multi stage exhumation of young uhp hp rocks timescales of melt crystallization in the d entrecasteaux islands southeastern papua new guinea abstract on the d entrecasteaux islands southeastern papua new guinea png a series of domes expose the youngest known ultrahigh pressure uhp to high pressure eclogites and associated gneisses abundant evidence of partial melting is preserved throughout the d entrecasteaux domes in the form of variably deformed leucosomes dikes and plutonic bodies in order to understand 1 the timing of melt emplacement relative to the uhp metamorphism and 2 the complete exhumation and deformational history of the eclogites and surrounding gneisses a series of leucosomes dikes and eclogites from the mailolo dome in western fergusson island were analyzed by u pb id tims zircon geochronology zircons extracted from the eclogite at the uhp locality yield 206pb 238u tims dates from 5 60 0 22 to 4 61 0 18 ma zircons from three foliation parallel leucosomes are interpreted to record melt crystallization from 3 49 0 01 ma to 2 98 0 02 ma in comparison weakly deformed granitic granodioritic dikes that cut the leucosomes yield zircon 206pb 238u dates of 2 48 0 01 ma 2 420 0 002 ma based on these new and previously published results the eclogites may have undergone uhp metamorphism for several million years from 7 1 0 7 ma to 4 61 0 18 ma based on tims dates alone a more restricted interval of 5 6 4 6 ma is proposed following uhp metamorphism the eclogite and gneisses were exhumed to lower crustal depths intruded by foliation parallel leucosomes by ca 3 5 3 0 ma and by ca 2 45 ma late discordant dikes multiple generations of leucosomes and dikes allow a timeline for the exhumation of the png uhp terrane to be constructed mantle 100 km depths to the base of the crust in 1 my storage in the lower crust for 1 my and final emplacement into the shallow crust 1 my later

the paleoproterozoic snowball earth a climate disaster triggered by the evolution of oxygenic photosynthesis although biomarker trace element and isotopic evidence have been used to claim that oxygenic photosynthesis evolved by 2 8 giga annum before present ga and perhaps as early as 3 7 ga a skeptical examination raises considerable doubt about the presence of oxygen producers at these times geological features suggestive of oxygen such as red beds lateritic paleosols and the return of sedimentary sulfate deposits after a 900 million year hiatus occur shortly before the 2 3 2 2 ga makganyene snowball earth global glaciation the massive deposition of mn which has a high redox potential practically requires the presence of environmental oxygen after the snowball new age constraints from the transvaal supergroup of south africa suggest that all three glaciations in the huronian supergroup of canada predate the snowball event a simple cyanobacterial growth model incorporating the range of c fe and p fluxes expected during a partial glaciation in an anoxic world with high fe oceans indicates that oxygenic photosynthesis could have destroyed a methane greenhouse and triggered a snowball event on timescales as short as 1 million years as the geological evidence requiring oxygen does not appear during the pongola glaciation at 2 9 ga or during the huronian glaciations we argue that oxygenic cyanobacteria evolved and radiated shortly before the makganyene snowball

postcollisional magmatism in the south tien shan variscan orogenic belt kyrgyzstan evidence for high temperature and high pressure collision abstract the south tien shan collisional belt consists of two segments divided by the largest in the central asia talas fergan diagonal dextral strike slip fault the narrow eastern kokshal segment where the late carboniferous collision was followed by continental subduction of the precambrian tarim platform beneath the caledonian kazakh continent is characterized by overthickened 60 65 km crust and ultrahigh pressure coesite eclogite regional metamorphism the permian postcollisional magmatism is represented there by a small volume of relatively cool two mica peraluminous leucogranites moderate volumes of k rich calk alkaline transitional from i to s type granites and several large plutons of a type rapakivi granites the latest could have formed by a two step process involving 1 syncollisional submersion of the tarim platform granulitic basement into the mantle accompanied by considerable heating of the source rocks 2 rapid postcollisional exhumation accompanied by decompression and extensive high degree of melting in the western alay segment which is much wider the collision was not followed by continental subduction the thickness of crust decreases westward dramatically from 60 to 45 km the alay segment is characterized by the high temperature low pressure regional metamorphism and significant volume of permian shoshonitic ultrapotassic magmatism connected with postcollisional strike slip tectonics the shoshonitic magmatism is indicative of lithosphere delamination and input of mantle derived melts and heat into the crust in contrast to the kokshal segment the postcollisional granitic magmatism in the alay segment is represented by relatively hot cordierite and sillimanite bearing strongly peraluminous s type granites locally rooted in the high temperature low pressure metamorphic rocks and large volume of calc alkaline i type granitoides of mixed crust mantle origin

size and exhumation rate of ultrahigh pressure terranes linked to orogenic stage abstract a growing set of data indicates a stark contrast between the evolution of two types of ultrahigh pressure uhp terranes large terranes that evolved slowly over 10 30 myr and small terranes that formed and were exhumed on timescales of

sclerosponges as a new potential recorder of environmental changes lead in ceratoporella nicholsoni lead concentrations have been analyzed on a 223 yr profile through the aragonitic skeleton of the reef building caribbean sclerosponge ceratoporella nicholsoni by using laser ablation inductively coupled plasma mass spectrometry a parallel study of the 13 c distribution in the skeleton validates the previously established mean annual growth rate of 230 m yr at least for long term important environmental changes the pb trend in the specimen displays a general increase from 0 30 ppm ca a d 1760 to 2 15 ppm ca a d 1984 a major threefold increase occurred after 1930 this pb profile is analogous to results acquired from ice or coral cores and clearly highlights the potential of sclerosponges as a new proxy of environmental changes for time series extending over several centuries

a reconstruction of archean biological diversity based on molecular fossils from the 2 78 to 2 45 billion year old mount bruce supergroup hamersley basin western australia abstract bitumens extracted from 2 7 to 2 5 billion year old ga shales of the fortescue and hamersley groups in the pilbara craton western australia contain traces of molecular fossils based on a combination of molecular characteristics typical of many precambrian bitumens their consistently and unusually high thermal maturities and their widespread distribution throughout the hamersley basin the bitumens can be characterized as probably of archean age accepting this interpretation the biomarkers open a new window on archean biodiversity the presence of hopanes in the archean rocks confirms the antiquity of the domain bacteria and high relative concentrations of 2 methylhopanes indicate that cyanobacteria were important primary producers oxygenic photosynthesis therefore evolved 2 7 ga ago and well before independent evidence suggests significant levels of oxygen accumulated in the atmosphere moreover the abundance of cyanobacterial biomarkers in shales interbedded with oxide facies banded iron formations bif indicates that although some archean bif might have been formed by abiotic photochemical processes or anoxygenic phototrophic bacteria those in the hamersley group formed as a direct consequence of biological oxygen production biomarkers of the 3 methylhopane series suggest that microaerophilic heterotrophic bacteria probably methanotrophs or methylotrophs were active in late archean environments the presence of steranes in a wide range of structures with relative abundances like those from late paleoproterozoic to phanerozoic sediments is convincing evidence for the existence of eukaryotes in the late archean 900 ma before visible fossil evidence indicates that the lineage arose sterol biosynthesis in extant eukaryotes requires molecular oxygen the presence of steranes together with biomarkers of oxygenic photosynthetic cyanobacteria suggests that the concentration of dissolved oxygen in some regions of the upper water column was equivalent to at least 1 of the present atmospheric level pal and may have been sufficient to support aerobic respiration

natural variability of skeletal elemental phosphorus p ca lead pb ca and barium ba ca in the western pacific sclerosponges acanthoceatetes wellsi and astrosclera welleyana

possible source dichotomy of contemporaneous post collisional barren i type versus tin bearing a type granites lying on opposite sides of the south tien shan suture abstract two granitoid complexes in the eastern kyrgyz tien shan situated north and south of the southern tien shan suture were studied the suture formed as a result of the closure of the turkestan ocean and collision of the tarim microcontinent in the south with the middle tien shan in the north the timing of collision is still disputed the deformed calc alkaline terektinsky complex situated immediately north of the suture represents one of the largest shear zone related intrusions in the tien shan 130 5 15 km in size small stocks of evolved a type granites of the inylchek complex hosting economic tin mineralization were emplaced immediately south of the suture opposite the terektinsky complex two samples from the terektinsky complex and 3 samples from three a type stocks were collected for u pb zircon shrimp ii geochronology the ages at 2 level obtained for the terektinsky complex north of the suture 294 5 ma and 291 5 ma and ages of the small granite bodies south of the suture 299 4 ma 295 4 ma 289 6 ma tashkoro inylchek and maida adir intrusions respectively are nearly identical within error limits they show that the southern tien shan suture in the eastern kyrgyz tien shan had already formed by 295 ma and had evolved into a transcrustal mega shear zone controlling emplacement of granitoids geochemical distinction between the two magmatic systems is based on 10 original bulk and trace analyses of rocks from this study and on a large dataset extracted from previously published research and unpublished reports geochemically the rocks of the terektinsky complex comprise calc alkaline high potassium i type series while the granites of the inylchek complex are typical a type granites with an elevated alumina saturation index and higher boron contents compared to a standard a type rapakivi granite contrasting metallogenic features of the two granitoid complexes south and north of the southern tien shan suture are defined by their sources a fertile fore arc complex and or passive margin sediments of tarim to the south and barren metamorphic precambrian basement of the middle tien shan to the north

ultrahigh pressure minerals and metamorphic terranes the view from china abstract ultrahigh pressure uhp metamorphism refers to mineralogical modifications of continental and oceanic crustal protoliths associated mafic ultramafic rocks initially formed or emplaced in shallow levels of the lithosphere but which subsequently have experienced p t conditions within or above the coesite stability field 2 7 gpa 700 c typical products include eclogite garnet peridotite and uhp varieties of metapelite quartzite marble paragneiss and orthogneiss uhp metamorphic assemblages require relatively cold lithospheric subduction to mantle depths some recrystallization even occurs under forbidden p t conditions characterized by a geotherm of the current explosion of research on continental uhp terranes reflects their significance for mantle dynamics and the tectonics of continental subduction collision exhumation mantle slab interactions and geochemical recycling a further characterization of uhp phases and positive identification of uhp minerals requires new experimental studies coupled with state of the art analyses for example the very rare occurrence of microdiamond inclusions in zircons from dabie sulu uhp rocks may reflect high f o 2 attending recrystallization inasmuch as epidote is rather common rutile needles within garnets from sulu uhp eclogitic rocks may not be the result of exsolution so in such cases the apparent uhp pressure may have been over estimated hadean igneous microdiamond inclusions in jack hills detrital zircons could have originated from mantle xenoliths whereas abundant detrital phanerozoic diamonds containing inclusions of coesite and other eclogitic minerals from new south wales might have been derived from unexposed uhp metamorphic terranes micro mineral intergrowth and nano size minerals may hold important key to deciphering the actual p t paths of subduction and mantle return flow although most exhumed terranes have returned surfaceward relatively rapidly after short time of uhp condition the long duration of storage at great depth and slow exhumation for the largest uhp terranes remain as major problems

nature and origin of proterozoic a type granitic magmatism in the southwestern united states of america the mountain ranges of arizona and adjacent california and nevada contain large areas underlain by proterozoic anorogenic granites comprising the southwesternmost portion of a transcontinental belt of 1 4 1 5 ga old anorogenic complexes that extends across north america northeast into labrador of these a two mica monazite bearing granitic suite resides in central and southeastern arizona as part of a peraluminous subprovince that is bordered on the south southern arizona to sonora and west western arizona and adjacent portions of california and nevada by marginally metaluminous granites bearing biotite sphene hornblende and fluorite all of these 1 4 ga granites are distinctly more potassic iron enriched relative to mg and depleted in ca mg and sr in contrast to typical orogenic granitoids in general the large ion lithophile element enriched composition is a consequence of limited melting of a water deficient crustal source at depths greater than 25 37 km for the peraluminous granites this contrast is less extreme perhaps resulting from a larger degree of melting as a consequence of a greater metasedimentary component and water in its crustal source the anorogenic granitic magmas intruded into the upper crust at depths of 8 17 km or shallower at temperatures up to 790 c the most dramatic variation in the crystallization intensive parameters resides in the oxygen fugacity which spans three orders of magnitude relative to other anorogenic suites all of the magmas crystallized at elevated levels of o2 as reflected in their assignment to the anorogenic magnetite series yet a regionally significant rise in primary o2 levels unmatched elsewhere in the transcontinental belt occurs for plutons in western arizona including the holy moses and hualapai granites the most extreme case is the hualapai granite whose biotite fe fe mg ratios drop due to high o2 to a low of 0 27 down from more typical levels of 0 54 to 0 75 such extreme variations in primary levels of oxygen fugacity must be an indirect imprint of regional changes of the level of oxidation of the lower crust the high fo2 holy moses and hualapai plutons have intruded near the regional boundary between the metaluminous and peraluminous granites and appear to be imaging a major change in the level of oxidation of the lower crust this boundary is also approximately equivalent to significant changes in the nd and pb isotopic compositions of these granites and the metamorphic and magmatic character of the older orogenic terrane on a global scale the crust forming orogenies ended by 1 6 ga ago and the continents entered a long lived era dominated by localized extension and transcontinental intrusion of anorogenic potassic rapakivi granite mafic dike swarms charnockite and anorthosite the absence of orogenic deformation implies that plate consumption became intraoceanic during this time the profuse and widespread nature of the igneous activity has no phanerozoic analogue and is considered to be unique to the proterozoic a crustal overturn model ties the magmatism to heating within a largely undepleted subcontinental mantle the eventual rise of mantle plumes and the transfer of heat into the youthful undifferentiated proterozoic crust subsequent melting and rise of potassic granitic magmas from the lower crust leads to considerable crustal reorganization a process that would continue until both the mantle and crust reached a stable configuration

mechanisms of continental subduction and exhumation of hp and uhp rocks abstract we discuss possible scenarios of continental collision and their relation to mechanisms of exhumation of hp and uhp rocks inferred from thermo mechanical numerical models accounting for thermo rheological complexity of the continental lithosphere due to this complexity mechanisms of continental convergence are versatile and different in many aspects from those that control oceanic subduction elucidating these mechanisms from conventional observations is difficult and requires additional constraints such as those derived from petrological data indeed exhumation of hp uhp rocks is an integral part of convergent processes and burial exhumation dynamics inferred from metamorphic p t t paths provides strong constraints on the collision scenarios metamorphic rocks also play an active role due to their contrasting physical properties rheology density fluid transport capacity numerical thermo mechanical experiments suggest that hp uhp exhumation can only be produced in subduction contexts as well as that long lasting 10 myr continental subduction can only occur in case of cold strong lithospheres t moho t e 50 km and of relatively high convergence rates 3 5 cm yr 1 in this case high density uhp material in the crustal part of subduction interface provides additional pull on the slab and is not always exhumed to the surface in case of slower convergence and or weaker lithosphere t e 1 is generally sufficient to drive continental subduction during the first several myr of convergence but pertinent subduction requires faster convergence rates 3 5 cm yr 1 we suggest that most continental orogenic belts could have started their formation from continental subduction but this process has been generally limited in time

vertical coupling and decoupling in the lithosphere recent advancements in the understanding of mountain belts have focused on vertical coupling of the lithospheric layers this volume describes the extent to which observed or inferred sub horizontal coupling or attachment zones provide vertical kinematic linkage between rheologically distinct layers in the continental lithosphere a common theme is whether the deformation which partitioned differently in each layer is linked kinematically across attachment zones and driven by flow in the deeper crust and mantle lithosphere the papers are divided into six sections the first analyses the extent to which mantle flow controls deformation of the overlying layers the vertical axis block rotations section uses geological and palaeomagnetic data to constrain the role and magnitude of basal shear across mid crustal attachment zones the lower crustal flow and topography section addresses the time dependent development of orogenic plateaux and their role in the orogenic cycle multiple examples of the spatial and temporal development of lithospheric coupling are given in both the orogenic examples and subduction examples sections finally rheological constraints of vertical coupling in the lithosphere are investigated

permian a type granites in tarim and western part of central asian orogenic belt caob genetically related to a common permian mantle plume abstract zircon u pb ages whole rock geochemical and zircon hf isotope data are reported for the permian a type quartz syenites granites in western tarim block northwest china zircon u pb dating indicates these alkali plutons were emplaced at 270 277 ma elemental geochemistry shows their typical a type signatures i e high total alkali hfse ree contents and ga al feo tot feo tot mgo and nb y ratios isotopically their epsilon nd values vary from 2 6 to 2 0 based on zircon hf isotope compositions they could be divided into two sub groups group i exhibits high positive ehf t ranging from 3 to 11 mostly within the range of 5 to 9 which is highly comparable with the syenites in bachu area located just south of these plutons group ii has ehf t ranging from 3 to 2 the second group exhibits comparable nd hf isotope compositions with the spatially and temporally related piqiang ultramafic mafic complex integrating geological geochemical and nd hf isotope data we suggest that the a type syenite granites were formed via intensive crystal fractionation from a common plume derived parental mafic magma coupled with variable extent of crustal contamination moreover the extent of the crustal contamination increase from inner tarim towards south tianshan collisional belt a comprehensive synthesis of the coeval a type granites in the western part of the central asian orogenic belt caob shows that they exhibit distinct geochemical features e g large range of end t and 87 sr 86 sr i values high y nb yb ta and low nb la ratios all these features argue that they were derived from juvenile mafic crust with variable addition of the mafic materials from mantle sources and some old crustal materials or mixing of mantle derived mafic magma with precambrian crustal components we suggest that both the permian a type granites from tarim and western section of caob were genetically linked to the permian tarim mantle plume which is concurrent with the two mantle domains for the permian tarim large igneous province lip

comparison of proterozoic and phanerozoic rift related basaltic granitic magmatism abstract this paper compares the 1 67 1 47 ga rapakivi granites of finland and vicinity to the 1 70 1 68 ga rapakivi granites of the beijing area in china the anorogenic 130 ma granites of western namibia and the 20 15 ma granites of the colorado river extensional corridor in the basin and range province of southern nevada in finland and china the tectonic setting was incipient aborted rifting of paleoproterozoic or archean continental crust in namibia it was continental rifting and mantle plume activity that led to the opening of southern atlantic at 130 ma the 20 15 ma granites of southern nevada were related to rifting that followed the triassic paleogene subduction of the farallon plate beneath the southwestern united states in all cases extension related magmatism was bimodal and accompanied by swarms of diabase and rhyolite quartz latite dikes rapakivi texture with plagioclase mantled alkali feldspar megacrysts occurs in varying amounts in the granites and the latest intrusive phases are commonly topaz bearing granites or rhyolites that may host tin tungsten and beryllium mineralization the granites are typically ferroan alkali calcic metaluminous to slightly peraluminous rocks with a type and within plate geochemical and mineralogical characteristics isotope studies nd sr suggest dominant crustal sources for the granites the preferred genetic model is magmatic underplating involving dehydration melting of intermediate felsic deep crust juvenile mafic magma was incorporated either via magma mingling and mixing or by remelting of newly hybridized lower crust in namibia partial melting of subcontinental lithospheric mantle was caused by the tristan mantle plume in the other cases the origin of the mantle magmatism is controversial for the fennoscandian suites extensive long time mantle upwelling associated with periodic migrating melting of the subcontinental lithospheric mantle governed by heat flow and deep crustal structures is suggested

postcollisional granites in the south tien shan variscan collisional belt kyrgyzstan abstract two major types of the potassium rich postcollisional granites of permian age were studied in the south tien shan variscan collisional belt the first type metaluminous granites of the jangart complex are located along the southeastern boundary of this belt with the precambrian tarim block the plagioclase rims on k feldspar megacrysts rapakivi texture extremely high feot feot mgo ratio indications of the low h2o and o2 fugacities high concentrations of the incompatible elements especially light rare earth elements lree ba nb along with heightened contents of the compatible elements especially ni cr and moderately initial 87sr 86sr ratio sr0 0 7075 make those granites similar to other rapakivi granites the second type peraluminous granites of the inylchek complex is located along the northwestern boundary of the belt with the caledonian kazakh microcontinent those granites are rich in f b li rb cs sn ta and heavy rare earth elements hree but are poor in ba sr ni and cr and are characterized by the relatively high initial 87sr 86sr ratio sr0 0 7098 li mica granites are distributed widely among them the granites of a transitional type uchkoshkon complex occupy an intermediate geographic position between major granite types the initial sr isotopic composition of the transitional granites varies widely sr0 from 0 7080 to 0 7256 the variation in chemical composition of the coeval postcollisional granites across the collisional belt together with the variability of initial sr isotopic ratios of the transitional granites are thought to indicate basement heterogeneity this heterogeneity in turn is probably related to thrusting of the tarim block under south tien shan during the collision

residence times of surface water and particle reactive 210pb and 210po in the east china and yellow seas 228ra 226ra 210pb and 210po were measured in the surface waters of the east china and yellow seas using mass balance equations for the ra isotopes we estimated the total flux of diffusion from sediments and desorption from suspended particles to be 0 1 dpm 226ra cm 2 a 1 and 1 dpm 228ra cm 2 a 1 and residence times to be 2 3 years for the waters on the east china sea shelf and 5 6 years for yellow sea waters box model calculations yielded generally congruent scavenging residence times for 210pb and 210po in the waters of 2 months on the shelf and 7 months in the kuroshio current these suggest that reactive heavy metals and pollutants discharged through rivers from the continent to the east asian continental shelf are largely deposited on the bottom sediments prior to transport to the pelagic ocean by lateral mixing

minor and trace elements in sclerosponge ceratoporella nicholsoni biogenic aragonite near the inorganic endmember abstract the trace and minor element composition have been investigated in the accretionary skeletons of two specimens of the caribbean sclerosponge species ceratoporella nicholsoni one from tongue of the ocean bahamas toto and the other from pear tree bottom jamaica ptb both sclerosponges were analyzed at high resolution using laser ablation icp ms la icp ms and verified using wet chemical methods icp oes the shallow ptb sclerosponge 25 m was analyzed for a short temperature calibrated record of trace and minor elements while the toto sclerosponge 146 m was analyzed for a century long record from subsurface waters the resulting ba ca mg ca pb ca and u ca ratios were compared with sr ca ratios which have been shown to reliably record seasonal scale temperature change in sclerosponges close to equilibrium precipitation of inorganic aragonite sclerosponge aragonite incorporates minor and trace elements according to general mineralogic constraints with less vital effects than other calcium carbonate secreting organisms this is perhaps most obvious in the behavior of mg ca ratios which show an inverse correlation to temperature unlike any other calcite or aragonite organism despite having mg concentrations 1 mmol mol within published estimates of equilibrium aragonite ratios of mg ca and ba ca show a strong positive correlation despite large differences in ionic radii and u ca values 3 15 mol mol are 2 5 higher in sclerosponge aragonite than in aragonite from corals supporting earlier work ratios of u ca show an insignificant correlation with temperature dependent sr ca ratios r 2 0 05 supporting existing theories that temperature signals recorded by u ca ratios can be convolved with ph co 3 2 and phosphate signals differences between sclerosponge aragonite and other calcium carbonate arising from siliceous spicule contamination are unlikely because of the small mole percent of silicon in the aragonite small differences between the two sclerosponges were noticed in pb ca and sr ca because of the average ages of the sampled material and average temperatures of the ambient environment respectively anomalies between la icp ms and icp oes were noticed in measurements of ba ca and pb ca due to standardization differences for la icp ms ba ca and measurements close to the instrument detection limits of pb icp oes

evolution of the cornubian ore field southwest england part i batholith modeling and ore distribution the cornubian ore field of southwest england is associated with an s type ilmenite series high heat production hhp two mica tourmaline bearing monzogranite batholith which formed between 270 to 295 ma base metal deposits are mainly in the form of steeply dipping lodes emplaced in the batholith roof and a hornfelsic sequence of upper paleozoic mud rocks sandstones and mafic volcanics the steep sided batholith has a gently sloping base 10 to 15 km below the present surface three dimensional modeling of gravity data indicates that it has a total volume of about 68 000 km 3 and is divisible into distinct western and eastern parts computer aided evaluation of mineral production statistics shows that most of the sn w cu and as production is located within the axial trace of the batholith with the western end enriched in sn cu and zn relative to the eastern end by contrast most of the fe as sb f ba and china clay production is located in the eastern end while pb and ag production is concentrated in the country rock filled south facing embayments on the flank of the batholith all significant wolframite production is from within the granite or within a 700 m distance of an observed or projected granite contact whereas 90 to 100 percent of the sn cu and as production occurs within 1 500 m of a contact by contrast 30 percent of the zn production and over 80 percent of the pb and ag production is from distances of more than 1 500 m from a granite contact pre syn and postbatholith faults and extensional fractures exert a fundamental control on ore distribution with most of the sn w cu as zn ores hosted by fractures trending parallel to the axial trace of the batholith and most of the pb sb ag ba and fluorite mineralization hosted by faults trending approximately normal to the axial trace of the batholith the nature of the sedimentary sequence also influenced metal distribution with most of the sn cu as production coming from areas underlain by devonian argillaceous rocks an important feature of the granite which has a bearing on its metallogenic potential is its high internal heat production due to its high total content of u th and k modeling of the cooling history of the granites reveals that temperatures in the deeper parts of the batholith were maintained close to or above the solidus for 10 to 20 ma after initial emplacement at 280 to 295 ma residual volatile and metal enriched magmas trapped within the batholith provided source materials for younger magmatism 270 280 ma and the main episode of lode formation which was related to the late magmatic events continued high heat flow throughout the mesozoic and cainozoic promoted thermally driven ground water convection and epithermal mineralization

miocene rapakivi granites in the southern death valley region california usa abstract rapakivi granites in the southern death valley region california include the 12 4 ma granite of kingston peak the ca 10 6 ma little chief stock and the 9 8 ma shoshone pluton all of these granitic rocks are texturally zoned from a porphyritic rim facies characterized by rapakivi textures and miarolitic cavities to an equigranular aplite core these granites crystallized from anhydrous and peraluminous to metaluminous magmas that were more oxidized and less alkalic than type rapakivi granites from southern finland chemical and isotope nd sr pb data suggest that rapakivi granites of the southern death valley region were derived by partial melting of lower crustal rocks possibly including mesozoic plutonic component with some mantle input as well they were emplaced at shallow crustal levels 4 km in an actively extending orogen

closing history of the southern tianshan oceanic basin western china an oblique collisional orogeny abstract the tianshan tien shan range is an important paleozoic collisional orogenic belt and the key to understand the central asia tectonic evolution this paper integrates our research results with the existing chinese and international literature on sedimentology geochemistry isotopic geochronology paleontonology and paleomagnetism of the tianshan and tarim regions to propose that the oblique collision may have played an important role in the late paleozoic closing of the southern tianshan oceanic basin as a result of the sinian latest proterozoic younger than 800 ma continental extension and rifting process the tarim and yili blocks separated from their parent continent in the late cambrian ordovician the southern tianshan oceanic crusts between the two blocks subducted northward beneath the southern margin of the yili block in the silurian during the devonian early carboniferous the tarim block rapidly drifted to the north and rotated about 46 clockwise this process induced the collision of the yili micro continent with the eastern segment present geographical position of the tarim continent in the late devonian and the southern tianshan oceanic crust evolved to be a west facing remnant oceanic basin during the late carboniferous early permian the tarim block located within an almost constant latitude range rotated about 26 clockwise with respect to the yili micro continent which ultimately closed the remnant oceanic basin in a scissors like manner from east to west and completed the tarim yili collision subsequent a type subduction of the tarim continental crust and lithosphere scale sinistral shearing generated a magmatic arc on the southern margin of the tarim yili suture zone the late permian early triassic clastics deposited in a peripheral foreland basin developed above the arc

late palaeozoic and meso cenozoic tectonic evolution of the southern kyrgyz tien shan constraints from multi method thermochronology in the trans alai turkestan alai segment and the southeastern ferghana basin abstract in this paper we present new geochronological and thermochronological data from the turkestan alai segment of the southern kyrgyz tien shan the ferghana basin transition and the trans alai pamir foreland in the southern and central parts of the alai range towards the alai valley mainly post collisional granitoids were targeted for zircon u pb dating by laser ablation inductively coupled plasma mass spectrometry la icp ms apatite fission track aft and apatite u th sm he ahe thermochronology these granitoids and their thermally metamorphosed contact aureole yielded middle permian zircon crystallization ages of 284 4 to 264 5 ma aft ages both using the traditional external detector approach as well as using la icp ms for these samples are constrained to the miocene and range between 22 3 1 1 and 8 4 0 3 ma while the ahe ages are somewhat younger between 12 5 0 8 and 5 0 0 3 ma this low temperature thermochronological data suggests an early miocene onset of denudation in this area in the tien shan orogen continuing through the miocene and pliocene this denudation is interpreted as a response to reactivation of the mountain belt in the framework of india eurasia convergence and specific to this region of the pamir tien shan interaction on the northern slopes of the alai range at the edge of the ferghana basin a late palaeozoic conglomerate yielded a reset early cretaceous aft age of 118 7 ma pointing to an older denudation event with respect to those identified in the southern and central parts of the alai range a mesozoic sediment sample from the same region only contains a late triassic age component of 223 ma mesozoic and cenozoic age components on the other hand are all detected in the cenozoic sediments of the trans alai range at the transition between the southern alai valley and the pamirs revealing several meso cenozoic denudation events in the adjoining basement source rocks the age components in these detrital apatites are 207 ma 75 ma 18 ma and 3 ma

paleozoic multiple accretionary and collisional tectonics of the chinese tianshan orogenic collage abstract subduction related accretion in the junggar balkash and south tianshan oceans paleo asian ocean mainly in the paleozoic gave rise to the present 2400 km long tianshan orogenic collage that extends from the aral sea eastwards through uzbekistan tajikistan kyrgyzstan to xinjiang in china this paper provides an up to date along strike synthesis of this orogenic collage and a new tectonic model to explain its accretionary evolution the northern part of the orogenic collage developed by consumption of the junggar balkash ocean together with paleozoic island arcs northern ili issyk kul and chatkal located in the west which may have amalgamated into a composite arc in the paleozoic in the west and by addition of another two roughly parallel arcs dananhu and central tianshan in the east the western composite arc and the eastern dananhu and central tianshan arcs formed a late paleozoic archipelago with multiple subduction zones the southern part of the orogenic collage developed by the consumption of the south tianshan ocean which gave rise to a continuous accretionary complex kokshaal kumishi which separated the central tianshan in the east and other paleozoic arcs in the west from cratons tarim and karakum to the south cross border correlations of this accretionary complex indicate a general southward and oceanward accretion by northward subduction in the early paleozoic to permian as recorded by successive southward juxtaposition of ophiolites slices of ophiolitic melanges cherts island arcs olistostromes blueschists and turbidites which are mainly paleozoic in age with the youngest main phase being late carboniferous permian the initial docking of the southerly tarim and karakum cratons to this complicated late paleozoic archipelago and accretionary complexes occurred in the late carboniferous early permian in the eastern part of the tianshan and in the late permian in the western part which might have terminated collisional deformation on this suture zone the final stages of closure of the junggar balkash ocean resembled the small ocean basin scenario of the mediterranean sea in the cenozoic in summary the history of the altaids is characterized by complicated multiple accretionary and collisional tectonics

multiple sources of lead in soils from a hawaiian chronosequence abstract we report lead isotopic ratios and concentrations from a basaltic soil chronosequence in hawaii substrate ages at the sites range from 300 years to 4 1 million years all soils show a net addition of pb above the contributions made by basaltic weathering indicating that atmospheric deposition of natural or pollutant sources is important across the sequence isotopic ratios from the chronoseqence soils indicate a mixture of basalt mineral aerosol and anthropogenic pb sources derived from both long range and local inputs locally derived anthropogenic pb dominates young soils intermediate age soils in remote locations have a strong mineral aerosol signature and likely contain some anthropogenic lead of asian origin older soils have undergone extensive leaching of both basaltic and eolian lead while the anthropogenic inputs in most sites are from less radiogenic local and asian sources we find evidence of j type lead of north american origin in a remote soil on kauai the diversity of anthropogenic lead sources suggests that at least two different weather patterns dominate atmospheric pb transport across the hawaiian island chain

rapakivi granites within phanerozoic collisional orogens as a possible consequence of continental subduction and following exhumation of the precambrian crust evidences from the permian jangart rapakivi in south tien shan collisional belt eastern kyrgyzstan abstract all worldwide known rare occurrences of phanerozoic a type granites with typical rapakivi texture do not usually have any significant volume of contemporaneous basic rocks in magmatic association and occur only in those collisional orogens which border ancient cratons and contain hp uhp metamorphic terranes suggesting connection of their petrogenesis with a deep continental subduction and subsequent exhumation of the ancient crust early permian jangart rapakivis and genetically related leucogranites and li mica granites widely spread within the saryjaz syntaxis which is distinguished by the shortest distance between the tarim craton and caledonian kazakh continent collided in the late carboniferous with the possibly deepest continental subduction of the tarim under the south tien shan collisional belt rapakivi plutons occur within the remarkable huge 20 120 km mega melange mega breccia terrane of diapiric not tectonic origin which was identified by the latest geological data and deciphering of satellite imagery according to geophysical data the most of subducted tarim continental crust was trapped within lithospheric mantle and never exhumed but in the saryjaz syntaxis where the collisional suture has been subjected to flecsure like oroclinal bending due to sinistral strike slip tectonics during oblique collision between the tarim and kazakh plates the subduction channel was weakened and exhumation occurred the suggested p t t path of exhumed slices of the subducted tarim continental crust presumes a relatively long around 20 ma residence time on a mantle depth as well as additional internal radiogenic heating and rapid around 2 ma isothermal exhumation which were favorable for extensive melting and subsequent rapakivi formation phanerozoic rapakivis originated from the same ancient lower crust granulite source rocks as their abundant proterozoic counterparts but mechanism of heating and melting of those source rocks was radically different

carbon isotope records from extant caribbean and south pacific sponges evolution of δ13c in surface water dic stable isotope records of demosponges from the caribbean and coral sea are described for the purpose of studying the influence of fossil fuel co2 on the carbon isotopic composition of dissolved inorganic carbon dic in surface water the slow growing sponges precipitate calcium carbonate in isotopic equilibrium with ambient sea water and are used to detect changes in 13cdic from pre industrial times early 19th century to the present we observed similar shapes and ranges in 13c curves measured on caribbean specimens collected from water depths of 25 84 and 91 m as well as a specimen collected in shallow waters off new caledonia the records reveal a highly significant correlation with atmospheric 13cco2 13cdic values for caribbean and coral sea surface waters were calculated using the 13c sponge records while 13c of atmospheric co2 decreased by about 1 4 from the early 19th century to 1990 13cdic of caribbean and coral sea surface waters decreased by 0 9 0 2 and 0 7 0 3 respectively no isotopic equilibrium between surface water dic and atmospheric co2 was observed either during the pre industrial steady state or during the last 100 years the lower amount of depletion in the surface water 13cdic with respect to the atmospheric anthropogenic signal is explained by the dilution of the surface waters by biologically altered subsurface water dic the lower 13c decrease in the coral sea points to a stronger influence of the subsurface water source compared to the caribbean

structural and geochronological study of high pressure metamorphic rocks in the kekesu section northwestern china implications for the late paleozoic tectonics of the southern tianshan abstract blueschist and eclogite facies high to ultrahigh pressure hp uhp metamorphic rocks occur in the southern tianshan belt their deformation and metamorphic history is important for understanding the paleozoic tectonics of the central asian orogenic belt our study focuses on the structural analysis and geochronology of the hp metamorphic rocks and the surrounding rocks in the kekesu section in the southern chinese tianshan geometric and kinematic analyses indicate three ductile deformation events a top to the north thrusting a top to the south shearing and a dextral wrenching new 40ar 39ar laser probe plateau ages were obtained on white mica from retrograde blueschist documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr

lead concentration and isotopic composition in the pacific sclerosponge acanthochaetetes wellsi reflects environmental lead pollution we measured pb ca and pb isotopes with high resolution in the high mg calcite skeleton of a pacific sclerosponge acanthochaetetes wellsi collected from the reef edge off the western coast of kume island east china sea to investigate its potential to be used as a proxy for lead contamination in the environment and atmospheric transportation and fallout over the last few decades skeletal pb ca ranged from 58 to 1642 nmol mol 10 higher than that of the aragonite skeleton of pacific corals and 2 5 higher than that of the aragonite skeletons of caribbean sclerosponges the pb ca timeseries recorded from 1967 through 2007 ce correspond to historical changes in atmospheric lead flux in anthropogenic aerosols pb isotopes 206pb 207pb and 208pb 207pb in the sclerosponge skeleton document that the main source of lead emissions shifted from japan 1970 1980 ce to china 1995 2005 ce as expected from the timing of legislation against the use of leaded gasoline in japan and china our results indicate that the skeleton of the pacific sclerosponge is a powerful proxy to monitor environmental lead pollution applying this methodology to long living and or fossil specimens could be useful in determining the interannual variability of atmospheric transport and dynamics over geologic time scales

permian bimodal dyke of tarim basin nw china geochemical characteristics and tectonic implications abstract this study reports for the first time the occurrence of bimodal dyke in the shuigongtuan area of bachu county tarim basin nw china here quartz syenite porphyry and diabase dykes occur in direct contact showing bimodal feature the quartz syenitic porphyry is metaluminous enriched in k2o na2o 10 11 wt and total rare earth elements ree with low mg mg fe ratios high lree hree and negative eu anomalies the chemical characteristics and tectonic discriminative diagrams show that the rocks have geochemical affinity with a type granites the diabase dyke shows 45 52 wt sio2 and mg mg fe ratio in the range of with high total ree high lree hree ratios and lack of eu anomalies broadly corresponding to tholeiitic composition based on low y nb as low as 0 4 and less than 1 2 enrichment in lile and hfse and uniform nb enrichment patterns in spider diagram for the quartz syenitic porphyry together with the geochemical patterns of the diabases this biomodal association is interpreted to be derived from a mantle source and formed under typical within plate environment the quartz syenitic porphyry and diabase have daly gap of 46 wt 67 wt in sio2 which is explained through formation under bimodal rifting the quartz syenitic dyke probably formed during early permian 277 ma and has geochemical affinity with the xiaohaizi syenitic body we propose that magmas sourced from the mantle intruded into middle upper crust and were emplaced as dykes which indicate large scale extension during the permian in tarim basin the bimodal dyke has genetic affinity with the huge volume of permian basalts and igneous rocks 248 292 ma that occur in the tarim basin the magmatism manifests the culmination of the major thermal event in the tarim basin

exhumation of uhp lt rocks due to the local reduction of the interplate pressure thermo mechanical physical modelling abstract spatial distribution of uhp lt terrains suggests that their exhumation is essentially a three dimensional process that occurs only locally in specific sites along mountain belts on the other hand the continental subduction resulting in the formation of uhp lt rocks takes place along the whole belt the previously performed by the authors 2 d thermo mechanical laboratory modelling of continental subduction has shown that exhumation of deeply subducted continental crust is possible only when the effective interplate pressure p n is lower than the lithostatic pressure low compression subduction regime at the same time this modelling showed that for the deeply subducted continental crust to be preserved at low temperature at great depth the continental subduction should be accompanied by the subduction of the fore arc block or the arc plate the latter process occurs only when p n is high high compression regime to reconcile both processes we suggest that within the background of a generally high compression regime the interplate pressure can be locally reduced in some specific situations which would then allow the local exhumation of uhp lt material using physical modelling technique we investigate one of such situations that occurs when the frontal part of the overriding plate undergoes subduction induced or not extension parallel to the plate boundary with activation or formation of a strike slip transform fault oblique to the plate boundary to the interplate zone the displacement along this fault results in a local reduction of the interplate pressure at the intersection of the fault with the interplate zone this pressure reduction permits the rise of the deeply subducted low density continental crust and sediments submitted to uhp lt conditions under buoyancy force a 10 km thick slice of crust detaches at 150 km depth and moves up along the interplate zone with a starting rate of ca 3 cm yr the ascent rate reduces when the unit reaches crustal depth the deformation of this unit is small when it first detaches and starts rising but increases when reaching the base of the overriding plate the exhuming material is sheared and stretched in a narrow passage at 70 km depth therefore in real conditions the deformation is mainly recorded when the unit is submitted to hp and not uhp conditions

intra annual variation in the stable oxygen and carbon and trace element composition of sclerosponges 1 this paper presents data to support the presence of 1 intra annual signals in the chemical composition 18o and sr ca of the skeletons of sclerosponges from the bahamas and 2 variable rates of skeletal accretion these conclusions are based on data obtained by using a microsampling method for the stable oxygen and carbon isotopes in which material was extracted at a resolution of one sample every 34 m and a laser microprobe which obtained trace element data every 20 m sr mg and pb an age model was established using a combination of changes in the concentration of pb the change in the 13c of the skeleton of the sclerosponges and u th isotopic measurements these methods yield a mean growth rate of 220 m yr but suggest that the growth rate in this particular sclerosponge was not constant the calculated growth rate is within error identical to that determined by u th methods the variable growth rate was confirmed through spectral analysis of the 18o and sr ca data that showed peaks corresponding to the annual cycle in these parameters as well as peaks corresponding to growth rates of approximately 128 212 270 and 400 m yr the presence of these additional frequencies suggests a growth rate between approximately 100 and 300 m yr these conclusions were supported by modeling of oxygen isotopic data measured on a scleractinian coral as well as model isotope data generated on synthetic time series these findings have important implications for the use of sclerosponges as proxies of paleoclimate because they emphasize the need for a precise yearly chronology in order that proxy data can be compared with climatic variables

the association of mafic ultramafic intrusions and a type magmatism in the tian shan and altay orogens nw china implications for geodynamic evolution and potential for the discovery of new ore deposits abstract the nw china region is characterised by tectonic and lithostratigraphic domains such as the tian shan and altay orogens the tarim junggar and turpan basins the tian shan and altay orogens are part of the central asian orogenic belt the nw china region was affected by a series of thermal events that occurred between the silurian and the triassic which resulted in the emplacement of numerous granitic plutons and mafic ultramafic intrusions a number of these granitic plutons are of a type affiliation which on the basis of the positive end values are likely to have been derived from mantle sources in addition at least two large igneous provinces lips can be recognised in nw china namely the 345 325 ma tian shan lip and the ca 270 280 ma tarim lip age and field data suggest a spatial and temporal relationship between the mafic ultramafic intrusions and a type granites within the lips in this paper we discuss mafic ultramafic intrusions that host magmatic ni cu sulphide deposits kalatongke in the altay huangshan and poyi poshi in the eastern tian shan these intrusions are typically zoned characterised by an envelope of early gabbroic rocks that enclose later ultramafic units these zoned mafic ultramafic intrusions have some features that are comparable with alaskan type complexes taking into consideration the spatial temporal relationship of the mafic mafic ultramafic rocks and a type granites we suggest that these magmatic events occurred during an extensional regime possibly related to a mantle superplume event that affected much of central asia during the permian of which the siberian traps and the emeishan continental flood basalts of sw china are part if the a type felsic magmatism took place during a superplume event we also suggest that these rocks may be conducive to host iron oxide copper gold iocg style mineralisation we conclude with a model that attempts to explain the relationship between the zoned mafic ultramafic intrusions and mantle plume activity in nw china during the permian

temporal evolution of the permian large igneous province in tarim basin in northwestern china abstract the temporal relations of different types of rocks in the tarim large igneous province tlip are studied using stratigraphic correlation lithologically spatial distribution and isotopic ages the tlip covers an area 250 000 km2 in the western and central part of the tarim basin the lithological units of the tlip include basalt diabase layered intrusive rock breccia pipe mica olivine pyroxenite olivine pyroxenite gabbro ultramafic dyke quartz syenite quartz syenite porphyry and bimodal dyke this is the first report for the spatial distribution of the tlip from the spatial section lines which shows the stratigraphic correlation among basaltic lava tuff interlayered mudstone siltstone and sandstone and the thicknesses of the basaltic lavas from different field sections and drill holes and the basalts from the kupukuziman and kaipaizileike formations were subdivided in the drill hole sections this indicates that the basaltic lavas were widely distributed in the tarim basin combined with previous study of geochemical and sr nd pb isotopic characterization from the basalts and their genetic link with mantle plume activity and large diabase swarms developments the permian igneous units constitute a tarim large igneous province zircon shrimp u pb dating firstly yields 284 3 2 8 ma for the quartz syenite porphyry recent shrimp and la icp ms zircon u pb and 40ar 39ar ages are used to discuss temporal relations of different rock units in the tlip formed between 290 and 274 ma and these data are more reliable than the k ar ages of 220 310 ma reported previously the sequence of magmatism of the tlip in the central and western parts of the tarim basin are basaltic lava in the kupukuziman and kaipaizileike formations 285 290 ma layered mafic ultramafic rock mica olivine pyroxenite breccia pipe diabase and ultramafic dyke quartz syenite quartz syenite porphyry and bimodal dyke 274 284 ma

geology and mineralization of the uchkoshkon tin deposit associated with a breccia pipe eastern kyrgyzstan abstract the uchkoshkon tin deposit is one of the largest deposits in the sn w saryjaz ore district of eastern kyrgyzstan the district coincides spatially with the saryjaz syntaxis which is the narrowest portion of the south tien shan collisional belt the syntaxis is distinguished by collisional thrust tectonics and postcollisional a type granite magmatism of permian age the uchkoshkon deposit is in the exocontact zone of a 260 km 2 273 279 ma ilmenite series high heat production biotite granite pluton a satellite granite stock 400 250 m and an explosive breccia pipe 450 150 m crosscutting the stock are the central structural features of the deposit area the main stock accompanied by li f felsite dykes controlled early stage mo w and sn w greisen stockwork mineralization that surrounds the apical portion of the stock the breccia pipe postdates the emplacement of the li f felsite dykes and greisen stockwork mineralization the pipe is rooted in main pluton and has been traced by a borehole to a depth of 800 m the breccia was injected by a swarm of tree like branching dykes with diffuse contours consisting of k and b rich rhyolite porphyry cementing the breccia fragments the main breccia body has been intruded by a much smaller 150 100 m hydrothermal breccia pipe with quartz tourmaline matrix which immediately preceded main stage lode mineralization the majority of the lodes occur outside the breccia pipe within a zone of pervasive scapolitization that surrounds the main pluton the main stage lodes are represented by quartz tourmaline cassiterite veins with minor sulfides which occupy a series of steeply dipping near parallel north northeast trending shear fractures that are related to postcollisional strike slip tectonics where quartz tourmaline cassiterite veins crosscut moderately dipping skarn deposits the latter are commercially mineralized with cassiterite nordenskioldine and borosilicate minerals the formation of both explosive breccia and main stage lode mineralization was related to the evolution of b and h 2 o rich residual magma deep within the main pluton the suggested formation model of the uchkoshkon tin deposit is generally applicable to other major sn and sn w deposits in the saryjaz ore district

exhumation of triassic hp lt rocks by upright extrusional domes and overlying detachment faults ishigaki jima ryukyu islands abstract the tomuru formation of ishigaki jima in the southernmost part of the ryukyu arc comprises blueschist facies subduction complex rocks metamorphosed in triassic time d1 structures related to subduction blueschist facies mineral growth and possibly early stages of exhumation are deformed by d2 structures that appear to reflect the last stage of exhumation d2 structures define several anticlines with parasitic overturned folds verging away from anticlinal axes the shortening recorded by this deformation appears to reflect upward extrusion relative to flanking material the anticlines are flanked by detachment faults with normal sense of shear parallel to d2 vergence hanging wall rocks that include the fusaki formation an accretionary prism with early cretaceous metamorphic ages and late eocene limestone conglomerate and andesitic volcanics the eocene strata contain metamorphic detritus derived from the tomuru and fusaki formations indicating pre late eocene surface exposure of these units ultramafic rocks and gabbro blocks of the tomuru formation were incorporated by sedimentary sliding into the trench prior to subduction and high pressure metamorphism rather than being emplaced as diapirs along a post metamorphic fault as previously proposed geochronologic metamorphic and thermal considerations suggest exhumation of the tomuru formation to relatively shallow crustal depths prior to or concurrent with early cretaceous metamorphism of the fusaki formation arcward vergent thrusting may have placed the younger and formerly structurally lower subduction complex fusaki formation over the older one tomuru formation d2 extrusional doming began after the emplacement of the fusaki formation at high structural levels the d2 transport directions are subparallel to the strike of the orogen suggesting that the upright extrusion may have occurred along a forearc strike slip fault system this final stage of exhumation concluded in the late eocene with extensional collapse and the development of detachment faults the progression from initial exposure of the tomuru and fusaki formations deposition of late eocene strata extrusional doming and late detachment faulting may have been associated with migrating step overs rather than changes in regional tectonics

continental vertical growth in the transitional zone between south tianshan and tarim western xinjiang nw china insight from the permian halajun a1 type granitic magmatism article i nfo the south tianshan collisional belt stcb and northern margin of the tarim block ntb are key areas for understanding the prolonged tectonic evolution of the central asian orogenic belt caob the halajun region in xinjiang province nw china is located within the tectonic transition zone between stcb and tarim blocks several granitic intrusions and one mafic ultramafic complex piqiang complex are exposed in this region zircon u pb dating whole rock major oxide trace element and nd isotopic data are presented for the huoshibulake tamu kezi ertuo and halajun ii granitic intrusions in this area new la icp ms u pb age for kezi ertuo intrusion coupled with previously published shirmp u pb ages for huoshibulake and halajun ii intrusions and piqiang complex reveals that all the igneous rocks in the halajun region are coeval 275 ma geochemically the four granitic intrusions show high contents of sio2 k 2o and total alkalis and possess trace element patterns characterized by rb nb ta zr and hf enrichment and significantly negative ba sr p eu and ti anomalies these features strongly favor an a1 type affinity for the halajun granitic intru sions among the four intrusions the kezi ertuo tamu and halajun ii intrusions possess positive to slightly negative end t values ranging from 0 9 to 0 6 whereas the huoshibulake intrusion displays less deplet ed end t values of 2 6 to 2 9 our new elemental and isotopic data suggest that the four granitic intru sions were generated by the partial melting of a common neoproterozoic gabbroic source probably as a result of the 275 ma underplating of the asthenosphere mantle derived magmas the variable involvement of the mantle components accounts for the range of end t values after the generation of the parental magma alkali feldspar arfvedsonite biotite fe ti oxides and zircon seem to have fractionated prior to the final emplacement of the granitic magmas in combination with the regional geological history we propose that the 275 ma a1 type granitic magmatism in the halajun region and other areas of the ntb provides a good proxy record for the vertical continental crustal growth in the southern margin of the caob during the permian our study in combination with other geological evidence indicates that these a1 type felsic and oib like mafic ultramafic rocks with ages from 282 ma to 275 ma in the southern margin of the caob are parts of the permian tarim large igneous province and could be genetically related to the tarim mantle plume

the vertical distribution of radiogenic heat production in the precambrian crust of norway and sweden geothermal implications the present geology of southern scandinavia offers the unique opportunity to sample deep and intermediate levels from the same crustal section for both heat flow and heat production in the central part of southern norway amphibolite facies terranes appear to lie on top of the same deeper crustal formations which crop out on their western and eastern margins an extensive data set on the geochemistry of all types of rocks in the region culled from the literature is used to derive values for radiogenic heat production for each kind of crustal facies using constraints from heat flow data in the same area allows a reliable model of the distribution of crustal heat production the average heat production of granulite facies terranes is 0 4 w m similar to values in other parts of the world for amphibolite facies rocks the value is 1 6 w m the present shield also includes heat producing element enriched granites formed in later events and the average heat production of presently exposed crust is 2 7 m using heat flow and radioactivity data from ten stations the reduced heat flow in the area is 22 2 mw m this corresponds to the heat flow at the top of 28 km of deep crustal facies implying that the mantle heat flow is probably as low as 10 mw m over the whole crustal thickness the average amount of radiogenic heat is 31 mw m

evolution and variability of the asian monsoon system state of the art and outstanding issues the asian monsoon is comprised of the indian and east asian subsystems these two components are linked to one another in varying degrees by regions of strong sensible heating indo asian landmass and strong latent heat export the western pacific warm pool and the southern subtropical indian ocean variability within the indian and east asian subsystems interactions among them and the extent to which they interact with other climate phenomena e g enso are current topics of modern and paleoclimate research this work provides an overview of past and current paleomonsoon research on tectonic to interannual time scales with a primary focus on marine sediment records while past and current work has contributed greatly to our understanding of paleomonsoon variability at all time scales additional efforts are required to make further progress in two critical areas 1 additional efforts are needed in terms of proxy development and evaluation requiring concerted efforts at long term sediment trap deployments in key monsoon influenced regions as well as development of adequate and widely available core top databases these are necessary to assess the impact of modern oceanographic and seafloor processes on potential monsoon proxies 2 additional effort is also needed in acquiring a sufficient geographic distribution of downcore records to assess linkages among the subsystems and their role in the context of extratropical climate change these records should have high sedimentation rates including varved sections this requires substantial survey support to identify the most appropriate coring and drilling targets c 2004 elsevier ltd all rights reserved