major types and time space distribution of mesozoic ore deposits in south china and their geodynamic settings the ore deposits of the mesozoic age in south china can be divided into three groups each with different metal associations and spatial distributions and each related to major magmatic events the first event occurred in the late triassic 230 210 ma the second in the mid late jurassic 170 150 ma and the third in the early mid cretaceous 120 80 ma the late triassic magmatic event and associated mineralization is characterized by peraluminous granite related w sn nb ta mineral deposits the triassic ore deposits are considerably disturbed or overprinted by the later jurassic and cretaceous tectono thermal episodes the mid late jurassic magmatic and mineralization events consist of 170 160 ma porphyry skarn cu and pb zn ag vein deposits associated with i type granites and 160 150 ma metaluminous granite related polymetallic w sn deposits the late jurassic metaluminous granite related w sn deposits occur in a ne trending cluster in the interior of south china such as in the nanling area in the early mid cretaceous from about 120 to 80 ma but peaking at 100 90 ma subvolcanic related fe deposits developed and i type calc alkaline granitic intrusions formed porphyry cu mo and porphyry epithermal cu au ag mineral systems whereas s type peraluminous and or metaluminous granitic intrusions formed polymetallic sn deposits these cretaceous mineral deposits cluster in distinct areas and are controlled by pull apart basins along the south china continental margin based on mineral assemblage age and space time distribution of these mineral systems integrated with regional geological data and field observations we suggest that the three magmatic mineralization episodes are the result of distinct geodynamic regimes the triassic peraluminous granites and associated w sn nb ta mineralization formed during post collisional processes involving the south china block the north china craton and the indo china block mostly along the dabie sulu and songma sutures jurassic events were initially related to the shallow oblique subduction of the izanagi plate beneath the eurasian continent at about 175 ma but i type granitoids with porphyry cu and vein type pb zn ag deposits only began to form as a result of the breakup of the subducted plate at 170 160 ma along the nne trending qinzhou hangzhou belt also referred to as qin hang or shi hang belt which is the neoproterozoic suture that amalgamates the yangtze craton and cathaysia block a large subduction slab window is assumed to have formed in the nanling and adjacent areas in the interior of south china triggering the uprise of asthenospheric mantle into the upper crust and leading to the emplacement of metaluminous granitic magma and associated polymetallic w sn mineralization a relatively tectonically quiet period followed between 150 and 135 ma in south china from 135 ma onward the angle of convergence of the izanagi plate changed from oblique to parallel to the coastline resulting in continental extensional tectonics and reactivation of regional scale ne trending faults such as the tan lu fault this widespread extension also promoted the development of ne trending pull apart basins and metamorphic core complexes accompanied by volcanism and the formation of epithermal cu au deposits granite related polymetallic sn w deposits and hydrothermal u deposits between 120 and 80 ma with a peak activity at 100 90 ma

molybdenite re os and muscovite 40 ar 39 ar dating of quartz vein type w sn polymetallic deposits in northern guangdong south china northern guangdong is an important part of nanling tungsten tin metallogenic belt south china the tungsten mineralization in this area consists of mainly quartz wolframite vein type mineralization with w sn polymetallic deposits mostly distributed at the outer contact zone between concealed late jurassic granitic stocks and cambrian ordovician low metamorphosed sandstones and shales molybdenite re os and muscovite 40ar 39ar isotopic dating of three typical tungsten vein type deposits yaoling meiziwo and jubankeng in northern guangdong show that two episodes of late jurassic w sn polymetallic mineralization occurred in this area an early episode during the late jurassic 158 159 ma represented by the yaoling hongling and meiziwo tungsten deposits and a younger event during the early cretaceous 138 ma represented by the jubankeng deposit analysis of available radiometric ages of several w sn deposits in the nanling region indicate that these deposits formed at several intervals during the mesozoic at 90 100 134 140 144 162 and 210 235 ma and that large scale w sn mineralization in this region occurred mainly between 150 and 160 ma

petroleum origin and accumulation in basin evolution a quantitative model basin data geologic geophysical geochemical hydrodynamic and thermodynamic can be combined for quantified hydrocarbon prediction a three dimensional deterministic dynamic basin model can be constructed to calculate all the measurable values with the help of mass and energy transport equations and equations describing the physical and or physicochemical changes in organic matter as a function of temperature input data consist of heat flux initial physical and thermal properties of sediments paleobathymetric estimates sedimentation rate and amount and type of organic matter subsequently the model computes pressure temperature physical and thermal properties of sediments maturity of organic matter and the hydrocarbon potential of any source rock as a func ion of space and time thus the complex dynamic processes of petroleum formation and occurrence in a given sedimentary basin can be quantified for example hydrocarbon potential maps for any given source rock and any geologic time slice of the basin evolution can be provided as computer printouts the computer model can be applied to any stage of an exploration campaign and updated as more information becomes available

highly evolved juvenile granites with tetrad ree patterns the woduhe and baerzhe granites from the great xing an mountains in ne china abstract in ne china voluminous granitoids were emplaced in late paleozoic and mesozoic times we report here sr nd o isotopic and elemental abundance data for two highly evolved granitic plutons woduhe and baerzhe from the great xing an mountains they show a rather juvenile sr nd isotopic signature and a spectacular tetrad effect in their ree distribution patterns as well as non charac charge and radius controlled trace element behavior the emplacement ages are constrained at 130 4 ma for the woduhe and 122 5 ma for the baerzhe granites by rb sr and sm nd isotope analyses both granites are also characterized by low but imprecise initial 87sr 86sr ratios of about 0 703 the nd sr isotope data argue for their generation by melting of dominantly juvenile mantle component with subordinate recycled ancient crust this is largely compatible with the general scenario for much of the phanerozoic granitoids emplaced in the central asian orogenic belt the parental magmas for both the woduhe and baerzhe granites have undergone extensive magmatic differentiation during which intense interaction of the residual melts with aqueous hydrothermal fluids probably rich in f and cl resulted in the non charac trace element behavior and the tetrad effect of ree distribution both the woduhe and baerzhe granites show the characteristic trace element patterns of rare metal granites but their absolute abundances differ by as much as two orders of magnitude the oxygen isotope compositions of the two granites have been severely disturbed significant 18o depletion in feldspar but not so much in quartz suggests that the hydrothermal alteration took place in a temperature condition of 300 500 c this subsolidus hydrothermal alteration is decoupled from the late stage magma fluid interaction at higher temperatures despite the two distinct and intense events of water rock interaction the rb sr and sm nd geochronological systems seem to have maintained closed hence suggesting that the two events occurred shortly after the plutonic emplacements

high thermal maturity in the lower saxony basin intrusion or deep burial abstract the lower saxony basin lsb is situated at the southern rim of the northern permian basin the most important hydrocarbon bearing province in europe in its southern part areas of high thermal maturation up to 6 rr occur which were previously explained as being caused by magmatic intrusions of turonian to santonian age that affected carboniferous to lower cretaceous rocks in this area 2d numerical basin modelling was carried out in order to reconstruct the temperature histories along two parallel n s trending seismic sections along these sections new data about maturity distribution and temperature history were obtained by vitrinite reflectance measurements and apatite fission track analysis for the areas with highest maturity values low coalification gradients were established which agree well with earlier published data on wells further towards the west this new information does not support previous hypotheses on high heat flows from magmatic intrusions even if lateral heat transport is taken into account instead comparisons with a recently published map of the subsurface structure of the lsb indicate that maturity distribution may be closely related to major tectonic structures deep burial of individual structures of the lsb which are bordered by deep e w to ese wnw trending faults is further suggested by a rapidly increasing thicknesses of preserved cretaceous strata towards the south and b structural restoration of one of the seismic sections to achieve a fit between measured and calculated palaeo temperature and vitrinite reflectance data deep burial of carboniferous source rocks during cretaceous time has to be assumed due to an inversion phase in the early and middle upper cretaceous major amounts of sediment were removed and further uplift occurred in tertiary times in contrast the northern part of the lsb experienced maximum burial and temperatures during tertiary times

thermal basin modelling of the arauco forearc basin south central chile heat flow and active margin tectonics abstract the arauco basin is part of the coastal forearc domain in south central chile during its evolution since the late cretaceous it was subject to multiple deposition cycles and the erosion of lower bathyal to beach and lagoon sediments these different environments were established in alternating accretional and erosive subduction tectonic settings along the south andean active margin whereas the general development is well understood inconsistencies arise regarding the origin of the high thermal maturity of eocene coals and the estimates of vertical movements of the whole area during the cenozoic thermal modelling of this forearc basin provides new insights regarding its thermal evolution and evaluation of the magnitudes of subsidence and inversion results are based on the analysis of coal samples from surface outcrops mines and drill cores of ten onshore wells from enap sipetrol newly derived vitrinite reflectance vr r measurements indicated a temperature in the range of 135 150 c for the oldest sediment unit of the arauco basin which was reached in post eocene times furthermore 1d basin modelling techniques indicate scenarios that could explain the coalification values in the basin s sediments the models were calibrated against vr r data from drill core samples supplied by enap sipetrol a miocene and an oligocene subsidence inversion scenario were considered while neither could be securely discarded based on the modelling results furthermore it can be shown that the current thermal maturity was not reached by an increased heat flow hf or a deep subsidence only consequently a structural inversion accompanied by the erosion of 3 0 0 4 km depending on the locality in combination with a high hf of 64 4 mw m 2 is the best explanation of the available data the hf which is high for a forearc setting can be attributed to the increased temperature of the relatively young subducted nazca plate and an additional influence of ascending hot fluids from the subduction zone the maximum temperature gradient inferred is

petrogenesis of the late mesozoic qijinfeng granite complex in the tongbai orogen geochronological geochemical and sr nd pb hf isotope evidence abstract the tongbai orogen is located in the northern hubei and southern henan provinces together with the qinling hong an and dabie orogens they constitute one of the most important orogenic belt separated the north china block and yangtze block among these orogens the tongbai receives less attention and its magmatic and tectonic evolution is still unclear in this paper we present a detailed study on geochronology geochemistry and sr nd pb hf isotopes of the five plutons daxianduo jinziling sanguanduo sanhedian and zhoulou that composes the qijianfeng granite complex in suizao area in order to better understanding the late mesozoic magmatic and tectonic evolution of the tongbai orogen the la icp ms u pb dating of zircon suggests an early cretaceous emplacement age 135 139 ma for the qijianfeng granite complex all the five plutons of the qijianfeng granite complex are weakly peraluminous and belong to high k calc alkaline series and post collisional i type granites the chemical and isotopic compositions of the qijianfeng granite complex show sio2 contents of 69 84 74 36 wt al2o3 of 13 85 15 62 wt mgo of 0 16 0 52 wt n2o k2o of 0 99 1 73 506 1205 ppm sr 3 4 12 9 ppm y 0 49 1 25 ppm yb eu eu values of 0 7 1 0 lree hree values of 3 1 9 5 87sr 86sr values of 0 7057 0 7080 and end t values of 16 59 to 6 18 which share similarities with the c type high k adakite the low mgo ni and cr contents further suggest that the qijianfeng granite complex belongs to adakite derived from partial melting of thickened lower continental crust combined with the geochemical characteristics of other contemporaneous intrusions in the whole orogen our study shows that the extensive early cretaceous adakitic magmatic activity is triggered by lower crustal thickened mountain basin coupling and crust mantle interaction in the tongbai orogeny

a method for assessing statistical significance and uncertainties for calibration of 1 d thermal basin maturation models basin modeling as a quantitative tool in petroleum studies necessarily implies knowledge about the limiting factors of the model especially because modeling methods are widely used when ranking exploration targets and assessing associated geologic risk commonly model validity is checked by time consuming trial and error calibrations against measured data attempting complicated modifications of the model to satisfy the highly nonlinear relationships between model parameters these procedures can result in an overinterpretation of model results inversion procedures however aim at finding the simplest set of model parameters that best agree with calibration data taking the known uncertainties into account in this article an easy to use and rapid pseudoinverse method is presented for one dimensional 1 d deterministic forward models by assessing uncertainties and some measure of the goodness of fit to observed data in this case vitrinite reflectance the significance of variations of different input parameters can be rapidly evaluated the method is illustrated on a data set from a detailed 1 d modeling study of a small region of the german variscan rhenish massif the significance and uncertainties of the two main parameters affecting vitrinite reflectance that is heat flow and burial depth during maximum burial are assessed and discussed besides using real data a theoretical approach is presented by approximating the residual surface using a polynomial or cubic spline interpolation for a few data points only the resolution limits sensitivity and uncertainty can be easily assessed and the residual surface can be converted to a pseudoprobability density function for use in later risking procedures

in situ la mc icp ms and id tims u pb geochronology of cassiterite in the giant furong tin deposit hunan province south china new constraints on the timing of tin polymetallic mineralization abstract the furong deposit located in southern hunan province china is a newly discovered giant tin deposit spatially associated with the a type qitianling granite the petrogenetic link between the giant furong tin deposit and the qitianling granite batholith remains controversial because of the lack of precise dating for the tin polymetallic mineralization here we report for the first time in situ u pb data on cassiterite obtained by la mc icp ms and the results are compared to id tims data the in situ la mc icp ms analyses of the cassiterites provide a reliable age constraint for tin polymetallic mineralization in the furong deposit yielding an isochron age of 159 9 1 9 ma at 95 confidence level mswd 18 which is indistinguishable from the id tims 206 pb 238 u weighted mean age of 158 2 0 4 ma the in situ u pb ages corroborate the ar ar dates published for the furong tin deposit which indicate that the mineralization is coeval with the emplacement of the qitianling granite batholith these results provide further evidence of a close temporal link between the pluton s emplacement and tin mineralization in the furong area the data obtained clearly demonstrate that in situ la mc icp ms u pb dating of cassiterite is a robust geochronometer for direct dating of tin polymetallic mineralization

magmatic evolution of li f rare metal granites a case study of melt inclusions in the khangilay complex eastern transbaikalia russia abstract we report compositions of homogenized quartz hosted melt inclusions from a layered sequence of li f rich granites in the khangilay complex that document the range of melt evolution from barren biotite granites to ta rich lepidolite amazonite albite granites the melt inclusions are crystalline at room temperature and were homogenized in a rapid quench hydrothermal apparatus at 200 mpa before analysis homogenization runs determined solidus temperatures near 550 c and full homogenization between 650 and 750 c the compositions of inclusions determined by electron microprobe and raman spectroscopy for h 2 o show regular overall trends of increasing differentiation from the least evolved khangilay units to apical units in the orlovka intrusion total volatile contents in the most evolved melts reach over 11 wt h 2 o 8 6 wt f 1 6 wt b 2 o 3 1 5 wt concentrations of rb range from about 1000 to 3600 ppm but other trace elements could not be measured reliably by electron microprobe the resulting trends of melt evolution are similar to those described by the whole rock samples despite petrographic evidence for albite and mica rich segregations previously taken as evidence for post magmatic metasomatism melt variation trends in most samples are consistent with fractional crystallization as the main process of magma evolution and residual melt compositions plot at the granite minimum in the normative qz ab or system however melts trapped in the highly evolved pegmatitic samples from orlovka deviate from the minimum melt composition and show compositional variations in al na and k that requires a different explanation we suggest that unmixing of the late stage residual melt into an aluminosilicate melt and a salt rich dense aqueous fluid hydrosaline melt occurred experimental data show the effectiveness of this process to separate k aluminosilicate melt from na hydrosaline melt and high mobility of the latter due to its low viscosity and relatively low density may explain local zones of albitization in the upper parts of the granite

characteristics of type iii kerogen in coal bearing strata from the pennsylvanian upper carboniferous in the ruhr basin western germany comparison of coals dispersed organic matter kerogen concentrates and coal mineral mixtures abstract quality quantity and maturity of coal and dispersed terrigenous organic matter were studied on six coal bearing intervals in duckmantian strata pennsylvanian upper carboniferous of the ruhr basin western germany between 10 and 40 samples were collected from fresh drill cores of each interval typically consisting of a coal seam as well as clastic roof and floor strata sandstone siltstone claystone coal seams constitute about 8 vol of the succession studied the samples were analysed by organic petrological methods and rock eval pyrolysis maturity expressed in terms of vitrinite reflectance is between 0 75 and 1 0 for the six successions studied the total amount of dispersed organic matter in clastic rocks is about half of that stored in coal seams both containing predominantly vitrinite significant differences between rock eval parameters determined on whole rock samples and kerogen concentrates were observed especially with respect to hydrogen index hi values thus the hi of the coal is about twice as high as that of the dispersed organic matter although the maceral composition is similar the effects of minerals were further examined by rock eval pyrolysis of artificial mixtures of coal lignite powder and different minerals reduced hi values are partly explained by the retention of generated hydrocarbons on mineral surfaces and partly by reactions of generated fluids with pyrite in kerogen concentrates

experimental evidence for a protracted enrichment of tungsten in evolving granitic melts implications for scheelite mineralization the solubility of scheelite in evolved granitic magmas qz ab or an system with minor feototal tio2 and cao added was studied experimentally at 200 mpa 750 850 c and relatively oxidizing condition logfo2 nno 2 3 where nno is ni nio oxygen buffer water saturated granitic melts have been equilibrated with seeds of scheelite crystals the resulted wo3 contents in the melts vary only slightly from 0 21 to 0 32 wt wo3 over the investigated temperature and compositional range 0 7 to 1 4 wt cao but tends to increase with increasing temperature and decreasing cao concentration one important message conveyed from the study is that wo3 concentrations at scheelite saturation are more dependent on temperature in evolved ca poor melts than in ca rich melts natural granitic rocks associated with scheelite mineralization and associated melt inclusions hosted in quartz have much lower w contents than the experimental melts equilibrated with scheelite this implies that enrichment of tungsten w at magmatic stages is not sufficient to produce significant scheelite mineralization and confirms the important role of w mobilization by magmatic hydrothermal fluids in the formation of scheelite deposits

the influence of oxygen fugacity on tungsten and molybdenum partitioning between silicate melts and ilmenite the partitioning of molybdenum and tungsten between ilmenite ilm and silicic melts has been determined at 800 degrees c 1 kbar of pressure and at two oxygen fugacities at the oxygen fugacity of the graphite methane water buffer d super ilm melt mo 0 42 and d super ilm melt w 0 39 near the nickel nickel oxide buffer d super ilm melt mo 0 22 and d super ilm melt w 0 5 the variations in the partition coefficients with f sub o 2 are significant at the 0 06 and 0 33 levels for molybdenum and tungsten respectively the observed variation with oxygen fugacity is tentatively extrapolated to more complex systems and implies that the oxygen fugacity which prevails during magmatic crystallization may play a role in determining the mo w ratio in porphyry skarn or other hydrothermal mineral deposits examination of the literature on molybdenum and tungsten bearing mineral deposits indicates that systems with high w mo ratios are rather reduced and exhibit high ch 4 co 2 ratios in fluid inclusions low fe super 3 fe super 2 ratios in iron bearing minerals and low oxygen fugacities in associated igneous rocks on the other hand deposits with high mo w ratios are associated with rather oxidized magmatic systems we suggest that f sub o 2 dependent sequestration of molybdenum and tungsten in ferromagnesian phases during plutonic consolidation exerts a control on the relative efficiencies of removal of these metals from magmas into ore forming fluids

magmatic evolution and related w mo mineralization in the larong deposit eastern tibet evidence from zircon u pb ages geochemistry and sr nd hf isotopes abstract the late cretaceous ca 92 ma larong porphyry w mo deposit 39 44 mt wo3 0 1541 is the first discovered giant w mo deposit in the leiwuqi zogang metallogenic belt sanjiang region multi stage granitoids including the dacite porphyry dp granodiorite porphyry gp biotite granite porphyry bgp monzogranite porphyry mp biotite granite bg and granite aplite ga have been identified in the larong deposit however the magmatic evolution and related w mo mineralization in this deposit are still poorly understood la icp ms zircon u pb dating of the dp gp bgp mp bg and ga yield weighted mean 206pb 238u ages of 214 0 0 7 ma 213 8 1 3 ma 104 4 0 9 ma 93 9 1 3 ma 91 7 0 5 ma and 36 2 0 6 ma respectively the late triassic dp and gp should be classified as peraluminous a cnk values of 0 95 1 57 s type granitoids they are characterized by pronounced negative end t values 10 01 to 13 92 and ehf t values 8 5 to 16 6 with old tdm2 nd and tdm2 hf ages 1 81 2 12 ga and 1 79 2 30 ga respectively indicating that the dp and gp were mainly derived from partial melting of ancient crustal materials after break off of the paleo tethyan oceanic slab the late cretaceous bgp mp and bg and late eocene ga have low a cnk ratios 0 92 1 06 but high sio2 70 57 77 34 and differentiation index di 87 55 98 06 similar to the characteristics of highly fractionated i type granite detailed elemental e g depletion in nb ta ti sr ba eu and p and isotopic data 87sr 86sr i 0 71192 0 72932 end t 11 81 to 9 11 ehf t 10 4 to 1 4 demonstrate that they were the result of magma mixing between ancient crust derived melts and mantle derived melts the bgp was produced during the final stage of bangong nujiang tethyan ocean bnto subduction the mp and bg were formed under a post collisional tectonic setting related to slab break off of the bnto and the ga was likely associated with delamination of the thickened eclogitic lower crust together with lithospheric mantle the w mo mineralization in the larong deposit is genetically associated with the mp with four favorable factors that can account for the formation of this deposit 1 high w background 2 multi stage magmatism 3 highly evolved relatively oxidized and f rich magmatic system and 4 sufficient calcium obtained by intense fluid rock interaction

peraluminous i type granites abstract s type granites always contain more al than the amounts of na ca and k in the rock required to form feldspars primarily owing to their derivation from source components that had previously been weathered those rocks are therefore always saturated in al or peraluminous many i type granites are also peraluminous despite i type source rocks typically not being saturated in al it has previously been suggested that this may result from the fractional crystallisation of amphibole however data from compositionally zoned high temperature plutons in the lachlan fold belt show that it is difficult to generate large quantities of peraluminous melt by removal of amphibole most of the i type granites 95 in the lachlan fold belt formed at lower temperatures and almost half of those rocks for which bulk chemical compositions are available are peraluminous among these granites there are 98 separate suites for which there are chemical data for two or more samples with 47 suites that include both metaluminous more mafic and peraluminous more felsic compositions the origin of those peraluminous compositions is fundamental to any understanding of i type granite petrogenesis in this region compositional variations caused by the assimilation or by partial melting of supracrustal rocks are very small as the isotopic variations within these rocks are dominantly between different suites not within suites the partial melting of more mafic source rocks rather than the fractional crystallisation of more mafic magmas is favoured for the origin of these rocks partial melting is the most likely process involved in the petrogenesis of felsic granites where broadly granodioritic monzogranitic batholiths are associated with lesser amounts of tonalite and very minor amounts of mafic rock experimental studies have shown that the melts generated by the partial melting of basaltic to andesitic rocks under crustal conditions are mostly peraluminous during the dehydrational melting of i type granite source rocks at pressures below the garnet stability field biotite and amphibole melt incongruently to yield pyroxenes the excess al is incorporated into the felsic liquid resulting in the generation of peraluminous melts in this instance the excess al in felsic i type granites is a function of the melting process and unrelated to the bulk composition of the source the observed gradation from peraluminous felsic granites to metaluminous compositions in less felsic rocks in largely isotopically closed systems could happen in two ways at higher temperatures of partial melting ca and other components of clinopyroxene could dissolve in the melt with the melt eventually becoming metaluminous alternatively minerals residual from partial melting dominantly pyroxenes and plagioclase could be incorporated in suspension in the melt so that the resulting bulk magma is metaluminous examples of these two extremes and of intermediate cases are well developed among the granites of southeastern australia

characterisation of non extractable macromolecular organic matter in palaeozoic coals abstract comprehensive organic geochemical investigations were applied to permian carboniferous and devonian coals the major goal of the investigation was to quantify differences in organic matter composition of the coals on a molecular level and to associate these differences with either i primary composition of the precursor plant material or ii diagenetic processes related to burial and temperature increase or iii evolutionary time trends the pre extracted samples were analysed by means of pyrolytic and chemical degradation techniques as well as ftir spectroscopy additionally rock eval pyrolysis and organic petrography were used to obtain information on the bulk of the coal samples the degradation analysis revealed a wide variety of individual compounds including n alkanes isoprenoids polycylic aromatic compounds fatty acids alkylbenzenes aromatic carboxylic acids and phenols relative concentrations of substances or compound groups were correlated with bulk parameters and age of the samples significant correlations of the chemical data were found out mainly for maturity parameters and maceral composition time depending changes in chemical composition were observed only to a minor extent thus the rapid morphologic evolution of higher land plants in the late palaeozoic is not reflected in a significant way by the chemical composition of the non extractable matter in the coal samples investigated

a new evaluation of palaeo heat flows and eroded thicknesses for the carboniferous ruhr basin western germany palaeo heat flows and thicknesses of eroded carboniferous overburden in the coal bearing ruhr basin western germany were estimated using one dimensional basin modelling techniques thermal and burial histories for 11 localities were calibrated by comparing measured and calculated vitrinite reflectance data based on the assumption of pre tectonic maturation in contrast to former studies the kinetic easy r0 approach applied for the calculation of vitrinite reflectance lopatin s tti algorithm was used in addition for one well in order to demonstrate the impact of the selection of the algorithm for vitrinite reflectance calculation on the simulation results simulated palaeo heat flows for the time of maximum burial most probably in the stephanian range from 64 to 83 mw m2 and decrease towards the south these heat flows are lower than values computed during earlier studies but are still relatively high in comparison to recent foreland basins the regional distribution of palaeo heat flows indicates that the crust beneath the ruhr basin was relatively thin and thickened towards the south at the end of the carboniferous after the stephanian 2200 3500 m of carboniferous overburden were eroded an observed southward increase in eroded thicknesses is caused by an uplift of the area studied which decreased towards the north at the end of the variscan folding large thicknesses of deposited and later eroded carboniferous sediments have to be postulated to explain the maturity data even along the present southern margin of the ruhr basin this indicates that the late carboniferous sediments originally extended far to the south geological arguments suggest that the deposition of carboniferous sediments in the entire ruhr basin continued until the stephanian

characterization and origin of aluminous a type granites from the lachlan fold belt southeastern australia the metaluminous to weakly peraluminous a type granites of the lachlan fold belt are a distinctive group of igneous rocks on the basis of chemical and mineralogical criteria those granites that contain 65 72 sio2 can be distinguished from other types on the basis of higher abundances of fetotal fetotal mg high field strength elements trivalent rare earth elements ga and zn mineralogically they contain fe rich hydrous mafic minerals and primary ilmenite and hence are reduced relative to the ni nio buffer however the extremely felsic a type granites sio2 72 have the same chemical and mineralogical characteristics as felsic fractionated i type granites recent analyses indicate that the lachlan fold belt a type granites have sc f alkali element trace transition element and h2o contents similar to those of other unfractionated i type granites rb sr and nd sm isotopic compositions are highly variable probably reflecting source region heterogeneity the metaluminous to weakly peraluminous a type granites of the lachlan fold belt are distinct from peralkaline rocks in terms of chemical composition petrography and field associations although these rocks have been grouped together as a single type in current classification schemes we propose that the metaluminous to weakly peraluminous a type granites such as those of the lachlan fold belt should be defined as aluminous a type granites and should not be grouped with peralkaline granites the lachlan fold belt aluminous a type granites have relatively high calculated zircon saturation temperatures we suggest that these granites were produced by high temperature partial melting of a felsic infracrustal source

generation of late mesozoic qianlishan a 2 type granite in nanling range south china implications for shizhuyuan w sn mineralization and tectonic evolution abstract the late mesozoic qianlishan granitic complex in the western nanling range south china is associated with the shizhuyuan giant w sn mo bi polymetallic deposit it mainly consists of three phases of intrusions p 1 porphyritic biotite granite p 2 equigranular biotite granite and p 3 granite porphyry all three phases of granite contain quartz plagioclase k feldspar and fe rich biotite they have geochemical affinities of a type granites e g high feot feot mgo ratios 0 84 0 99 total alkali na2o k2o 7 50 9 04 wt high ga al ratios 10 000 ga al 2 6 and high zr nb y ce concentrations 350 ppm high y nb ratios 1 2 suggest that the qianlishan complex belongs to a2 type granite zircon u pb ages indicate a short age interval decreasing from 158 157 ma to 158 155 ma and to 154 ma for the p 1 p 2 and p 3 granites respectively these ages are similar to the mineralization age of the shizhuyuan tungsten polymetallic deposit within error the qianlishan granites were generated at low oxygen fugacity conditions based on the low values of zircon ce4 ce3 ratios 1 53 198 and significantly negative eu anomalies eun eun 0 03 0 13 in apatite new zircon ehf t values for the p 3 granite range from 13 0 to 4 4 similar to those previously obtained for the p 1 and p 2 granites both the granite and apatite grains therein are characterized by high f but low cl concentrations suggesting the influx of a high f cl component the p 2 granites especially contain higher f contents 1840 8690 ppm and w 7 158 ppm and sn 6 51 ppm concentrations and with stronger evolution features positive trends between f and w and sn of qianlishan complex indicate that high f source is crucial for mineralization of w and sn we consider that the lithospheric mantle source may have been metasomatized by subduction fluids in the far end of subduction zones to produce the a2 feature of the qianlishan granite and the fluorine was introduced through breakdown of phengite in the oceanic slab partial melting of the lithospheric mantle was induced by upwelling of the asthenospheric mantle as a consequence of slab rollback tungsten and tin have been enriched in reduced granitic magmas through fractionation enhanced by high f contents forming the giant polymetallic deposits

palaoecologic trends and petroleum potential of upper carboniferous coal seams of western germany as revealed by their petrographic and organic geochemical characteristics abstract petrographic compositions of microscopically homogeneous vertical sections in coal profiles from the ruhr basin northwestern germany are reported the studied coal seams of late westphalian age are between 0 4 and 2 4 m thick mean vitrinite reflectivities in the range of 0 1 0 thus indicating high volatile a bituminous coal changes in the organic facies within the coal profiles are common and can be linked to changes of plant communities and preservation conditions in the depositional environments also associated variations in mineral content are usually found although patterns of changes in maceral and mineral contents are complex some general trends have been observed continuous development from seat earth to coal with vitrinitic roots and detritic liptinites and inertinites representing the initial stage of peat and coal evolution just above the base thick vitrinite rich sections with abundant mudstone layers are overlain by inertinite rich sections with low mineral and high sporinite contents the latter may represent highly degraded oxidized peats that accumulated at morphologically elevated areas deposition of clastic roof strata had only a minor influence on organic facies coals and dispersed organic matter in these clastic rocks are in the main similar in maceral group composition organic geochemical characterization of selected lithotypes revealed significant differences between coals and dispersed organic matter this can be explained by trapping of generated hydrocarbons in the coals differences in elemental compositions of coals of the same organic facies at different ranks vitrinite reflectance of 0 70 and 0 92 respectively reflect a loss of about 20 wt co 2 bitumen water during this maturation stage gas chromatographic mass spectrometric analyses of the saturated hydrocarbon fraction in solvent extracts separated from selected samples reveal that all samples contain the same classes of compounds namely straight chain alkanes hopanoids and isoprenoids but that there is a significant difference in the relative abundance of these classes of compounds in the different coals

cretaceous granitic magmatism and mineralization in the shanhu w sn ore deposit in the nanling range in south china abstract abundant jurassic cretaceous w sn ore deposits are distributed in the nanling range in south china however the exact mineralization ages relationships between mineralization and granitic rocks and tectonic settings of these deposits remain controversial as a giant quartz vein type w sn deposit hosted in devonian sedimentary strata the shanhu orebodies are featured by located about 4 km far away from the yantianling muscovite granite zircon u pb dating of the yantianling granite yielded ages of 101 0 1 5 ma and 100 4 1 1 ma consistent with cassiterite u pb ages of quartz vein ores 100 2 1 0 ma and 100 5 1 1 ma indicating a close genetic relationship between the granitic magmatism and quartz vein type w sn mineralization the yantianling muscovite granite is characterized by highly silicious 72 01 74 62 wt high alkali na2o k2o 5 32 7 89 wt and strongly peraluminous a cnk 1 11 1 81 the granite is enriched in rb ta nd and u and depleted in sr ti and p it displays right declining chondrite normalized ree patterns with strongly negative eu anomalies and has low nb ta and zr hf ratios indicating that the granite experienced strong magmatic differentiation the yantianling granite has low whole rock end t values 9 5 to 9 3 zircon ehf t values 12 7 to 7 8 and paleoproterozoic model ages the granite belongs to s type and was derived from partial melting of meta sedimentary crust the low ce4 ce3 ratios averaging 47 of zircon from the yantianling granite indicated low oxygen fugacity similar to other w bearing granites in south china this study indicated that cretaceous granitic magmatism in the nanling range also has strong w sn mineralization potential combined with previous studies on coeval magmatic rocks and tectonic activities we propose that the yantianling s type granite and associated w sn mineralization in the nanling range were formed during the regional lithospheric extensional environment

controls on gas storage characteristics of upper paleozoic shales from the southeastern ordos basin abstract potential shale gas resources in china are not only of marine but also of marine terrigenous transitional and continental origins to analyze the controls on gas storage capacity of shales from the carboniferous benxi and permian shanxi formations high pressure temperature methane sorption isotherms up to 25 mpa and 120 c and porosity have been measured on 12 samples from the yishan slope total organic carbon toc content of shanxi and benxi shales are low to moderate from 0 1 to 80 is stored on clay minerals illite smectite mixed layer and kaolinite controlling both sorption capacity and porosity toc content due to its low values is of minor importance benxi and shanxi shales possess comparatively low gas storage capacities compared to producing marine shale gas systems combined with the large amount of clay minerals that make hydraulic fracturing more difficult they are regarded unfavourable for shale gas exploitation although a substantial amount of gas can be stored sorbed in excess of the free gas in gas shales methane sorption has a negligible effect on gas production at pressures above 10 mpa this has major implications for deep reservoirs where pore pressures in the matrix may not be reduced sufficiently before production ceases

numerical modelling of burial and temperature history as an approach for an alternative interpretation of the bramsche anomaly lower saxony basin the lower saxony basin germany is one of the several sedimentary basins within the central european basin system in its southwestern part anomalously high maturity of organic matter has been observed to reach 4 5 vrr in upper jurassic and lower cretaceous sedimentary rocks in an area which coincides with a magnetic and a positive gravimetric anomaly this anomaly was often interpreted as the consequence of a deep seated igneous intrusion the so called bramsche massif however results obtained from calibrated numerical modelling are not in accordance with this scenario instead a burial by approximately 4 km of now eroded cretaceous rocks was revealed to be the probable cause for the anomaly data and modelling results from six boreholes and two pseudo wells support this view

geochemistry and organic petrography of cretaceous sediments of the calabar flank southeastern nigeria abstract detailed bulk geochemistry and organo petrography of outcrop cretaceous sediments with no significant effects of weathering from the calabar flank southeast nigeria were performed to understand the organic carbon source accumulation and degradation and paleo climatic paleoceanographic and paleoenvironmental conditions in west africa during early cretaceous aptian to maastrichtian times this study was based on microscopic elemental analyses organic carbon nitrogen iron and sulphur rock eval pyrolysis and carbon isotope analyses in general the calabar flank shales are characterised by highly variable total organic carbon toc contents which range between 0 1 in aptian albian mfamosing limestone and 9 9 in the awi formation sediments the organic matter om is a mixture of immature to early mature marine and terrigenous om of types iii and iv this is indicated by low hydrogen indices hi value 10 190 mg hc g toc tmax 417 460 c vitrinite reflectance ro 0 39 0 62 ro low to high c n ratios 3 4 1158 0 and high amounts of terrigenous macerals vitrinite inertinite based on carbon isotope c n ratios and sulphate reduction index sri om degradation up to 70 sri 2 5 is most pronounced for shales deposited in a marine environment the geochemical and petrographic data indicate that local factors such as low bioproductivity down slope transport and redeposition of sediments from a fluvial deltaic basin to nearshore facies shallower oxic and mildly oxygen deficient environments humid arid paleogeographic conditions specifically controlled the amount and quality of the om during aptian mastrichtian stages where marine sediments have been assumed to be deposited during the global anoxic events therefore the order of the main factors controlling om content in sediments are input of terrigenous material transported from the land low om productivity by marine photoautotrophs low preservation

critical evaluation of an upper carboniferous tight gas sandstone reservoir analog diagenesis and petrophysical aspects upper carboniferous sandstones are one of the most important tight gas reservoirs in central europe we present data from an outcrop reservoir analog piesberg quarry in the lower saxony basin of northern germany this field based study focuses on the diagenetic control on spatial reservoir quality distribution the investigated outcrop consists of fluvial 4th order cycles which originate from a braided river dominated depositional environment westphalian c d stratigraphy sedimentary thicknesses and exposed fault orientations nnw sse and w e reflect tight gas reservoir properties in the region further north diagenetic investigations revealed an early loss of primary porosity by pseudomatrix formation present day porosity 7 on average and matrix permeability 0 0003 md on average reflect a high temperature overprint during burial the entire remaining pore space is occluded with authigenic minerals predominantly quartz and illite this reduces reservoir quality and excludes exposed rocks as tight gas targets the correlation of petrographic and petrophysical data show that expected facies related reservoir quality trends were overprinted by high temperature diagenesis the present day secondary matrix porosity reflects the telogenetic dissolution of mesogenetic ankerite cements and unstable alumosilicates faults are associated with both sealed and partially sealed veins near the faults indicating localized mass transport around w e striking faults dissolution is higher in leached sandstones with matrix porosities of up to 26 3 and matrix permeabilities of up to 105 md the dissolution of ankerite and lithic fragments around the faults indicates focused fluid flow however a telogenetic origin cannot be ruled out the results of this work demonstrate the limits of outcrop analog studies with respect to actual subsurface reservoirs of the greater area whereas the investigated outcrop forms a suitable analog with respect to sedimentological stratigraphic and structural inventory actual reservoirs at depth generally lack telogenetic influences these alter absolute reservoir quality values at the surface however the temperature overprint and associated diagenetic modification which caused the unusually low permeability in the studied outcrop may pose a reservoir risk for tight gas exploration as a consequence of locally higher overburden or similar structural positions

shrimp u pb zircon geochronology and geochemistry of metavolcanic and metasedimentary rocks in northwestern fujian cathaysia block china tectonic implications and the need to redefine lithostratigraphic units abstract northwestern fujian province is one of the most important pre palaeozoic areas in the cathaysia block of south china metavolcano sedimentary and metasedimentary rocks of different types ages and metamorphic grades granulite to upper greenschist facies are present and previously were divided into several formations and groups tectonic contacts occur between some units whereas deformed unconformities have been reported between others new shrimp u pb zircon ages presented here indicate that the original lithostratigraphy and the old group and formation terminology should be abandoned thus the tianjingping formation was not formed in the archaean or palaeoproterozoic as previously considered but must be younger than its youngest detrital zircons 1790 ma but older than regional metamorphism 460 ma besides magmatic zircon ages of 807 ma obtained from metavolcano sedimentary rocks of the nanshan formation and 751 728 ma for the mamianshan group many inherited and detrital zircons with ages ranging from 1 0 to 0 8 ga were also found in them these ages indicate that the geological evolution of the study area may be related to the assembly and subsequent break up of the rodinia supercontinent the new zircon results poorly constrain the age of the mayuan group as neoproterozoic to early palaeozoic 728 458 ma and not palaeoproterozoic as previously thought many older inherited and detrital zircons with ages of 3 6 2 8 2 7 2 6 2 5 2 0 1 8 and 1 6 ga were found in this study a 3 6 ga detrital grain is the oldest one so far identified in northwestern fujian province as well as throughout the cathaysia block nd isotope tdm values of eight volcano sedimentary and clastic sedimentary rock samples centre on 2 73 1 68 ga being much older than the formation ages of their protoliths and thus showing that the recycling of older crust played an important role in their formation these rocks underwent high grade metamorphism in the early palaeozoic 458 425 ma during an important tectono thermal event in the cathaysia block

lithological dependency and anisotropy of vitrinite reflectance in high rank sedimentary rocks of the ibbenburen area nw germany implications for the tectonic and thermal evolution of the lower saxony basin abstract covering a depth interval of 1200 m thirty one rock samples were collected from a well drilled in the beust field of the ibbenburen anthracite mine lower saxony basin nw germany these rock samples consist of high rank coals anthracites claystones siltstones and sandstones of pennsylvanian age analytical methods include the measurement of random vitrinite reflectance vr r rotational reflectance vr rot as well as maximum and minimum reflectances vr max and vr min enabling the evaluation of the lithological influence on vitrinite reflectance as well as the indication of tectonic stresses in the lower saxony basin by applying the ris reflectance indicating surface analysis method this study shows that not only due to the high rank of the studied samples and associated anisotropic character but also due to lithological dependency a partially significant scatter of measured vr r can be observed the scatter in coals is significantly less than in other sedimentary rocks e g standard deviation in coals can be up to 7 less than in siltstones the expected increase of standard deviation with increasing rank and accordant anisotropy was not observed for vr r but rather for vr max with the exception of coals displaying a relatively constant and low deviation throughout the depth maturity interval mean vr r values of coals differ from those of other sedimentary rocks at equal depths vr r measured in claystones is consistently higher compared to associated coal seams and can be elevated by up to 10 silt and sandstones always display lower vr r with differences of up to 16 at very high levels of thermal maturity vitrinite reflectance depends not only on maximum paleotemperature but also on lithology leading to differences in pressure propagation and thus deformation additionally radioactive trace elements in coals and organic matter rich claystones provide a local secondary heat source 40 k and 232 th are preferentially bound to clay particles which are enriched in the studied claystones and depleted in the silt and sandstones possibly leading to higher vitrinite reflectance observed in the claystones ris analysis shows a predominantly negative biaxial distribution indicating the absence of thermal overprinting by a possible intrusion bramsche massif during the late cretaceous which would have induced a uniaxial distribution instead this implies in addition to vertical stresses due to depositional loading the presence of a secondary stress field not perpendicular to bedding which is related to the inversion of the lower saxony basin this information presents in combination with previous basin modeling results additional evidence for deep subsidence with subsequent uplift being the cause for the present day maturity patterns observed in the lower saxony basin

allochthonous versus autochthonous organic matter in cenozoic sediments of the norwegian sea evidence for the onset of glaciations in the northern hemisphere the cenozoic sediments sampled in odp leg 104 on the voring plateau show a distinct variability of the total organic carbon content toc and the accumulation rates of toc based on the geochemical and organic petrographic characterization of the sedimentary organic matter om the allochthonous and autochthonous proportion of the om could be quantified the results clearly demonstrate that high toc percentages and toc accumulation rates in cenozoic sediment sections display a generally high input of allochthonous organic matter oxidized and partly well rounded organic particles built up the main portion of om within the miocene toc rich sediments the most probable source of this oxidized om are reworked sediments from the scandinavian shelf changes in the input of these organic particles are to some degree correlative with sea level changes the cenozoic accumulation of autochthonous om is low and does not reveal a clear variation during the miocene and early pliocene in spite of a high accumulation rate of biogenic opal during the early miocene the accumulation rate of autochthonous toc is low the autochthonous particle assemblage is dominated by relatively inert om like dinoflagellate cysts this points to an intensive biological and or early diagenetic degradation of the marine om under well oxidized bottom water conditions during the last 23 myr nevertheless a continuation of marine om degradation during later stages of diagenesis cannot be excluded a prominent dominance of allochthonous om over autochthonous is documented with the beginning of the pliocene at 2 45 ma the episodic occurrence of ice rafted thermally mature om reflects the onset of the glacial erosion of mesozoic coal and black shale bearing sediments on the scandinavian and barents sea shelves the first occurrence of these in view of the actual burial depth thermally overmature om particles is therefore a marker for the beginning of the strong scandinavian glaciation and the advance of the glacial front toward the shelves

nb ta fractionation in peraluminous granites a marker of the magmatic hydrothermal transition in their late stages of evolution peraluminous granitic melts exsolve large amounts of fluidswhich can modify the chemical composition of granitic whole rock samples the niobium tantalum nb ta ratio is expected to decrease during the magmatic differentiation of graniticmelts but the behavior of both elements at the magmatic hydrothermal transition remainsunclear using a compilation of whole rock geochemical data available in the literature wedemonstrate that fractional crystallization alone is not sufficient to explain the distribution ofnb ta in most peraluminous granites however we notice that most of the granitic samplesdisplaying evidence of interactions with fluids have nb ta 5 we propose that the decreaseof the nb ta ratio in evolved melts is the consequence of both fractional crystallization andsub solidus hydrothermal alteration we suggest that the nb ta value of 5 fingerprints themagmatic hydrothermal transition in peraluminous granites furthermore a nb ta ratio of 5appears to be a good marker to discriminate mineralized from barren peraluminous granites

gold and metal enrichment in natural granitic melts during fractional crystallization metal evolution in a composite granitic pluton was tracked by analyzing melt inclusions in 11 quartz samples from 7 zones at the timbarra gold deposit australia we present the first quantitative microanalyses of gold au in granitic silicate melt inclusions using laser ablation inductively coupled plasma mass spectrometry and show how au and other metals become enriched during fractional crystallization in a granite intrusion au was enriched during fractionation from a monzogranite to a highly fractionated alkali feldspar granite similar enrichment behavior for other metals implies that no gold enriched precursor melt is required and fractional crystallization can enrich the au concentration to economic levels the low content of accessory oxides and sulfides the absence of early cl bearing fluids the volatile content in the melt and a prolonged crystallization constitute important factors for extensive metal enrichment during crystal fractionation these characteristics play a crucial role in felsic highly fractionated plutons and their associated deposits such as intrusion related au deposits the gold enrichment during fractionation also implies that au is directly sourced from the granites

dehydration melting and water saturated melting of basaltic and andesitic greenstones and amphibolites at 1 3 and 6 9 kb

coalification history of the stephanian cinera matallana pull apart basin nw spain combining anisotropy of vitrinite reflectance and thermal modelling the stephanian cinera matallana basin of nw spain comprises 1 500 m of alluvial to lacustrine coal bearing sediments which were deposited in a late variscan transtensional transpressional pull apart setting the relationship between coalification pattern and rock deformation was evaluated by measurements of the anisotropy of vitrinite reflectance avr the avr ellipsoids reveal both pre tectonic elements related to the bedding fabric and syn tectonic elements related to folding producing biaxial ellipsoid shapes with the maximum reflectance parallel to fold axes the mean coalification gradient for the stephanian succession is about 0 62 rr km calculations of the mean palaeo geothermal gradient are presented on the basis of three different empirical equations a palaeo geothermal gradient of 85 c km is considered the most realistic with an overburden of about 1 000 m 1 d numerical modelling of the burial history results in two possible scenarios the most preferable involving a palaeo heat flow of 150 mw m2 and an overburden of ca 1 050 m these results indicate that maximum coalification was related to a localised but high palaeo heat flow geothermal gradient the anisotropy of vitrinite reflectance highlights the interactive and transitional nature of sedimentary compaction and rock deformation on the maturation of organic material within strike slip fault zones

experimental melts from crustal rocks a lithochemical constraint on granite petrogenesis abstract many studies of experimental petrology have devoted to partial melting of crustal rocks in order to provide lithochemical constraints on granite petrogenesis this paper presents a compilation and synthesis of available experimental data for the major element compositions of felsic melts derived from partial melting of natural or synthetic materials in the compositional range of crustal rocks the experimental melts are categorized into four types according to the species of hydrous minerals in starting materials i amphibole bearing ii amphibole and biotite bearing iii biotite bearing and iv biotite and muscovite bearing if dehydration melting takes place at normal crustal conditions p 5 10 kbar t 1000 c experimental melts are rich in sio 2 but poor in mgo feo t except those from amphibole bearing sources a comprehensive comparison of compositions between experimental melts and starting materials indicates that geochemical fractionation is variable for different major elements and their ratios source composition and melting temperature exert stronger controls on the compositional variations of experimental melts than pressure and fluid by comparing the experimental melts with natural granites the following insights into granite petrogenesis can be got 1 while peritectic assemblage entrainment may be the dominant mechanism for the compositional variations of garnet cordierite rich s type granites fractional crystallization of diverse melts from heterogeneous metasedimentary precursors probably governs the compositional variations of garnet cordierite poor s type granites 2 relatively k 2 o rich mafic to intermediate rocks are appropriate sources for calc alkaline i type granites the compositional variations of calc alkaline granites are jointly controlled by peritectic assemblage entrainment and subsequent fractional crystallization 3 while dehydration melting at t 950 c is appropriate for the production of ferroan and alkali rich granitic melts from intermediate magnesian tonalite or granodiorite it is also possible for ferroan alkali rich and fluorine rich granitic melts to be produced by dehydration melting of moderately magnesian mica bearing materials at t 900 c nevertheless the low t melts are more peraluminous than the high t ones therefore the composition of source rocks exerts the first order control on the composition of granitic melts in closed systems in addition the dehydration melting of crustal rocks under different conditions is also responsible for variations in the composition of granites

review and update of the applications of organic petrology part 1 geological applications abstract organic petrology developed as coal petrology at the beginning of the 20th century dedicated mainly to the study of coals because of their utilization in industry coal petrology was then considered a branch of coal science later with the development of specialized nomenclature classification of coal components and the standardization and improvement of analytical microscopical methods this discipline expanded in interests and name becoming organic petrology organic petrology carries a broader context being as well a tool applied in the study of dispersed organic matter in sedimentary rocks due to its importance in exploration for fossil fuel resources at present organic petrology is a discipline widely recognized for its role in fundamental and applied research with respect to both coal utilization and in geosciences throughout the 20th century several important monographs have been published on the discipline of organic petrology including stach s textbook of coal petrology 1st edition 1935 2nd 1975 3rd 1982 updated as the more general organic petrology by taylor et al 1998 more recently the text applied coal petrology the role of petrology in coal utilization was published by suarez ruiz and crelling 2008 this review is the first in a two part review series that describes and updates the role of organic petrology in geosciences a second part complementing this one and focused on the applications of organic petrology to other scientific fields will follow

geochronological geochemical and sr nd hf isotopic constraints on the petrogenesis of late cretaceous a type granites from the sibumasu block southern myanmar se asia abstract the late cretaceous to paleogene granitoids occur widespread in the sibumasu block within myanmar se asia which show a close association with tin tungsten mineralization however the precise timing petrogenesis and tectonic significance of these granitoids are poorly constrained so far in this study we present a detailed study on geochronology elemental and sr nd hf isotopic geochemistry for the hermyingyi and taungphila granites in southern myanmar with the aim of determining their petrogenesis and tectonic implications la icp ms u pb dating of zircon grains from the two granites yield ages of 69 70 ma indicating a late cretaceous magmatic event these granitic rocks are weakly peraluminous and belong to the high k calc alkaline series they are both characterized by high sio2 k2o na2o feot feot mgo and ga al ratios and low al2o3 cao mgo p2o5 and tio2 contents enriched in rb th u and y but depleted in ba sr p and eu suggesting an a type granite affinity moreover they display prominent tetrad ree patterns and non charac trace element behavior which are common in late magmatic differentiates with strong hydrothermal interaction or deuteric alteration the granites belong to a2 type and probably formed at a high temperature and anhydrous condition they have zircon ehf t values from 12 4 to 10 0 and whole rock end t values from 11 3 to 10 6 with paleoproterozoic tdm2 ages 1741 1922 ma for both hf and nd isotopes geochemical and isotopic data suggest that these a type granites were derived from partial melting of the paleoproterozoic continental crust dominated by metaigneous rocks with tonalitic to granodioritic compositions without significant input of mantle derived magma and followed by subsequent fractional crystallization by integrating all available data for the regional tectonic evolution in se asia and adjacent regions we attribute the formation of the late cretaceous a type granites to a back arc extension in the hinterland behind the subduction zone which is induced by the rollback of the flat neo tethyan subducting slab around ca 70 ma

petrology and genesis of upper carboniferous seams from the ruhr region west germany abstract the petrology of 21 seam profiles of upper carboniferous age westphalian c and b has been studied in order to determine their depositional environments and diagenetic history the youngest profile was drilled at a depth of 790 m and is mainly overlain by cretaceous sediments the oldest seam was reached at a depth of 1470 m the seam thicknesses vary from 0 4 to 2 5 m the main petrographic compounds are vitrinite intertinite liptinite and minerals the last group occurs as clay bands with illite kaolinite minor chlorite and minor quartz contents or as crack or pore filling calcite fe dolomite siderite pyrite or marcasite or as syngenetic siderite concretions and pyrite crystals the percentages of the different macerals and minerals vary mainly because of different depositional environments diagenetic loss or genesis of compounds is a less important factor in their distribution three types of profiles are distinguished by their different petrologies type i is most abundant and contains much vitrinite many clay bands and syngenetic iron sulfides whereas type iii is rich in inertinite and certain characteristic spores type ii is intermediate but generally contains only low percentages of minerals generally this type is vitrinite rich in the lower and inertinite rich in the central and upper parts of the profiles spores and other liptinites are much better preserved in all the seams than in clay partings or in siltstones and sandstones above and below the seams the seams are interpreted to be former autochthonous peats type i profiles are probably derived from swamps which were sometimes inundated and covered by overbank deposits type ii and iii seams represent former peats which were not inundated by rivers and partly grew under the influence of more oxidizing conditions therefore they contain more inertinite and less sulfide and clay bands they can be interpreted as former raised bogs diagenetic changes are expressed as increases of vitrinite reflectances from 0 65 to 1 0 and of liptinite reflectances a red shift of fluorescence of liptinites was found increasing amounts of exudatinite and micrinite and decreasing amounts of fluorinite and resinite were found minerals seem to be less affected by diagenesis illite crystallinity for example remains poor

isometamorphic variations in the reflectance and fluorescence of vitrinite a key to depositional environment abstract petrographic investigations of serial ply samples from five high to medium volatile bituminous coal seams from australia 4 and canada 1 reveal substantial in seam variations in the reflectance and monochromatic microfluorescence intensities of the maceral subgroup telovitrinite the variations consist of one case of reflectance enhancement and fluorescence suppression and four cases of reflectance suppression and fluorescence enhancement the single case of reflectance enhancement and fluorescence suppression is due to the oxidation of the vitrinite nuclei at the sequence boundary between the bayswater and upper wynn seams in new south wales the four cases of reflectance suppression and fluorescence enhancement result from the syn and epigenetic absorption by the vitrinite nuclei of hydrogen donated by presumably anaerobic bacteria generated lipids two of the coals are marine influenced the liskeard seam from the bowen basin by combined syngenetic and epigenetic effects and the greta seam from the sydney basin mainly by epigenetic contact with sea water for both coals the results are strong vitrinite reflectance suppression and fluorescence enhancement the remaining two coals the bulli seam from the sydney basin and a coal seam from the gates formation in british columbia show moderate epigenetic effects on the optical properties of telovitrinite by fresh water in the bulli seam which was studied in two adjacent localities the reflectance suppression and fluorescence enhancement of telovitrinite are stronger under sandstone roof than under shale roof in some cases the epigenetic effects are superimposed on syngenetic telovitrinite reflectance and fluorescence variations resulting from the cogeneration and mixing of different telovitrinite precursors for example autochthonous roots and hypautochthonous or allochthonous shoots a measure of the degree of dispersal and mixing is the coefficient of variation of telovitrinite reflectance and or fluorescence this coefficient correlates well with detrital minerals and dispersed macerals e g inertodetrinite and to a lesser extent sporinite some comments are made on slitted so called pseudovitrinite which is regarded as a telovitrinite that was subjected to very weak post coalification desiccation and possibly oxidation without losing much of its thermoplastic properties

should fluorescence alteration replace vitrinite reflectance as a major tool for thermal maturity determination in oil exploration abstract the fluorescence alteration multiple macerals famm technique is closely related to vitrinite reflectance until recently fluorescence alteration study of dispersed organic matter dom in sedimentary rocks has been regarded as technically difficult with the introduction of optical microprobes equipped with small continuous wave gas lasers having a very stable output of blue radiation readily focused to 1 2 m on the sample this work has now become routine famm has important advantages over vitrinite reflectance stemming from the possibility of resolving the data into two parameters one related to the level of maturation and the other related to the hydrogen richness of a maceral this enables the resolution of what are often difficult problems for the single parameter vitrinite reflectance technique namely the identification of indigenous vitrinite in dom the recognition of caved and reworked organic matter and the suppression of vitrinite reflectance for these reasons famm is a powerful tool for investigating vitrinite reflectance anomalies especially those associated with unconformities it is also well suited to investigate the tacit assumption in the vitrinite reflectance technique that all telocollinite matures along a single compositional pathway the famm technique is not without problems the range is restricted to equivalent mean random vitrinite reflectance rm o 0 4 1 2 the results are more sensitive to ambient temperature oxidation than vitrinite reflectance and the technique demands a high level of technical expertise the famm technique is calibrated on coals and it is therefore more likely to give high quality results on types ii and iii kerogens rather than type i kerogens which have not yet been intensively investigated although famm is unlikely to replace vitrinite reflectance considerable confidence may be had in a maturation assessment when consistent results are obtained from these two closely related but independent techniques

organic matter maturation under the influence of a deep intrusive heat source a natural experiment for quantitation of hydrocarbon generation and expulsion from a petroleum source rock toarcian shale northern germany four shallow boreholes were drilled in the hils syncline northern germany in order to determine quantitatively the amount of hydrocarbons generated and expelled during maturation of a typical kerogen type ii bearing source rock the holes penetrated the carbonceous lias shales posidonia shale lower toarcian and part of the adjacent dogger and lias mudstones the maturity of the organic matter in the cores recovered ranges from immature 0 48 r0 to overmature 1 45 r0 due to location of the hils syncline in the vicinity of the vlotho massif which is deep seated intrusive body facies variations of the lias within the short geographical distances in the study area are negligible organic matter mass balance calculations were based on detailed organic geochemical analyses of residual material in the lias shales kerogen bitumen etc and on the evidence of a uniform initial composition of these sediments in the study area dead carbon determinations supported this latter criterion but were not used as a parameter in the calculations about 50 of the initial kerogen was transformed into oil gas and inorganic compounds during the vitrinite reflectance increase from 0 48 to 0 88 ro and only marginally more during the maturity increase from 0 88 to 1 45 ro only a small portion of the generated material remained in the source rock even at a relatively early stage of generation 0 68 ro expulsion efficiency of oil plus gas reached a value of 86 at the end of the main generation stage 0 88 ro

gas generation from source rocks aspects of a quantitative treatment abstract quantitative aspects of gas generation in source rocks are discussed first in terms of stoichiometric considerations based on the elemental compositions of different kerogen types i ii iii and coal the maximum amounts of available carbon and hydrogen for the formation of hydrocarbons during maturation were calculated considering a closed source rock system type i kerogen has the highest and coal the lowest specific gas yield the second part discusses the problem whether experimentally derived gross kinetic parameters activation energies and frequency factors can be applied to hydrocarbon generation reactions in the geological environment the third part comprises a detailed case history of gas formation in the upper carboniferous of northern germany for three selected wells in the study area the temperature histories were defined using a computer aided integrated basin modelling approach significantly different temperature histories in those three wells were then used to compute the gas generation from 320 myr ago to present the drastic influence of changes in the kinetic input parameters 50 or 54 kcal mol 1 for the activation energy of oil cracking on timing and duration of gas formation has been demonstrated the results confirmed that accurate knowledge of both the temperature history and the kinetic parameters is of equal importance

hydrocarbon distribution in coals and in dispersed organic matter of different maceral compositions and maturities more than 60 samples from 5 coal seams and adjacent siltstones and sandstones were selected from a well through westphalian b sediments from northern germany in order to study bitumen generation and migration the cores were drilled between 1200 und 1530 metres depth in this interval vitrinite reflectance rr is increasing from 0 70 to 0 92 results reveal high hydrocarbon generation potentials for all coal samples but not for adjacent clastic rocks although maceral compositions of both are quite similar yields and compositions of thermal extracts from the coals depend on maceral compositions and rank however the bulk of the already generated bitumen has not been removed during natural coalification and is not easily releasable by thermovaporisation a mass balance based on elemental composition of dull coals indicates that in the rather narrow rank interval 0 70 0 92 rr a total mass loss of 20 may have occurred by migration this is evidenced by a loss of about 20 of the original hydrogen the rest being stored in the coals

insights into the effects of matrix retention and inert carbon on the petroleum generation potential of indian gondwana shales abstract the rock eval pyrolysis and total organic carbon toc analysis technique is widely used for organic geochemistry screening of source rocks and potential unconventional petroleum reservoirs the rock eval derived parameters the hydrogen index hi which is the ratio between hydrocarbons released under the s2 curve hydrocarbon formed by thermal pyrolysis s2 is an indicator of petroleum generation potential and total organic carbon toc can be used to infer the type of organic matter present in a rock however hi is often under estimated due to retention of some hydrocarbons included under the s2 curve by the rock matrix and the presence of inert carbon within the rock here we describe and correct the matrix retention and inert carbon effects on hydrocarbon generation from a suite of shale samples from indian gondwana shale reservoirs removal of the petrographically identified inert carbon component from the samples tested leads to less scatter in the toc s2 relationship obtained the ratio of volume percentage of organic matter identified through optical microscopy to toc is calculated and that ratio was least in the one heat affected sample but higher in low toc shales 12 5 with decreasing toc content in the sample set analyzed the corrected hi values calculated using the s2 toc intercept increase significantly this correction can therefore lead to false indications about the type of organic matter present a key novel finding of this work is the need while correcting hi for matrix retention effects to consider samples with a specific range of toc contents and to match them to the kerogen types present e g types iii and iv in the samples analyzed filters should also be applied to adjust for the degree of thermal maturity and organic facies

petroleum generation and migration in coal seams of the carboniferous ruhr basin northwest germany a series of 64 coal and clastic rock samples of westphalian age was taken from five narrow 3 m depth intervals between 1200 and 1530 m depth and studied by geochemical and petrological methods maturity increases regularly with increasing depth as indicated by several maturity parameters the influence of organic facies is evident in the uppermost coal seam 0 70 rr where a hand picked vitrinite contains less total extract and less saturated long chain hydrocarbons than a directly adjacent sporinite rich coal extracts from deeper and more mature coals are less affected by facies changes probably due to enhanced petroleum redistribution in the seams total yield and gross composition of extracts in the deepest seam 0 92 rr which is directly overlain by sandstone seem to be influenced by the preferential expulsion of saturated hydrocarbons

the permian sn metallogenic event and its geodynamic setting in east kunlun nw china evidence from zircon and cassiterite geochronology geochemistry and sr nd hf isotopes of the xiaowolong skarn sn deposit abstract abundant granitoids are exposed along the east kunlun orogenic belt ekob and many skarn deposits occur at the contacts between intrusions and strata one such is the xiaowolong deposit a skarn type tin polymetallic deposit that is temporally and spatially associated with porphyry monzogranite tin mineralization is mainly hosted by the skarn in this study we reported zircon and cassiterite u pb ages whole rock geochemistry and sr nd hf isotopic data and used these to constrain the timing of intrusion and mineralization in the xiaowolong deposit and identify the origin of the ore related granites and the link between sn mineralization and granitic magmatism age determinations by la icp ms u pb zircon dating indicated that the porphyry monzogranite formed at 260 0 0 7 ma cassiterite from the ore bearing skarn yielded a tera wasserburg u pb lower intercept age of 258 0 3 7 ma these ages suggested that both granitic intrusion and related sn mineralization in the xiaowolong deposit were initiated during the permian ca 260 ma the porphyry monzogranites had high sio2 71 26 73 13 wt and al2o3 13 84 14 46 wt contents were alkali enriched k2o na2o 7 08 7 69 wt had a cnk values that ranged from 1 01 to 1 05 were enriched in light rees and large ion lithophile elements such as rb th u and k were depleted in high field strength elements and had relatively low zr nb y and ce contents they thus exhibited the geochemical characteristics of i type granite the porphyry monzogranite had consistent negative whole rock nd t 6 8 to 7 1 and magmatic zircon hf t values ranging from 7 4 to 1 6 and two stage hf model ages ranging from 1393 ma to 1758 ma detailed elemental and isotopic data demonstrated that the porphyry monzogranite were derived from partial melting of ancient crustal source and emplacement in a subduction tectonic setting the xiaowolong tin mineralization event indicated that the ekob has great potential for exploration focusing on permian triassic sn skarn deposits

thermal maturity evaluation from inertinites by raman spectroscopy the ramm technique abstract a new thermal maturity evaluation tool ramm raman maturity method enables determination of equivalent vitrinite reflectance from raman spectra of inertinite except for the avoidance of liptinites the method does not require identification of maceral type measured assemblages ranging from all inertinite to all vitrinite are suitable the method uses five parameters derived from the first order vibrational spectrum of carbon data from about a dozen humic grains are averaged although a reasonable estimate of thermal maturity can be obtained from a single inertinite grain ramm yields equivalent vitrinite reflectance ramm eqvr values based on a multilinear regression equation derived from data on 163 macerals from ten reference coals having vitrinite reflectances ranging from 0 4 to 1 2 cross calibration on the reference coals and application to a suite of 14 other coals spanning this rank range agree well with measured vr values limited data on isometamorphic coals suggest that ramm eqvr can solve the problems caused by vitrinites with high h c atomic ratios and consequent suppressed vitrinite reflectance this is accomplished by deriving normal reflectance values in a similar way as inertinites with low h c are referred back to their equivalent vitrinite reflectance values the ramm method is affected by post sampling maceral oxidation but to what degree is uncertain at present the methodology and calibration have been established and future work will demonstrate applications to dispersed organic matter in samples from petroleum exploration wells especially where vitrinite is absent or rare

comparative organic petrology of interlayered sandstones siltstones mudstones and coals in the upper carboniferous ruhr basin northwest germany and their thermal history and methane generation in the coal mining ruhr area upper carboniferous rocks ca 4000 m consist of interlayered sandstones siltstones mudstones and coals they were deposited in a tropical paralic environment where alternating fluvial sedimentation occasional marine ingressions and swamp growth resulted in an irregular cyclic succession the total sedimentary package contains on an average 6 vol of organic matter about 70 vol of the organic matter occurs in coal seams the rest as dispersed organic matter in clastic rocks the organic matter is autochthonous in the coals and allochthonous in associated sandstones and siltstones it consists of about 70 vitrinite 20 inertinite and 10 liptinite the overall maceral group composition is the same for coals and dispersed organic matter this surprising similarity is caused by a nearly exclusive input of land plant derived organic matter to swamps and fluvial systems and a similar degree of preservation highest average liptinite contents of total macerals were found in unrooted mudstones highest average inertinite contents in coarse grained siltstones and highest average vitrinite percentages in sandstones

maturity modelling integrated with apatite fission track dating implications for the thermal history of the mid polish trough poland abstract the mid polish trough mpt is situated in the easternmost part of the central european basin system cebs and stretches nw se across the polish basin it was characterised by pronounced subsidence and thick sediment accumulation between the permian and the late cretaceous late cretaceous early paleogene basin inversion led to the formation of the mid polish swell mps the study area is located within the pomeranian segment of the mpt mps nw poland and experienced up to 7 km permian mesozoic subsidence petromod 1 d modelling was performed on several well sections in order to study permian to recent burial uplift evolution the modelling was calibrated with new vitrinite reflectance vrr data and allowed to constrain the magnitude of uplift and related erosion as well as provided a first overview of the temperature history the base of the studied permian mesozoic successions attained maximum burial depths of 4800 5400 m before the onset of the inversion less than in the axial trough area the thickness of pre and most probably also syn inversion upper cretaceous deposits is estimated as 300 m erosion associated with inversion processes removed between 900 and 1400 m of the mesozoic sediments i e 1000 1500 m less than in the most inverted central part of the trough vrr data suggest constant permian mesozoic heat flows corresponding to present day values 40 45 mw m2 apatite fission track aft ages modelled with the petromod module petrotracks show a good fit with aft ages directly measured on well samples and further support the assumption of steady heat flow in the range 40 45 mw m2 palaeotemperatures appear to have decreased towards the east european craton margin which is compatible with the present day distribution of heat flow thermal history modelling shows a relatively simple permian mesozoic heat flow pattern in the pomeranian segment of the mpt such a scenario implies that the present day heat flow distribution has not changed essentially since mesozoic times

optical properties of organic matter in relation to thermal gradients and structural deformation the general response of macerals to the coalification process the effectiveness of organic geochemical and petrological parameters as estimators of coalification and the applicability of different microscopical parameters in the assessment of rank are reviewed the central role of vitrinite reflectance as the most widely used estimator of coalification from brown coals to the low grade metamorphic zone is established on the basis of its relatively uniform variation with rank specificity ease and rapidity of measurement and cheapness factors influencing the optical properties ofvitrinites are considered temperature has the dominant influence in modifying optical properties with rank but time static pressure and stress can all have significant influences upon the course of optical properties depending upon particular geological conditions static pressure has a retarding effect on the coalification process but it is also responsible for creating increasing anisotropy within the condensing aromatic structures as rank rises hydrostatic pressures and pore pressures can contribute to the overpressuring of sediments thus affecting their thermal conductivities and consequently the rate of coalification stress is responsible for the development of biaxicity in the reflectance indicatrix fast and high levels of heating from igneous bodies cause textural effects on vitrinites as a result of carbonization that are quite different from those of coalification recognizing these different influences upon the optical properties of vitrinites examples are given of the use and application of vitrinite reflectance in the preparation of rank maps in the burial histories of basins in the timing of coalification in relation to orogenesis and igneous activity and in the zones of anchimetamorphism and low grade metamorphism consideration is also given to the problem of provincialism in correlations between chemical and physical parameters and to the future development of optical studies in organic petrology and their relation to organic geochemical investigations

fluid inclusion and isotopic c h o s and pb constraints on the origin of late mesozoic vein type w mineralization in northern guangdong south china abstract northern guangdong of south china occurs many large tungsten deposits including shirenzhang meiziwo and yaoling quartz vein type wolframite deposits in this study we carried out a detailed study on fluid inclusions and c h o s pb isotopic analyses of mineral separates for these three deposits in order to resolve the origin and evolution of ore forming fluids and the ore deposition mechanism the ore veins in these deposits present a similar mineral paragenesis that could be divided into three stages i pre ore stage ii syn ore stage and iii post ore stage the pre ore stage is the magmatic hydrothermal transition stage which is marked by fluid exsolution from the highly fractionated granites accompanied with potassic alteration and greisenization the syn ore stage can be further divided into two stages silicate oxide stage stage ii 1 that is characterized by significant tin tungsten mineral deposition and sulfide stage stage ii 2 that is characterized by abundant sulfide minerals deposition the post ore stage is dominated by quartz and fluorite the three deposits show similar temperature and salinity variations for syn ore and post ore stages in the shirenzhang deposit the fluid temperature and salinity range from 239 to 301 c and 1 4 to 8 7 wt nacl equiv in stage ii 1 from 206 to 256 c and 1 4 to 7 0 wt nacl equiv in stage ii 2 and from 186 to 236 c and 1 4 to 8 6 wt nacl equiv in stage iii in the meiziwo deposit the fluid temperature and salinity range from 242 to 310 c and 1 1 to 8 6 wt nacl equiv in stage ii 1 from 196 to 252 c and 1 4 to 8 1 wt nacl equiv in stage ii 2 and from 188 to 234 c and 1 2 to 7 3 wt nacl equiv in stage iii in the yaoling deposit the fluid temperature and salinity range from 230 to 304 c and 1 2 to 9 0 wt nacl equiv in stage ii 1 from 203 to 258 c and 1 4 to 6 5 wt nacl equiv in stage ii 2 and from 184 to 231 c and 1 6 to 8 3 wt nacl equiv in stage iii the ore forming fluids in the three deposits belong to a medium temperature low salinity h2o nacl system with trace amounts of volatile components including co2 ch4 and n2 the c h o isotope data 13cco2 18 9 to 6 7 18owater 1 1 to 6 3 dh2o 78 to 55 indicate that the ore forming fluids were mainly magmatic water which might be modified by fluid rock interaction and mixing with meteoric water sulfur 34s 7 0 to 0 3 and pb isotope data 206pb 204pb 18 531 18 693 207pb 204pb 15 728 15 753 208pb 204pb 38 902 39 081 suggest that the ore metal and sulfur are of magmatic origin the involvement of both organic matter in metasedimentary rocks during fluid rock interaction and oxidized meteoric water may have been responsible for the negative 34s and 13c values fluid boiling fluid rock interaction and minor input of meteoric water might have been effective factors for the precipitation of wolframite cassiterite and scheelite the sulfide precipitation may have resulted from cooling and dilution of magmatic fluids by mixing with meteoric water

geochemical factors revealing the differences between the xitian and dengfuxian composite plutons middle qin hang belt implications to the w sn mineralization abstract the xitian and dengfuxian ore fields located in the middle qin hang belt are known for hosting large scale w sn polymetallic deposits the xitian ore field hosts a series of small to large scale sn w deposits including skarn quartz vein and structurally altered rock type whereas the dengfuxian ore field mainly contains a medium scale quartz vein type w deposit these granitic rocks are composed of ore barren triassic and ore related jurassic granites in this study la icp ms zircon u pb dating of three representative samples from dengfuxian triassic granites dtg xitian jurassic granites xjg and dengfuxian jurassic granites djg yields weighted mean 206pb 238u ages of 231 2 2 5 ma 152 5 1 2 ma and 155 9 1 6 ma respectively chemical compositions of the xitian triassic granites xtg and dtg indicate that they belong to relatively lower fractionated granites whereas the xjg and djg are highly fractionated granites the xtg and dtg have similar lu hf isotopic compositions which have peak ehf t values of ca 5 9 and tdmc ages of ca 1 57 ga and peak ehf t values of ca 5 7 and tdmc ages of ca 1 57 ga respectively however the xjg have higher peak ehf t values of ca 5 4 and younger tdmc ages of ca 1 52 ga than those of the djg with peak ehf t values of ca 7 6 and tdmc ages of ca 1 70 ga respectively furthermore the xtg have end t values of 10 5 to 9 40 and nd model ages tdm2 of 1 86 to 1 76 ga which are similar to those of the dtg with end t values of 11 7 to 9 67 and nd model ages tdm2 of 1 95 to 1 79 ga wu et al 2016 cai et al 2015 the xjg have end t values of 11 0 to 9 1 and younger tdm2 ages of 1 69 1 84 ga which are fairly distinct to the reported nd isotopes of the djg cai 2013 it is proposed that the xtg and dtg were originated from the similar magma chamber and formed from partial melting of the proterozoic basement rocks of the south china block scb at low temperatures ca 690 c and oxygen fugacity log fo2 values of ca 17 involved with a certain amount of mantle derived magma magmas of the xjg and djg might be mainly originated from the partial melting of proterozoic basement rocks of the scb in contrast the formation of xjg and djg are involved with a considerable and little mantle derived magma respectively in addition the magma temperatures and log fo2 values of xjg are of ca 856 c and ca 15 respectively which are higher than those of the djg ca 716 c and ca 17 that the xitian and dengfuxian triassic granites did not induce w sn mineralization is likely attributed to their low fractionated signatures the key factors leading to the sn w mineralization in the xitian ore field and w mineralization in the dengfuxian ore field might be magma source and temperature since additional sn could be provided by the mantle and or released by melting of those sn bearing minerals at high temperatures over than 780 c

origin of the granites and related sn and pb zn polymetallic ore deposits in the pengshan district jiangxi province south china constraints from geochronology geochemistry mineral chemistry and sr nd hf pb s isotopes the pengshan sn and pb zn polymetallic deposits are located in the south margin of the jiujiang ruichang jiurui district of the middle lower yangtze river metallogenic belt in south china four large deposits include huangjinwa zengjialong jianfengpo and zhangshiba the former three are sn dominant deposits which occur as stratiform orebodies in the contact zones of the pengshan granites and within the country rock strata whereas zhangshiba consists of stratiform pb zn orebodies within the precambrian metasedimentary strata in this study we present results on zircon u pb ages major and trace elements and mineral chemistry as well as sr nd hf isotope data of the granites pb and s isotopes of both the sn dominant and pb zn dominant deposits and u pb dating of cassiterite from the pengshan district shrimp and la icp ms zircon u pb dating shows that the pengshan granites were emplaced in the early cretaceous 129 128 ma which is in good agreement with the u pb dating 130 128 ma of cassiterite from the jianfengpo sn deposit the pengshan granites consist mainly of weakly peraluminous highly fractionated i type affinity granitic rocks detailed elemental and isotopic data suggest that the granites formed by partial melting of mesoproterozoic metamorphic basement materials with minor input of mantle derived melts the mineral chemistry of biotite demonstrates that the pengshan granitic magma had a low oxygen fugacity thereby precluding the tin dominantly partitioning into the rock forming silicate minerals and favoring accumulation in the exsolved residual liquid during magma crystallization stages sulfur isotopes show a relatively heavy sulfur isotopic composition from 5 8 to 17 6 and no difference for sulfur isotopes between the sn deposits 5 8 13 4 huangjinwa zengjialong jianfengpo and the pb zn deposit mostly 7 1 13 0 except for one 17 6 zhangshiba the sulfur isotope data of pyrite from the host sedimentary rocks show relatively higher 34s values of 22 7 28 7 lead isotopes indicate that the granites have higher 206pb 204pb 207pb 204pb and 208pb 204pb ratios than the host precambrian metasedimentary rocks and the sulfide minerals from the orebodies fall in between them again there is no difference for pb isotopes between the sn deposits huangjinwa zengjialong jianfengpo and the zhangshiba pb zn deposit the coincidence in s and pb isotope compositions for sn and pb zn deposits suggests that similar sources for these mineralization possibly derived from a mixed source of the granitic magmas and the precambrian metasedimentary rocks these data therefore favor of a magmatic hydrothermal origin for both the sn and pb zn polymetallic mineralization in the pengshan district

middle to late jurassic felsic and mafic magmatism in southern hunan province southeast china implications for a continental arc to rifting abstract extensive middle to late jurassic felsic and mafic magmatism occurred in the southern hunan province southeast china shrimp zircon u pb dating mineral chemical element geochemical and sr nd hf isotopic data have been determined for these rocks the results indicate that the middle jurassic 178 170 ma changchengling and ningyuan basaltic rocks belong to tholeiitic series and alkaline series respectively and were formed by fractional crystallization of the parent magmas that were derived from partial melting of asthenospheric mantle triggered by the slab released fluids of the subducted paleo pacific plate the late jurassic 152 146 ma daoxian basalts and guiyang lamprophyre dikes are low ti high mg potassic rocks they were derived directly by partial melting of shallower 60 100 km lithospheric mantle composed of amphibole and phlogopite bearing lherzolite in response to thermal perturbations associated with the rifting of continental arc the middle jurassic 164 ma tongshanling granitic rocks belong to calc alkaline series and are strongly peraluminous they were formed by partial melting of palaeoproterozoic metasedimentary basement in the lower crust plus additional input from coeval basaltic magma the late jurassic 156 ma jinjiling and xishan granitic rocks show a2 subtype affinity they were generated by partial melting of granulitized palaeoproterozoic metamorphic basement in the lower crust in response to injection of coeval low ti high mg potassic magmas a moderate degree 56 58 of fractionation of these pure crustal melts could account for more felsic end member of granitic rocks detailed petrologic and geochemical data for the middle to late jurassic felsic and mafic rocks from the southern hunan imply that during the middle jurassic time se china on the southeast of the shi hang zone was a continental arc coupled with the subduction of the palaeo pacific plate and since the beginning of late jurassic time an intra arc rift has been formed along the shi hang zone as a consequence of slab roll back

nature of source material for hydrocarbons in cooper basin australia the cooper basin which produces a large proportion of australia s natural gas also includes small oil fields source rocks for the hydrocarbons are believed to be the terrestrial coal measure sediments of the permian gidgealpa group dispersed organic matter in the sediments of the gidgealpa group in the patchawarra trough cooper basin ranges between 1 and 5 by volume through seven formations less than 10 of the dispersed organic matter is exinite and less than 30 is vitrinite if these two macerals only are considered as source material for the liquid hydrocarbons none of the formations contains the 0 5 organic carbon currently deemed necessary for a sediment to be classified as a source rock if inertinite is regarded to have generating potential then most of the formations rate as good to excellent source rocks recent studies on vitrinites and inertinites from a variety of coal seams suggest that if vitrinite is accepted as a possible source of liquid hydrocarbons then inertinite is equally prospective consequently dispersed inertinite in the gidgealpa group sediments is proposed as one of the sources for the liquid hydrocarbons in the cooper basin

the world class nanling metallogenic belt jiangxi china w and sn deposition at 160 ma followed by 30 m y of hydrothermal metal redistribution abstract the w sn maoping deposit and related w sn deposits from the world class nanling range in southeast china formed at ca 160 ma and experienced several phases of metal addition and metal redistribution between 160 and 130 ma isotopic dating of ore mineral wolframite of maoping demonstrates that w was deposited first during a hydrothermal event at ca 160 ma successive fluid episodes at ca 156 ma mo and sn rich fluid and 152 ma ree rich fluid resulted in the formation of ree and fe cu zn sulfide minerals a last fluid event occurring at ca 130 ma was responsible for the deposition of zr ree nb ta minerals that are attributed to magmatic fluids derived from unexposed magmatic bodies the three episodes of fluid circulation post dating w deposition resulted in partial to complete resetting of the isotopic systems mica wolframite xenotime which are conventionally used for dating such deposits we show that w and sn mineralization in the nanling range formed during a unique fluid event at ca 160 ma later fluid episodes redistributed the previously deposited metals and sequentially introduced additional metals including mo sn fe cu zn and zr ree nb ta direct dating of paragenetically well constrained minerals is therefore critical for determining the age and the duration of mineralizing processes and for characterizing the fluid evolution of magmatic hydrothermal systems as exemplified in the nanling range

highly fractionated jurassic i type granites and related tungsten mineralization in the shirenzhang deposit northern guangdong south china evidence from cassiterite and zircon u pb ages geochemistry and sr nd pb hf isotopes abstract the shirenzhang tungsten deposit is a classic wolframite quartz vein type deposit located in northern guangdong province eastern segment of the nanling w sn polymetallic belt the ore veins controlled by the nw striking fault system are mainly hosted in the ordovician metasedimentary rocks and can also be found with less amount in the cupola of the concealed granitic stock displaying a typical five floor vertical zonation proposed by the chinese geologists the concealed granitic stock mainly comprises two intrusive facies the porphyritic biotite granite g1 in the outer zone and the medium to fine grained monzogranite g2 in the inner zone in this paper we report new cassiterite u pb ages and pb isotopes of sulfides for the shirenzhang tungsten deposit combined with new zircon u pb ages and hf isotopes elemental geochemistry and sr nd pb isotopes of the concealed granitic rocks with aims to elucidate the origin of the ore related granites and the link between the tungsten mineralization and granitic magmatism la icp ms zircon u pb dating gives the weighted mean ages of 164 2 ma for g1 and 162 4 ma for g2 respectively cassiterite from the wolframite bearing quartz vein and the drusy quartz vein yield the weighted mean ages of 164 2 ma and 160 2 ma respectively these ages suggest that both the granitic intrusion and related w sn mineralization in the shirenzhang deposit were initiated during the late jurassic ca 160 ma the shirenzhang granitic rocks are weakly peraluminous highly fractionated i type granites detailed elemental and isotopic data demonstrate that the granitic rocks were derived from partial melting of the paleoproterozoic basement rocks at a relatively shallow depth of 30 km triggered by underplating of basaltic magma and underwent extensive fractional crystallization of hornblende biotite feldspar and monazite and or allanite a continental arc setting induced by northwesterly subduction of the paleo pacific plate is suggested for the genesis of the shirenzhang i type granites the comparable pb isotopic compositions of feldspar and sulfides imply that the lead in the ore veins was of magmatic origin integrating the spatial temporal relationship between the ore veins and the concealed granitic rocks with the pb isotopes from the sulfides and granites we suggest that the tungsten mineralization is genetically linked with the concealed granitic rocks in the shirenzhang deposit fractional crystallization and melt fluid interaction may play an important role on the formation of the granite related tungsten mineralization

relict proterozoic basement in the nanling mountains se china and its tectonothermal overprinting 1 the basement beneath the caledonian belt in se china has been overprinted by indosinian and yanshanian events and is poorly known in situ u pb and hf isotope analysis of zircons from granites and surrounding rocks in the nanling mountains area of the fold belt reveal that the lanhe felsic gneiss is an outcrop of mesoproterozoic basement probably with a partly late archean protolith this is consistent with nd model ages of granites in this region and exposures of cathaysia basement in the coastal area of se china in the nanling mountains this basement was reactivated to generate granitoid rocks during the caledonian indosinian and yanshanian tectonothermal events the caledonian overprint is documented in extensive exposures of the zhuguang migmatites 425 470 ma and by previous u pb zircon dating of adjacent granites the jiangnan granite may be of similar age but strongly reworked the indosinian overprint resulted in the formation of granites such as the luxi and xiazhuang bodies 233 246 ma in the guidong complex the yanshanian overprint produced the most widely distributed granites circa 160 ma such as the jiufeng and fogang bodies and parts of the guidong complex hf isotope data show that all of the phanerozoic magmatic rocks were derived from the mesoproterozoic basement and minor archean components without obvious contributions from juvenile sources the presence of zircons with archean age 2 5 2 7 ga in both the lanhe gneiss and devonian sediments indicates that the badu and mayuan groups may not be the oldest basement of the cathaysia block some archean basement circa 2 5 2 7 ga may still be exposed but unrecognized in this region and cathaysia may include archean microcontinental fragments

high precision u pb zircon ages for mesozoic igneous rocks from hong kong abstract sixteen new high precision u pb zircon ages are reported from jurassic and early cretaceous silicic volcanic and plutonic rocks of hong kong when combined with the existing age dataset the new ages constrain more tightly the timing of major periods of volcanism and plutonism at 162 6 4 5 ma 146 7 1 1 ma 143 0 1 0 ma and 140 8 0 6 ma however two ages of 151 9 0 2 ma and 148 1 0 2 ma from eastern new territories and southern hong kong indicate additional and therefore more continuous albeit pulsed magmatic activity than previously thought

the crust of cathaysia age assembly and reworking of two terranes abstract u pb dating and hf isotope data from detrital zircons have been used to analyse the crustal evolution of the eastern and western parts of the cathaysia block in se china zircons from the oujiang river in eastern cathaysia indicate that the basement is dominantly paleoproterozoic 1850 1870 ma 2100 2400 ma in age with minor archean components it was extensively reworked in jurassic cretaceous time 100 155 ma to produce the widespread yanshanian magmatic suite both the 1850 1870 ma event and the yanshanian magmatism show wide ranges in hf isotope composition consistent with mixing between crustal and juvenile magmas marked downstream changes in the relative proportions of zircon age populations emphasize the care required in using detrital zircon data to estimate continental growth rates zircons from the north river indicate that the crust of western cathaysia was generated mainly during neoproterozoic time although it contains some archean 2500 3500 ma to mesoproterozoic components this crust was strongly reworked during caledonian ca 450 ma indosinian ca 240 ma and early yanshanian ca 160 ma thermal events there is little evidence for juvenile crustal growth in any of these events although the yanshanian granitoids of the eastern and western parts of the cathaysia give similar mean hf model ages consistent with published nd model ages this is a coincidence they have different crustal sources the distinct patterns of crustal evolution suggest that eastern and western cathaysia may represent separate microcontinents accreted to the older yangtze craton and transposed by extensive strike slip faults

multiple origins for the middle jurassic to early cretaceous high k calc alkaline i type granites in northwestern fujian province se china and tectonic implications abstract a comprehensive study of zircon u pb dating and in situ hf isotopes whole rock major and trace element geochemistry and sr nd isotopes was carried out for three late mesozoic granitic plutons waitun shipi and taiyuan in northwestern fujian province se china we assess the origin of the granites and their relationship to the evolution of the late mesozoic volcanic intrusive complex belt in se china la icp ms zircon u pb dating shows that three plutons were emplaced in the middle jurassic to early cretaceous 168 109 ma in which the waitun and shipi plutons are intrusive complexes all the plutons are composed of high k calc alkaline i type granites with a great diversity in elemental and isotopic compositions the granites have sio 2 contents of 68 3 78 5 wt showing a gradual decrease in initial 87 sr 86 sr 0 7181 to 0 7091 and increase in e nd t 16 7 to 8 1 and e hf t in situ zircon 20 6 to 6 9 with decreasing emplacement ages geochemical data suggest that the middle jurassic 168 ma waitun granites are of purely crustal origin derived by partial melting of a mixed source of paleoproterozoic metaigneous 78 and metasedimentary 22 rocks at a depth of 30 40 km triggered by underplating of basaltic magma mixing of such crustal melts with about 10 basaltic magma could account for the origin of the late jurassic 161 ma waitun granites the late jurassic 156 ma shipi and early cretaceous 134 ma taiyuan granites were produced by extensive fractional crystallization of primary crustal melts the source of which show relatively high proportion 82 of metaigneous rocks the early cretaceous 109 ma shipi granites were generated by partial melting of a mixed source of paleoproterozoic metaigneous 92 and metasedimentary 8 rocks at a depth of 30 km plus additional 15 input from coeval basaltic magma the granites were formed in a continental arc setting induced by northwestward subduction of the paleo pacific plate progressive slab rollback since the middle jurassic from inland to the coastal area is the most likely mechanism for the generation of the granites

fluvial channel and overbank deposits from the westphalian of the durham coalfield ne england the westphalian upper carboniferous coal measures of the durham coalfield in ne england were deposited in lower and upper delta plain environments distributary channels crossed the plain and were separated by shallow interdistributary lakes and bays detailed observation of three dimensional 3 d opencast surface mine exposures in collaboration with subsurface borehole analysis has revealed the existence of five varieties of channel deposits and two associated overbank facies within the durham coal measures major distributary channels were the major avenues of sediment transport across the coal measures plain were variably sinuous mostly 1 2 km wide and deposited elongate belts of sand mostly up to 5 km wide proximal major crevasse splay channels formed by the breaching of major channel banks during flood events were straight sand filled and up to 400 m wide minor distributary channels formed by the sustained operation of such crevasses varied from straight to highly sinuous and deposited shoestring sand mud belts up to a few hundred metres wide minor crevasse channels generally straight and up to 50 m wide were formed through bank breaching of minor and in a few cases major distributaries distal feeder channels formed down palaeocurrent extensions of minor distributaries which supplied interdistributary minor delta subsystems were generally straight and up to 200 m wide of the two types of channel overbank levee deposits recognized one comprising thinly interbedded fine grained sandstone and siltstone claystone is mostly though not exclusively associated with major distributary channels the other consisting of massive siltstones with regularly spaced thin claystone bands is uniquely developed at the margins of minor distributary channels the lower part of the westphalian a succession in the northern pennines records a change in the depositional environment upwards from a lower to upper delta plain through this transition major channel deposits show evidence of having evolved from being of dominantly low sinuosity to being more variable in morphology channel sedimentation was profoundly influenced by regular possibly seasonal variations in flow stage and sediment load

u pb geochronology and hf nd isotopic geochemistry of the badu complex southeastern china implications for the precambrian crustal evolution and paleogeography of the cathaysia block abstract the oldest rocks of the cathaysia block south china comprise the badu complex and paleoproterozoic granites in the wuyishan area southern zhejiang and northwestern fujian provinces new zircon u pb ages hf isotopes and trace elements for metamorphic rocks from the badu complex and bulk nd isotope compositions of these rocks and granites in the wuyishan area provide important constraints on the precambrian crustal evolution of the cathaysia block inherited cores of zircon grains from the metamorphic rocks are of magmatic origin predominantly formed at ca 2 5 ga while overgrowth rims reflect two episodes of granulite facies metamorphism related to collisional orogeny at 1 89 1 88 ga and 252 234 ma the unimodal age distribution 2 5 ga of detrital zircons and the positive hf t of most neoarchean zircons suggest that the detritus of these sedimentary protoliths of the badu complex came from a proximal volcanic arc and that they were deposited in an arc basin synchronously with 2 5 ga volcanism zircon u pb ages and hf isotopes with whole rock nd isotopes suggest that the juvenile crust of the eastern cathaysia block was generated mainly at 2 5 ga and 2 8 ga and minor at 3 5 3 3 ga with some evidence for the generation at 3 7 3 6 ga and 4 0 ga a strong 1 9 ga orogeny and the 3 3 3 0 ga thermal event only involved the reworking of older crust material paleoproterozoic 1 89 1 86 ga granitic magmatic activity and high grade metamorphism in the eastern cathaysia block were synchronous with the assembly of the columbia supercontinent using integrated geochronological hf nd isotopic and petrologic data as a barcode we compare the cathaysia block with other paleoproterozoic orogens worldwide and argue that its closest affinity is with the south korean peninsula and the lesser himalaya of nw india consequently the eastern cathaysia block and the south korean massif as the united cathay south korea terrane was close to the lesser himalaya terrane in the paleoproterozoic configuration of the columbia supercontinent the spatial linkage was maintained for ca 1 ga until the fragmentation of the rodinia supercontinent during neoproterozoic time

tertiary deltaic and lacustrine organic facies comparison of biomarker and kerogen distributions abstract biological marker and kerogen compositional data in tertiary deltaic and lacustrine settings were compared and contrasted the two settings are represented by a coals and organic carbon rich shales in a ick deltaic sequence from the far east constituting three distinct organic facies and b humic coals and spropelic oil shales in a restricted intermontane freshwater lacustrine sequence from western montana u s a constituting two distinct organic facies wedistinguish the organic facies in each depositional setting by systematic differences in gross compound class distributions kerogen and infrared spectral characteristics molecular character of pyrolyzates sterane carbon number distribution and sterane hopane ratios the kerogens of the three deltaic organic facies are characterized by varying quantities of vitrinite resinite sporinite cutinite and fluorescent amorphinite triterpane distributions reveal numerous terrigenous compounds including oleanane oleanenes and unidentified c 30 presumably resin derived components the two organic facies of the freshwater lacustrine setting are distinguishedased upon either a vitrinite or an alganite fluorescent amorphinite predominance in the kerogen numerous characteristics facies related markers are also present including dehydroabietane land plant resins and 4 methylsteranes perhaps from freshwater dinoflagellate input the available molecular and petrographic data are evaluated and characteristics are proposed for distinguishing five organic facies of these two depositional settings the successful simultaneous use of molecular geochemistry and organic petrography in this study provides a format for refining the organic facies concept

petrogenesis of jurassic tungsten bearing granites in the nanling range south china evidence from whole rock geochemistry and zircon u pb and hf o isotopes abstract the nanling range nlr is the largest tungsten metallogenic province in china and perhaps in the world the tungsten mineralization is believed to be related to jurassic granitic magmatism however the petrogenesis of these granites and their relation to the tungsten mineralization are still debated whole rock geochemical and sr nd hf isotopic data and zircon in situ u pb ages and hf o isotopes are reported for w bearing granitic intrusions from the southern jiangxi province in the nlr in order to constrain their magmatic sources and petrogenesis the nlr granites include biotite granites two mica granites and garnet muscovite granites sims and la icpms u pb dating of zircons and monazites give emplacement ages of 161 154 ma for these rocks the granites are metaluminous to strongly peraluminous with high sio 2 72 3 wt and high k 2 o 3 7 wt petrographic and geochemical features show that they are highly fractionated i type granites the biotite granites are enriched in light rare earth elements lrees relative to heavy rees have weakly negative eu anomalies and are depleted in nb ba p and ti in contrast the two mica and garnet bearing muscovite granites have tetrad type ree patterns with strongly negative eu anomalies and are extremely depleted in ba nb sr p and ti magmatic garnets are mainly almandine and spessartine and have low mn cores and high mn rims their y hree contents are high and generally decrease from core 1 2 wt to rim average 4955 ppm all of these granites are characterized by variable whole rock initial 87 sr 86 sr 0 7053 0 8000 e nd t 12 6 to 9 4 and e hf t 12 3 to 8 5 as well as variable zircon e hf t and 18 o with values of 16 3 to 7 4 and 7 6 to 10 0 respectively they contain abundant zircon xenocrysts and xenoliths of micaceous schist all of these features are consistent with a process of crystal fractionation of crustally derived magmas coupled with strong assimilation of sedimentary rocks the assimilation of meta sedimentary materials increased the concentrations of tungsten alumina and manganese in the magmas whereas high degrees of crystal fractionation further enriched them in the evolved granitic rocks the w enriched magmatic fluids formed the tungsten bearing quartz veins revealing the genetic relationship between tungsten mineralization and emplacement of garnet bearing two mica or muscovite granites in the nlr

petrogenesis of jurassic fractionated i type granites in southeast china constraints from whole rock geochemical and zircon u pb and hf o isotopes abstract whole rock geochemical and sr nd hf isotopic data and zircon in situ u pb ages and hf o isotopes are reported for twelve granitic intrusions from inland to coastal areas of the cathaysia block southeast se china in order to constrain their magma sources and petrogenesis they are mainly composed of biotite granites with minor granodiorites zircon u pb dating by la icpms and sims methods gave emplacement ages of 165 154 ma for these rocks which are metaluminous to weakly peraluminous a cnk 0 95 1 10 with variable sio 2 contents and high k 2 o contents they are all depleted in high field strength elements hfses and enriched in light rare earth elements lrees and large ion lithophile elements liles and show negative sr ba and eu anomalies in the spidergrams petrographic and geochemical features suggest the granodiorites that contain hornblende to be typical of i type while the biotite granites without hornblende are fractionated i type granites their variable major and trace element concentrations are due to fractional crystallization of feldspar biotite hornblende and accessory minerals including apatite allanite and monazite moreover our data indicate significant variations in isotopic compositions of these granitoids from inland to coastal areas the inland granites from the lapu fogang xinfengjiang and baishigang plutons have relatively high initial 87 sr 86 sr ratios 0 7105 0 7155 and low e nd t 11 2 to 7 3 and e hf t 10 9 to 6 3 values for whole rocks and variable 18 o values of 7 69 9 25 and e hf t values of 13 5 to 6 7 for zircons in contrast the coastal granites from the longwo wushikeng lianhuashan shigushan chiliao hulutian mantoushan and fenghuang plutons show relatively low initial 87 sr 86 sr ratios 0 7056 0 7110 and high e nd t 7 6 to 6 2 and e hf t 6 5 to 2 8 values for whole rocks together with e hf t values of 7 2 to 3 9 and 18 o values of 6 69 8 38 for zircons the spatial isotopic variations suggest that these jurassic granitoids were generated by different percentage mixing of mantle and ancient paleoproterozoic crust derived magmas with subsequently minor crustal assimilation our results highlight that jurassic fractionated i type granites occur widely from inland to coastal areas of se china arguing against the previous view that jurassic granites occur only in inland while coastal granites are mainly cretaceous the widespread occurrence of jurassic granitoids in se china is attributed to ascending of mantle derived magmas which provide heat for partial melting of lower crustal materials in an extensional setting

quaternary fluvial tufas of sarikavak area southwestern turkey facies and depositional systems abstract in the quaternary sarikavak fluvial tufa deposits situated in south western turkey different facies have been identified and their mutual relationships have been unravelled this tufa formation is located at the northern part of acigol graben the development of the sarikavak tufas represents typical fluvial and fluvio palustrine environments in total eight tufa lithofacies have been differentiated namely moss tufa facies oncolitic tufa facies stromatolitic tufa facies phytoclastic tufa facies intraclastic tufa facies extra formational clastic tufa facies sapropelitic tufa facies and palaeosol preliminary u th datings indicate that these deposits formed prior to 219 ka and continued until 80 ka mis 7 till 5 13c signatures 0 78 to 1 63 v pdb best can be explained by limestone dissolution processes or respiration from c4 plant vegetation into the soil or both for that reason the sarikavak tufa deposits can be classified as travitufa which precipitated in a distal facies system of travertine occurrences 18o values 7 49 to 10 83 v pdb of the whole data set reflect some significant changes which is interpreted in terms of temperature variations reflecting warm and cold periods among mis 7 interglacial mis 6 glacial and mis 5 interglacial the development of the sarikavak tufa deposits are related to the maymundagi fault that borders the acigol graben in the north this fault and its synthetic fault segments play a pivotal role with regard to the palaeo flow direction of water and control the basin topography these structural structures are likely responsible for all active and ancient springs in the study area as well as their respective carbonate precipitates

a possible linkage between highly fractionated granitoids and associated w mineralization in the mesozoic yaogangxian granitic intrusion nanling region south china abstract the yaogangxian ygx w deposit in the central nanling w province south china is one of the largest w deposits worldwide both vein type wolframite and skarn type scheelite orebodies were exposed in ygx these scheelite and wolframite mineralization are spatially associated with the ygx granitic intrusion the exposed intrusion contains two main intrusive phases lower zone coarse grained two mica granite and upper zone fine grained muscovite granite an integrated study of whole rock geochemistry la icp ms zircon u pb geochronology and zircon hf isotopic geochemistry of the ygx granitic intrusion was undertaken to constrain its magmatic source and petrogenesis cassiterite la icp ms u pb dating was also undertaken to constrain the connection between the intrusion and hydrothermal w mineralization zircon u pb dating yielded weighted mean ages of 161 3 and 157 2 ma for the two mica and muscovite granites respectively cassiterite crystals from wolframite quartz veins display growth zonation under cathodoluminescence and have a weighted mean zircon u pb age of 158 2 ma the formation of the muscovite granite and related w mineralization in the ygx deposit was thus initiated during the early yanshanian the ygx granites display typical metaluminous to strongly peraluminous characteristics with high sio2 73 5 79 1 wt and k2o 3 0 5 0 wt contents they are enriched in heavy rare earth elements rees comparative to light rees notably they exhibited strong negative eu anomalies and are depleted in sr ba p and ti in addition muscovite granites in ygx are more significantly enriched in heavy rees relative to light rees than two mica granites indicating that the former experienced higher degree fractionation than the latter zircon grains of the ygx granitoids have strongly negative ehf t 15 to 10 3 with two stage hf model ages of 2 15 1 86 ga indicating a magma source of reworked ancient crustal material without obvious involvement of juvenile materials the results of petrology and geochemistry indicate that the ygx granitic intrusion is a highly fractionated s type granite emplaced during widespread 160 150 ma granitic magmatism in the nanling region further evolution to late stage for multiphase ygx granitic intrusion is needed to enrich ore forming elements after magmatic emplacement it is suggested that the extensional environment of continental lithosphere caused by the northwest subduction of the paleo pacific plate may play an key role in the genesis of ygx s type granite w rich proterozoic basement rocks and fractional crystallization may provide material for the formation of the granite related tungsten mineralization

steranes and triterpanes generated from kerogen pyrolysis in the absence and presence of minerals abstract steranes and triterpanes generated from pyrolysis of immature monterey formation kerogen in the presence and absence of calcite illite and montmorillonite reveal results that are both consistent and divergent with published data that reflect the use of these biological markers as maturation indicators the extent of isomerization of biomarkers generated from pyrolysis of kerogen at 300 c for 2 hours at c 20 in 14 h 17 h steranes at c 22 in 17 h 21 h hopanes and of 17 h 21 h hopanes correspond to early diagenetic stages in rock extracts from sedimentary basins isomerization increases with heating time and after 1000 hours attains values which correspond to the catagenetic stage in sedimentary basins or equivalent to that of mature oil stepwise pyrolysis of the kerogen indicates faster isomerization rates for steranes and triterpanes in the bitumen than for those retained in the kerogen structure confirming earlier studies presence of a mineral matrix can influence the isomerization of steranes and triterpanes considerably comparisons with results from kerogen heated alone for a given maturation stage show that calcite inhibits illite catalyzes slightly and montmorillonite has a pronounced catalytic effect on these reactions this effect results in early isomerization of steranes and hopanes corresponding to the catagenetic stage in the presence of montmorillonite while kerogen or kerogen with calcite held at the same temperature 300 c and time 10 hours only yield isomerized products which correspond to a diagenetic stage further illite and montmorillonite affect various isomerization reactions differently the fastest reaction is the isomerization at c 20 in 14 h 17 h steranes followed by that at c 22 in 17 h 21 h hopanes and the slowest is the formation of 14 h 17 h steranes these results show that maturation measurements of rock or oil samples from sedimentary basins which use biological markers have to take into account the mineral matrix effects which have been largely ignored until present

u pb zircon geochemical and sr nd hf isotopic constraints on age and origin of jurassic i and a type granites from central guangdong se china a major igneous event in response to foundering of a subducted flat slab abstract the mesozoic geology of se china is characterized by widespread jurassic to cretaceous igneous rocks consisting predominantly of granites and rhyolites and subordinate mafic lithologies however the tectonic regime responsible for the inland jurassic granites remains controversial we report here u pb zircon ages geochemical and sr nd hf isotopic data for the nankunshan alkaline granite and the fogang granitic batholith in central guangdong mineralogical and geochemical features suggest that the fogang and nankunshan rocks are i and aluminous a type granites respectively shrimp u pb zircon analyses yield consistent ages ranging from 159 3 ma to 165 2 ma for four samples from the fogang batholith and an age of 158 5 ma for the nankunshan granite the fogang granites having i sr 0 7098 0 7136 e nd t 4 3 to 12 2 and e hf t 11 5 to 3 1 for the magmatic zircons were derived from paleoproterozoic mafic intermediate igneous protolith with minor addition of mantle derived magmas the nankunshan rocks have relatively lower i sr 0 706 0 708 higher e nd t 0 3 to 2 4 and e hf t 5 7 to 1 1 for the magmatic zircons and some oib like trace element ratios they were likely generated through extensive fractional crystallization of mantle derived alkaline parental magma associated with crustal assimilation these 160 ma i and a type granites in central guangdong were emplaced coeval with the widespread 165 155 ma i and a type granites and syenites following the initiation of intraplate basaltic and or bimodal igneous magmatism at 180 170 ma in the adjacent regions we interpret these jurassic igneous rocks as anorogenic magmatism formed during a major igneous event in response to foundering of an early mesozoic subducted flat slab beneath se china continent

cretaceous granitic intrusions in fujian province cathaysia block implications for slab rollback and break off of the paleo pacific plate abstract the geodynamic transformation of the cathaysia block and its relationship with the cretaceous granitic intrusions have been controversial in recent decades in this study petrology zircon u pb ages lu hf isotopic composition whole rock geochemistry and sr nd isotopes were carried on cretaceous granites that were collected from the fujian province se china combining previously published ages with the new ages obtained in this study indicates that the magmatism in the study area occurred in three distinct stages at 145 137 ma 136 118 ma and 107 86 ma the first stage i type granites were intruded at 137 1 ma and 145 1 ma which are characterized by low end t values of 7 3 to 6 8 and ehf t values of 12 5 to 2 5 it was formed by partial melting of mesoproterozoic medium to high k basaltic rocks in the thickened crust of 40 km without significant hybridization of mantle derived magmas and fractional crystallization the second stage highly differentiated i type granites yield zircon u pb ages of 125 1 ma and 128 1 ma which contain slightly negative end t values of 5 4 to 5 3 and ehf t values of 8 4 to 3 2 it was generated by partial melting of the mesoproterozoic basement at the depth of 30 40 km triggered by underplating of a small amount of mantle derived magma with primary crustal melts undergoing plagioclase dominated fractionation crystallization the third stage i type granites yield zircon u pb ages of 104 1 ma and 105 1 ma which contain end t values of 1 7 to 7 3 and ehf t values of 6 0 to 0 5 it was derived from partial melting of mesoproterozoic basaltic source at a depth of 30 km besides a mass of mantle derived magma was mixed into the crustal melts accompanied with plagioclase dominated fractionation crystallization combining previously published data and those obtained in this study provides significant information for the tectonic evolution of paleo pacific in stage 1 145 137 ma the existence of i type granites and adakitic rocks suggests that the dip angle subduction of the paleo pacific plate led to the partial melting of the thickened lower crust under the compressional environment in stage 2 136 118 ma the generation of i type and a type granitic magmas imply the thinning of the lithospheric crust under the extensional environment and the upwelling of the asthenospheric mantle which are caused by slab rollback of paleo pacific in stage 3 107 86 ma the appearance of much more i type and a type granites indicates that the break off of the paleo pacific plate led to much stronger crust mantle interactions under the extensional environment

zircon u pb and sm nd geochronology and geochemistry of the sn w deposits in the northern guposhan ore field nanling range southern china abstract the guposhan ore field located in the central part of the nanling range and close to the giant central south peninsula tin ore belt is well known for its large scale sn w mineralization and hosts a series of middle to large scale sn w deposits in this study medium to fine grained biotite granite outcropped in the mining area have zircon u pb ages of 162 8 1 3 ma mswd 0 54 and 162 7 1 2 ma mswd 0 66 respectively these zircon ages are consistent to the sm nd isotopic age of minerals garnet hornblende clinopyroxene and orthopyroxene from the skarn type ores which is 160 4 4 8 ma mswd 1 3 these granites are characterized by high content of sio2 k2o na2o and rees and high ga al ratios indicating that they belong to highly fractionated a type granites with high k calc alkaline and aluminous peraluminous signatures the zircon lu hf isotopes of these granites have ehf t values and tdmc ages of 2 66 to 1 71 and 1 32 1 38 ga respectively combined with the previous studies it was proposed that the magma was formed by the mixing of crust mantle components ca 50 and ca 50 respectively in addition magmas are characterized by low temperatures of ca 710 c and oxygen fugacity log fo2 values of 18 5 to 16 4 formation of these granites were likely related to an intraplate extensional tectonic setting triggered by roll back of the subducted paleo pacific plate beneath the south china block scb these granites are in favor of the sn w mineralization making the guposhan ore district a large scale sn w mineralization ore field in the nanling range

gas generation and accumulation in the west siberian basin we appreciate the discussion by murris 2001 and take the opportunity to clarify some of his objections and discuss some of the still open questions in more detail murris s main objections to the conclusions of littke et al 1999 concern first the influence of overpressure in the lower cretaceous and upper jurassic on hydrocarbon distribution and second the model of gas release by exsolution degassing from deep ground water as the main mechanism for accumulating the huge gas fields of northern west siberia the first objective of murris s discussion is how the overpressure in jurassic strata might have influenced the distribution of hydrocarbons in the overlying cretaceous sediments two crucial points regarding this question are the reason and timing of overpressuring and its influence on hydrocarbon movement we agree with murris that the effect of compaction disequilibrium is not sufficient to explain the extent of overpressure in the urengoy area and that hydrocarbon generation in the bazhenov formation has contributed to the buildup of overpressure two dimensional basin modeling along a seismic line through the urengoy field however showed that hydrocarbon generation in jurassic source rocks bazhenov and the tyumen formations did only generate sufficient overpressure to explain the recent situation if the models were laterally completely sealed this sealing appears to be highly unlikely furthermore hydrocarbon generation ceased during the miocene when the tectonic movement started to lift the source rocks into shallower depths where lower temperatures were reached thus any overpressure caused by petroleum generation must have been preserved over a period of about 5 20 m y in addition the overpressure is not restricted to the jurassic bazhenov formation but extends into the cretaceous including the achimov sands uplift might have contributed to the overpressure however maximum pore pressure from the stage of deepest burial might have

geology mineralization and fluid inclusion characteristics of the kumbel oxidized w cu mo skarn and au w stockwork deposit in kyrgyzstan tien shan the kumbel deposit is located within a metallogenic belt of w mo cu mo au w and au deposits along the late paleozoic active continental margin of tien shan the deposit is related to a late carboniferous multiphase pluton with successive intrusive phases from early olivine monzogabbro through monzonite quartz monzonite to granodiorite and granite with the latest monzogabbro porphyry dikes the deposit represents an example of a complex w cu mo au magmatic hydrothermal system related to magnetite series high k calc alkaline to shoshonitic igneous suite it contains large bodies of w cu mo oxidized prograde and retrograde skarns with abundant andradite garnet magnetite and especially hematite as well as k feldspar molybdoscheelite chalcopyrite and molybdenite with transitions to zones of intense quartz k feldspar with minor andradite and hematite veining the skarns are cut by quartz carbonate adularia sericite veins locally sheeted and stockworks bearing scheelite and minor cu zn pb sulfides as well as au bi te and as mineralization the association of these veins with the oxidized skarns and magnetite series intrusion is consistent with the general oxidized intrusion related w mo cu au type of deposit with an affinity to the alkalic silica saturated cu au mo porphyry deposits the fluid inclusion data show the predominance of magmatic hydrothermal aqueous chloride fluid during the formation of skarns and quartz carbonate scheelite sulfide veins the high fluid pressures 1 750 bars together with their high temperature up to 600 c and high salinity 50 60 wt nacl equiv suggest the formation of skarns and quartz k feldspar andradite hematite veins under conditions typical of magmatic hydrothermal transition depth of 4 5 km of intrusion related mineralized system possibly by exsolution of the fluids from crystallizing magma the auriferous quartz carbonate scheelite sulfide veins formed from high to moderate salinity from 40 to 20 wt nacl equiv and high pressure from 1 200 bars to 850 900 bars aqueous chloride fluids under decreasing temperature from 370 to 120 c the massive deposition of molybdoscheelite in retrograde skarn and scheelite in quartz carbonate scheelite sulfide veins could correspond to enrichment of fluids in ca up to 18 25 wt cacl2 likely from crystallizing magma

the key role of mica during igneous concentration of tantalum igneous rocks with high ta concentrations share a number of similarities such as high ta nb low ti lree and zr concentrations and granitic compositions these features can be traced through fractionated granitic series formation of ta rich melts begins with anatexis in the presence of residual biotite followed by magmatic crystallization of biotite and muscovite crystallization of biotite and muscovite increases ta nb and reduces the ti content of the melt titanium bearing oxides such as rutile and titanite are enriched in ta and have the potential to deplete ta at early stages of fractionation however mica crystallization suppresses their saturation and allows ta to increase in the melt saturation with respect to ta and nb minerals occurs at the latest stages of magmatic crystallization and columbite can originate from recrystallization of mica we propose a model for prediction of intrusion fertility for ta

organic matter provenance and depositional environment of marine to continental mudstones and coals in eastern ordos basin china evidence from molecular geochemistry and petrology abstract cyclothems composed of interbedded mudstone coal and sandstone layers make up the taiyuan and shanxi formations in the late carboniferous to early permian in north china under a marine to continental depositional environment the cyclothems act as important fossil energy hosts such as coalbeds hydrocarbon source rocks and unconventional natural gas reservoirs organic geochemistry and petrology of mudstones and coals in the taiyuan and shanxi formations in the eastern ordos basin were studied to reveal the organic matter sources and paleoenvironments total organic carbon toc contents vary from 1 1 wt mudstone to 72 6 wt coal the samples are mainly within the oil window with the tmax values ranging from 433 to 469 c organic petrology and source biomarkers indicate that the mudstones were sourced from a mixed organic matter input and terrigenous organic matter predominates over aquatic organic matter the coals are mostly sourced by terrigenous organic matter inputs high concentrations of hopanes argue for a strong bacterial input some m z 217 mass chromatograms have peaks at the hopanes retention times as a result of high hopane to sterane ratios these hopane derived peaks do not interfere the identification of the steranes because the hopanes and the steranes have different retention times maturity dependent biomarkers demonstrate that the samples have been thermally mature which agree with the tmax values anomalously low c29 20s 20s 20r and c29 sterane ratios are present in all the samples and are interpreted as due to the terrigenous organic matter input or the coal related depositional environment in addition biomarkers and iron sulfide morphology indicate that the organic matter of the mudstones deposited in a proximal setting with shallow brackish fresh water bodies with consideration of preservation of organic matter the redox conditions are dysoxic redox oscillations resulted in the records of oxic conditions in some samples finally the coals and the mudstones mainly generate gas and have poor oil generative potential

evolution of pennsylvanian late carboniferous peat swamps of the ruhr basin germany comparison of palynological coal petrographical and organic geochemical data abstract this study focuses on the reconstruction of the environment during peat swamp development eight coal and sedimentary organic rock bearing seam successions were examined all belonging to the duckmantian pennsylvanian late carboniferous 410 samples were analysed with coal petrographical methods 155 of these also by palynological methods in addition on 55 samples organic geochemical investigations were carried out with respect to n alkanes and iso alkanes the established coal petrographical parameters gelification index gi tissue preservation index tpi groundwater index gwi and vegetation index vi were used to characterize different periods of peat swamp development furthermore the new index wci water cover index was introduced to reflect water level conditions by using the ratio between hydrophilous hygrophilous and mesophilous plants in this study the index is based on palynological data but can be equally applied when quantitative macrofloral counts are available gi versus tpi values show two general trends of peat swamp evolution low gi and tpi values as indicator for drier swamp conditions like ombrogenous mires and high gi and tpi values which show a trend to water covered environments like topogenous mires in addition ash yields and gwi versus vi data also emphasize a general trend from topogenous to ombrogenous mires a decrease in water level towards the top of the seams and thus resulting in the development of domed mires is reflected by the newly introduced wci hence these parameters show recurrent peat swamp successions characterized by mineral and vitrinite rich coals typical for topogenous swamps and an evolution towards inertinite liptinite rich coals with low ash yield typical for ombrogenous swamps n alkane ratios like the carbon preference index cpi pristane n c17 phytane n c18 pristane phytane and the n c17 n c27 relationship indicate a strong correlation of these parameters with thermal maturity e g cpi values correlate with vitrinite reflectance sulphur organic carbon s toc ratios are quite uniform in clastic rocks with low to moderate toc contents but highly variable in coals probably reflecting variable sulphate availability during deposition of peats sphenophyll rich floral assemblages are restricted to low sulphur environments