provenance and tectonic setting of middle upper devonian sandstones in the qinling orogen shanyang area new insights from geochemistry heavy minerals and tourmaline chemistry abstract devonian sandstones in the shanyang area crop out in the southern part of the qinling orogenic belt geochemical analyses show that the sandstones are enriched in zr and have high th u and rb sr ratios indicating the sandstones underwent repeated recycling zircon tourmaline apatite rutile and anatase are the predominant heavy minerals while minor minerals include spinel pyroxene ilmenite and magnetite the mineral compositions of detrital tourmaline grains indicate that the alkali compositional subgroup dominates schorl and dravite are the main tourmaline species a tourmaline composition environment discrimination diagram shows that about 70 grains are consistent with metapelite metapsammite and calc silicates sources and about 30 of grains are from granitoids and associated pegmatites and aplites metamorphic and granitic rocks in the qinling complex area are potential provenance overall data from geochemistry heavy minerals and tourmaline chemistry suggests the devonian sandstones were extensively recycled in a foreland basin setting rather than at a passive continental margin

grain size effect on multi element concentrations in sediments from the intertidal flats of bohai bay china abstract in the intertidal flats of bohai bay china the spatial distribution of the grain size of sediments becomes coarser from landward to seaward to study the grain size effect on multi element concentrations in sediments samples along the coastline and 3 horizontal cross sections were collected from the intertidal flats of bohai bay china in 1998 total concentrations of 49 elements including alkali alkaline earth trace metal rare and rare earth elements were measured by icp aes icp ms and inaa the results show that sediment texture plays a controlling role on the concentrations and their spatial distribution principal component analysis and cluster analysis were carried out based on the grain sizes of the sediments and the samples were classified into 3 groups mud silt mud and silt significant differences among the element concentrations in the 3 groups were observed and the concentrations of the elements in each group are reported in this study most of the elements have their highest concentrations in the fine grained mud samples in comparison with the silt and silt mud samples with clay minerals possibly playing an important role in contrast concentrations of ba sr hf and zr are elevated in the coarse silt samples ba and sr may reside in feldspars while zr and hf are present in zircons landward to seaward spatial variation of element concentrations in the sediments is observed which is in line with the spatial distribution of the grain size and is related to the seawater hydrological dynamics in the intertidal flats

inferring tectonic provenance of siliciclastic rocks from their chemical compositions a dissent abstract chemical compositions of siliciclastic sedimentary rocks are commonly used to infer their tectonic provenance we have tested the universal applicability of the underlying principle in a small but controlled study expecting 100 confirmation of the practice a comparison is made between the chemical composition of the 1480 ma butler hill granite in an uplifted cratonic block of the st francois mountain igneous complex and that of a small 1 m thick regolith body a weathered granite sample and the basal quartz arenites of the 520 ma lamotte formation immediately above the regolith the results show that in plots of k 2 o na 2 o vs sio 2 al 2 o 3 the regolith and sandstone samples correctly plot in the passive margin field although the weathered granite plots in the arc field in plots of th sc zr 10 and la th sc the results plot in the passive and active continental margins and their extensions in other common plots to discriminate tectonic provenance e g sio 2 vs k 2 o na 2 o fe 2 o 3 mgo vs al 2 o 3 sio 2 fe 2 o 3 mgo vs tio 2 sc cr vs la y a few points plot in the passive margin field but scatter into and outside of other fields of tectonic provenances the chondrite normalized ree distributions show variable degrees of negative eu anomalies with flat hree conforming to a felsic source the lree distributions show both positive and negative ce anomalies that can be ascribed to the variability of redox conditions during weathering and diagenesis of the original siliciclastic sediments the variability of the eu anomaly was likely affected by post erosion processes in addition to whatever was inherited from the parent rocks we conclude that chemical compositions can provide good clues but are neither strong indicators nor unique identifiers of their tectonic provenance rather they indicate a dominantly felsic or dominantly mafic or a mixed set of source rocks

mantle dynamics uplift of the tibetan plateau and the indian monsoon convective removal of lower lithosphere beneath the tibetan plateau can account for a rapid increase in the mean elevation of the tibetan plateau of 1000 m or more in a few million years such uplift seems to be required by abrupt tectonic and environmental changes in asia and the indian ocean in late cenozoic time the composition of basaltic volcanism in northern tibet which apparently began at about 13 ma implies melting of lithosphere not asthenosphere the most plausible mechanism for rapid heat transfer to the midlithosphere is by convective removal of deeper lithosphere and its replacement by hotter asthenosphere the initiation of normal faulting in tibet at about 8 3 ma suggests that the plateau underwent an appreciable increase in elevation at that time an increase due solely to the isostatic response to crustal thickening caused by india s penetration into eurasia should have been slow and could not have triggered normal faulting another process such as removal of relatively cold dense lower lithosphere must have caused a supplemental uplift of the surface folding and faulting of the indo australian plate south of india the most prominent oceanic intraplate deformation on earth began between about 7 5 and 8 ma and indicates an increased north south compressional stress within the indo australian plate a tibetan uplift of only 1000 m if the result of removal of lower lithosphere should have increased the compressional stress that the plateau applies to india and that resists india s northward movement from an amount too small to fold oceanic lithosphere to one sufficient to do so the climate of the equatorial indian ocean and southern asia changed at about 6 9 ma monsoonal winds apparently strengthened northern pakistan became more arid but weathering of rock in the eastern himalaya apparently increased because of its high altitude and lateral extent the tibetan plateau provides a heat source at midlatitudes that should oppose classical symmetric hadley circulation between the equator and temperate latitudes and that should help to drive an essentially opposite circulation characteristic of summer monsoons for the simple case of axisymmetric heating no dependence on longitude of an atmosphere without dissipation theoretical analyses by hou lindzen and plumb show that an axisymmetric heat source displaced from the equator can drive a much stronger meridianal monsoonlike circulation than such a source centered on the equator but only if heating exceeds a threshold whose level increases with the latitude of the heat source because heating of the atmosphere over tibet should increase monotonically with elevation of the plateau a modest uplift 1000 2500 m of tibet already of substantial extent and height might have been sufficient to exceed a threshold necessary for a strong monsoon the virtual simultaneity of these phenomena suggests that uplift was rapid approximately 1000 m to 2500 m in a few million years moreover nearly simultaneously with the late miocene strengthening of the monsoon the calcite compensation depth in the oceans dropped plants using the relatively efficient c4 pathway for photosynthesis evolved rapidly and atmospheric co2 seems to have decreased suggesting causal relationships and positive feedbacks among these phenomena both a supplemental uplift of the himalaya the southern edge of tibet and a strengthened monsoon may have accelerated erosion and weathering of silicate rock in the himalaya that in turn enhanced extraction of co2 from the atmosphere thus these correlations offer some support for links between plateau uplift a downdrawing of co2 from the atmosphere and global climate change as proposed by raymo ruddiman and froehlich mantle dynamics beneath mountain belts not only may profoundly affect tectonic processes near and far from the belts but might also play an important role in altering regional and global climates

arkose subarkose quartz sand and associated muds derived from felsic plutonic rocks in glacial to tropical humid climates abstract in the range of climates from high latitude glacial to equatorial tropical the mineral and chemical compositions of over 600 modern nonmarine first cycle sands and muds produced from felsic crystalline basement provenance in various tectonic settings were studied under glacial conditions sediments are developed by mostly mechanical weathering and thus are mineralogically and chemically similar to their source rocks humid tropical climates yield quartz rich sands kaolinite rich muds along with si mg ca na and k in solution between these extremes a wide range of detrital sediment compositions are developed in arid to wet climates in arid climate and semi arid climate sands feldspar is commonly more abundant than quartz and plagioclase k feldspar except in the cases of granite source rocks the muds are feldspathic with smectite dominant in the clays with increasing temperature and moisture in temperate to subtropical climates mafic silicates and feldspars are destroyed so that the sands range from arkoses with plagioclase as the major feldspar to subarkoses with dominant k feldspar through this range of climate muds become more kaolinitic and thus more aluminous with increasingly severe weathering typically feldspathic sands are associated with feldspathic muds with decreasing feldspar in sands there is less feldspar in muds with increasingly intense chemical weathering rare earth elements ree are more fractionated into muds typically sands contain 150 ppm ree with much of the ree in heavy minerals abundance differences are greatest between humid tropical sands and muds in many samples the ree are mostly in monazite allanite sphene and apatite more intensely weathered samples contain more xenotime and zircon evidenced by yb enrichment

geochemistry and provenance of the altendorf feldspathic sandstone in the middle bunter of the thuringian basin germany an integrated mineralogical and geochemical study of the altendorf feldspathic sandstone in the middle bunter of the thuringian basin germany was carried out to obtain more information on its provenance sedimentological history and geochemistry the fine to coarse grained sandstone has an average composition of 66 63 71 quartz 30 27 35 feldspar and a fine grained illitic matrix the heavy mineral assemblage consists mainly of tourmaline zircon rutile apatite and opaque fe ti minerals it is inferred that this terrigenous material was laid down at the margin of the bunter basin high abundances of igneous quartz grains determined by cathodoluminescence cl the lack of metamorphic heavy minerals as well as alkali feldspar with an average k2o na2o ratio of 14 9 point to material of mostly granitic origin regional geologic and paleogeographic observations suggest that granites of the older and younger intrusive complex of the western erzgebirge are possible source rocks of the feldspathic sandstone the geochemical signature of the alkali feldspar k2o na2o ratio bao content points to the bergen and kirchberg granites as possible parent rocks comparing the mineralogical and geochemical data of the presumed source granites with those of the altendorf sandstone provides information on the sedimentation processes weathering fluvial transport and sedimentation under arid climatic conditions have caused complete decomposition and removal of plagioclase and biotite lowered the bulk ree content and led to the development of a positive eu anomaly the immobile trace elements e g ta th zr sc co ti are best suited for provenance determination because of their relatively low mobility during sedimentary processes elemental ratios such as la sc th sc co th and th ta have inherited the signature of the parent rocks and thus may be particularly useful for provenance studies to evaluate the control of specific minerals and grain size fractions on the distribution of trace elements in the sandstone separated fractions of quartz feldspar the 20 m fraction and heavy minerals were additionally analyzed the concentration densities elemental concentration in the fraction fraction weight reveal that with exception of hf the influence of the heavy mineral fraction on the whole rock geochemistry is insignificant although this fraction generally plays the most important role as carrier of trace elements quartz feldspar and the 20 m fraction have similar concentration densities between 20 and 40 for the ree with exception of eu which is mainly hosted in feldspar strong positive eu anomaly the influence of the 20 m fraction on the distribution of the ree and the elements u th sc ta strongly depends on the abundance of this fraction in the sediment alkali feldspar contains most of the ba sr rb and cs in the samples concentration densities of up to 97 thus differences in the abundances of these elements in whole rock samples can be related to changes in the mineralogical composition quartz feldspar ratio of the sediment

chemical and mineralogical comparison of the pennsylvanian fountain formation colorado u s a an uplifted continental block to sedimentary rocks from other tectonic environments the mineralogic and chemical composition of composites of cobble and pebble sized rock clasts clay stones siltstones fine sandstones and size fractions of two sandstones of the fountain formation near beulah colorado were determined the sandstones are arkosic and most plot in the basement uplift or transitional continental fields of qfl diagrams the mineralogic composition of the sandstones is similar to that of the composite of rock clasts at a given location al mg fe ti mn sc th ree and cs are concentrated in the clay minerals or heavy minerals and are diluted by quartz or feldspar consequently they are inversely correlated with si cr hf k rb ba and sr are poorly correlated with si cr is concentrated in clay and in heavy minerals in the silts k rb ba and sr are correlated with k feldspar mica or clay mineral abundances sedimentary rocks from the fountain formed from an uplifted continental block the element concentrations plot in the fields of active or passive continental margins in many tectonic discrimination diagrams probably as a result of derivation from granitoid sources of similar composition the ree patterns eu anomaly size k and rb concentrations of the fine sandstones are mostly similar to those of the corresponding composite of rock clasts at a given location suggesting that these parameters might be the most reliable in distinguishing sources the most reliable discrimination diagram for uplifted tectonic blocks like the fountain may be a plot of k2o vs eu anomaly size since both of these parameters were very similar in concentration in both the sedimentary rocks and presumed source of the fountain most sedimentary rocks in this study have larger negative eu anomalies than those from the nasc north american shale composite or mcps midcontinent platform sediment this suggests a more evolved source for the fountain than that for average platform sediment

origin of loess deposits in the north tian shan piedmont central asia abstract loess deposits are widely distributed along the mountain piedmonts of central asia the transport processes and origins of central asian loess sediments remain poorly understood here we investigate the origin and formation of loess along the northern piedmont of the tian shan based on trace element including rare earth element ratios and multidimensional scaling analysis our results indicate that the loess has undergone weak chemical weathering using a selection of geochemical fingerprinting techniques based on pearson correlation and kruskal wallis h tests we establish a genetic link between alluvial proluvial fans plains deserts and loess along the tian shan piedmont in northern kyrgyzstan and southern kazakhstan the unsorted sediments on the piedmont slopes and alluvial proluvial plains are common sources for both deserts and loess to the north of the tian shan dune sediments are not the main source of the fine grained loess origin and formation of central asian loess is strongly dependent on local topographic context and wind dynamics only once loess provenance and formation has been understood across both space and time can reliable interpretations of palaeoclimatic proxies in these deposits be made

quartz and zircon decoupling in sandstone petrography and quartz cathodoluminescence of the early triassic continental buntsandstein group in germany

a geological database for parameterization in numerical modeling of subsurface storage in northern germany underground land use can play a significant role in future concepts of energy and gas storage and requires an improved understanding of the parameters of potential storage formations saline aquifers for instance of porosity and permeability and also of mineralogical and gas compositions this study aims at providing data examples and calculating vertical spatial variations through variogram analyses of important north german geological reservoirs from dogger rhaetian middle buntsandstein and rotliegend sub groups and formations focusing on the western part of the north german basin vertical correlation lengths of porosity and permeability data range between 0 and 30 m while most results are calculated at approximately 2 4 m and do not show relevant differences among the evaluated formations in the majority of the regarded formations the kozeny carman relationship between porosity and permeability is supported as long as low porosity and permeability values are excluded from the evaluation mineral percentages varied significantly among the evaluated sediments besides quartz ankerite is the main compound in the dogger group while feldspars and clay minerals were more frequent in the rhaetian middle buntsandstein and rotliegend sediments methane was the main gas compound in the reservoirs followed by nitrogen ethane and carbon dioxide this study serves as preparatory work to allow for the parameterization of geological models and a subsequent simulation of fluid transport to evaluate long term safety and impacts of geothermal and gas storage projects

onshore offshore wind influence on breaking waves an empirical study abstract beach based and in situ observations of plunging and spilling breakers with associated localised wind data have isolated important characteristics regarding breaking waves in the surf zone offshore winds enhance the development of plunging breakers onshore winds the development of spilling breakers extremely strong offshore or onshore winds may re introduce more spilling or plunging breaker type characteristics respectively

mineral leucosome trace element partitioning in a peraluminous migmatite a laser ablation icp ms study abstract low pressure peraluminous migmatites from the pena negra complex central spain stayed partially molten for 5 10 ma until the latest hercynian deformations allowed the segregation of melt as discordant leucosome veins due to long residence within its source the melt had time enough to equilibrate with residual phases other than accessories included within major refractory minerals we estimated crystal melt partition coefficients as the concentration ratios between leucosome samples appearing to be pure melts and mesosome minerals which were analyzed for trace elements with a laser probe coupled to an icp mass spectrometer our data reveal that when biotite is stable li rb cs tl sc v cr ni nb and ta become strongly compatible the role of biotite in fractionating y th u and the ree is insignificant cordierite strongly fractionates li and be and also has some effect on the hree and u garnet produces extreme fractionation of sc y and the hree the ree partition coefficients for ferromagnesian silicates increase with the atomic number this effect being progressively more important through biotite cordierite and garnet k feldspar strongly fractionates ba and pb but plays a secondary role to biotite for rb and cs k feldspar fractionation does not change the lree hree ratio but plagioclase fractionation produces a significant decrease in the lree hree ratio both feldspars greatly fractionate sr and eu monazite fractionation produces a dramatic depletion in ree th and u as well as a decrease in the lree hree and th u ratios apatite also fractionates the ree although in contrast with monazite it increases the lree hree ratio and does not affect the th u ratio zircon fractionation like apatite and garnet produces a strong depletion in the hree and a concomitant increase in the lree hree ratio in contrast with monazite zircon fractionation causes the th u ratio to increase

diagenetic albitization in the tera group cameros basin ne spain recorded by trace elements and spectral cathodoluminescence abstract this paper deals with the diagenetic albitization of both plagioclases and k feldspars in the tithonian fluvial sandstones of a rift basin cameros basin the sandstones in the lower part of the rift record have not suffered this albitization process a clear relationship is observed between sodium contents as the main element of some feldspars and their cathodoluminescence cl color the higher the sodium content the lower is their cl intensity in conclusion albitization processes are detectable by decreased cl intensities and changes in the cl spectra in addition very different trace element compositions are obtained by laser ablation when comparing trace elements of non albitized feldspars in sandstones of the lower part of the rift record with those of albitized feldspars in sandstones of the infill top non albitized k feldspars show rb sr ba and pb contents of up to 1000 ppm in contrast very flat profiles of trace element contents cl spectra from non albitized and albitized k feldspars and plagioclases revealed marked differences non albitized k feldspars present blue main emission band at 460 nm and brownish cl colors 590 nm sometimes in the same grain brownish colors are related to weathering processes the primary blue emission is related to al o al centers enhanced probably by al incorporation due to the coupled substitution of ba2 al3 m si4 weathered k feldspars present 4 8 times lower ba content than fresh blue luminescent ones the brownish colors are related to the external border or fractured grain zones altered by weathering processes therefore the observed 590 nm emission is assumed to be caused by structural defects resulting from weathering and alteration albitized k feldspars are usually weak luminescent with a typical cl emission band at 620 nm sometimes relicts of the original blue luminescence 460 nm band are still present the leaching of probably both al and ba can be responsible for the decrease in the blue band the characteristic 620 nm band is also dominant in albitized weak luminescent plagioclases two additional emission bands at 440 nm al o al center and 565 nm mn2 occur when albitized plagioclases preserved their original cl characteristics green cl color another spectral peak at ca 720 nm can be explained by fe3 activation due to fe3 al3 substitution the spectral cl measurements indicate that changes in luminescence due to albitization 620 nm emission seem to be more related to structural defects than to trace element activation or quenching

late paleozoic tectonics of the solonker zone in the wuliji area inner mongolia china insights from stratigraphic sequence chronology and sandstone geochemistry abstract the geology in the wuliji area including the enger us and quagan qulu areas is important for understanding the late paleozoic tectonics of the solonker zone ultramafic mafic rocks in the enger us area previously interpreted as an ophiolitic suture are actually lava flows and sills in a permian turbiditic sequence and a small body of fault breccia containing serpentinite subduction zone features such as accretionary complexes magmatic arc volcanics or lp hp metamorphism are absent early permian n morb mafic rocks and late permian radiolarian cherts accompanied by turbidites and tuffeous rocks indicate a deep water setting in the quagan qulu area outcrops of the late carboniferous to permian amushan formation are composed of volcano sedimenary rocks and guyot like reef limestone along with a late permian volcano sedimentary unit a dacite lava in the late permian volcano sedimentary unit yields a zircon u pb age of 254 ma the gabbros in the quagan qulu area are intruded into the amushan formation and caused contact metamorphism of country rocks sandstones in the upper member of the amushan formation contain detrital clasts of volcanic fragments and mineral clasts of crystalline basement rocks i e biotite muscovite and garnet geochemical analysis of volcaniclastic sandstones shows a magmatic affinity to both continental island arc cia and active continental margin acm tectonic settings a late permian incipient rift setting is suggested by analyzing the lithostratigraphic sequence and related magmatism in the wuliji area the volcano sedimentary rocks in the wuliji area experienced a nearly n s shortening that was probably related to the early mesozoic nearly n s compression well developed in other areas close to the wuliji area

geochemical evolution of archean shales from south africa i the swaziland and pongola supergroups abstract the fig tree group and moodies group part of the swaziland supergroup are exposed in the barberton mountain land and are 3 3 3 5 ga old shales from the fig tree group are characterized by variable rare earth element ree patterns with lan ybn 5 5 1 8 95 confidence and eu eu 0 97 0 18 shales from the moodies group have more fractionated ree patterns lan ybn 8 7 2 0 and less variable eu anomalies eu eu 0 92 0 02 both groups are characterized by very high abundances of cr and ni modelling of those trace elements which are relatively unfractionated during sedimentary processes ree th sc is consistent with the derivation of these sedimentary rocks from a mixture of the archean bimodal igneous suite mafic volcanics tonalites trondhjemites felsic volcanics with the moodies group requiring a larger percentage of the felsic end member the data for shales from the swaziland supergroup support models suggesting that the archean exposed crust was of more mafic composition than the post archean upper crust and that intracrustal melting was relatively unimportant in differentiating the archean crust the pongola supergroup is younger than the swaziland supergroup but older than 2 9 ga shales and mudstones from the nsuze and mozaan groups show ree characteristics intermediate between the older shales of the swaziland supergroup and typical post archean shales one quartzite sample from the witwatersrand supergroup ca 2 6 ga has a ree pattern virtually parallel to average post archean shales but with much lower abundances the change from typical archean to post archean sedimentary trace element patterns has been documented in early proterozoic successions from canada and australia this change has been related to a short interval of intense growth and chemical differentiation of the continental crust during the late archean 2 7 2 5 ga in southern africa this change appears to have taken place much earlier 3 2 2 9 ga but can be related to similar processes thus the period of crustal evolution related to the archean proterozoic boundary while virtually episodic regionally occurred over a protracted period world wide during the period ca 3 2 2 5 ga

interoceanic variation in the rare earth major and trace element depositional chemistry of chert perspectives gained from the dsdp and odp record rare earth element ree major and trace element abundances and relative fractionations in forty nodular cherts sampled by the deep sea drilling project dsdp and ocean drilling program odp indicate that the ree composition of chert records the interplay between terrigenous sources and scavenging from the local seawater major and non ree trace element ratios indicate that the aluminosilicate fraction within the chert is similar to nasc north american shale composite with average pacific chert including 7 nasc like particles indian chert 11 nasc atlantic chert 17 nasc and southern high latitude shl chert 53 nasc using la as a proxy for ree approximations of laex the amount of la in excess of that supplied by the detrital aluminosilicate fraction indicate that pacific chert contains the greatest laex 85 of latotal and shl chert the least 38 of latotal as shown by interelement associations this laex is most likely an adsorbed component onto aluminosilicate and phosphatic phases accordingly chert from the large pacific ocean where deposition occurs relatively removed from significant terrigenous input records a depositional ree signal dominated by adsorption of dissolved rees from seawater pacific chert cece 1 and lanybn 0 8 1 resulting from adsorption of local ce depleted seawater and preferential adsorption of lrees from seawater e g lanybn 0 4 which increases the lanybn ratio recorded in chert chert from the atlantic basin a moderately sized ocean basin lined by passive margins and with more terrigenous input than the pacific records a mix of adsorptive and terrigenous ree signals with moderately negative ce anomalies and lanybn ratios intermediate to those of the pacific and those of terrigenous input chert from the shl region is dominated by the large terrigenous input on the antarctic passive margin with inherited cece 1 and inherited lanybn values of 1 2 1 4 cece does not vary with age either throughout the entire data base or within a particular basin overall cece does not correlate with p2o5 concentrations even though phosphatic phases may be an important ree carrier this and previous studies of the large scale controlling parameters of sedimentary rees across ocean basins collectively indicate that ree indices of depositional regime e g cece lanybn laex are reproducible in a variety of sediment and rock lithologies ages and ocean basins and present a coherent tool for paleoceanographic and tectonic basin reconstructions

geochemistry of shales of the upper cretaceous hayang group se korea implications for provenance and source weathering at an active continental margin abstract shales of the upper cretaceous hayang group in the yeongyang subbasin southeastern korea were deposited in fluvio lacustrine environments as the paleo pacific izanagi plate obliquely subducted beneath the asian continent major and trace element compositions derived from shales analyzed from the hayang group reveal geochemical signatures that are different from post archean average australian shale paas but are typical of igneous rocks found in the continental margin island arc settings for example most major element concentrations are depleted relative to paas among them mgo and mno depletions are most pronounced in all shales cao enrichment is notable in some formations due to the presence of secondary calcite as dispersed micro calcite nodules sc y and th concentrations are also slightly depleted relative to paas while chondrite normalized ree data for shales from the hayang group show moderate to large uniform lree enrichment but variable hree depletions in addition they are more fractionated than paas and have significant negative eu anomalies moreover the chemical index of alteration and a cn k relations comply that the source area was dominated by non steady state weathering regimes indicative of active uplift along an active continental margin these regions were punctuated by two periods of steady state weathering or alternatively by enhanced recycling of sediments the latter interpretation is in accord with the timing of exposure of a cherty sequence in the source area mixing calculations based on ree data suggest that the average shale in the hayang group was derived from sources composed of precambrian granitic gneiss arc basaltic rocks triassic yeongdeok granite in the subbasin and the mino accretionary complex of sw japan with ratios around 43 7 31 8 73 2 26 4 15 8 36 7 15 4 2 8 33 9 14 5 0 0 33 8 however these proportions change up sequence

field investigation of suspended sediment clouds under plunging breakers abstract breaking waves nearshore force the suspension of beach material and so play an important role in surf zone sedimentological regimes the analysis of cinemato graphical records of wave breaking and bottom sediment response for eight plunging and eight plunging transition breakers has enabled the study of sand cloud initiation evolution and decay the characteristics of the suspended sediment clouds can be explained in terms of breaker energy dissipation some of the sand cloud features are common to both plunging and plunging transition breakers although the total spatial and temporal history of the cloud is controlled by the water surface profile evolution during breaking observations of breaker kinematics in the aerated region after breaking highlight the importance of breaker induced vortices in controlling the initiation concentration elevation and longevity of suspended material in the surf zone

understanding the arabian sea reflections on the 1994 1996 arabian sea expedition abstract the arabian sea expedition now five years past its field observations is at a stage when some of its dominant themes can be summarized of the large range of possible topics five are considered here 1 is the arabian sea a source or sink for carbon dioxide 2 is the arabian sea mother nature s iron experiment 3 do grazing zooplankton control carbon flux to the seabed 4 does the paleoceanographic record help us predict the ocean s response to climate change and 5 what are the predominant physical processes of the arabian sea a short history of each issue and results from the field work of 1994 1996 are presented

analysis of surf zone turbulence measurements of turbulent kinetic energy k under surf zone waves are analyzed to show how k varies over depth between breaker point and shoreline and how k depends on the beach slope it is found that the variation of k over depth is remarkably weak large values being measured a few percent of the depth above the bottom a simple model for the dissipation mechanism makes it possible to derive an empirical formula for the time averaged k that accurately describes all the data considered reliable

authigenic k feldspar in the bromsgrove sandstone formation triassic of ccntral england abstract authigenic k feldspar is a ubiquitous feature of the bromsgrove sandstone formation triassic in central england it occurs mainly as partially to completely developed euhedral overgrowths on detrital k feldspar cores the authigenic k feldspar is virtually pure kalsi3o8 potassian low sanidine and occurs as optically continuous overgrowths on detrital sanidine and optically discontinuous overgrowths on detrital orthoclase differences in structure and al si disorder thus control the degree of optical continuity of the overgrowths an important feature is the presence of optically and compositionally zoned overgrowths due to minor fluctuations in the bao and na2o content the formation of the overgrowths was dependent upon intrastratal dissolution of detrital grains for a supply of potassium aluminum and silicon precipitation took place within the k2o na2o al2o3 sio2 h2o system and in association with other phases in this system the diagenetic sequence 1 illite 2 quartz 3 k feldspar 4 illite 5 kaolinite is consistent with a progressive increase in k h ratio or h4sio4 activity followed by a general decrease so that the later interstitial fluids were much depleted in k ions and kaolinite was the final phase to precipitate

geochemistry of agates a trace element and stable isotope study abstract agate samples of acidic intermediate and basic volcanics from 18 localities around the world and of different age precambrian to tertiary were studied by trace element and stable isotope analysis to provide information about the process of agate formation and the origin of mineral forming fluids trace element data are similar for agates from acidic and basic volcanics the general chondrite normalized ree distribution pattern is characterized by a slope from la to lu with enriched lree and a positive eu anomaly in some samples the similarity in the shape of the ree patterns between agates and the parent volcanic rocks suggests that the elements are mobilized by circulating fluids during syn and postvolcanic alteration of the volcanic wall rocks observed positive eu anomalies in agates probably originate from feldspar alteration deuterium and oxygen isotope analyses of agates and associated quartz incrustations d 44 to 130 18o 16 4 to 33 4 reveal variations in isotopic composition between samples of different localities but also within single agate samples up to 10 for 18o in general oxygen isotope compositions become heavier as volcanic host rocks grow more acidic furthermore agates have higher 18o values than associated quartz incrustations variations within single agate samples can be explained either by kinetic effects during isotope fractionation e g the formation of agate from a noncrystalline precursor or by mixing processes of meteoric and magmatic fluids remarkably high 18o values of the parent volcanic rocks up to 19 5 suggest that the circulation of 18o enriched hydrothermal fluids originated from heated meteoric water and or residual magmatic fluids this conclusion is supported by 13c and 18o data of paragenetic calcite the temperature of agate formation was calculated for different fluid compositions and they indicate a temperature range of ca 50 c to 250 c

northern arabian sea variability from topex poseidon altimetry data an extension of the us jgofs onr shipboard adcp study abstract sea level anomalies sla derived from the topex poseidon t p altimetry and inferred geostrophic currents within the northern arabian sea were examined for the period from march 1993 through november 1996 the primary objective of this study was to confirm and extend our understanding of the upper ocean mesoscale variability observed in the shipboard acoustic doppler current profiler adcp data collected during the us jgofs onr arabian sea expedition september 1994 january 1996 the accuracy of the t p altimetry data 3 cm rms results in an uncertainty in the altimeter derived velocities comparable to the adcp measurement error thus the t p data provide a reasonable method for extending studies of the mesoscale dynamics for the region comparison of the t p derived geostrophic velocities with concurrent adcp data showed good correlation with an r 2 between 0 7 and 0 9 and rms differences of 10 cm s 1 the t p data confirm both the overall spatial and seasonal current patterns observed by the adcp the monsoonally averaged rms sea level anomalies indicate a high degree of intraseasonal variation due to the generation of squirts jets and eddies all along the coast the variability of which increases in both intensity and areal extent during the southwest monsoon the sla data indicate a much reduced degree of variability over the shelf the sla derived eddy kinetic energy eke fields are consistent with those derived earlier from the adcp data in both distribution and magnitude there is a large increase in eke to the west and southwest and to a lesser extent to the south and a large area of relatively reduced eddy activity over much of the eastern and northern arabian sea the area of reduced eddy activity coincides with the location of the most intense portions of the oxygen minimum zone found in the northern arabian sea the spatial scales of the eddies responsible for the eke distribution over the study area range between 200 and 500 km in the nearshore region decreasing to 100 200 km offshore while there is significant energy variability in annual and semi annual time scales a substantial portion of the energy is found between 50 and 120 days and the relative importance of this frequency band increases offshore spectra indicate a distinct break in the frequency content of the eddy field at about 15 n with little energy at less than annual periods south of this latitude

upper ocean currents in the northern arabian sea from shipboard adcp measurements collected during the 1994 1996 u s jgofs and onr programs abstract a large upper ocean velocity data set was obtained using a shipboard acoustic doppler current profiler adcp on seventeen rv t g thompson cruises during the jgofs and onr expedition to the northern arabian sea from september 1994 through january 1996 seven of the cruises followed a large area survey track centered over the arabian basin four cruises conducted seasoar surveys on either side of the findlater jet axis and six cruises were for the deployment and maintenance of moored instrumentation together providing some 380 cruise days and 96 000 track kilometers of coverage the adcp data extended over the upper 250 400 m of the water column depending upon the temporal spatial distributions of acoustic scatterers the velocity data revealed several items that differed significantly from the historical perspective maximum current magnitudes in this area varied from more than 1 m s 1 along the arabian coast to 10 20 cm s 1 well offshore perhaps the most important result was the complete dominance of the velocity field by eddies that had offshore correlation length scales of roughly 100 km a spectral peak at around 300 km and kinetic energies that ranged from 70 to more than 90 of the total kinetic energy the total kinetic energy was highest within about 300 km of the shore and decreased significantly in magnitude and vertical extent offshore within the coastal region the temporal variability was such that currents of 50 cm s 1 or more could completely reverse within a two week period seemingly independent of any local atmospheric forcing mean and seasonal velocities also differed from historical results there was a large anti cyclonic feature located for most of the year south of ras ash shabatat 58 e which intensified during the southwest monsoon there was a strong jet like current off ras al hadd 22 n which also intensified during the southwest monsoon although itflowed southwestward against the wind in contrast to the historical ship drift data which indicated that the surface currents followed the monsoonal winds the adcp data over the upper 200 400 m was highly variable with overall seasonal means that were often directed against the wind except within 100 200 km of the arabian coast the mean currents were generally toward the southwest with a mean transport in the upper 150 m between the coast and 10 n of approximately 9 10 6 m 3 s 1

the chemical signature of source rocks in size fractions of holocene stream sediment derived from metamorphic rocks in the wet mountains region colorado u s a eight stream sediments draining primarily mixed silica rich and silica poor metamorphic rocks in the wet mountains colorado were analyzed at their source for their mineralogic and selected elemental composition the low silica source rocks include amphibolite hornblende schist and muscovite biotite schist the high silica source rocks include granodioritic to leucocratic granitic gneisses the high silica source rocks tend to contain higher concentrations of ree th hf and ba lower concentrations of fe sc and cr higher la sc and thsc ratios and more negative eu anomalies than the low silica source rocks especially those low silica source rocks derived from basic sources rather than weathered silicic sources the stream sediments draining this mixed metamorphic rock terrain are dominated by sands and gravels and they are composed of feldspar quartz and 25 heavy minerals the silts contain more total biotite hornblende pyroxene and opaque minerals and less quartz and feldspar than the sands and gravels sediment especially the silts derived from mixed low and high silica sources tends to be intermediate in elemental composition between those of the end member sources so there is some hope that source rock signatures may be preserved in the sediment elemental ratios of la sc th sc la co th co and ba co and th la sc plots most clearly distinguish sediment derived from the most silicic and most basic source rocks in addition finer sediment near the source can potentially distinguish silicic sources higher ree and more negative eu anomalies from those of basic sources the clay and silt fractions contain negative eu anomalies normalized to the mcps north american mid continent platform sediment and the sands and gravels have positive eu anomalies normalized to the mcps most size fractions are similar to more enriched in la sc th sc la co and th co ratios than the mcps this suggests local sources in the wet mountains are on the average more silica rich than those that formed the mcps

chemical behavior of detrital feldspars in mudrocks versus sandstones frio formation oligocene south texas abstract in both sandstones and mudrocks dissolution and replacement can cause substantial modification of detrital feldspar assemblages over burial depths from 1 km to 5 5 km in the frio formation oligocene of south texas mudrocks lose most k feldspar and ca plagioclase both of these minerals however survive to greater depths in mudrocks than in associated sandstones and are not completely removed even in the deepest samples examined albite is the most abundant replacement phase calcite and al rich sphene are common sphalerite pyrite and tio2 also occur as replacements of detrital feldspar replacement phases are introduced subsequent to dissolution of the detrital grain and require transport of material over minimum distances of tens of microns from sources exter al to the detrital feldspar

geochemical signature of provenance in sand size material in soils and stream sediments near the tobacco root batholith montana u s a abstract trace element geochemistry of sandstones are being used to determine provenance we have conducted preliminary and limited experiments to determine to what extent daughter sands retain the geochemical signature of parent rocks six sets of first order stream sediments soils from adjacent slopes and a variety of parent rocks were collected from southwestern montana u s a sampling in a low relief area ensured that climate and residence time of soils on slopes could be eliminated as variables sand size fractions of stream sediments and soils and the corresponding parent rocks granodiorite quartz monzonite granite gneiss biotite tonalite gneiss and amphibolite were analyzed for most major elements and selected trace elements petrologic modal analysis of the parent rocks and the 0 25 0 50 mm fraction of each sand was done to monitor major mineralogic control if any on chemical compositions of the samples our data show that the abundances of the si and al in sediments do not discriminate provenance abundances of ca mg fe and ti may broadly distinguish between sands derived from metamorphic and igneous source rocks at least in the area studied differences in abundances of the ba and th and the ratio of la lu between granitic tonalitic and amphibolitic parent rocks are preserved in the daughter sediments that we studied however the size of the eu anomaly in the ree patterns of different daughter sediments is not diagnostic of parent rocks abundances of co and sc distinguish between sediments derived from felsic and mafic rocks a better provenance discrimination is obtained if the ratios la sc th sc la co ba sc and ba co are used petrologic modal data show that mineral contents and chemical compositions of parent rocks are compatible with each other the chemical composition of the sands may be roughly correlated to the petrological modal data but the abundances of some minor and trace elements of sediments cannot be inferred from modal mineralogy this is expected because these elements may concentrate in accessory minerals and or may weather out into aqueous or clay mineral fractions it is also compatible with conclusions of previous studies that some of these elements do not reside in sand size fractions of siliciclastic sediments

the carbon dioxide system in the arabian sea in 1995 the whoi c goyet and miami f j millero groups participated on a number of research cruises in the arabian sea as part of the u s joint global ocean flux study jgofs sponsored by the national science foundation nsf this paper gives the results of our total inorganic carbon dioxide tco2 total alkalinity ta and potentiometric ph measurements made on arabian sea water samples during these cruises measurements made on certified reference material crm indicate that the reproducibility of the measurements was 0 007 in ph 3 2 mol kg 1 in ta and 1 2 mol kg 1 in tco2 n 180 the surface measurements 0 30 m of ph and normalized tco2 and ta were quite uniform throughout the year ph 8 1 0 05 ntco2 1950 20 mol kg 1 and nta 2290 5 mol kg 1 the larger variations in ntco2 in the surface waters are related to changes in primary production and upwelling in the coastal waters the depth profiles of ph pco2 ta and tco2 were similar to those in the equatorial pacific ocean the components of the carbonate system co2 hco 3 co2 3 and the saturation state for calcite and aragonite were determined from the measurements of ta and tco2 the waters below 600 and 3400 m in the arabian sea were undersaturated 1 0 for aragonite and calcite respectively the co2 measurements have been combined with the nutrient data to examine the stoichiometric ratios of c n c p c o2 and c sio2 of the waters marked differences were found for the waters above and below the oxygen minimum zone the surface water results have been used to develop the following stoichiometry for phytoplankton in the arabian sea ch2o 125 nh3 14 h3po4 sio2 13 the oxidation of this material is due to reactions with o2 77 and no3 23 with the resultant formation of n2 and n2o the maximum amount of organic carbon oxidized has been estimated to be 3 1 mol kg 1 in the deep waters with as much as 0 9 mol kg 1 in the oxygen minimum zone with no3 the maximum amount of caco3 dissolved in the deep waters is 116 mol kg 1 these results together with the organic material collected from the sediment traps should be useful in characterizing the formation and degradation of plant material in the arabian sea

the age of the latest thermal overprint of tin and polymetallic deposits in the erzgebirge germany constraints from fluorite u th sm he thermochronology the erzgebirge region of germany records two major episodes of hydrothermal activity which includes a late carboniferous to early permian event associated with significant sn w mineralization that is related to late variscan granite magmatism and a mesozoic episode of polymetallic vein mineralization in contrast to the first event the age of the younger hydrothermal activity is poorly constrained for the latter various geochronological methods yielded a wide age range from permian to early tertiary here we apply fluorite u th sm he thermochronology fhe on both types of mineralization with a twofold goal 1 to investigate the sensitivity and applicability of the new fhe method evans et al 2005 and 2 to constrain the thermal history of ore deposits in the erzgebirge region two hundred and thirty three aliquots from seven mineralization localities have been dated fluorite from six deposits yielded cretaceous fhe ages between 112 to 79 ma which are independent of their paragenesis in contrast fluorite from the sadisdorf sn w deposit yielded an age of 234 ma the younger ages are interpreted as cooling ages indicating the time of the last thermal overprint including possible hydrothermal activity in the erzgebirge the oldest triassic fhe ages at sadisdorf indicate that the mesozoic thermal overprint only partially reset the u th sm he system of the late variscan mineralization thermal modeling based on fhe ages and he diffusion parameters in fluorite results in thermal histories comparable to the results from the well established apatite based thermal modeling this study emphasizes the applicability of fluorite u th sm he thermochronology which is especially suited for ore deposits where apatite is lacking

distribution of ree and trace elements in size and mineral fractions of high purity quartz sands eight sample sets raw quartz sand quartz fraction 2 m clay fraction 2 20 m fraction and heavy minerals of the cretaceous quartz sand deposits of haltern and weferlingen central germany and the tertiary quartz sand of frechen western germany were studied to characterize the distribution of ree and trace elements and to get genetic information about provenance and sedimentologic history of the sediments the quartz sand samples from different localities have rather similar trace element distribution and ree patterns with enriched lree and negative eu anomalies however these relations can be modified by local changes in syn or postsedimentary geochemical conditions adsorption of ree and trace elements on humic substances under reducing conditions and postsedimentary weathering in the quartz sand of weferlingen resulted in significantly modified element abundances the concentration of trace elements is most important in the 2 m fraction and in the heavy mineral fraction where they may be enriched by a factor of up to 100 the chondrite normalized ree distribution of the 2 m fraction is quite similar to those in the north american shale nas with average eu sm ratios of 0 21 and layb cn of 6 1 low trace element abundances in the 2 and 2 20 m fractions were attributed to quartz dilution and quantified among the common minerals in the heavy mineral fractions especially zircon and the fe 1bti oxides rutile ilmenite magnetite influence the trace element distribution investigations concerning the provenance of the quartz sands illustrate that the host sediments have a rather homogeneous geochemical signature due to their sedimentological history taking into account th ta variations the quartz sands of weferlingen and haltern can be distinguished from the frechen quartz sand additionally discriminations based on element ratios within the quartz fraction th sc ba sc ba co cs sc or li sc seem to be promising

superposition of burial and hydrothermal events post variscan thermal evolution of the erzgebirge germany the post variscan thermal history of the erzgebirge germany is the result of periods of sedimentary burial exhumation and superimposed hydrothermal activity the timing and degree of thermal overprint have been analysed by zircon and apatite u th he and apatite fission track thermochronology the present day surface of the erzgebirge was exhumed to a near surface position after the variscan orogeny thermal modelling reveals permo mesozoic burial to temperatures of up to 80 100 c although the sedimentary cover thins out towards the north resulting in maximum burial temperatures of less than 40 c this thermal pattern was locally modified by cretaceous hydrothermal activity that reset the zircon u th he thermochronometer along ore veins the thermal models show no significant regional exhumation during cenozoic times indicating that the peneplain like morphology of the basement is a late cretaceous feature

random breaking waves field verification of a wave by wave algorithm for engineering application abstract a simple numerical algorithm is utilized to test the wave by wave approach to modeling random wave transformation caused by shoaling breaking and reforming across nearshore profiles of arbitrary shape histograms of wave height and associated statistics predicted by the model show favorable comparison to measurements from the nine tests of the duck 85 field experiment with a root mean square error less than 10 for most wave statistics although suitable for use in many engineering applications the model does overpredict the number of waves that reform as they pass over a trough formation which is one facet that warrants improvement using the model predictions as a point of reference the qualitative effects of 1 an offshore wind 2 wave reflection and 3 surf beat are identified and discussed

coherent response of arabian sea upwelling and pollen transport to late quaternary monsoonal winds the indian summer monsoon causes large seasonal changes in the environments of both eastern africa and the arabian sea here we compare time series 140 kyr long of selected pollen types and foraminiferal upwelling faunas preserved in marine sediments to identify the frequencies of their variability and the coherence and phase of the terrestrial and marine responses to monsoonal circulation during interglacial intervals the pollen and upwelling records of the western arabian sea indicate stronger monsoons and are both coherent and in phase at periodicities near the precession of the earth s rotational axis 23 kyr we conclude that the strength of the monsoonal southwesterlies accounts for this high coherence of marine and terrestrial records during interglacial intervals low correlation during glacial phases indicates weaker monsoons and some decoupling of these two records these data indicate that two distinct modes of monsoon variability may exist an interglacial mode with strong monsoons and effective coupling of terrestrial and marine records and a glacial mode with both weaker monsoons and decreased linkage between arabian sea pollen and upwelling records

short term changes in the morphodynamic states of beaches and surf zones an empirical predictive model a time series of 6 5 years of daily observations of beach states and wave characteristics from southeastern australia was analyzed with the aim of determining the degree to which time varying beach state can be explained and predicted the six commonly occurring beach states dissipative longshore bar trough rhythmic bar and beach transverse bar and rip low tide terrace and reflective discussed earlier were related by means of discrete discriminant analyses to the parameter hb wst where hb is breaker height ws is the fall velocity of the beach sand and t is peak breaker period using a total of 1545 cases two values were used in the analyses the immediate value occurring on the day the particular state was observed and a weighted mean value expressing recently antecedent conditions the immediate value made a negligible contribution to explaining day to day beach state observations however the antecedent conditions showed a strong relationship and provide a successful means of prediction by examining cases where the time derivatives of both state and were near zero it was possible to define the equilibrium conditions associated with each state directions of change erosional or accretionary are predicted in terms of departures of from the equilibrium value appropriate to the beach state prevailing at the time change begins