zircon hf o isotope evidence for recycled oceanic and continental crust in the sources of alkaline rocks post orogenic and intraplate extensional alkaline rocks are believed to have formed by partial melting of metasomatized ultramafic rocks in the subcontinental lithospheric mantle their variable incompatible element abundances and radiogenic isotopic ratios reflect recycling of subducted oceanic or continental crustal material into their source reservoirs however whole rock geochemical and sr nd isotopic data do not well constrain the nature of this recycled crustal material because of complex petrogenetic processes i e crustal assimilation fractional crystallization magma mixing and post magmatic alteration here we present an integrated study of in situ hf o isotopes in zircons from two triassic alkaline complexes in the northeastern sino korean craton i e the hekanzi and saima alkaline complexes the hekanzi alkaline rocks have zircon ehf t values of 2 5 to 0 6 and sub normal mantle 18o 3 8 to 5 4 indicating a component of high temperature altered oceanic crust involved in their mantle source prior to magma generation in contrast the saima alkaline rocks have extremely negative zircon ehf t 11 to 14 and elevated 18o 7 1 to 8 4 values suggesting continental crust recycled into their mantle source prior to magma generation our results show that the combined zircon hf and o isotopes are powerful tracers to distinguish recycled continental crust from recycled oceanic crust and importantly provide compelling evidence for recycled continental crust in the sources of alkaline rocks

rapid oscillations in vostok and grip ice cores we investigate the spectral properties of climatic times series derived from two recent ice cores in greenland and east antarctica we find that the signals behave in a similar way in the high frequency part of their spectra the rapid oscillations found in the grip ice core were closely correlated to heinrich events a comparable spectral feature is detected in the vostok ice core we discuss the possibilities of connections between the two hemispheres and proper ice sheet oscillations in the light of simple oscillating climate models

early mesozoic basin development in north china indications of cratonic deformation we integrated a systematic sedimentary data into a regional early mesozoic stratigraphic framework which demonstrated a detailed picture of spatiotemporal variations in basin deposition and formation in the north china craton the early mesozoic basin sedimentary evolution is utilized to interpret polyphase tectonism and to unravel the craton deformation the late triassic nearly wnw trending giant intracratonic ordos basin was widely distributed across most of north china craton with a southern wedge top depozone along the northern east qilian qinling orogenic belt and a northwestern rift depozone along the helanshan the continuous subsidence and deposition within the basin were dominantly related to the thrust load of the east qilian qinling belt and inferred mantle flow effects associated with paleotethys plate subduction and the rift in the northwestern ordos was driven by nearly north vergent compression of the eastern north qilian north qinling active margins with the stable north china craton this intracratonic ordos basin formation initiated the deformation of the north china craton formation of the jurassic nne trending walled intracratonic ordos basin and the broken flexural basins indicates the north china craton underwent the second even more abroad nearly nne trending crustal deformation with lithosphere thickening in the eastern part of the north china craton and dynamic subsidence in the west which may have been driven by nearly northwestward subduction of the izanagi plate and the eastward extrusion and underthrusting of the western north china craton crustal basement

recent warming in eastern canada inferred from geothermal measurements borehole temperature measurements from several sites in eastern canada were analyzed to determine recent step changes in ground surface temperature inversion of the data suggests a warming by 1 to 2 c in the last 100 years for most of the sites analyzed

distribution pattern of age and geochemistry of 2 18 2 14 ga i and a type granites and their implication for the tectonics of the liao ji belt in the north china craton abstract determining the petrogenesis and tectonic environment of the 2 18 2 14 ga liaoji granites is important to understand the paleoproterozoic tectonic evolution of the liao ji belt in the north china craton the muniuhe granitic pluton is one representative of the liaoji granites it is located in the northwestern part of the liao ji belt and is composed of syenogranite and granodiorite that intruded at 2 18 ga and were metamorphosed at 1 88 ga geochemically the muniuhe granitic pluton shows a magnesian and weakly peraluminous character with low rees 10 000 ga al and zr nb ce y values and negative nb and ta anomalies typical of arc related i type granite it was formed by partial melting of archean crustal material at low temperatures in oxygenated and hydrous conditions and then underwent crystallization differentiation of feldspar the results of this study together with those of previous studies investigating the liaoji granites indicate that the formation of the 2 18 2 14 ga liaoji granites including the muniuhe granitic pluton can be subdivided into three stages 1 the formation of 2 18 ga granites with a2 type characteristics the mafeng longchang jiguanshan and laoheishan yongdian granitic plutons and 2 18 ga granites with arc related i type characteristics the muniuhe granitic pluton in the northwestern and southeastern parts of the liao ji belt 2 the formation of 2 16 ga granites with arc related i and a2 type characteristics hupiyu hadabei simenzi gujiabao and qianzhuogou granitic plutons in the central part with a ne trending distribution and 3 the formation of 2 14 ga granites the dafangshen granitic pluton with a2 type characteristics in the central part the intrusion ages show a trend to become younger from the margins to the center and the geochemical characteristics of these plutons indicate that they formed during the extension of a back arc basin related to partial melting of the archean continental crust together with the liaohe group and 2 13 2 11 ga mafic intrusions the liaoji granites indicate that the existence of a back arc basin extension during 2 18 2 11 ga in the liao ji belt

on the structure and dynamics of indian monsoon depressions abstractera interim reanalysis data from the past 35 years have been used with a newly developed feature tracking algorithm to identify indian monsoon depressions originating in or near the bay of bengal these were then rotated centralized and combined to give a fully three dimensional 106 depression composite structure a considerably larger sample than any previous detailed study on monsoon depressions and their structure many known features of depression structure are confirmed particularly the existence of a maximum to the southwest of the center in rainfall and other fields and a westward axial tilt in others additionally the depressions are found to have significant asymmetry owing to the presence of the himalayas a bimodal midtropospheric potential vorticity core a separation into thermally cold 1 5 k and neutral 0 k cores near the surface with distinct properties and the center has very large cape and very small cin variability as a function of background state has also been explo

precambrian crustal evolution of the eastern north china craton as revealed by u pb ages and hf isotopes of detrital zircons from the proterozoic jing eryu formation abstract simultaneous in situ u pb dating trace element and hf isotopic analyses have been carried out on detrital zircons obtained from sandstones in the neoproterozoic jing eryu formation from the eastern block north china craton ncc with the aim of constraining the ages of magmatic and metamorphic events and hence the precambrian crustal evolution of the ncc two groups of zircons i e magmatic and metamorphic in origin have been identified based on cathodoluminescence images zircon ti temperatures and th u ratios zircon u pb dating shows two main magmatic events with ages of 2 55 2 47 ga and 1 80 1 70 ga and four metamorphic events with ages of 2 51 2 48 ga 1 96 1 90 ga 1 87 1 85 ga and 1 80 ga in the ncc no zircons with ages of 3 8 ga have been identified in this study indicating either these were covered at the time of deposition or the limited presence of 3 8 ga rocks in the ncc the hf isotopic data show the 2 5 ga magmatic zircons have variable hf t values including both positive and negative values and with crustal model ages of 2 7 2 9 ga which can be interpreted to indicate mixed sources for their parental rocks i e ancient crust 3 8 ga or 3 3 ga and depleted mantle implying significant continental crustal growth at 2 5 ga however paleoproterozoic magmatic zircons all have negative hf t and archean hf model ages suggesting that their parental rocks were formed from recycled archean materials the widespread 2 5 ga metamorphism in the eastern block coupled with extensive 2 5 ga magmatism and crustal growth are consistent with a mantle plume beneath the eastern block of the ncc during the neoarchean whereas a progressive increase in 1 85 ga metamorphic zircon westward across the eastern block toward the trans north china orogen is best explained by collision between the eastern and western blocks at this time

interannual and decadal cycles in river flows of southeastern south america abstract the time series of annual streamflow of four rivers in southeastern and south central south america the negro paraguay parana and uruguay rivers for the period 1911 93 are analyzed application of the multitaper method shows that the following features are significant at the 95 level 1 a nonlinear trend 2 a near decadal component and 3 interannual peaks with enso timescales the trend and near decadal components are most marked in the two more central rivers the paraguay and parana with enso timescale variability most pronounced in the negro and uruguay rivers in the southeast composites of sst are made for each of the statistically significant oscillatory components of river flow by reconstructing each component using singular spectrum analysis these composites confirm the influence of enso on the streamflow variability of the negro and uruguay rivers with el nino associated with enhanced streamflow on the decadal timescale high river runoff is associated with anomalously coo

the dynamics of heat lows a numerical model is used to investigate dynamical aspects of the structure and evolution of a heat low in an idealized flow configuration with an area of land surrounded by sea of particular interest is the evolution of the distributions of relative vorticity and potential vorticity while the heat low has a minimum surface pressure in the late afternoon following strong solar heating of the land the relative vorticity is strongest in the early morning hours following a prolonged period of low level convergence thus the heat low is not approximately in quasi geostrophic balance the low level convergence is associated with the sea breeze and later with the nocturnal low level jet the effects of differing sea area land area and coriolis parameter on various aspects of the heat low are investigated although a cyclonic vortex the heat low is characterized by an anticyclonic potential vorticity anomaly relative to its environment throughout much of the lower troposphere on account of the greatly reduced static stability in the convectively well mixed boundary layer however the surface temperature maximum over land corresponds with a cyclonic potential vorticity anomaly at the surface the reduced static stability in the mixed layer has the further consequence that the horizontal components of relative vorticity and horizontal potential temperature gradient make a non negligible contribution and of opposite sign to the potential vorticity in certain flow regions two processes associated with the flow evolution in the model appear to be fundamental to understanding a range of low level atmospheric phenomena over the arid interior of australia these are the deep convective mixing over land during the daytime and the development of a nocturnal low level jet which leads to convergence in the trough such phenomena include the diurnal behaviour of dry cold fronts and the generation of nocturnal wind surges and bores it is reasonable to assume that similar processes operate in other arid regions of the world where deep convective mixing over land produces local maxima of diabatic heating in the lower atmosphere

boundary lines within petrologic diagrams which use oxides of major and minor elements use of some petrologic diagrams applied to analyses of volcanic rocks is unnecessarily difficult due to lack of data for construction of discriminant lines between rock series coordinates are provided for sufficient points to enable accurate plotting of the boundary lines within seven diagrams viz 1 tas total alkalies na2o k2o vs sio2 2 k2o vs sio2 3 afm 4 jensen 5 ktp k2o tio2 p2o5 6 fms feo mgo vs sio2 and 7 taktip k2o na2o k2o vs tio2p2o5 different versions of these boundaries are collated to indicate their variable position and it is demonstrated that inter laboratory analytical precision suffices to account for almost all of their spread on the tas and k2o vs sio2 diagrams

tracing magma mixing and crystal melt segregation in the genesis of syenite with mafic enclaves evidence from in situ zircon hf o and apatite sr nd isotopes abstract alkaline rocks contain essential information on post collisional intraplate extensional magmatic processes within the continental lithosphere the erhulai syenitic pluton in the liaodong peninsula north china craton consists of quartz syenite mafic enclaves and porphyritic k feldspar granite field observations and zircon u pb dating reveal that the quartz syenite and the hosted mafic enclaves were coeval with identical emplacement ages of 129 126 ma and slightly older than the porphyritic k feldspar granite ca 123 ma the mafic enclaves have relatively low sio2 and high mgo contents up to 3 0 and lack ba or eu anomalies whole rock analyses of the mafic enclaves and accessory minerals in the enclaves show relatively low initial 87sr 86sr ratios 0 7056 to 0 7078 and variable end t 11 2 to 2 0 and ehf t 15 8 to 5 5 values large proportion of zircons from the mafic enclaves possess mantle like 18o values these geochemical features suggest an enriched mantle source with the addition of crustal material the quartz syenites have relatively high sio2 and low cao and mgo contents as well as significantly positive k ba and eu anomalies all the quartz syenites show variable 87sr 86sr i ratios 0 7073 to 0 7081 and end t values 10 4 to 8 6 for the whole rocks and apatites ehf t values of 12 4 to 3 6 for the zircons and zircon 18o values of 4 4 to 7 0 mainly greater than 5 3 all these features can be isotopically produced by the partial melting of ancient crustal material with the involvement of mantle derived magma crystal fractionation process such as k feldspar crystallization and accumulation played an important role in the formation of the quartz syenite the porphyritic k feldspar granites possess relatively evolved geochemical compositions with high silica contents sio2 69 wt and remarkable negative ba and eu anomalies which are chemically complementary to the quartz syenite a crystal mush model was employed to establish the genetic link between the porphyritic k feldspar granite and the quartz syenite with the granite representing the interstitial melt extracted from the crystal mush and the quartz syenite representing the residual accumulation of crystals the variable isotopic compositions of the quartz syenite and the porphyritic granite were mainly the result of extensive interaction of isotopes between mantle and crust derived magmas during magma mixing in situ analyses of the sr nd hf and o isotopes of accessory minerals coupled with field observations and whole rock geochemical data for the erhulai syenitic pluton indicate a complex multi stage magmatic process involving magma mixing crystal melt segregation and wall rock assimilation our study also shows that in situ isotopic analyses of accessory minerals provide unique information on and are powerful geochemical tracers of mantle crust interactions and magmatic processes

coherent synoptic disturbances in the australian monsoon abstractcoherent synoptic scale weather systems within the australian monsoon are identified and tracked in the isentropic potential vorticity pv field from the ecmwf interim reanalysis era interim dataset during the southern hemisphere summer the resulting dataset is then used to compile statistics and synoptic composites of australian monsoon disturbances on average a synoptic system is found in the region every 2 5 days however the time interval between consecutive events is highly variable meaning that the synoptic activity in the australian monsoon is not well represented by commonly employed spectral techniques the analysis reveals that most synoptic systems originate within the australian monsoon but at the 315 k level approximately 700 hpa a significant proportion of systems are first detected near the east coast of the continent where extratropical rossby waves are observed to frequently break the average australian monsoon weather system propagates from east to west at approximatel

temperature trends over the past five centuries reconstructed from borehole temperatures for an accurate assessment of the relative roles of natural variability and anthropogenic influence in the earth s climate reconstructions of past temperatures from the pre industrial as well as the industrial period are essential but instrumental records are typically available for no more than the past 150 years therefore reconstructions of pre industrial climate rely principally on traditional climate proxy records each with particular strengths and limitations in representing climatic variability subsurface temperatures comprise an independent archive of past surface temperature changes that is complementary to both the instrumental record and the climate proxies here we use present day temperatures in 616 boreholes from all continents except antarctica to reconstruct century long trends in temperatures over the past 500 years at global hemispheric and continental scales the results confirm the unusual warming of the twentieth century revealed by the instrumental record but suggest that the cumulative change over the past five centuries amounts to about 1 k exceeding recent estimates from conventional climate proxies the strength of temperature reconstructions from boreholes lies in the detection of long term trends complementary to conventional climate proxies but to obtain a complete picture of past warming the differences between the approaches need to be investigated in detail

borehole climate reconstructions spatial structure and hemispheric averages 1 ground surface temperature gst reconstructions determined from temperature profiles measured in terrestrial boreholes when averaged over the northern hemisphere estimate a surface warming of 1 k during the interval ad 1500 2000 other traditional proxy based estimates suggest less warming during the same interval mann et al 2003a have raised two issues with regard to borehole based reconstructions the first focuses on the need for spatial gridding and area weighting of the ensemble of borehole based gst reconstructions to yield an average hemispheric reconstruction the second asserts that application of optimal detection techniques show that the gst only weakly displays the spatial structure of the surface air temperature sat we demonstrate the consistency of gst warming estimates by showing that over a wide range of grid element area and occupancy weighting schemes the five century gst change falls in the range of 0 89 1 05 k we examine the subhemispheric spatial correlation of gst and sat trends at various spatial scales in the 5 degree grid employed for optimal detection we find that the majority of grid element means are determined from three or fewer boreholes a number that is insufficient to suppress site specific noise via ensemble averaging significant spatial correlation between sat and gst emerges in a 5 degree grid if low occupancy grid elements are excluded and also in a 30 degree grid in which grid element means are better determined through higher occupancy reconstructions assembled after excluding low occupancy grid elements show a five century gst change in the range of 1 02 1 06 k index terms 1645 global change solid earth 1699 global change general or miscellaneous 3309 meteorology and atmospheric dynamics climatology 1620 3322 meteorology and atmospheric dynamics land atmosphere interactions 3344 meteorology and atmospheric dynamics paleoclimatology keywords boreholes paleoclimate spatial analysis surface temperature

early mesozoic deformations of the eastern yanshan thrust belt northern china the yanshan thrust belt ytb is located at the northern edge of the north china plate because of the intense thicking and subsequent delamination of the lithosphere in north china geologists have been focused on the late mesozoic deformation in the yanshan belt the yanshan belt has been regarded as part of a stable craton from the proterozoic to the early mesozoic in this paper the authors present that the yanshan area was deformed during the early mesozoic this deformation could be related to ocean basin closure along the northern margin of north china or related to the collision between the north china and yangtze plates along the qinling dabie ultrahigh pressure belt three stages of early mesozoic deformation are identified in the eastern yanshan at lingyuan county the first stage is characterized by westward thrusting d1 the second stage comprises a top to east thrust system d2 and the third stage comprises extensional gravity induced collapse and landsliding d3 the timing of these evens is constrained by both the crosscutting relationships of faults and the isotopic dating of volcanic rocks and gravels the d1 and d2 events took place in the late triassic and early jurassic whereas d3 event occurred at the end of the middle jurassic the dengzhangzi formation was deposited during the d1 d2 period and recorded a rapid uplift erosion and deposition sequence these early mesozoic contractional deformations in the ytb were probably related to the closure of ancient asian ocean and ancient qinling ocean the later crustal extension was caused by gravitational collapse of the eastern china plateau during early mesozoic

role of ocean mesoscale structures in shaping the angola low pressure system and the southern africa rainfall southern african climate is under the influence of both tropical and subtropical systems which result in a complex region where important interactions co exist over a large spectrum of spatiotemporal scales the angola low al situated on boundary between tropical and subtropical southern africa has been diagnosed as a key driver of moisture distribution in the region on daily to seasonal time scales it has been demonstrated that the al pressure system is sensitive to the dynamics of the neighbouring oceans but to date no study has considered the model resolution of air sea interactions required to simulate this sensitivity using sensitivity experiments with a regional atmospheric model which differ only in the mesoscale sea surface temperature sst forcing characteristics either the full spectrum of sst variability or only its large scale components are included we first quantify the importance of sst gradients on the al strength and variability the results suggest that the mesoscale sst variability of the angola benguela frontal zone abfz plays a key role in al activity particularly during the late summer synoptic scale tropical lows which form the al are automatically detected and the results suggest more extreme events occur when the model is forced by mesoscale ssts everywhere and in the abfz area only the rainfall resulting from those events suggests that tropical low episodes are associated with nearly 15 of the total rain in angola and namibia the link between al dynamics and wet spells is also discussed with the former showing a different spatial pattern as well as frequency when the ocean is fully resolved

the dynamics of heat lows in simple background flows a three dimensional numerical model is used to study the evolution of an idealized heat low that develops over an isolated level land mass surrounded by sea calculations are carried out without a background flow and for simple background flows in all cases the flow shows a significant diurnal variation in which the sea breeze circulations are the prominent feature during the daytime and the nocturnal low level jet is the prominent feature at night if the land area is large enough so that the sea breezes do not cover it entirely during the diurnal cycle strong convergence associated with the low level jet leads to the formation of intense but shallow cold fronts along the inland boundaries of sea breeze air these fronts decay rapidly after sunrise when surface heating leads to renewed vertical mixing which destroys the low level stable layer the presence of a uniform easterly flow leads to the formation of a west coast trough similar to the situation commonly observed over western australia the trough broadens during the day due to the heating of the land while at night it sharpens and again frontogenesis occurs at low levels near the leading edge of the sea breezes to form shallow cold fronts in these calculations there is an east west asymmetry in the sea breeze circulations the cool air behind the west coast sea breeze is shallower than that behind the east coast sea breeze but the vertical circulation associated with the west coast sea breeze is deeper the east coast sea breeze front penetrates further inland but is more diffuse and is recognizable more by its signature in the relative vorticity than by that in the horizontal temperature gradient the presence of a horizontal shear flow leads to the deformation of the heat trough a process that appears to play an important role in the formation of cold fronts over central australia again the calculations show the formation of shallow fronts over the land during the night which frontolyse rapidly after sunrise despite the idealized nature of the calculations the associated patterns of low level vorticity divergence and horizontal temperature gradient that develop overnight show remarkable similarity to those observed over central australia indeed the calculations help to interpret the observations of nocturnal frontogenesis over this region copyright 2005 royal meteorological society

out of sequence thrusting in polycyclic thrust belts an example from the mesozoic yanshan belt north china craton the ew trending yanshan belt an intraplate fold thrust belt located in the northern north china craton that has experienced several episodes of deformation widely separated in time is characterized by out of sequence thrusts according to detailed mapping in the central yanshan belt five geometric and stratigraphic criteria used to aid in determining whether a thrust has an out of sequence geometry or not can be recognized they are 1 unconformable relationships 2 inclination of fault surfaces 3 irregular changes in apparent offset along strike 4 short fault length relative to apparent offset and 5 in sequence geometry with the help of these criteria two generations of out of sequence thrusts that postdate the original in sequence thrusting in the central yanshan belt are recognized the ancestral southward verging fold and thrust belt that formed prior to 180 ma was deformed and cut by two younger generations of faults that are probably more deeply rooted and are constrained to between 172 165 ma and 152 135 ma a series of thrusts with opposite vergence formed during the last period resulting in abundant abnormal field relationships such as younger on older thrust relations fold truncation and cutting down section the nature and occurrence of faults in the yanshan belt implies that superimposed deformation a common feature in polycyclic orogenic belts is a mechanism for the generation of out of sequence thrusting this adds to mechanisms already described in the literature such as maintaining constant critical taper at an orogenic scale inhibition of the deformation front and lateral changes in the nature of the decollement horizons

pbsl dating of garnet and staurolite constraints on the paleoproterozoic crustal evolution of the eastern block north china craton abstract it is well accepted that the north china craton formed by assembly of the eastern and western blocks along the trans north china orogen with cratonization in the paleoproterozoic 1 85 ma however there is controversy about the formation of the eastern and western blocks themselves especially the timing of cratonization of the eastern block the jiao liao ji orogenic belt is the most important paleoproterozoic orogenic belt in the eastern block and consists mainly of the north and south liaohe groups and the liaoji granitoids the timing of metamorphism of the liaohe group is the key to understanding the evolution of the eastern block of the north china craton because the isotope systematics of metamorphic minerals can be used to date parts of the prograde thermal histories of metamorphic belts dating of minerals such as garnet and staurolite has the distinct advantage that time information can be related directly to the pressure temperature deformation history recorded by the same mineral in this paper we present results of precise 207pb 206pb stepwise leaching pbsl dating of garnet and staurolite from the metasedimentary rocks of the south liaohe group the primitive pb and radiogenic pb are selectively extracted from garnet and straurolite by leach steps and determined by multiple collector mc icp ms the garnet and staurolite record two groups of 207pb 206pb ages at 1 93 1 91 ga and 1 86 ga respectively these constrain the time of peak metamorphism of the liaohe group during collision between the longgang block in the north and the liaonan nangrim block in the south and a subsequent post collisional event respectively our data for the south liaohe group and previously published data for the liaoji granite combined with key lithological structural and metamorphic information indicate that the cratonization of the eastern block of the north china craton occurred at 1 93 1 91 ga

ground temperature histories for central and eastern canada from geothermal measurements little ice age signature deep borehole temperature profiles have been analyzed to determine ground temperature histories in central and eastern canada clear signs of a cold period between 1500 and 1800 a d corresponding to the little ice age have been found a warming trend after 1800 a d was detected throughout eastern and central canada temperature profiles from western ontario are consistent and were inverted simultaneously to yield a regional ground temperature history the recent warming appears to be correlated with the increase of atmospheric co2 reported for a greenland ice core

african hydroclimatic variability during the last 2000 years abstract the african continent is characterised by a wide range of hydroclimate regimes ranging from humid equatorial west africa to the arid deserts in the northern and southern subtropics the livelihoods of much of its population are also vulnerable to future climate change mainly through variability in rainfall affecting water resource availability a growing number of data sources indicate that such hydroclimatic variability is an intrinsic component of africa s natural environment this paper co authored by members of the pages africa 2k working group presents an extensive assessment and discussion of proxy historical and instrumental evidence for hydroclimatic variability across the african continent spanning the last two millennia while the african palaeoenvironmental record is characterised by spatially disjunctive datasets with often less than optimal temporal resolution and chronological control the available evidence allows the assessment of prominent spatial patterns of palaeomoisture variability through time in this study we focus sequentially on data for six major time windows the first millennium ce the medieval climate anomaly 900 1250 ce the little ice age 1250 1750 ce the end of the lia 1750 1850 ce the early modern period 1850 1950 and the period of recent warming 1950 onwards this results in a continent wide synthesis of regional moisture balance trends through history allowing consideration of possible driving mechanisms and suggestions for future research

phanerozoic magma underplating and crustal growth beneath the north china craton evidence for post archaean crustal growth via magma underplating is largely based on u pb dating of zircons from granulite facies xenoliths however whether the young zircons from such xenoliths are genetically related to magma underplating or to anatexis remains controversial the lower crustal xenoliths carried by igneous rocks in the chifeng and ningcheng north china craton have low sio2 and high mgo indicating that parental melts of their protoliths were of unambiguous mantle origin the xenoliths contain abundant magmatic zircons with late palaeozoic ages and have more radiogenic zircon hf isotope compositions and hence younger model ages than ancient crustal magmas and the reworking array of the basement rocks our data suggest that the granulites represent episodic magmatic underplating to the lower crust of this craton in phanerozoic time considering the observation that regional lowermost crust 5 km is mafic and characterized by phanerozoic zircons this work reports an example of post archaean crustal growth via magma underplating

rapid exhumation and cooling of the liaonan metamorphic core complex inferences from 40ar 39ar thermochronology and implications for late mesozoic extension in the eastern north china craton the liaonan metamorphic core complex formed during crustal extension in the liaodong peninsula eastern north china craton and consists of the jinzhou detachment fault proterozoic paleozoic sedimentary rocks in its upper plate and exhumed high grade archean metamorphic rocks and early cretaceous granitic plutons in the lower plate exhumation of its footwall from mid crustal levels is evidenced in the detachment fault zone by the temporal transition from amphibolite facies mylonitization at depth through retrograde chloritic shearing and brecciation to brittle faulting during final uplift the footwall mylonite zone is 2 5 3 5 km thick and includes early cretaceous 128 118 ma granitic rocks together with older metamorphic rocks the 40ar 39ar ages of muscovite hornblende biotite and k feldspar from the mylonitic rocks record that the core complex cooled between ca 120 and 107 ma from the time of initial crystallization of zircons 122 118 ma at 700 800 c in syntectonic leucocratic dikes and granitic rocks to closure of argon diffusion in hornblende micas and k feldspar at 500 to 200 c throughout the eastern north china craton the synchroneity of cooling and exhumation of metamorphic core complexes the formation of pull apart basins and regional alkaline igneous activity reflects regional extensional tectonics in the early cretaceous this accompanied lithospheric thinning possibly resulting from the rollback of the subducted pacific plate along the eastern asian margin during the early cretaceous

destruction of the north china craton in the mesozoic the north china craton ncc was originally formed by the amalgamation of the eastern and western blocks along an orogenic belt at 1 9 ga after cratonization the ncc was essentially stable until

multiple sources for the origin of granites geochemical and nd sr isotopic evidence from the gudaoling granite and its mafic enclaves northeast china geochemical and sr and nd isotopic data have been determined for mafic to intermediate microgranular enclaves and host granitoids from the early cretaceous gudaoling batholith in the liaodong peninsula ne china the rocks include monzogranite porphyric granodiorite and quartz diorite monzogranites have relatively high 87rb 86sr ratios 0 672 0 853 low initial 87sr 86sr ratios 0 7052 0 7086 and e nd t values 18 5 to 20 9 indicating that they were mainly derived from a newly underplated crustal source with a short crustal residence time quartz diorites have high initial 87sr 86sr ratios 0 7118 0 7120 and negative e nd t values 13 2 to 18 1 coupled with high al2o3 and mgo contents indicating they were derived from enriched lithospheric mantle with contributions of radiogenic sr from plagioclase rich metagreywackes or meta igneous rocks i e ancient lower crust two groups of enclaves with igneous textures and abundant acicular apatites are distinguished dioritic enclaves and biotite monzonitic enclaves dioritic enclaves have low al2o3 13 5 16 4 wt and high mgo mg 72 3 concentrations low initial 87sr 86sr ratios 0 7058 0 7073 and negative e nd t values 7 2 and are enriched in liles and lrees and depleted in hfses suggesting they were derived from an enriched lithospheric mantle source biotite monzonitic enclaves have sr and nd isotopic compositions similar to the monzogranites indicating they were crystal cumulates of the parental magmas of these monzogranites granodiorites have transitional geochemistry and nd and sr isotopic compositions intermediate between the monzogranites quartz diorites and the enclaves geochemical and sr and nd isotopic compositions rule out simple crystal liquid fractionation or restite unmixing as the major genetic link between enclaves and host rocks instead magma mixing of mafic mantle derived and juvenile crustal derived magmas coupled with crystal fractionation and assimilation of ancient lower crust is compatible with the data this example shows that at least some calc alkaline granitoids are not produced by pure intracrustal melting but formed through a complex multi stage hybridization process involving mantle and crustal derived magmas and several concomitant magmatic processes crystal fractionation crustal assimilation and crustal anatexis

nd hf o isotopic evidence for subduction induced crustal replacement in ne china abstract convergent plate margins represent an ideal setting to understand the formation and evolution of the earth s crust nevertheless the geodynamic processes involved in crustal evolution remains highly debatable based on a large geochemical dataset of permian cretaceous granitic rocks from the yanbian area in ne china we propose a new geodynamic model involving crustal replacement to decipher crustal evolution during a superimposed multi stage subduction system these phanerozoic granitic rocks from two adjacent zones show contrasting hf nd isotopic variation trends with decreasing age of magmatism whole rock end t and zircon ehf t decrease gradually in the north granite zone ngz but show the opposite trends in the south granite zone sgz zircon 18o shows a slight rise in the ngz but it initially increases from permian to jurassic and then decreases to cretaceous in the sgz the nd hf o isotopic compositions of the cretaceous granitic rocks in both zones converge four crustal components are identified in the source of granites across the yanbian area including 1 juvenile crust 2 subduction accretionary complex 3 new arc crust and 4 precambrian crust the contributions made to the bulk crustal melting source of granites by the juvenile crust component in the ngz and by the precambrian crust in the sgz were both gradually decreased whereas the proportion of the new arc crust increased in both zones pre existing crustal components were extensively eroded destructed diluted and replaced by the new arc crust formed during paleo pacific slab subduction considering the prevalence of these two nd hf o isotopic variation trends in many orogenic belts subduction induced crustal replacement represents an important mechanism for crustal evolution in convergent plate margins

deep soil temperature as proxy for surface air temperature in a coupled model simulation of the last thousand years 1 the relationship between terrestrial deep soil temperature tdst and surface temperature sat at interannual and centennial timescales has been investigated in a simulation of the last millennium with a three dimensional climate model driven by estimations of historical external forcing tdst is loosely related to borehole temperature profiles which have been recently used to reconstruct long term temperature trends in the last centuries recently questions about the validity of boreholes based reconstructions have been raised in the simulation at interannual time scales the connection between tdst and sat is stable being stronger in the summer half year than in the winter half year at long timescales annual tdsl is a good proxy for annual sat and their variations are almost indistinguishable from each other both tdsl and terrestrial sat overestimate the variations of global mean sat this may be a source for the disagreement between statistical reconstructions of global sat and terrestrial borehole measurements

characterizing the synoptic expression of the angola low the angola low is a key feature of the southern africa wet season atmosphere that influences precipitation across the continent this paper uses era interim to show that the synoptic expression of the angola low is a combination of dry heat lows and moist tropical low pressure systems the angola heat low and angola tropical low composites are contrasted against similar lows observed in other continental tropical regions and found to be broadly comparable the implications that the distinction between dry and moist events has for the interannual relationship among the angola low precipitation and enso are examined the tropical lows exhibit unusual semistationary behavior by lingering in the angola region rather than traveling offshore this behavior is proposed to be caused by an integrated sea breeze anabatic wind that enhances inhibits cyclonic vorticity stretching and convection inland near the coast the combined effect of the heat lows and the anchored tropical lows creates the angola low in the climatological average by elucidating the mechanisms of the angola low this research improves the foundation of process based evaluation of southern africa present and future climate in cmip and amip models

the mesozoic accretionary complex in northeast china evidence for the accretion history of paleo pacific subduction abstract the mesozoic accretionary complex in northeast china which mainly consists of the jilin heilongjiang high pressure hp metamorphic belt and the nadanhada accretionary complex are the key area to understand the paleo pacific subduction accretion the jilin heilongjiang hp belt is a hp metamorphic zone between the jiamusi and songliao blocks and consists of the heilongjiang blueschist belt and the zhangguangcai complex previously published and our new geochronological data indicate that the collision between the jiamusi and songliao blocks along the jilin heilongjiang hp belt occurred between 210 and 180 ma suggesting that the jilin heilongjiang hp belt is an important unit for characterizing the geodynamic switch from the north south closure of the central asian orogenic belt to the onset of westward accretion related to subduction of paleo pacific plate in the latest triassic to early jurassic early permian igneous rocks with arc affinity in the eastern margin of the jiamusi block are more likely related to the mongol okhotsk subduction rather than the paleo pacific subduction or the collision between the jiamusi and khanka blocks as previously considered the nadanhada accretionary complex lies to the east of the jiamusi block and is composed of the yuejinshan and raohe complexes compilation of published geochronological data indicate that the yuejinshan complex was probably formed between 210 ma and 180 ma similar to ages for the jilin heilongjiang hp belt along the western margin of the jiamusi khanka block the raohe complex was formed later in the late jurassic to early cretaceous 170 137 ma likely more related to the subduction accretion of paleo pacific plate the final accretion in the target area took place in the early cretaceous 137 130 ma

the angola low relationship with southern african rainfall and enso the main states of the angola low al are identified using clustering analysis applied to daily anomalous patterns of 700 hpa wind vorticity over angola and adjacent countries from november to march for the 1980 81 2014 15 period at the daily timescale we examine the extent to which the main states of the al modulate daily rainfall over southern africa at the interannual timescale we assess both the relationship between the occurrence of these al states and el nino southern oscillation enso and the role of the al in explaining enso s failure in driving southern african rainfall at times three reanalyses are considered to account for uncertainties induced by the scarcity of data available for assimilation over southern africa three preferential states of the angola low are identified al state close to its seasonal climatology with slight zonal displacements anomalously weak al state and anomalously strong al state with meridional displacements these different states all significantly modulate daily southern african rainfall near climatological al state promotes wet rainfall anomalies over eastern subtropical southern africa and dry rainfall anomalies over its western part a slight westward shift in the near climatological position of the al leads to reversed zonal gradient in rainfall the remaining regimes significantly modulate the meridional gradient in southern african rainfall anomalously weak and anomalously northward al states promote wet rainfall anomalies over tropical southern africa and dry rainfall anomalies over subtropical southern africa the reverse prevails for anomalously southward al at the interannual timescale enso significantly modulates the seasonal occurrence of most al states in the three reanalyses anomalously weak and southward al states are more strongly correlated with regional rainfall than enso in all reanalyses suggesting that accounting for al variability may improve seasonal forecasts case study analysis of the major 1982 83 and 1997 98 el nino events suggests that the weak rainfall anomalies and strong seasonal al in 1997 98 may result from counteracting effects between enso and indian ocean coupled modes of variability

a petrographic and geochemical record of climate change over the last 4600years from a northern namibia stalagmite with evidence of abruptly wetter climate at the beginning of southern africa s iron age abstract stalagmite dp1 a speleothem 1 6 m in length from dante cave in northeastern namibia provides a paleoclimate record of a gradual transition from wetter to drier conditions from 4 6 to 3 3 ka bp a variable but pronounced dry period from 3 3 to 1 8 ka and a wetter but variable period from 1 8 ka to the present this record is based on 30 u th radiometric dates and their resulting calculated growth rates and on c and o stable isotope data relative proportions of aragonite and calcite in layers measurements of stalagmite width along layers and observation of petrographic surfaces suggestive of changes from drier to wetter conditions and vice versa the stalagmite s first deposition which seemingly followed conditions too wet for deposition coincided with desiccation in the sahara and the end of the african humid period there gradual drying continued and led to a sustained very dry period from 3322 11 to 1786 10 bp a 2 3 ka bp dry period that dry period began and ended abruptly the abrupt transition from drier to wetter conditions at 1 8 ka coincides with the beginning of the iron age in southern africa suggesting that wetter conditions facilitated migrations and or changes in food production that may have contributed to a transition in human technologies and lifestyles this transition is coeval with transitions to colder conditions in ice core records from greenland and antarctica the dp1 record suggests considerable change over the past 1800 years with at least three wet dry cycles the wettest conditions may have occurred relatively recently between 230 and 100 bp a d 1720 and 1850 so that early european explorers may have seen and or heard reports of conditions among the wettest during the later holocene in southern africa

circulation anomalies associated with tropical temperate troughs in southern africa and the south west indian ocean daily rainfall variability over southern africa sa and the southwest indian ocean swio during the austral summer months has recently been described objectively for the first time using newly derived satellite products the principle mode of variability in all months is a dipole structure with bands of rainfall orientated northwest to southeast across the region these represent the location of cloud bands associated with tropical temperate troughs ttt this study objectively identifies major ttt events during november to february and on the basis of composites off ncep reanalysis data describes the associated atmospheric structure the two phases of the rainfall dipole are associated with markedly contrasting circulation patterns there are also pronounced intra seasonal variations in early summer the position of the temperate trough and ttt cloud band alternates between the swio and southwest atlantic in late summer the major ttt axis lies preferentially over the swio associated with an eastward displacement in the indian ocean high in all months positive events in which the ttt cloud band lies primarily over the swio are associated with large scale moisture flux anomalies in which convergent fluxes form a pronounced poleward flux along the cloud band this suggests that ttt events are a major mechanism of poleward transfer of energy and momentum moisture transport occurs along three principle paths 1 the northern or central indian ocean where anomalous fluxes extend eastward to the maritime continent 2 south equatorial africa and the equatorial atlantic 3 from the south within a cyclonic flow around the tropical temperate trough the relative importance of 2 is greatest in late summer thus synoptic scale ttt events over sa swio often result from large scale planetary circulation patterns hovmoeller plots show that ttt development coincides with enhanced tropical convection between 10 30 e itself exhibiting periodicity of around 5 days and often with convergence of eastward and westward propagating convection around 40 e harmonic analysis of 200 hpa geopotential anomalies show that ttt features are forced by a specific zonally asymmetric wave pattern with wave 5 dominant or significant in all months except february when quasi stationary waves 1 2 and 3 dominate these findings illustrate the importance of tropical and extratropical dynamics in understanding ttt events finally it is suggested that in november januar ttt rainfall over sa swio may be in phase with similar rainfall dipole structures observed in the south pacific and south atlantic convergence zones

2 8 1 7 ga history of the jiao liao ji belt of the north china craton from the geochronology and geochemistry of mafic liaohe meta igneous rocks abstract the assembly and long term evolution of the eastern block of the north china craton are poorly constrained here we use bulk rock geochronological and geochemical data from mafic meta igneous rocks hornblendites amphibolites and a metagabbro of the liaohe group to reconstruct the neoarchean to paleoproterozoic history of the jiao liao ji belt located between the longgang and nangrim blocks that together form the eastern block of the north china craton the mafic ultramafic meta igneous rocks have intrusive or tectonic contacts with the liaoji granitic rocks 2 2 2 0 ga which form the basement of the jiao liao ji belt the major and trace element data indicate that the protoliths had calc alkaline composition and formed along an active continental margin subduction zone the mafic rocks form a whole rock 176lu 177hf isochron with an age of 2 25 0 31 ga overlapping with u pb zircon ages for mafic and granitic rocks from the jiao liao ji belt and consistent with being the emplacement age of the mafic protoliths along the active continental margin in contrast the whole rock 147sm 144nd isochron age of 2 83 0 18 ga is likely to reflect the average age of the lithospheric mantle source from which the mafic ultramafic protoliths were extracted together with geological evidence we propose that the southwestern portion of the longgang block was an active continental margin since at least the early paleoproteorozic literature age data from metamorphic zircons show that peak granulite metamorphism took place at 1 96 1 88 ga resulting from the collisional event that fused the longgang and nangrim blocks into the eastern block of the north china craton our bulk rock 207pb 206pb age of 1824 19 ma and our 87rb 86sr age of 1671 58 ma reflect retrograde cooling stages during the exhumation of the jiao liao ji belt after the orogenesis

an investigation of interannual rainfall variability in africa abstract interannual variations in african rainfall are examined using rotated principal component analysis pca applied to anomalies from the annual mean as well as seasonal anomalies the rotated pca loading patterns suggest several preferred continental scale rainfall anomaly patterns the dominant features of year to year variations in african rainfall appear to be the high spatial coherence of rainfall anomalies over large portions of the continent in addition several dipole regions that is adjacent regions which tend to experience rainfall anomalies of opposite sign are found and discussed one dipole region the sub saharan region appears to have a relationship with a characteristic atlantic sea surface temperature anomaly pattern during boreal summer during austral summer the tendency for a large scale dipole pattern in southeast africa is apparent as is an association of this pattern with the warm and cold phases of the el nin southern oscillation enso phenomenon normalized rainfal

shrimp u pb zircon geochronology of palaeoproterozoic metasedimentary rocks in the north china craton evidence for a major late palaeoproterozoic tectonothermal event abstract although metasedimentary successions are widely distributed across the north china craton those of palaeoproterozoic age are restricted to three orogenic belts namely the trans north china orogen the khondalite belt and the jiao liao ji belt prior to this work some of those successions were considered to be archaean in age the palaeoproterozoic metasedimentary rocks contain detrital igneous zircon grains with ages ranging from 3 0 to 2 1 ga with the majority recording an age between 2 3 and 2 0 ga this latter group define a series of magmatic events that occurred between formation of the archaean basement and deposition of the metasedimentary rock protoliths the metasedimentary rocks occur as two associations older volcano sedimentary units that formed between 2 37 and 2 0 ma and younger sedimentary units that formed mainly between 2 0 and 1 88 ga all these rock associations were then subjected to metamorphism during the late palaeoproterozoic 1 88 and 1 85 ga tectonothermal event named the luliang movement in early chinese literature which was a continent continent collision that led to the amalgamation of the north china craton

monazite and xenotime u th pb geochronology by ion microprobe dating highly fractionated granites at xihuashan tungsten mine se china zircon monazite and xenotime have proven to be valuable chronometers for various geological processes due to their commonly high u th and low common pb contents however zircons that have crystallized in highly fractionated granites often have such high u contents that radiation damage can lead to scattered u pb ages when measured with secondary ion mass spectrometry sims in this study monazite and xenotime were separated from a number of highly fractionated granites at the xihuashan tungsten mine southeast china for alternative dating methods by sims for monazite analysis obvious excess 204 pb signal mainly from interference of 232 th 144 nd 16 o 2 was observed in high th 2 wt monazite which hinders 204 pb based common pb correc tions a 207 pb based common pb correction method was used instead by employing power law relationships between pb u versus uo2 u p b th versus tho2 th and suitable exponentials monazites with tho2 contents in the range of 3 19 do not exhibit this matrix effect inde pendent sims u pb ages and th pb ages of three phases of xihuashan granite samples were consistent with each other and yielded dates of 158 7 0 7 158 0 0 7 and 156 9 0 7 ma respectively xenotime does show marked matrix effects due to variations of u th and y or total rare earth element ree referred as rree hereafter contents suitable correction factors require end member standards with extremely high or low u th and y or rree con tents no excess 204 pb was observed indicating that the 204 pb based common pb correction method is feasible independent 207 pb 206 pb ages can be obtained although multi collector mode is necessary to improve precision the main difficulties with dating xenotime are when high th u mineral inclusions are ablated we can identify when this occurs however by comparing the measured uo2 u and tho2 th with those in xenotime standards three xeno time samples from the first phase of xihuashan granite yielded a weighted mean 207 pb 206 pb date of 159 5 4 4 ma mswd 1 0 and a 206 pb 238 u date of 159 4 0 9 ma mswd 1 6 which are consistent with mona zite u pb and th pb ages from the same granites this study demonstrates that monazite and xenotime are better sims chronometers for highly fractionated granites than zircon which can yield doubtful ages due to high u contents

late jurassic to early early cretaceous tectonic nature on the ne asian continental margin constraints from mesozoic accretionary complexes abstract it is widely accepted that subduction of the paleo pacific plate beneath eurasia began in the early mesozoic however the tectonic nature and processes of the ne asian continental margin in the late jurassic to early early cretaceous remain unclear in this contribution lithological provenance and metamorphic deformation data are used to constrain the formation of mesozoic accretionary complexes ac along the ne asian continental margin and determine the tectonic relationship between the ne asian continental margin and the paleo pacific plate in the late jurassic to early early cretaceous the mesozoic ac formed during the late jurassic including the raohe ac in ne china the khabarovsk samarka and taukha acs in the russian far east and the mino tamba ac in japan and early cretaceous including the shimanto ac in japan and the kiselevka manoma ac in the russian far east the jurassic ac underwent a complex evolution including the formation of seamounts middle late jurassic terrigenous clastic sedimentation adjacent to the trench collision of seamounts with eurasia northward migration of the ac early early cretaceous terrigenous clastic sedimentation a second period of accretion and final emplacement the earliest mesozoic ac arrived at the trench at ca 195 ma combined with the occurrence of early mesozoic calc alkaline igneous rocks along the ne asian continental margin we suggest that subduction of the paleo pacific plate beneath eurasia began in the early jurassic jurassic ac in japan was affected by a regional high p t metamorphic event at 160 ma which might have been related to subduction collision of seamounts with eurasia at the trench ages and hf isotopic compositions of detrital zircon grains from the middle upper jurassic and cretaceous ac sandstones together with paleontological and paleomagnetic data indicate that jurassic clastic sediments were sourced mainly from the south china block scb whereas the lower cretaceous sandstones were sourced from the eastern central asian orogenic belt caob the inferred northward migration of jurassic ac in the late jurassic to early early cretaceous indicates that the boundary between the ne asian continental margin and the paleo pacific plate was characterized by strike slip tectonics at this time likely due to a small angle of obliquity in the subduction of the paleo pacific plate beneath eurasia in the late early cretaceous westward subduction of the paleo pacific plate beneath eurasia resulted in the emplacement of the raohe and khabarovsk acs at 137 130 ma and the formation of acs in the russian far east and japan

the dynamics of heat lows over flat terrain the numerical model for a heat low developed by racz and smith is extended to include a representation of radiative heating and cooling the model is run with a higher horizontal resolution than the original version and is used to investigate additional dynamical aspects of the structure and evolution of a heat low over a subcontinental or continental scale circular island surrounded by sea of particular interest is the diurnal and day to day evolution of the upper and lower level circulations and the degree of balance that exists in these the heat low is surmounted by an anticyclone the development of which is closely tied to the outflow branch of the sea breeze the anticyclone has a much smaller diurnal variation than the heat low and unlike the heat low is largely in balance except in the region affected by the upward propagating gravity wave induced by the inland penetrating sea breeze there is a strong analogy to certain aspects of tropical cyclones which have a warm core a shallow unbalanced boundary layer and which are surmounted also by an anticyclone principles governing the absolute angular momentum budget are the same as those relating to the tropical cyclones and to the zonal mean flow over antarctica implications of these principles for obtaining a realistic steady state in long term integrations of axisymmetric models are discussed copyright 2008 royal meteorological society

drylines in southern africa rediscovering the congo air boundary abstractprojected rainfall decline in southern africa is likely to be highly sensitive to subtleties in the local atmospheric circulation in an effort to understand the regional circulation comple

african easterly jet south control maintenance mechanisms and link with southern subtropical waves the african easterly jet south aej s is an important feature of the central african mid tropospheric circulation and has been identified as a key contributor to convection over the region this study uses 21 year 1983 2003 reanalysis data sets of era interim ncep2 and merra2 to establish mechanisms related to aej s dynamics results demonstrate that aej s is dominated by rotational circulation and is maintained by a mid level high that forms over the kalahari region during september to november because of the role played by this high pressure system in the aej s dynamics an effort is made to understand how this anticyclone develops we show that this mid tropospheric high over the kalahari region is established in response to lower tropospheric dry convection over the region from september to november at the core of this high anticyclonic circulation is induced and maintains aej s located at the northern flank of the high a link between aej s dynamics and southern subtropical westerly waves is also revealed it is shown that when waves amplify over the southern subtropics they modify lower tropospheric heating depending on the phase of the wave this modifies the cross latitude temperature gradient throughout equatorial regions therefore modulating the intensity of the jet by clarifying the mechanisms that govern the aej s this research work contributes to insight into central africa climate mechanisms and also suggests a link between central africa and southern africa climate systems this research work also improves the foundation of new mechanisms that help to identify suitable metrics for the evaluation of global models over the central africa region

the zhayao tectonic window of the jurassic yuantai thrust system in liaodong peninsula ne china geometry kinematics and tectonic implications abstract liaodong peninsula on the northeastern north china block that witnessed the spectacular late mesozoic tectonics is a key area to probe the transition from compression to extension borehole data clearly reveals that the cambrian limestone overlay the jurassic limestone which identified the yuantai thrust system in liaodong peninsula zircon grains from a granodiorite dike that intruded the thrust system yielded u pb age of 128 3 1 3 ma further constraining the timing of the thrusting between late jurassic to early early cretaceous a detailed field study of three dimensional fault zone exposures in the zhayao tectonic window are conducted to decipher the thrust tectonics before the extension in liaodong peninsula the key observations are 1 meter scale asymmetric folds in deformed mid cambrian rocks 2 decameter scale recumbent folds and secondary imbricate thrusts in deformed middle jurassic rocks and 3 non foliated breccia fault gouge and brittle porphyroclasts adjacent to fault planes the combined brittle ductile style of deformation indicates that the fault zone operated under near surface conditions in addition we infer that the folds were formed first at the propagating fault tip and subsequently dismembered by normal faults we interpret the zhayao thrust which is located around the margin of the tectonic window as the frontal thrust of the yuantai thrust system furthermore by applying the theory of fault related folds we deduce that the zhayao frontal thrust is a secondary duplex based on our field observations and borehole data we propose an imbricate thrust model for the fold and thrust belt of the southern liaodong peninsula the structural data indicate that the transport direction of the yuantai thrust system was top to the southeast suggesting that the thrust system was resulted due to northwest ward subduction of the paleo pacific plate during the mesozoic

nonlinear variability of the climatic system from singular and power spectra of late quaternary records stable isotope records from seven marine cores and one ice core provide invaluable information on the intricate behavior of the climatic system over time scales of 104 to 105 years these records in conjunction with a simple coupled climate model help us understand major mechanisms of paleoclimatic variability the time intervals covered by the records include the last glacial interglacial cycle in spite of the difference in the nature of the records common features are revealed by advanced spectral analysis tools the dominant features are the presence of orbital frequencies on the one hand and a low number of internal degrees of freedom on the other the climatic system appears therefore to act on the quaternary time scales considered as a forced nonlinear oscillator the internal mechanisms giving rise to the aperiodic oscillations include ice albedo feedback precipitation temperature feedback and interactions between the ice sheets and the bedrock

investigating the origins and significance of low frequency modes of climate variability an analysis of the 130 year record of the earth s global mean temperature reveals a significant warming trend and a residual consistent with an auto correlated red noise process whose predictability decays with a timescale of two years thus global temperatures in isolation do not indicate oscillations at 95 confidence against a red noise null hypothesis weak signals identified in the global series can however be traced to significant sea surface temperature oscillations in the equatorial atlantic period 10 years and the el nino region of the pacific 3 5 years no robust evidence is found in this data for interdecadal oscillations the 10 year atlantic oscillation corresponds to a pattern of temperature anomalies which has been associated with interannual variations in west african rainfall and in u s hurricane landfall frequency

the impact of enso on southern african rainfall in cmip5 ocean atmosphere coupled climate models we study the ability of 24 ocean atmosphere global coupled models from the coupled model intercomparison project 5 cmip5 to reproduce the teleconnections between el nino southern oscillation enso and southern african rainfall in austral summer using historical forced simulations with a focus on the atmospheric dynamic associated with el nino overestimations of summer rainfall occur over southern africa in all cmip5 models abnormal westward extensions of enso patterns are a common feature of all cmip5 models while the warming of the indian ocean that happens during el nino is not correctly reproduced this could impact the teleconnection between enso and southern african rainfall which is represented with mixed success in cmip5 models large scale anomalies of suppressed deep convection over the tropical maritime continent and enhanced convection from the central to eastern pacific are correctly simulated however regional biases occur above africa and the indian ocean particularly in the position of the deep convection anomalies associated with el nino which can lead to the wrong sign in rainfall anomalies in the northwest part of south africa from the near surface to mid troposphere cmip5 models underestimate the observed anomalous pattern of pressure occurring over southern africa that leads to dry conditions during el nino years

multi stage jurassic magmatism in the liaodong peninsula constraints on crustal evolution beneath the eastern north china craton abstract whole rock geochemical and in situ zircon u pb and hf o isotope compositions have been measured for the jurassic granitoids in the liaodong peninsula in order to investigate their genesis and reveal the jurassic crustal evolution of the eastern north china craton our new data combined with field and petrological observations indicate multi stage jurassic magmatism now represented by early to middle jurassic biotite granites and monzogranites and late jurassic two mica monzogranites the early to middle jurassic granitoids have relatively low sio2 contents 64 4 69 6 wt and k2o na2o ratios 0 4 1 0 adakitic characteristics with enriched lree and depleted hree contents high sr y ratios 52 189 positive eu and ba anomalies and negative nb and ta anomalies together with their highly negative zircon hf t 26 6 to 16 1 and mantle like 18o 4 6 to 6 3 values partial melting of a basaltic lower crust which formed at ca 2 5 ga can be proposed for the magma source of the early to middle jurassic granitoids these source rocks have not experienced significant water rock alteration after formation in contrary the late jurassic two mica granitoids exhibit relatively differentiated geochemical characteristics with high sio2 contents 72 wt and k2o na2o ratios and variable eu anomalies their parental magma was also enriched in lrees and depleted in hrees with high sr y 49 8 134 and la yb n 22 6 38 0 ratios the magmatic zircons have extremely negative hf t 37 5 to 19 6 and relatively high 18o 6 9 to 9 6 values indicating the involvement of an ancient crustal component with high 18o values such as metasedimentary rocks we propose therefore that the late jurassic two mica monzogranites originated from partial melting of reworked ancient crustal materials at the depth of lower crust and with the magma subsequently evolving as a result of plagioclase dominated fractional crystallization during early to middle jurassic westward subduction of the paleo pacific plate resulted in the partial melting of the mafic lower crust and the burial of ancient crustal materials in to deep crust while crustal stretching in late jurassic might account for the decompression melting of the ancient crustal source thus multi stage jurassic magmatism in the liaodong peninsula recorded a complex crustal evolution history which closely related to the westward subduction of the paleo pacific plate

archean blocks and their boundaries in the north china craton lithological geochemical structural and p t path constraints and tectonic evolution an examination of lithological geochemical geochronological structural and metamorphic p t path data suggests that the basement of the north china craton can be divided into eastern and western blocks separated by major crustal boundaries that roughly correspond with the limits of a 300 km wide zone called the trans north china orogen the eastern block consists predominantly of late archean domiform tonalitic trondhjemitic granodioritic ttg batholiths surrounded by anastomosing networks and linear belts of open to tight synforms of minor volcanic and sedimentary rocks metamorphosed from greenschist to granulite facies at 2 5 ga with anticlockwise p t paths some early to middle archean rocks are locally present in the eastern block but their tectonic history is unclear due to reworking by the 2 5 ga tectonothermal event the western block has a late archean assemblage structural style and metamorphic history similar to that of the eastern block but it differs in the absence of early to middle archean assemblages and in being overlain by and interleaved with paleoproterozoic khondalites which were affected by a 1 8 ga metamorphic event involving clockwise p t paths a mantle plume model is proposed for the formation and evolution of late archean basement rocks in the eastern and western blocks based on a combination of extensive exposure of ttg gneisses affinities of mafic rocks to continental tholeiitic basalts presence of voluminous komatiitic rocks dominant diaprism related domiform structures anticlockwise p t paths and a short time span from the primary emplacement of ttg and ultramafic to mafic rocks until the onset of regional metamorphism between the two blocks is the trans north china orogen which is bounded by two major fault systems and is composed of late archean to paleoproterozoic ttg gneisses and granitoids interleaved with abundant sedimentary and volcanic rocks that are geochemically interpreted as having developed in magmatic arc and intra arc basin environments these rocks underwent multiple phases of compressional deformation and peak high pressure metamorphism followed by rapid exhumation during the late paleoproterozoic at 1 8 ga as a result of collision between the eastern and western blocks resulting in the amalgamation of the north china craton

a global climatology of monsoon low pressure systems the first global climatology of monsoon low pressure systems is presented here based on the era interim reanalysis low pressure systems are classified into three intensity categories and particular focus is given to systems in the category corresponding to a traditional definition of monsoon depressions vortex tracks are identified using an automated algorithm applied to the distributions of 850 hpa relative vorticity sea level pressure and surface wind speed for 1979 2012 roughly two to three times as many monsoon low pressure systems form in the northern hemisphere as in the southern hemisphere during local summer the frequency of genesis typically peaks in local summer but low pressure systems form throughout the year in every monsoon region interannual variability is weak with standard deviations of summer counts typically being below 10 of the long term summer mean regional composites reveal that monsoon depressions in india the western pacific and northern australia share a common structure consisting of a warm over cold core and a top heavy column of potential vorticity that extends from the surface to the upper troposphere a separate class of monsoon low pressure systems develops over dry regions of west africa and western australia with a shallow composite structure having a warm core in the lower troposphere and cyclonic potential vorticity confined to a thin near surface layer low pressure systems in nearly all monsoon regions are estimated to account for a large fraction from about 40 to more than 80 of summer precipitation on the poleward edge of the climatological mean precipitation maxima

relationship between air and soil temperature trends and periodicities in the permafrost regions of russia 1 soil temperature is an important indicator of frozen ground status driven at least partly by air temperature variability in this study we apply singular spectrum analysis ssa to detect trends and oscillations in annual and seasonal time series of surface air temperature sat and soil temperature st we investigate soil temperatures at depths of 0 4 1 6 and 3 2 m for five permafrost occupied regions in russia we use sat data for 1902 1995 and st data for 1960 1990 the trends show an increase in annual sat and st from the end of the 1960s across all five regions and this warming exceeds that of the preceding period in the central siberian plateau and transbaikalia oscillations in annual sat and st time series are coincident in the west siberian plain 7 7 year period and in the western central siberian plateau and transbaikalia 2 7 year period in general on a seasonal basis 2 3 year oscillations in st and sat are coincident during winter spring and autumn across the regions and are also evident in the annual st time series in the central siberian plateau and transbaikalia we also find a decadal oscillation 9 8 year period which is coincident for winter sat and st over the western central siberian plateau only although summer sat and st oscillations 5 8 year periods are coincident for all investigated territories except to the east of the lena river in the annual st time series they are identified only for the west siberian plain we document the degree to which sat controls st in each region and explore the causative factors for some of the dominant periods the maximum effect of sat increases on permafrost may be observed in the central siberian plateau and transbaikalia while elsewhere the observed st increases do not threaten permafrost areas

the south indian convergence zone and interannual rainfall variability over southern africa abstract the south indian convergence zone sicz is identified in this paper as a region of enhanced precipitation extending off the southeast coast of southern africa during austral summer unlike the south pacific convergence zone the sicz is a land based convergence zone lbcz with position and intensity at least partially determined by surface conditions over southern africa an idealized gcm simulation is used to explore the basic dynamics of lbczs in the tropics and subtropics output from a realistic gcm simulation and the national centers for environmental prediction national center for atmospheric research 40 year reanalysis are analyzed to apply this basic dynamical framework to the case of the sicz in contrast to the intertropical convergence zone where column moisture convergence is primarily due to meridional wind convergence in the moist environment precipitation within the sicz and the lbczs in general is also supported by zonal wind convergence moisture convergence by transient eddy

uncoupled o and hf isotopic systems in zircon from the contrasting granite suites of the new england orogen eastern australia implications for studies of phanerozoic magma genesis abstract the permo triassic granites of the new england orogen eastern australia were emplaced into a volcanic arc complex accreted to the eastern gondwana margin in the late devonian or early carboniferous zircon u pb dating shows that the s type hillgrove 297 ma and bundarra 287 ma supersuites predated intrusion of the i type moonbi supersuite 250 ma by up to 50 ma the high 18ozrn of the s type granites 10 0 11 5 and range of u pb ages 370 300 ma and 18ozrn 5 10 of their inherited zircon cores show that their source rocks were predominantly weathered carboniferous volcaniclastics the youngest deposited

comparison of climate and environment on the edge of the palaeo agulhas plain to the little karoo south africa in marine isotope stages 5 3 as indicated by speleothems abstract given the steep present day climatic gradients in southern south africa comparative studies of its coastal and inland paleoclimate provide important insight into the region s spatial climate dynamics we present a comparative study of new speleothem stable oxygen 18o and carbon 13c isotopic composition from efflux cave ec 113 19 ka hiatus between 105 and 94 ka in the little karoo inland basin and herolds bay cave hbc 93 62 ka at the boundary between the cape coastal lowlands and the palaeo agulhas plain gaussian kernel based cross correlation analyses against palaeoclimate proxy records show that rainfall seasonality at ec is related to rainfall amount in the south african interior whereas hbc is similar to the south african east coast our new proxy records corroborated by archaeological evidence from the cape coastal lowlands and the little karoo suggest that in both regions surface water was readily available and grassland ecosystems with variable amounts of c4 and c3 grasses as well as fynbos communities could be found nearby cross correlation analyses of the new records from ec and hbc compared to previously published speleothem records from southern south africa show only limited statistical correlation however there are some similarities in overall trends of palaeoclimate change in the cape coastal lowlands and the little karoo whereby marine isotope stage mis 5b mainly greenland interstadial 22 and 4 generally have more summer rainfall and higher abundances of c4 vegetation than mis 5a and mis 3

petrogenesis of late triassic granitoids and their enclaves with implications for post collisional lithospheric thinning of the liaodong peninsula north china craton abstract major and trace element sr nd and hf isotope zircon u pb and hf isotope data are reported for mafic microgranular enclaves and host granitoids from the xiuyan pluton in the liaodong peninsula of the eastern north china craton in order to investigate their sources petrogenesis and tectonic implications the zircon u pb age of the enclaves 211 1 ma is identical to that of the host granite 210 1 ma establishing that the mafic and felsic magmas were coeval the enclaves have high mgo concentrations at low silica contents and positive ehf t values they are enriched in large ion lithophile and light rare earth elements and depleted in high field strength elements which can be explained as melts derived from a depleted asthenospheric mantle with some crustal contamination the host granitoids have high sio2 contents variable initial 87sr 86sr ratios and highly negative end t and ehf t values suggesting they were mainly derived from an ancient crustal source heated by the input of asthenospheric mantle derived magmas field observations geochronology geochemistry sr and nd isotopic and zircon hf isotopic compositions point to a complex petrogenesis where asthenospheric mantle and crust derived magma mixing was coupled with crystal fractionation thus explaining the genetic link between enclaves and host rocks identification of an asthenospheric mantle component in the xiuyan granitoids suggests asthenospheric mantle upwelling and decompressional melting of the mantle indicating that post collisional lithospheric thinning in the liaodong peninsula was initiated in the late triassic

a geothermal climate change observatory first year results from emigrant pass in northwest utah temperature depth profiles measured in boreholes contain a temporal record of past changes in surface ground temperature and provide valuable constraints on climatic variations over the last few centuries however the linkage between ground temperature and meteorological variables including air temperature is imperfectly known to understand that linkage better and to document in detail how the surface ground temperature changes propagate into the subsurface where they are later measured in temperature depth logs in boreholes we have designed and installed a geothermal climate change observatory installed in arid northwest utah our emigrant pass observatory epo consists of an array of thermistor strings in the subsurface and a meteorological station at the borehole collar results from our first complete annual cycle november 1 1993 though october 31 1994 are presented ground and air temperatures generally track each other but with important time varying offsets the mean surface ground temperatures for the period are 11 3 c on the granite outcrop and 9 5 c for the partially shaded regolith site mean air temperature at a 2 m mast height above the ground is 8 8 c the ground air temperature differences are variable on timescales from days to seasons largely governed by level of absorbed solar radiation marginal precipitation 8 6 mm and ephemeral snow cover did not significantly disturb the ground air temperature difference during the year monitored instrumental measurement of air temperature has nonrandom sampling biases that present problems for observing long term changes the calculation of average annual air temperature at epo decreases by 0 34 k as the sampling rate of air temperature is decreased from 60 s to every 12 hours the attenuation and phase lag of thermal waves with depth confirm that heat conduction theory adequately describes the transient temperature field at this site and yield in situ estimates of thermal diffusivity a quantity needed to reconstruct surface ground temperature histories thermal diffusivity for the granite and regolith is 0 88 10 6 m2 s 1 and 0 45 10 6 m2 s 1 respectively energy flux calculations for the emigrant pass observatory site suggest that a geothermal climate change observatory has the capability of detecting a century scale energy perturbation that is one part in a million of the instantaneous flux

petrogenesis of late triassic intrusive rocks in the northern liaodong peninsula related to decratonization of the north china craton zircon u pb age and hf o isotope evidence abstract major and trace element whole rock sr nd and hf isotopes and zircon u pb age and hf o isotope data have been determined for mafic to felsic intrusive rocks from the late triassic mayihe myh longtou chaxinzi xiaoweishahe lcx and nankouqian xidadingzi nx intrusions in the northern liaodong peninsula ne china in order to investigate their sources and petrogenesis related to decrationization of the north china craton the rocks include clinopyroxene diorite monzodiorite quartz diorite granodiorite monzogranite and mafic microgranular enclaves laser ablation inductively coupled plasma mass spectrometry la icpms and secondary ion mass spectrometer sims u pb analyses of zircon from myh lxc to nx intrusions yield late triassic ages of 224 218 ma establishing that the mafic and felsic magmas were coeval the clinopyroxene diorites from the myh pluton have high mgo concentrations at low silica contents with positive whole rock e nd t up to 3 8 and e hf t up to 6 2 and zircon e hf t values and some mantle like 18 o values they are enriched in large ion lithophile liles and light rare earth elements lrees and depleted in high field strength elements hfses which can be explained as melts derived from a depleted mantle with some subsequent crustal contamination however the diorites from the lxc and nx intrusions are high k rocks and have high mgo concentrations and mantle like 18 o values but with negative whole rock e nd t 12 9 to 7 6 and e hf t 14 0 to 5 6 and zircon e hf t values distinct from those of myh pyroxene diorites indicating that their parental magmas were derived from partial melting of an ancient lithospheric mantle the granitoids from three plutons have high sio 2 contents and low mgo concentrations suggesting they were mainly derived from crustal sources however the myh monzogranite and granodiorite have positive whole rock e nd t and e hf t up to 3 0 and zircon e hf t values indicating a juvenile crustal source whereas the lxc and nx granitoids have strong negative and variable whole rock e nd t and e hf t and zircon e hf t values indicating that they were derived from partial melting of ancient lower crustal materials with involvement of mantle components field observations geochronology geochemistry sr nd hf isotopic and zircon hf o isotopic compositions point to a complex petrogenesis where mantle and crust derived magma mixing was coupled with crystal fractionation thus explaining the genetic link between mafic and felsic rocks identification of four components i e depleted and enriched mantle and juvenile and ancient crust in the late triassic magmatism in the northern liaodong peninsula suggests a strong mantle crust interaction process related to decratonization of the north china craton

petrogenesis and geodynamics of late archean magmatism in eastern hebei eastern north china craton geochronological geochemical and nd hf isotopic evidence abstract the eastern part of the north china craton contains large volumes of late archean hornblenditic tonalitic dioritic granodioritic and granitic rocks la icpms zircon u pb dating of three plutons from eastern hebei eastern north china craton record emplacement ages of 2526 2515 ma and metamorphic ages of 2500 2490 ma for the diorite granodiorite and monzogranite and 2440 ma for the k feldspar granite hornblendites have high mgo 8 6 10 6 wt cr 674 1126 ppm ni 125 159 ppm and v 224 315 ppm at low basic silica contents sio2 45 7 49 0 wt they are enriched in light rare earth elements lrees and large ion lithophile elements liles and depleted in high field strength elements hfses with positive nd t values 1 2 to 2 0 indicating they were derived from an enriched mantle source the monzogranites have high sr and ba contents and sr y and la yb ratios low y and hrees abundances and positive nd t and zircon hf t values with nd and hf model ages less than 3 0 ga reflecting that they were derived from partial melting of a juvenile lower crust at high pressure however the k feldspar granites with low sr and ba concentrations and high hree and y contents are considered to have originated from partial melting of juvenile crustal materials at shallow crustal levels the diorites and granodiorites have variable major and trace element concentrations magmatic zircons from these rocks have heterogeneous hf t values but record uniform homogeneous u pb ages indicating they resulted from mixing of mafic and felsic magmas coupled with fractional crystallization because of the widespread distribution of late archean magmatism and evidence for magma mixing possibly related to mafic magma underplating it appears likely that this event in the eastern north china craton may relfect mantle plume activity that resulted in significant growth of continental crust during the late archean

ground warming patterns in the northern hemisphere during the last five centuries abstract changes in the earth s surface energy balance recorded underground were used to reconstruct the temperature of the ground surface for the last 500 years in the northern hemisphere we reconstructed ground surface temperature histories gsths from temperature versus depth profiles measured at 558 sites distributed between 30 and 60 n in the northern hemisphere we show that the ground has warmed about 0 5 k in the last 100 years spatial analysis reveals that spatial variability is important and that the weighted average northern hemisphere gsth shows some consistency with multiproxy and meteorological records reconstructions for the last two centuries

interactions between synoptic intraseasonal and interannual convective variability over southern africa after removing the annual cycle a principal component analysis is applied to the daily outgoing longwave radiation anomaly field used here as a proxy for atmospheric convection the analysis is carried out over the southern african region 7 5 e 70 e 10 s 40 s for austral summer november through february for the period 1979 1980 to 2006 2007 the first five principal components pc are retained the first two pcs describe spatial patterns oriented north west to south east from tropical southern africa sa to the mid latitudes they are interpreted to be different possible locations for synoptic scale tropical temperate troughs ttt one dominant rainfall producing synoptic system in the region the phase relationship between these two pcs describes a tendency for these ttt to propagate eastwards from sa to the mozambique channel and southern madagascar the next three pcs describe convective fluctuations respectively located over the north west the south and the centre of sa their time series are significantly associated with madden julian oscillation mjo activity in the tropics however we find that ttt systems are statistically independent of the mjo i e they are equally liable to occur during any phase of the mjo three pcs out of five also show a significant association with el nino southern oscillation confirming that el nino years mostly coincide with suppressed convection at the intraseasonal time scales a result consistent with its impact on seasonal averages diagnosed in previous studies

tropical extratropical interactions over southern africa three cases of heavy summer season rainfall abstract the synoptic evolution of three tropical extratropical te interactions each responsible for extreme rainfall events over southern africa is discussed in detail along with the consideration of previously studied events common features of these heavy rainfall producing tropical temperate troughs ttts over southern africa are discussed it is found that 2 days prior to an event northeasterly moisture transports across botswana set up by the angola low are diverted farther south into the semiarid region of subtropical southern africa the ttts reach full maturity as a te cloud band rooted in the central subcontinent which is triggered by upper level divergence along the leading edge of an upper tropospheric westerly wave trough convection and rainfall within the cloud band is supported by poleward moisture transports with subtropical air rising as it leaves the continent and joins the midlatitude westerly flow it is shown that these systems fit within a theoretical framework describing

regional atmospheric circulation and rainfall variability in south equatorial africa abstractthis study examines daily precipitation data during december march over south equatorial africa sea and proposes a new zonal asymmetric pattern zap that explains the leading mode of weather scale precipitation variability in the region the eastern and western components of the zap separated at about 30 e appear to be a consequence of an anomalous zonal atmospheric cell triggered by enhanced low level westerly winds the enhanced westerlies are generated by a diagonal interhemispheric pressure gradient between the southwestern indian and north tropical atlantic oceans in eastern sea these winds hit the east african plateau producing low level convergence and convection that further intensifies the westerlies in western sea a subsiding branch develops in response closing the circulation cell the system gradually dissipates as the pressure gradient weakens through this mechanism simultaneous changes in two hemispheres generate a regional zonally oriented circulation that relies on clima

on the likelihood of tropical extratropical cloud bands in the south indian convergence zone during enso events abstractthe southern hemisphere subtropical convergence zones are important regions of rainfall in the subtropics the south indian ocean convergence zone sicz has the strongest seasonality and exhibits substantial interannual variability in strength and position during austral summer on synoptic time scales the sicz is a preferred region for the formation of tropical extratropical te cloud bands with local maxima over the southern african mainland and madagascar this study investigates how the seasonality in satellite observed cloud band frequency emerges from the interplay between the asynchronous seasonal cycles in convective instability and upper level flow as represented by reanalysis data these atmospheric mean states are diagnosed with a gross convective instability metric and a method to distinguish between subtropical and eddy driven jet axes month by month analysis of these diagnostics elucidates how mean state perturbations during enso events modify cloud band likelihood typically 1

hf isotopic compositions of the standard zircons and baddeleyites used in u pb geochronology abstract zircon and baddeleyite u pb geochronological dating is widely used in solid earth sciences and the advent of rapid in situ methods of analysis such sims and icp ms has re emphasized the importance of having uniform standards recently it has been shown that hf isotopic data can provide important information on these minerals since they contain high concentrations of hf but have low lu hf ratios which results in negligible age correction however the complex internal structures that result from multiple thermal events such as inherited cores and metamorphic overgrowths require that the hf isotopic data be measured with high spatial resolution however the isobaric interferences of 176 yb and 176 lu on 176 hf hamper the precise determination of the 176 hf 177 hf ratio during in situ laser ablation mc icpms analysis it is shown here that mass biases of yb yb and hf hf change with time during analyses and behave differently for solutions and solid material therefore it is suggested that the mean yb value of the individual spot be used to obtain the precise isotopic composition for in situ zircon and baddeleyite hf isotopic analyses for low yb hf 176 yb 177 hf yb value have little effect on the accuracy of the hf isotopic composition however the appropriate yb isotopic abundance is necessary for high yb hf 176 yb 177 hf 0 001 zircons and baddeleyites since the interference of 176 yb on 176 hf is significant using the mean yb value of the individual spot and newly published yb isotopic abundance data six standard zircons and two standard baddeleyites have been investigated using a neptune mc icpms with 193 nm laser for zircons the obtained 176 hf 177 hf ratios are 0 282307 31 2sd for 91500 0 282680 31 2sd for temora 0 281729 21 2sd for cz3 282177 17 2sd for cn92 1 0 282983 17 2sd for fm0411 and 281234 11 2sd for phalaborwa the baddeleyites from phalaborwa and sk10 2 have 176 hf 177 hf ratios of 0 281238 12 and 0 282738 13 2sd these results agree well with the values obtained by the solution method and indicate that these standards have different hf isotopic compositions in which the extremely low 176 lu 177 hf and 176 yb 177 hf values of cz3 zircon and phalaborwa baddeleyite make them excellent standards for machine calibration during in situ zircon hf isotopic measurement with the other standards being more suitable for the development of the correction method

sea surface temperature fluctuations during the holocene off the south coast of africa implications for terrestrial climate and rainfall models of southern african palaeoclimate implicate surface atmospheric circulation anoma lies as forcing large scale changes during the late quaternary the available proxy data are insufficient to test the models since they provide information about temperature and rainfall rather than surface circulation a conceptual model is proposed which links coastal ocean temperatures with atmospheric circulation and allows a history of surface circulation to be inferred from sea temperature data a holocene sea surface temperature sst record was constructed by measuring the oxygen isotope composition of marine mollusc shells preserved in an archaeological cave deposit on the coast of the eastern agulhas bank southern africa radiocarbon dating of individual shells allowed definition of the timing and timespan of events in the record by serially sampling along the growth axis of each shell information was obtained about intra annual variability as well as millennial scale trends during the early holocene th