate melts with implications for the early differentiation of the moon mineral melt trace element partition coefficients for a large number of trace elements zr hf ta nb v co cu zn sr ree sb sn mo cr w u th were determined experimentally for ilmenite fetio3 ulvospinel fe2tio4 minerals of the armalcolite solid solution fe mg ti2o5 the measured partition coefficients indicate that the high field strength elements zr hf nb and ta and some transition metals v cr co sn are moderately compatible in iron titanium oxides whereas other elements ree y sr u th mo sb and w are strongly incompatible the partition coefficients for u are always significantly higher than the th partition coefficients which makes fe ti oxides efficient in fractionating u from th our data also indicate that ilmenite and other iron titanium oxides are able to fractionate w from hf the latter of which is much more compatible this makes the iron titanium oxides very effective agents to influence hf w isotopic ratios during the evolution of the moon in addition we also present some trace element partition coefficients for iron and titanium bearing orthopyroxene

experimentally determined mineral melt partition coefficients for sc y and ree for olivine orthopyroxene pigeonite magnetite and ilmenite our current lack of understanding of the partitioning behavior of sc y and the ree rare earth elements can be attributed directly to the lack of a sufficiently large or chemically diverse experimental data set to address this problem we conducted a series of experiments using several different natural composition lavas doped with the elements of interest as starting compositions microprobe analyses of orthopyroxene pigeonite olivine magnetite ilmenite and co existing glasses in the experimental charges were used to calculate expressions that describe ree partitioning as a function of a variety of system parameters using expressions that represent mineral melt reactions versus element ratio distribution coefficients it is possible to calculate terms that express low ca pyroxene melt partitioning behavior and are independent of both pyroxene and melt composition compositional variations suggest that sc substitution in olivine involves either a paired substitution with al or more commonly with vacancies the partitioning of sc is dependent both on melt composition and temperature our experimentally determined olivine melt ree ds partition coefficients are similar to but slightly higher than those reported by mckay 1986 and support their conclusions that olivines are strongly lree depleted y and ree mineral melt partition coefficients for magnetite range from 0 003 for la to 0 02 for lu ilmenite partition coefficients range from 0 007 for la to 0 029 for lu these experimental values are two orders of magnitude lower than many of the published values determined by phenocryst matrix separation techniques

contrasted mineralogy and textural relationships in the uppermost titaniferous magnetite layers of the bushveld complex in the bierkraal area north of rustenburg disseminated fe ti oxides and ore rich concentrations of these minerals in a 1 230 m vertical borehole section through the top of the upper zone of the bushveld complex are described the succession consists of a layered sequence of highly fractionated olivine rich rocks that range in composition from ferrogabbro to diorite the fe content of the olivine increases systematically from fa 65 at the base to a maximum of fa 94 at the top of the section fe ti oxides axe present throughout this interval and are divided into three distinct groups on the basis of their mineralogy and chemistry 1 an apatite poor high ti magnetite association 2 an apatite rich high ti magnetite association and 3 an apatite poor low ti magnetite association the ti magnetite in each of these associations exhibits a wide variety of ulvoespinel and or ilmenite microintergrowths the development of which can be interpreted in terms of the ambient f sub o 2 at various stages of subsolidus cooling certain ti magnetite crystals are characterized by the development of radiating eutectoidlike intergrowths of magnetite and ilmenite or ulvoespinel that appear to represent duplex cell decomposition products of magnetite ulvoespinel solutions the apatite poor high ti magnetite represents the dominant opaque oxide association and is present both as disseminations and distinct ore rich layers particularly toward the base of the study section the greatest concentration of this association occurs at a depth of between 1 033 to 1 060 m below the top of the intrusion the lowermost 14 m of this interval consist of a thick composite ti magnetite layer that contains numerous silicate inclusions and partings this is believed to represent the equivalent of the uppermost ti magnetite layer layer 21 in the eastern bushveld complex groups of minor ti magnetite layers are also present at depths of 412 and 225 m below the top of the intrusion the ti content of the magnetite increases with increasing stratigraphic height from 55 mole percent ulvoespinel at the base to 65 mole percent near the top of the study section where it gives way to the ti poor association the beginning of ti poor magnetite precipitation 225 m below the roof of the intrusion marks the onset of ti depletion in the residual liquid ilmenite is virtually the only fe ti oxide phase present in the uppermost 100 m of the complex both these associations formed in response to normal fractional crystallization processes the formation of discrete ore rich layers being triggered by episodic increases in f sub o 2 the apatite rich high ti magnetite association is present both as disseminations and in ore rich concentrations but is restricted to three relatively narrow horizons within the study section these are developed at the following depths below the top of the intrusion 233 to 283 m 677 to 700 m and 1 033 to 1 108 m discrete ore rich concentrations consisting almost entirely of ti magnetite ilmenite approximately 70 vol and apatite approximately 30 vol are present in the lower 2 m of the middle horizon the upper and lower horizons contain only disseminated opaque oxide apatite assemblages the formation of these assemblages is interpreted in terms of the separation of immiscible fe ti mn ca p ree enriched liquids from the late stage dioritic residual melt

biomarker transformations as constraints for the depositional environment and for maximum temperatures during burial of opalinus clay and posidonia shale in northern switzerland abstract samples from two argillaceous formations opalinus clay and posidonia shale of near identical maturity from northern switzerland were subjected to a geochemical characterisation of organic matter and to confined system pyrolysis experiments throughout the study area the characteristics of organic matter are similar indicating a spatially homogeneous sedimentary facies posidonia shale contains marine organic matter deposited in a reducing environment while a predominantly terrigenous source and a more oxidising environment of deposition was identified for opalinus clay in the western and central parts of the study area organic maturity is close to the onset of oil generation in the easternmost part a higher maturity has been reached due to a deeper burial below thick tertiary molasse deposits isothermal pyrolysis experiments were conducted at temperatures between 250 and 390 c over 24 h bitumen yields increase along similar pathways for both opalinus clay and posidonia shale but the maximum values are displaced by 10 20 c data pertaining to maturity were determined from gc ms analyses of saturated hydrocarbons and specific attention was given to c 29 sterane and c 32 hopane isomerisation ratios the evolution of these parameters with rising temperature is slightly different in the two formations which is attributed to the contrasting organic facies the pyrolysis data together with literature data from natural basins were used to calculate kinetic parameters for c 29 sterane and c 32 hopane assuming a single step isomerisation scheme according to the arrhenius law the resulting values based on pyrolysis data alone are very similar to those based on the combination of pyrolysis and natural data activation energies are similar in both formations while the frequency factors are up to one order of magnitude higher for posidonia shale when compared to opalinus clay for the benken site maximum temperature during cretaceous burial was calculated on the basis of the kinetic data using the tti approach the resulting temperatures of 75 80 c are 5 10 c below those derived in the literature from apatite fission track analysis vitrinite reflectance and basin modelling

phase relations and liquid lines of descent in hydrous ferrobasalt implications for the skaergaard intrusion and columbia river flood basalts crystallization experiments using a hydrous ferrobasalt as starting material conducted at 200mpa 940 12008c at a wide range of water activities 0 1 1 and redox conditions qfm 3 to qfm 4 where qfm is the quartz fayalite magnetite oxygen buffer show that h2o influences significantly the differentiation history of ferrobasaltic magmas a combination of our data with published experiments on dry ferrobasalt at 1atm provides an extensive experimental database for modeling and quantifying crystallization and differentiation processes within a typical fe rich tholeiitic system under both dry and hydrous conditions the addition of h2o decreases liquidus temperatures and changes significantly the proportions temperature range and sequence of crystallizing mineral phases the dry liquidus is at about 11708c whereas the liquidus for h2o saturated melts is at 10608c the main phases crystallizing from h2o bearing ferrobasalt at the investigated conditions are olivine ol clinopyroxene cpx plagioclase pl magnetite mt hematite hm ilmenite ilm and amphibole am the phase assemblage is similar to that of the dry system except for the presence of hm at extremely oxidizing conditions and am at low temperatures 59508c and h2o saturated conditions the important observation made in this study is that the stability of fe ti oxides and in particular mt as well as the simultaneous coprecipitation of mtand ilm are almost independent of the activity of h2o ah2o in the system whereas the liquidus temperatures of the silicate minerals are dramatically depressed by increasing ah2o the stabilities of oxides are controlled mainly by the redox conditions prevailing in the system the most pronounced effect of ah2o on the liquidus temperatures of silicates is observed for pl which shows a considerable delay in crystallization with progressive magma differentiation early crystallization of fe ti oxides in h2o bearing ferrobasaltic compositions precludes any significant fe enrichment during differentiation as fe enrichment is a characteristic feature of the skaergaard intrusion it implies that the skaergaard parental magma did not contain considerable amounts of water on the other hand our experiments indicate that the differentiation of some ferrobasaltic series from the columbia river flood basalt province might have occurred in magmatic systems containing significant amounts of volatiles 0 5 3 wt h2o

preservation of lateral pressure disequilibrium during the uplift of shale reservoirs a pressure gradient increase from normal pressure in oil zones to overpressure in dry gas zones indicates a lateral disequilibrium of pore pressure in many shale reservoirs in this work conditions for the preservation of the lateral pressure disequilibrium during uplift and erosion are investigated numerical simulations were conducted by coupling pressure volume temperature pvt and fluid dynamic calculations results show that temperature decrease and pore volume expansion during erosion tends to increase the pressure gradient in the gas or condensate zone and tends to decrease the pressure gradient in the black oil zone therefore the pvt effect tends to enhance lateral pressure disequilibrium during erosion low permeability is crucial for the preservation of the lateral pressure disequilibrium the persistence of disequilibrium over geological time tens of millions of years requires extremely small vertical permeability sub picodarcy range and horizontal permeability 10 nd or even lower the horizontal permeability is 10 100 times smaller than laboratory measurements on shale plugs indicating a discontinuity of laminations and fractures within a shale formation

trace element partitioning between apatite and silicate melts we present new experimental apatite melt trace element partition coefficients for a large number of trace elements cs rb ba la ce pr sm gd lu y sr zr hf nb ta u pb and th the experiments were conducted at pressures of 1 0 gpa and temperatures of 1250 c the rare earth elements la ce pr sm gd and lu y and sr are compatible in apatite whereas the larger lithophile elements cs rb and ba are strongly incompatible other trace elements such as u th and pb have partition coefficients close to unity

organic geochemistry and petrology of posidonia shale lower toarcian western europe the evolution from immature oil prone to overmature dry gas producing kerogen abstract kerogen concentrates as well as whole rock samples of the lower jurassic posidonia shale representing a complete maturity series from immature to highly overmature were analyzed using organic petrography palynology bulk geochemical analysis ft ir and curie point pyrolysis gc ms cp py gc ms in order to investigate changes in kerogen composition with increasing maturation vitrinite reflectance vrr ranges from 0 5 to 3 hi values reflect the maturity trend very well with little scatter in contrast tmax oi and pi values show more scatter and greater differences between kerogen concentrates and whole rock samples ft ir spectra show a decrease in functional group bands with increasing maturation which has been quantified cp py gc ms analyses indicate an increase in hydrocarbons especially for short and medium length n alkanes with a strong predominance of short length alkanes at highest maturities about 3 vrr this effect however depends also on the applied pyrolysis temperature where higher temperatures 920 c as compared to 650 c favor generation of short length n alkanes especially for samples at high levels of maturation ratios of aromatic over aliphatic hydrocarbons or alkenes over alkanes show a non steady evolution depending also on the applied pyrolysis temperatures indicating that higher pyrolysis temperatures are needed for pyrolytic alkene formation with a maximum alkene formation for samples within early overmature maturities 1 4 vrr aromaticity first decreases but increases at high levels of maturation finally weathering of the highly overmature sample 3 vrr resulted in strong oxidation of organic matter with impact on rock eval ftir and curie point pyrolysis data

partitioning behavior of chlorine and fluorine in the system apatite silicate melt fluid the partitioning behavior of cl among apatite mafic silicate melt and aqueous fluid and of f between apatite and melt have been determined in experiments conducted at 1066 to 1150 c and 199 205 mpa the value of dclapatite melt wt fraction of cl in apatite cl in melt 0 8 for silicate melt containing less than 3 8 wt cl at higher melt cl contents small increases in melt cl concentration are accompanied by large increases in apatite cl concentration forcing dclapatite melt to increase as well melt containing less than 3 8 cl coexists with water rich vapor that containing more cl coexists with saline fluid the salinity of which increases rapidly with small increases in melt cl content analogous to the dependency of apatite composition on melt cl content this behavior is due to the fact that the solubility of cl in silicate melt depends strongly on the composition of the melt particularly its mg ca fe and si contents once the melt becomes saturated in cl additional cl must be accommodated by coexisting fluid apatite or other phases rather than the melt itself because cl solubility depends on composition the cl concentration at which dclapatite melt and dclfluid melt begin to increase also depends on composition the experiments reveal that dfapatite melt 3 4 in contrast to cl the concentration of f in silicate melt is only weakly dependent on composition mainly on melt ca contents so dfapatite melt is constant for a wide range of composition the experimental data demonstrate that the fluids present in the waning stages of the solidification of the stillwater and bushveld complexes were highly saline the cl rich apatite in these bodies crystallized from interstitial melt with high cl f oh ratio the latter was generated by the combined processes of fractional crystallization and dehydration by its reaction with the relatively large mass of initially anhydrous pyroxene through which it percolated

high temperature gc evidence for the early formation of c 40 n alkanes in coals abstract high temperature gc analyses were performed on a coal sourced waxy oil from the toka 1 well in the taranaki basin and on three bitumens extracted ultrasonically with boiling toluene from coals from the tara 1 well in the great south basin new zealand the coals represent an evolutionary trend from immature to post oil expulsion in all samples the c 40 alkanes were characterised by dominant straight chain members up to about c 65 which decreased significantly in abundance in bitumen with increasing maturity they are present at an early stage of maturity prior to the main phase of n alkane generation and may be liberated from cutan cutin sources within kerogen by thermal decarboxylation of esters or have an earlier origin in the bitumen inherited from diagenesis an odd over even predominance in the c 40 n alkanes was most marked in the c 51 c 57 range and decreased with increasing maturity suggesting that minor amounts of c 40 n alkanes with a cpi approaching 1 are also generated during catagenesis however the observed c 40 n alkane distributions may be affected to a degree by decreasing efficiency of solvent extraction with increasing n alkane molecular weight and by further long chain n alkanes generated during catagenesis being partially inaccessible to solvent extraction

maturity related variation in the bulk transformation kinetics of a suite of compositionally related new zealand coals abstract bulk hi transformation kinetics were determined by open system pyrolysis for a suite of compositionally related late cretaceous to paleocene coals from tara 1 well great south basin new zealand these coals span a maturity range encompassing the onset of significant oil generation and expulsion kinetic parameters were also obtained for one of the immature samples following artificial maturation by hydrous pyrolysis kinetic models were based on three modes of optimisation of kinetic parameters discrete e act distribution with single variable a value discrete e act distribution with fixed a 10 14 s 1 and gaussian e act distribution with single variable a value hi transformation rate vs temperature envelopes for the naturally matured coals exhibited an abrupt jump to higher temperature near rank s r 12 5 apparently coinciding with the onset of significant paraffinic oil expulsion for all optimisation modes the artificially matured sample does not predict this shift in transformation envelopes which suggests that certain of the reactions that occur under natural maturation do not occur during laboratory pyrolysis the structural rearrangements occurring up to the expulsion threshold some or all of which are responsible for the increase in hi up to rank s r 11 are not manifested in changes in hi transformation rate envelopes however the presence of adsorbed bitumen may mask the influence of structural rearrangements during optimisation of the kinetic data which could explain the behaviour of the transformation rate envelopes in the rank s r 11 0 12 5 range obtained from the discrete e act free a optimisation this behaviour involves a regression in transformation rate envelopes to lower temperatures as the amount of retained bitumen increases prior to expulsion the almost perfect nesting of transformation rate envelopes subsequent to oil expulsion suggests either that any further structural rearrangement does not produce a significant change in the a and e act distributions of hydrocarbon generating bonds or that the expulsion drastically reduces the degree of further rearrangements involving hydrocarbon generating moieties within the kerogen it follows that kinetic parameters for immature coals should not be considered ideal for modelling the whole phase of hydrocarbon generation nevertheless the kinetic parameters for the least mature tara coal rank s r 8 5 reproduced the normalised hi trend for the entire suite of coals with reasonable accuracy over the maturity range considered rank s r 8 5 15 0 only slightly underestimating conversion at the lower maturity levels and overestimating it slightly at the higher levels

the cumulate paradigm reconsidered the cumulate terminology outlined by wager and coworkers provided a logical system for describing the textures of the rocks of layered intrusions but recent work shows that this model fails to accommodate all the processes responsible for the petrographic features of coarse grained rocks textures of adcumulates and orthocumulates in the skaergaard intrusion cannot be correlated with concentrations of incompatible elements representing trapped liquid compaction and open system percolative processes have altered their textures modes and even bulk compositions although a rock may be a cumulate in the absence of other evidence it can be misleading to refer to it in terms of the cumulate nomenclature

new experimental approach to understanding igneous texture thin sections containing a magma like mixture of three crystalline ammonium compounds and intercrystalline melt can be prepared and observed microscopically during crystallization melting and deformation the aim of such observations is to establish links between active processes in the crystal melt mixture and the textural signatures of the processes the hope is to improve the basis for process interpretation of textures in rocks although the value of the experimental system in this regard is still unknown three unexpected processes are seen creation of growth centers for later blocky grains by isothermal decomposition of early dendritic grains migration of grain boundaries early in the crystallization history and growth of porphyroblast like grains by phase boundary migration with abundant melt nearby textural metamorphism begins in this material well before its melt present history is complete

the formation of p rich fe ti oxide ore layers in the taihe layered intrusion sw china implications for magma plumbing system process abstract the taihe intrusion is one of the layered intrusions that host giant fe ti oxide deposit in the central part of the emeishan large igneous province sw china different from the other layered intrusions the taihe intrusion has a massive fe ti oxide ore layer at the top of the lower zone lz particularly the rocks of both middle and upper zones contain as much as 5 12 apatite and the most important fe ti oxide ore layers apatite magnetite clinopyroxenite occur at the bases of cyclic units in the middle zone mz rather than in the lower zone lz high cr and ni concentrations of clinopyroxene 65 263 ppm and 66 83 ppm respectively and high an contents of plagioclase 79 80 of the lz rocks indicate their more primitive parental magmas the clinopyroxene and plagioclase of the mz rocks are characterized by low cr and ni contents 1 21 ppm and 0 4 10 ppm respectively and low an 51 67 indicating more evolved parental magma the fe ti oxide ore layers in the mz are not only high in fe and ti but also enriched in p2o5 and rare earth elements indicating an unusual fe ti p rich parental magma it is speculated that the mz represents a later intrusion of fe ti p rich magmas that were produced by the fe ti enriched magma from a deep seated magma chamber mixing with the extensively evolved p rich magma in a middle level magma chamber early crystallization and cumulation of fe ti oxide and apatite together with clinopyroxene from the fe ti p rich magmas from the middle level magma chamber resulted in the formation of fe ti oxide ore layers in the mz fe ti p rich magma and apatite magnetite clinopyroxenites occur in the base of cyclic units whereas apatite gabbros are presented at the upper parts of each cyclic unit the upper zone uz is the product of the crystallization of highly differentiated magma consists chiefly of apatite gabbro and minor intercalated apatite clinopyroxenite

halogen geochemistry of the great dyke zimbabwe apatite from the great dyke of zimbabwe is relatively rich in the hydroxy fluorapatite end members the mole fraction of fluorapatite increases from approximately 40 in cumulates of the ultramafic sequence to over 60 in a sample near the top of the exposed mafic sequence the chlorapatite component decreases from a typical high of 10 20 mole in the ultramafic sequence to about 1 in the uppermost part of the mafic sequence however within sample variation may be as great as the entire stratigraphic variation halogen contents of marginal samples generally are similar to axial samples but tend not to have as high cl concentration and tend to oh enrichment biotite compositions approach hydroxyl end member compositions and apatite biotite oh f exchange geothermometers give an average closure temperature of 564 c apatite from the umvimeela dyke an unlayered dike that parallels the great dyke over much of its length contains less cl than is seen in the ultramafic sequence cumulates of the great dyke while the overall stratigraphic trend is characterized by a decrease in the cl f ratio with stratigraphic height within the p1 unit at the top of the ultramafic sequence there is a positive correlation between cl and other incompatible elements such as na and ce the apparent contradiction between the general stratigraphic trend of decreasing cl f ratio with fractionation and the apparent increase in cl and other incompatible elements seen in the p1 unit can be explained by assuming that the great dyke magma chamber was degassing near its top where confining pressure was lowest and cl was preferentially lost to a separating volatile rich fluid as cumulates formed on the floor they entrapped liquid that was increasingly depleted in cl at the higher stratigraphic levels however at any given stratigraphic interval either local fluid enrichment or the eventual crystallization of halogen bearing minerals that incorporate the smaller f ion in preference to the larger cl ion led to a local increase in the cl f ratio

kinetics of oil generation from brackish lacustrine source rocks in the southern bohai sea east china abstract oil generation c14 hydrocarbons of three type ii kerogen samples isolated from brackish lacustrine mudstones from palaeogene strata ed3 es1 es3 in the southern bohai sea was simulated by closed system gold tube experiments in addition a series of complementary analyses rock eval pyrolysis total organic carbon vitrinite reflectance trace element x ray diffraction and flash pyrolysis gas chromatography mass spectrometry were also performed to identify the bulk geochemistry palaeo environment and chemical composition of the kerogen the aim of this study was to achieve a better understanding of the kinetics of oil generation from lacustrine source rocks in the southern bohai sea the results show that the three samples are type ii source rocks deposited in similar palaeo environments hot and arid climates anoxic conditions and brackish water in shallow to semi deep lakes with consequent similarity in the chemical compositions of their kerogens the organic matter inputs are predominantly composed of lacustrine microalgae with a relatively small contribution from land plants the activation energies of oil generation from these samples show a range of 44 52 kcal mol with a frequency factor varying from 1 116 1014 to 1 274 1014 s 1 due to the similar palaeo environments and chemical composition samples in this study exhibit strong consistencies in kinetic parameters transformation ratio tr evolution curves of oil generation from the three samples calculated under a linear heating rate 3 k ma exhibit a slight difference which varies within 4 c at a given tr due to the great similarities of the three kinetic models an average kinetic model for the type ii brackish lacustrine source rocks in the southern bohai sea was established this model integrates the characteristics of the three kinetic models and is still dominated by activation energy of 52 kcal mol the geological temperature of the oil generation phase for the average model in the southern bohai sea is from 92 to 137 c

open magma chamber processes in the formation of the permian baima mafic ultramafic layered intrusion sw china abstract the baima mafic ultramafic layered intrusion of the 260 ma emeishan large igneous province elip hosts the second largest fe ti v oxide deposit in the panxi region sw china it is a 1600 m thick layered body intruded by slightly younger syenitic and granitic plutons the intrusion includes the lower and upper zones troctolite and olivine pyroxenite of the lower zone contains conformable oxide ore layers whereas the upper zone consists of olivine gabbro and gabbro with abundant apatite in the higher level the crystallization order of the silicates in the baima intrusion is olivine plagioclase clinopyroxene fe ti oxides titanomagnetite and ilmenite crystallized after olivine and possibly plagioclase the oxide ores in the lower zone show slightly lree enriched patterns with la yb n values between 2 0 and 6 4 and positive eu anomalies eu eu of 1 0 to 2 7 in contrast olivine gabbros in the lower zone display stronger lree enrichments la ybn 7 7 14 0 and positive eu anomalies eu eu 2 8 3 3 gabbros in the upper zone have ree profiles characterized by intermediate lree enrichments with la yb n values of 3 2 to 11 2 and positive eu anomalies of 2 1 to 3 0 primitive mantle normalized trace element patterns are characterized by negative la ce th sm and positive nb ta ba and ti anomalies in oxide ores and negative th u zr hf and positive ba sr and ti anomalies in olivine gabbro and gabbro fo of olivine and an of plagioclase remain roughly constant from 0 to 90 m in the lower zone indicating that the magma chamber was continuously filled by compositionally similar magmas during the initial stage three magma replenishments occurred afterwards in the upper part of the lower zone and the upper zone based on compositional reversals of plagioclase olivine and sr isotope mass balance calculations show that the baima parental magma can produce all oxide ores under closed system conditions a wide range of an values of plagioclase within thin sections and disequilibrium sr isotopic compositions of plagioclase both along the stratigraphic profile 87sr 86sri 0 70312 0 70510 and within thin sections indicate convection and co accumulation of cumulus plagioclase that had crystallized from different magmas we propose that the 1600m thick baima intrusion formed in an open and isotopically heterogeneous magma chamber that was periodically recharged by compositionally similar or more primitive magmas in each replenishment cycle the magma underwent progressive crustal contamination and fractional crystallization convection and sorting of crystals based on density differences result in igneous layering characterized by intervals of oxide ores troctolite and olivine gabbro

quantitative modelling of hydrocarbon expulsion and quality grading of tight oil lacustrine source rocks case study of qingshankou 1 member central depression southern songliao basin china the quality of source rocks plays an important role in the distribution of tight and conventional oil and gas resources despite voluminous studies on source rock hydrocarbon generation expulsion and overpressure a quality grading system based on hydrocarbon expulsion capacity is yet to be explored such a grading system is expected to be instrumental for tight oil and gas exploration and sweet spot prediction this study tackles the problem by examining late cretaceous lacustrine source rocks of the qingshankou 1 member in the southern songliao basin china by evaluating generated and residual hydrocarbon amounts of the source rock the extent of hydrocarbon expulsion is modelled through a mass balance method the overpressure is estimated using petromod software through correlation between the hydrocarbon expulsion and source rock evaluation parameters total organic carbon toc kerogen type vitrinite reflectance ro and overpressure three classes of high quality effective and ineffective source rocks are established high quality class contains toc 2 type i kerogen ro 1 0 overpressure 7mpa sharp increase of hydrocarbon expulsion along with increasing toc and overpressure and high expulsion value at ro 1 source rocks with toc and ro 0 8 type ii2 iii kerogen overpressure 3mpa and low hydrocarbon expulsion volume are considered ineffective rocks with parameters between the two are considered effective the high quality class shows a strong empirical control on the distribution of tight oil in the songliao basin this is followed by the effective source rock class the ineffective class has no measurable contribution to the tight oil reserves because the hydrocarbon expulsion efficiency of source rocks is controlled by many factors the lower limits of the evaluation parameters in different basins may vary however the classification method of tight source rocks proposed in this paper should be widely applicable

evidence for distinct stages of magma history recorded by the compositions of accessory apatite and zircon accessory minerals contain a robust and accessible record of magma evolution however they may reflect relatively late stage conditions in the history of the host magmas in the normally zoned criffell granitic pluton scotland whole rock wr compositions reflect open system assimilation and fractional crystallisation at depths of 11 km whereas amphibole barometry and the absence of inherited zircon suggest that the observed mineral assemblages crystallised following emplacement of magmas with little or no crystal cargo at depths of 4 6 km the crystallisation history is documented by large trace element variations amongst apatite crystals from within individual samples decreasing lree and th concentrations in apatite crystals from metaluminous samples reflect broadly synchronous crystallisation of allanite whereas lower lree and th and more negative nd anomalies in apatites from peraluminous samples reflect the effects of monazite crystallisation wr evolution is likely to have occurred within a deep crustal hot zone where h2o rich 6 wt low viscosity magmas segregated and ascended adiabatically in a super liquidus state leading to resorption of most entrained crystals stalling emplacement and crystallisation resulted from intersection with the h2o saturated liquidus at 4 km h2o contents are as important as temperature in the development of super liquidus magmas during ascent blurring distinctions between apparently hot and cold granites the trace element contents of most accessory minerals are controlled by competitive crystallisation of other accessory minerals in small melt batches consistent with the incremental assembly of large granitic plutons

al in olivine thermometry evidence for the mantle plume origin of the emeishan large igneous province abstract the emeishan large igneous province elip is renowned for its world class ni cu pge deposits and its link with the capitanian mass extinction the elip is generally thought to be associated with a deep mantle plume however evidence for such a model has been challenged through geology geophysics and geochemistry in many large igneous province settings olivine melt equilibrium thermometry has been used to argue for or against the existence of plumes however this method involves large uncertainties such as assumptions regarding melt compositions and crystallisation pressures the al in olivine thermometer avoids these uncertainties and is used here to estimate the temperatures of picrites in the elip the calculated maximum temperature 1440 c is significantly 250 c higher than the al in olivine temperature estimated for the average morb thus providing compelling evidence for the existence of thermal mantle plumes in the elip