towards radiocarbon calibration beyond 28 ka using speleothems from the bahamas we present a new speleothem record of atmospheric 14c between 28 and 44 ka that offers considerable promise for resolving some of the uncertainty associated with existing radiocarbon calibration curves for this time period the record is based on a comprehensive suite of ams 14c ages using new low blank protocols and u th ages using high precision mc icpms procedures atmospheric 14c was calculated by correcting 14c ages with a constant dead carbon fraction dcf of 22 7 5 9 based on a comparison of stalagmite 14c ages with the intcal04 reimer et al 2004 calibration curve between 15 and 11 ka the new 14c speleothem record shows similar structure and amplitude to that derived from cariaco basin foraminifera hughen et al 2004 2006 and the match is further improved if the latter is tied to the most recent greenland ice core chronology svensson et al 2008 these data are however in conflict with a previously published 14c data set for a stalagmite record from the bahamas gb 89 24 1 beck et al 2001 which likely suffered from 14c analytical blank subtraction issues in the older part of the record the new bahamas speleothem 14c data do not show the extreme shifts between 44 and 40 ka reported in the previous study beck et al 2001 causes for the observed structure in derived atmospheric 14c variation based on the new speleothem data are investigated with a suite of simulations using an earth system model of intermediate complexity data model comparison indicates that major fluctuations in atmospheric 14c during marine isotope stage 3 is primarily a function of changes in geomagnetic field intensity although ocean atmosphere system reorganisation also played a supporting role

a paleogene flora from the upper bonnet plume formation of northeast yukon territory canada palaeontological exploration of the bonnet plume basin in northwestern yukon territory canada has revealed a late paleocene to early eocene macrofloral assemblage from a channel fill deposit the flora is typified by cosmopolitan taxa and dominated by deciduous angiosperms with the notable presence of zizyphoides ettingshausenia and corylites floras with a similar composition are known from late cretaceous through early eocene deposits in alaska and the canadian arctic archipelago where they have been interpreted as evidence for warm equable temperatures this collection represents the most diverse known paleogene plant macrofossil assemblage from the yukon territory and helps to expand our knowledge of ancient high latitude floras

the apollo 14 regolith petrology of cores 14210 14211 and 14220 and soils 14141 14148 and 14149 new modal data are presented for continuous polished thin sections from double drive tube 14210 14211 and single drive tube 14220 and for polished grain mounts of four soils from the double drive tube one from the single drive tube and the soils 14148 trench top 14149 trench bottom and 14141 cone crater modal data show that the cone crater soil is immature whereas the smooth plains soils are mature and rich in agglutinates and breccias neither core exhibits any major variations with depth microprobe analyses of mineral and glass fragments are consistent with derivation of the soils predominantly from the local rocks with 5 11 exotic mare component indicated by the modal data about 4 of the glasses are sio2 and k2o rich granitic glasses which are comminuted mesostasis from the local melt rocks the soils are depleted in feldspar relative to the source rocks the preferred explanation for this depletion is that feldspar is concentrated in the 10 m fines and is consumed in the formation of agglutinates regolith breccias and feldspathic glass

understanding the lunar surface and space moon interactions the surface of the moon is a critical boundary that shapes our understanding of the moon as a whole all geologic mapping and remote sensing techniques utilize only the outermost portion of the moon before leaving the moon for study in our laboratories all lunar samples that have been studied existed at or very near the surface with the exception of the deeply probing geophysical techniques our understanding of the interior of the moon is derived from surficial but not superficial information coupled with boundary of the lunar crust it is the lower boundary layer of the tenuous lunar atmosphere and constitutes both a source and a sink for atmospheric gases the surface is also where the moon interacts with the space environment causing changes in the physical nature of lunar materials and provides a laboratory for the study of processes that occur on all airless bodies the data obtained remotely by the galileo clementine and lunar prospector missions as well as data derived from lunar meteorites have resulted in major changes to our understanding of global distributions of chemistry and rocks this chapter summarizes the current understanding of this critical interface the surface of the moon in its role as the lower boundary of the lunar atmosphere the upper boundary of the crust and the window through which we view through remote sensing the composition of the crust and the history of the moon in this post lunar prospector time the view of the moon has changed lending new perspectives to lunar samples and lunar processes but the new view will likely remain in flux as we continue to digest the results from these recent space missions and move forward to a new era of lunar exploration despite the freshness of our perspective this is an important moment to capture

the first high resolution stalagmite record from taiwan climate and environmental changes during the past 1300 years abstract this paper presents the first high resolution holocene stalagmite record of taiwan from jianfei cave 22 50 873 n 120 21 255 e in dagangshan mountain south taiwan the 13 6 cm long stalagmite dgs 1 has been dated by ams 14 c dating spanning from ad 700 to ad 1933 the 18 o 13 c and xrf scanned elemental profiles reveal interannual variations in climate and environmental conditions with light 18 o and 13 c excursions reflecting wet climate and better vegetation coverage under stronger east asia summer monsoon easm dark layers in dgs 1 containing high fe mn and sr contents were formed during dry episodes five periods with different climate regimes and vegetation conditions can be identified in the dgs 1 record period i ad 700 1200 and period v ad 1810 1933 had warm and wet climates with good vegetation coverage a drying trend probably corresponding to the switch from el nino like to la nina like oceanic condition occurred during period ii ad 1200 1400 cold but relatively wet climates with good vegetation coverage were prevailed during period iii ad 1400 1610 whereas cold and dry climates with poor vegetation coverage were dominated during period iv ad 1610 1810 based on the rainfall record of tainan since ad 1897 and the stalagmite record we found that stronger total solar irradiation tsi resulting in strong easm produces heavy rainfall in south taiwan on interannual to decadal scales and vice versa the 117 yr instrumental rainfall record of tainan showed that rainfall in tainan decreased during april to june and strongly increased during july to september in many la nina years positive soi and negative nino 3 4 this may be because weaker meiyu rainfall but stronger tropical equatorial pacific cyclones or typhoon under la nina condition thus it is better to use seasonal rainfall for detecting relationship between tainan rainfall and enso on decadal to centennial scales strong el nino like state and warm pacific decadal oscillation pdo phase are in favor of wet conditions in south taiwan

high precision and high resolution carbonate 230th dating by mc icp ms with sem protocols abstract to facilitate the measurement of u th isotopic compositions suitable for high precision and high resolution 230th dating of coral and speleothem carbonates secondary electron multiplier sem protocol techniques for multicollector inductively coupled plasma mass spectrometry mc icp ms have been developed the instrumental sensitivities are 1 2 with a precision of 1 2 2 for abundance determination of 50 200 fg 234u 1 4 ng 238u or 230th this method features chemistry refinements improvements to procedural and instrumental blanks spectral inference reductions and careful consideration of non linear sem behavior measurement consistency of this mc icp ms combined with previous mass spectrometric results on u th standards and a variety of carbonates demonstrates the validity of the sem protocol method for fossil corals a routine u th isotopic determination at permil level precision requires only 10 50 mg of carbonate as little as 200 mg of young coral with an age of less than 20 yr can be dated with a precision of 0 3 0 8 yr about 20 200 mg speleothem samples with sub ppm to ppm u are required to earn a 5 precision on ages from 5 to 100 kyr requirement of small sample size 10 100s mg carbonate can permit high temporal resolution to date speleothems with slow growth rates i e 1 10 mm kyr this high precision 230th chronology is critical to accurately establish age models date events and splice geochemical proxy time series records from multiple samples in the fields of paleoclimatology and paleoceanography the u th isotopic determination techniques described here can also be applied to different environmental samples such as waters rocks and sediments

potential influence of temperature changes in the southern hemisphere on the evolution of the asian summer monsoon during the last glacial period abstract a precisely 230th dated 18o record of a stalagmite from yangkou cave chongqing southwest china is proposed to reconstruct the evolution of the east asian summer monsoon easm during the last glacial period lgp from 37 8 to 48 7 ka bp the 18o record reveals dansgaard oeschger d o 8 12 and heinrich h4 h5 climatic events the inferred d o events at easm territory do not exhibit the asymmetrical feature of rapid warming slow cooling recorded in greenland ice cores the yangkou record is consistent with other records of hulu and xiaobailong caves in the chinese monsoon realm changes in the period from d o 12 to d o 9 and h4 events in the stalagmites is similar to the temperature changes recorded in the european project for ice coring in antarctica epica dronning maud land ice core edml this similarity implies that southern hemisphere thermal condition could affect the easm the location of the intertropical convergence zone itcz and also the hadley circulation changes in d o 12 and the end of the h5 in chinese records are different from those in socotra island located in the indian summer monsoon ism region which are concurrent with ngrip records during the h5 period in the southern hemisphere temperature increased gradually to a maximum and the hadley circulation intensity in the southern hemisphere decreased simultaneously the southeast trade winds in the southern hemisphere gradually weakened resulting in the weakening of the ism and eventually the weakest ism at 47 2 ka bp our records support that the evolution of the summer monsoon in the low latitude asian zones was not only affected by summer insolation and climatic changes in the high latitudes of the northern hemisphere but also by temperature changes in the southern hemisphere

the origin and evolution of lunar high ti basalts periodic melting of a single source at mare tranquillitatis abstract five groups of basalts a b1 b2 b3 d with three principal ages exist at the apollo 11 site these range from the low k low rare earth element ree groups b1 b2 and b3 to the low k high ree group d basalts to the high k high ree group a basalts the group a basalts are the only high k 0 2 wt k2o basalts and youngest with an age of 3 59 02 ga groups b3 and b1 are 3 71 02 and 3 67 02 ga respectively group b2 basalts are the oldest at 3 85 02 ga group d basalts have not been dated fractionation modelling for major and trace elements indicates that the b1 basalts could have formed from a b3 like parent liquid the b2 and d basalts can also be related to liquids similar to the b3 b1 composition through the presence of varying amounts of modal whitlockite thus the entirety of low k high ti basalts at apollo 11 may have formed through melting of the same source region the group a basalt compositions are consistent with formation from a different parent liquid with the composition of apollo 11 orange glass modelling of major and trace elements in the apollo 11 orange glass indicate that the composition of the group a basalts is consistent with fractionation of this glass coupled with some assimilation 7 5 15 of an evolved kreep like material however this component is much younger than primitive kreep 4 4 ga this neukreep component similar to the composition of quartz monzodiorites described from the apollo 15 site probably represents evolved material formed during plutonism prior to the formation of the apollo 11 orange glass liquid

a new look at the apollo 11 regolith and kreep although the apollo 11 mission landed in mare tranquillitatis 50 km from the nearest exposure of highlands small nonmare particles are conspicuous in the regolith the nonmare portion of the apollo 11 regolith is compositionally similar to the apollo 16 regolith at both sites most of the nonmare material is from the feldspathic highlands but some is mafic impact melt breccia with the chemical signature known as kreep for its high concentrations of k rare earth elements and p the composition of the apollo 11 regolith corresponds best to a mixture of 66 crystalline mare basalt 5 orange volcanic glass 20 material of the feldspathic highlands 8 kreep bearing impact melt breccia and 1 meteoritic material the volcanic glass and kreep bearing melt breccia components account for the high concentrations of mg and cr in the regolith the most kreep rich sample known from apollo 11 10085 1187 is an impact melt breccia that bears a strong textural and compositional similarity to a unique apollo 16 melt breccia 64815 although not of the maria such breccias are also not of the highlands provenance global data obtained from orbit show that kreep bearing materials are most common at low elevations in the imbrium procellarum region and are rare at high elevations thus as at apollo 16 the kreep bearing breccias of apollo 11 are probably ejecta from the imbrium impact into the low lying procellarum kreep terrane on the basis of these observation and others we suggest that the general acceptance of kreep as a material of the highlands is not supported by the data and results largely from historical accident

lunar granulites and their precursor anorthositic norites of the early lunar crust lunar granulites are breccias with metamorphic textures they are not pristine having been contaminated with meteoritic siderophiles nonetheless they constitute an abundant class of highlands rocks that are important because they are ancient and kreep free they may represent our best samples of the early lunar crust the granulites can be divided into ferroan and magnesian groups and each group can be subdivided on the basis of mineral composition and ree concentrations textural and compositional data show that some of the granulites especially 67215 and 67415 may be derived from distinct anorthositic norite precursors while some other granulites 79215 78155 are clearly polymict even the polymict granulites probably had anorthositic norites as their dominant precursors and not anorthosites norites or troctolites the granulites have compositions similar to those of the two lunar meteorites one of which yamato 791197 is ferroan the other alha81005 magnesian these meteorites are soil breccias from an unknown location distant from the apollo landing sites and contain anorthositic norites as abundant clasts compositions of granulites and lunar meteorites more closely resemble the average composition of lunar highlands as determined by remote sensing than do those of any other returned lunar samples the predominance of plutonic anorthositic norite precursors in material having the composition typical of highlands suggests that plutonic anorthositic norites were more abundant in the early lunar crust than is implied by their scarcity among pristine rocks from apollo missions

subdivision of the mg suite noritic rocks into mg gabbronorites and mg norites mg suite noritic rocks can be divided into two groups the mg gabbronorites and the mg norites the rocks of these groups differ in ratios of high ca pyroxene to total pyroxene compositions of pyroxene and plagioclase assemblages of ti nb and zr bearing minerals compositions of chrome spinel bulk rock ti sm and sc sm and measured ages the two groups probably crystallized from different types of parent magmas two hypotheses are offered for the differences in composition of the parent magmas one hypothesis ascribes the differences to compositional heterogeneity of the mantle source areas the other hypothesis ascribes the differences to variations in extent of partial melting of the mantle source regions and variations in extent of assimilation of the anorthosite and the highly differentiated residual liquid that were produced during the primordial lunar differentiation

δ18o δ13c elemental content and depositional features of a stalagmite from yelang cave reflecting climate and vegetation changes since late pleistocene in central guizhou china abstract a 13 5 cm long stalagmite from yelang cave in central guizhou provides another example of ams 14 c dating on stalagmites which are not suitable for 230 th u dating due to very low u content and low 230 th 232 th ratio this record duplicates the published stalagmite record of 20120824 13 from the same cave zhao et al 2015 not only on 18 o and 13 c records but also on major growth hiatuses facilitating speleothem 18 o and 13 c as climate and vegetation proxies respectively based on the two stalagmite records climate and vegetation conditions can be deciphered as follow relatively cool and dry climates with c4 dominated plants during 33 4 36 ka very cold and dry climates with poor vegetation coverage during the last glacial maximum cold and dry climates with poor vegetation during younger dryas warming and very wet climates with the best vegetation mainly c3 plants coverage during 9 11 5 ka bp corresponding to a maximum insolation drying climate and decreased vegetation intensity from 9 ka to 8 ka relatively good vegetation coverage during 5 6 ka the summer monsoon strength decreased from 5 ka to 1 5 ka bp but increased during the medieval warm period to produce wet climates and abundant vegetation and strongly decadal variations in moisture budget and strong deforestation due to human impact during the past 600 years high fe mn and al contents from detritus caused dark bands near the hiatuses strong positive correlation of mg and sr with high mg sr values 23 in this study reflects source control on the mg and sr variations so that mg sr is not a function of cave temperature in such a case for pure calcite without detrital influence mg sr may register changes in cave temperature with higher mg sr indicating warmer temperature this study calls for the attention to find out climatic conditions in central guizhou during the bolling allerod warming and the middle holocene 6 8 ka intervals because of lacking deposition during these intervals in yelang cave using stalagmite 18 o alone to decipher climatic conditions on decadal to millennial scales needs to consider multiple factors such as amount source and temperature effects on the 18 o

chemistry of the apollo 11 highland component chemical data 28 major minor and trace elements were obtained by instrumental neutron activation analysis inaa for 38 hand picked highland fragments 1 20 mg from coarse fines 10085 the apollo 11 highland chemical groups are represented by a range of petrographic types six major chemical highland groups are identified in the apollo 11 fragments these are 1 high k kreep 2 anorthosite e g 15415 60015 with 10 chondrite rare earth elements ree abundances a positive eu anomaly anorthosite with 30 chondrite abundances and a positive eu anomaly 3 anorthosite norite troctolite ant 67075 4 low k fra mauro lkfm 77135 5 anorthositic gabbro 68415 with no eu anomaly anorthositic gabbro 65055 67955 with a positive eu anomaly and anorthositic gabbro 68516 60015 with a negative eu anomaly and 6 apollo 11 dominant highland component 2 10 chondrite ree abundances with a positive 10 14 chondrite eu anomaly there are three newly recognized groups in the apollo 11 highland suite based on the ree patterns these are a ant with 5 chondrite la 22 chondrite abundances and a positive eu anomaly b 10 chondrite flat pattern with 14 chondrite positive eu anomaly and c 2 3 chondrite flat pattern with 10 chondrite positive eu anomaly the apollo 11 highland suite is very low in potassium non kreepy overall the apollo 11 highland suite is quite similar to the apollo 16 suite most previously recognized highland chemical groups are represented in the apollo 11 highland component

petrology of apollo 11 regolith breccias petrographic and mineral chemical data for 16 apollo 11 regolith breccias show that 1 the regolith breccias differ from soil 10084 with respect to a agglutinate content b glass population c plagioclase compositions and d proportions of high k mare and low k mare basalt components 2 the a 11 breccias and soil have highland components that are similar both in abundance and petrology and 3 lunar regolith breccias provide a better comparison with howardites than do lunar soils the data and observations are consistent with formation of the regolith breccias from immature soil it appears that little or no highland material has been added to the tranquillitatis regolith since the formation of the breccias

changes in climate and vegetation of central guizhou in southwest china since the last glacial reflected by stalagmite records from yelang cave abstract two stalagmites 6 cm and 18 cm long from yelang cave 26 2 28 n 105 44 11 e in central guizhou of china have been dated by icp ms 230th u 210pb and ams 14c dating methods low u but high th contents in the young stalagmites were difficult to apply 230th u dating instead ams 14c dating solved the chronological problem of these stalagmites both stalagmites had fast growth rates during holocene optimum and the last 600 years but absent growth between 4 and 8 ka the 18o record of stalagmite 20120824 13 agrees well with the dongge 18o records on centennial or longer scales showing dry climates during the last glacial maximum lgm and younger dryas and wet climates during holocene optimum following the solar insolation trend the summer monsoon strength decreased from 4 12 ka to 1 5 ka but increased during the medieval warm period to produce wet climates and abundant vegetation in the study area the 18o record during the last 600 years exhibits strongly decadal variations twelve light 18o excursions on decadal scales during the last 600 years can be identified agreeing with the local dry wet index record the pacific decadal oscillation pdo strongly affects decadal variability of the moisture budget in the study area with cold pdo la nina condition in favor of stronger easm and wet climates the 13c record indicates that natural vegetation in the study area was strongly destroyed by human activity after the reign of emperor yong zheng ad 1722 1735 of qing dynasty since then the karst desertification in central guizhou has been strongly developed due to rapidly increased population and land use

petrology of the apollo 11 highland component new data for 38 highland fragments hand picked from apollo 11 coarse fines are reported petrographic mineralogic and bulk chemical data show that 1 the apollo 11 highland component is non kreepy and like that of apollo 16 2 poikilitic rocks granulitic breccias and the anorthosite norite troctolite suite are the most abundant rock types followed by polymict breccias and glasses 3 both the ferroan anorthosite and mg rich plutonic suites are represented in the apollo 11 highland component 4 except for one sample the intermediate k fra mauro and high k fra mauro groups are not represented the data and observations are consistent with local derivation of the highland material from beneath relatively thin basalt flows and addition to the regolith via vertical mixing

lunar meteorite queen alexandra range 94281 glass compositions and other evidence for launch pairing with yamato 793274 abstract lunar meteorite queen alexandra range 94281 is remarkably similar to yamato 793274 pairing in the conventional earth entry sense is difficult to reconcile with the 2500 km separation between the find locations for these two samples nonetheless both of these regolith breccias are dominated by very low ti vlt mare basalt the pyroxenes of which feature exsolution lamellae on a remarkably coarse scale typical lamella width 0 5 1 m by mare standards the pyroxenes also show similar compositional variations e g fe vs ti trends which confirm parentage from vlt mare basalt plots using al2o3 or feo as a tracer of the highland component indicate indistinguishable internal mare highland geochemical mixing trends the same two distinctive glass types dominate the mare glass populations of both breccias glass type yq1 features 0 37 0 63 wt tio2 10 17 wt mgo and 9 11 wt al2o3 glass type yq2 features higher tio2 0 99 1 22 wt which is inversely correlated with mgo 12 6 13 8 wt and nearly constant 8 8 wt al2o3 all of these similarities suggest that y 793274 and que 94281 are a launch pair which we designate yq most of these similarities also extend to another mare breccia meteorite elephant moraine 87521 however the eet 87521 mare basalt is unusually v poor 88 g g whereas the yq mare component contains 166 g g queen alexandra range 94281 features a variety of textural domains discrete patches of dark matrix material appear to represent clods of mature regolith that have been mixed with a coarser relatively immature material interior to a frothy fusion crust are areas of massive glass that probably formed as a splash coating on que 94281 when it was still on the moon the coarse yq and eet 87521 pyroxene exsolution features imply relatively slow cooling in either a very shallow sill or an unusually thick ponded lava and or later annealing within a cryptomare mare pyroclastic glasses including the two yq varieties are systematically mgo rich compared to crystalline mare basalts this disparity may be a consequence of limited survival of graphite the main fuel for explosive volcanism during formation of the mare source regions as magma ocean cumulates graphite 2 2 g cm3 survived preferentially in regions that avoided extensive early melting and thus remained mgo rich an apparent bimodality in the tio2 contents of mare volcanics especially the pyroclastic glasses also seems a plausible consequence of petrogenesis by remelting of magma ocean cumulates cumulates deposited after the magma ocean evolved to ilmenite saturation had vastly higher tio2 contents than cumulates deposited shortly before the yq regolith s subequal proportions of mare and highland matter are consistent with derivation from a terrain close to a mare highland boundary however a similar mixture might also develop through vertical mixing in a cryptomare or a region of thin mare coverage thus unfortunately the yq bulk composition is not a very useful clue to the identity of the source crater

rb sr analyses of apollo 16 melt rocks and a new age estimate for the imbrium basin lunar basin chronology and the early heavy bombardment of the moon rb sr model ages on 7 impact glass bombs and internal rb sr isochrons for two crystalline impact melt rocks from the apollo 16 collection have been determined the post cayley glass bombs with model ages between 4 75 0 45 ae and 3 97 0 08 ae can be classified according to their calculated single stage 87rb86sr i ratios 67728 67946 and 67627 8 point to a kreep free precursor terrain the descartes highlands whereas 63566 67567 67627 10 and 67629 are derived from the more heterogeneous cayley plains the very feldspar rich impact melt rock 65795 which is compositionally similar to the group of feldspathic microporphyritic melt breccias fm suite yields a crystallization age of 3 81 0 04 ae 2 87rb 1 42 11yr and isr of 69929 3 in the subophitic impact melt rock 60635 5 two ages were recorded one isochron with 3 87 0 02ae and isr of 0 69920 3 gives the crystallization age of a fine grained internal clast at 3 75 0 03 ae this fragment was incorporated into the host lithology of 60635 which is a member of the anorthositic noritic melt rock anmr group this group has a crystallization age of about 3 75 ae the anmr rocks and several samples of apollo 14 crystalline impact melt rocks belong to a suite of young crystalline impact melt rocks ranging in age from 3 71 to 3 81 ae these ages are in conflict with the canonical age of the imbrium event 3 85 ae it is argued that the young apollo 14 and 16 melt rocks cannot represent solid exotic fragments or melt splashes ejected from post imbrium local or distant craters instead these rocks are derived from coherent impact melt sheets of pre imbrian craters with diameters larger than 5 7 km they are interpreted as clasts of the fra mauro and cayley formation breccia deposits and therefore their ages are used as an upper limit for the age of the imbrium event we suggest that the imbrium basin and the related fra mauro and cayley formations were formed 3 77 0 02 ae ago and could be even as young as 3 75 ae as a consequence we adopt 3 92 0 03 ae 3 87 0 03 ae and 3 84 0 04 ae as ages for the nectaris serenitatis and crisium basins respectively in agreement with the relative crater densities measured on the ejecta blankets of these basins wilhelms 1984 the proposed age sequence leads to an average formation interval for the observed 12 13 nectarian basins of 7 to 14 m y leaving 30 pre nectarian basins of unknown age these facts suggest that there is no late terminal lunar cataclysm in the sense of a culmination of the lunar impact rate at 3 8 ae ago rather the observations are compatible with a steeply and steadily decreasing flux of impactors hartmann 1980 in the sense of an early heavy bombardment which started at the time of the moon s accretion and terminated around 3 75 ae ago

noritic dykes of southern west greenland early proterozoic boninitic magmatism two major swarms of early proterozoic ca 2 1 ga basic dykes occur within the archaean craton of southern west greenland one swarm comprises ophitic and sub ophitic tholeiitic dolerites while the other the bn dyke swarm constitutes mainly norites in which pyroxenes and olivine are enclosed by plagioclase oikocrysts the close geochemical similarity between a quenched norite and the coarser grained varieties indicates that the composition of the latter type has not been significantly modified by crystal accumulation the bn dykes are geochemically distinctive most having high mgo ca 16 cr and ni contents in conjunction with relatively high sio2 light rare earth ree and large ion lithophile lil element concentrations the texture mineral chemistry and petrochemistry of the quenched noritic dyke all bear strong resemblances to those features in modern boninitic lavas the bn dykes also correspond to proposed parental liquids of the bushveld complex and other major layered basic igneous intrusions the two dyke swarms are petrogenetically distinct the tholeiitic dolerites were derived from a relatively undepleted primordial mantle while the noritic dykes originated from a metasomatized harzburgitic source the wide spread distribution of similar proterozoic intrusions suggests crustal underplating by harzburgitic mantle on a world wide scale at this time

trace element partition coefficients in the calcite water system and their paleoclimatic significance in cave studies abstract speleothems stalactites stalagmites formed in limestone caves have been found to contain much information on the timing and intensity of past climates from analysis of their u th 13c and 18o contents because the incorporation of certain trace elements e g mg mn and zn in calcite is known to be temperature dependent it may be possible to use variations in trace metal content of fossil speleothems as an alternative paleotem perature indicator using specially developed ion exchange sampling techniques analysis of trace metal content of seepage water and associated fresh calcite deposits in caves in vancouver island and jamaica shows that mg is distributed between phases in a consistent manner within the temperature regimes of the caves 7 and 23 c respectively average values of the distribution coefficient for mg are respectively 0 017 and 0 045 at these temperatures these results indicate that the mg content of calcite varies directly with temperature and in a sufficiently pronounced manner that a 1 c rise in depositional temperature of a speleothem containing 500 ppm mg at 10 c would be seen as an increase of 35ppm mg a readily determinable shift other factors affecting mg content of a speleothem are considered