nearshore internal bores and turbulent mixing in southern monterey bay 1 we observed transient stratification and mixing events associated with nearshore internal bores in southern monterey bay using an array of instruments with high spatial and temporal resolution the arrival of the bores is characterized by surging masses of dense cold water that tend to stratify the water column the bore is followed by a gradual drop in the temperature throughout the water column over several hours defined here as the bore period until a sharp warm front relaxation followed by high frequency temperature fluctuations returns the column back to nearly its original state defined here as the mixing period mixing periods revealed increased temperature variance at high frequencies n as well as a greater percentage of events where dynamic instabilities may be present ri 0 25 suggesting active mixing of the stratified water column turbulent dissipation rates in the stratified interior during the mixing period estimated using the technique of isopycnal slope spectra revealed mean values the same order of magnitude as near bed bottom generated turbulence observations indicate that local shear produced turbulent kinetic energy by the warm front relaxations dominates mixing in the stratified interior the non canonical nature of these bore and relaxation events is also investigated with a numerical model and the dynamics are shown to depend on the internal iribarren number our results suggest that nearshore internal bores interacting with local bathymetry dramatically alter local dynamics and mixing in the nearshore with important ecological implications

the ultrapotassic rocks from southeastern spain the ultrapotassic rocks of orenditic affinity from southeastern spain have variable sio2 and mgo contents high k2o p2o5 ni cr ba ce th zr values and high k2ona2o nimgo ratios on the contrary tio2 nb y are moderate and feot cao v sc are low the parent magmas possibly generated from a phlogopite bearing mantle source enriched in many incompatible elements by metasomatic processes and probably they were characterized by very co2 co2 h2o ratio the low tip ratio and the moderate tio2 and nb contents in spite of the high alkaline element contents of the magmas suggest that titanium and niobium were retained in the source of the metasomatic fluids the low na contents may depend in part on the loss of this element via naf separation during the latest stage of crystallization crustal contamination cannot be excluded

early to mid tertiary inverted metamorphic gradient under the colorado plateau evidence from eclogite xenoliths in ultramafic microbreccias navajo volcanic field mid tertiary ultramafic microbreccia diatremes from the navajo volcanic field in the four corners area of the colorado plateau contain an ultramafic xenoliths suite in which lower temperature prograde metamorphic eclogites are associated with higher temperature garnet clinopyroxenites that were retrograded and hydrated to chlorite eclogite assemblages and directions of metamorphic reactions are consistent with the model of a laramide age inverted metamorphic gradient established as prograde reactions in a dehydrating oceanic slab caused hydration and cooling in the overlying subcontinental upper mantle wedge comparison with an inverse metamorphic gradient in the pelona schists inferred to represent an exposed part of the same subduction system in southwestern arizona and southern california confirms the shallow dip of the laramide subduction zone predicted by the regional distribution of subduction related volcanic rocks

observations of shoaling nonlinear internal bores across the central california inner shelf abstractwe present observations of shoaling nonlinear internal bores off the coast of central california the dataset includes 15 moorings deployed during september october 2017 and cross shore shi

alkali basalts and leucitites in an extensional intracontinental plate setting the late cenozoic calatrava volcanic province central spain the calatrava volcanic province cvp of central spain is characterised by a intracontinental plate magmatic association of leucitites melilitites nephelinites and olivine basalts extruded during the late miocene to quaternary most of the rocks represent relatively primitive magmas and less than 45 have experienced small degrees 25 of crystal fractionation melilitites nephelinites and olivine basalts form a suite generated by variable degrees of partial melting f 5 17 of a nearly homogeneous enriched up to x18 chondritic values for the highly incompatible elements and 3 for the moderately incompatible mantle source composed of ol opx cpx gt phl the leucitites appear to be derived by low degrees of partial melting 4 from a different mantle source characterized by higher rb ba k and 87sr enrichment and the presence of residual apatite phlogopite contributed to the leucititic liquids in a higher proportion than in the basaltic suite whereas clinopyroxene participated in lower amounts the geochemical characteristics of the primary liquids suggest a contribution from two source components 1 a subcontinental lithospheric component which appears to be a strongly enriched garnet lherzolite with phlogopite apatite and 2 an asthenospheric diapir component with characteristics similar to the himu reservoir these conclusions combined with geophysical observations indicate that the cvp magmatism could develop in two stages in a first stage a himu like mantle diapir would trigger magma generation in the overlying subcontinental lithosphere by melting of pervasive enriched streaks or veins with phlogopite apatite giving rise to small amounts of leucititic liquids and to initial extension of the upper crust in subsequent steps the extension developed the lithosphere becomes stripped of its enriched components and the asthenospheric diapir starts to melt giving rise to the basaltic liquids which are virtually oib like magmas this model is also supported by the available k ar radiometric ages as the leucitites were extruded first 7 6 ma followed by the basaltic suite 4 6 1 75 ma this volcanic region is linked with the rift system which developed from late miocene to quaternary times in western central europe and shows strong geochemical similarities with this volcanism in which both lithospheric and asthenospheric components have been detected

upwelling rebound ephemeral secondary pycnoclines and the creation of a near bottom wave guide over the monterey bay continental shelf several sequential upwelling events were observed in fall 2012 using measurements from the outer half of the continental shelf in monterey bay during which the infiltration of dense water onto the shelf created a secondary near bottom pycnocline this deep pycnocline existed in concert with the near surface pycnocline and enabled the propagation of near bottom cold semidiurnal internal tidal bores as well as energetic high frequency nonlinear internal waves of elevation iwoe the iwoe occurred within 20 m of the bottom had amplitudes of 8 24 m periods of 6 45 min and depth integrated energy fluxes up to 200 w m 1 iribarren numbers 0 03 indicate that these iwoe were nonbreaking in this region of the shelf these observations further demonstrate how regional upwelling dynamics and the resulting bulk cross margin hydrography is a first order control on the ability of internal waves at tidal and higher frequencies to propagate through continental shelf waters

origin of the rudstone floatstone beds in the upper jurassic arab d reservoir khurais complex saudi arabia abstract detailed description and analysis of cores from more than 50 wells through the kimmeridgian arab d reservoir arab d member and upper part of the jubaila formation in khurais abu jifan and mazalij oil fields are used to establish a consistent depositional model that represent a shift in the conceptual understanding of the upper jurassic carbonates of saudi arabia the jubaila fm and arab d mb conform to a shallowing upward carbonate evaporite succession in which three main carbonate facies belts occur capped by anhydrite the lower facies belt corresponds to the jubaila formation and consists of a series of eventites triggered by breaking internal waves interbedded peloidal wackestones represents the background sedimentation where neritic lime mud was churned by pellet producing benthonic fauna eventites consist of a lower intraclastic rudstone floatstone interval a middle grainstone packstone interval and an upper barren mudstone interval the middle facies belt is made of microbial coral stromatoporoid buildups the upper facies belt consists of the following shallow water lithofacies with cladocoropsis green algae foraminifers peloids and oolitic grainstones and oolitic cryptomicrobial mudstone to grainstone the stacking patterns of the internalites internal wave deposits in the jubaila fm suggests alternating periods with different internal waves activity namely different strength and bathymetric position of the pycnocline and intermittent production and accumulation of the neritic lime mud this interpretation represents a change to previous interpretations turbidites and tempestites and has important implications in both the perceptions of depositional processes in play and the criteria behind stacking lithofacies into parasequences and sequences

observation of very large and steep internal waves of elevation near the massachusetts coast 1 we report on near bottom waves of elevation with amplitude nearly half the 25 m water column very steep and propagating into a sheared turbulent wave guide the waves contained trapped cores transporting parcels of water shoreward these large waves depart strongly from weakly nonlinear and weakly nonhydrostatic conditions and challenge established paradigms they can also represent an important factor in the across shore transport of plankton and contaminants

zoned minerals in garnet peridotite nodules from the colorado plateau implications for mantle metasomatism and kinetics some garnet peridotite nodules from the thumb a minette neck on the colorado plateau in the southwestern united states contain zoned minerals zoning does not exceed 1 5 wt for any oxide but some relative changes are large in one garnet tio2 and cr2o3 ranges are 0 05 0 65 and 3 5 5 0 wt respectively in two porphyroclastic nodules garnet rims are depleted in mg and enriched in fe ti and na compared to cores and one garnet is irregularly zoned in ti and cr olivine crystals in these rocks are unzoned and pyroxene zoning is slight yet matrix olivine and pyroxene contain more fe and ti and less mg and cr than inclusions of these phases in garnet in three coarse nodules garnet rims are ti rich compared to cores and ca fe mg and cr zoning patterns are complex several nodules appear to have partially equilibrated near 1200 c and 35 kb and under these conditions cation mobility in pyroxene was greater than in garnet

circulation and larval distribution in internal tidal bore warm fronts internal tidal bore warm fronts were observed during the summer of 1996 off the coast of southern california warm bore fronts had concentrating currents resulting from high frequency internal motions and from a larger two way flow the two way flow featured surface currents onshore and bottom currents offshore a sharp thermocline depression and high frequency large amplitude internal motions followed the leading edge of the bore with downwelling currents on the trailing side of the crest of the nonlinear internal waves and upwelling currents in front of the crest warm bores propagated onshore with a propagation speed c that ranged from 10 6 to 19 6 cm s 1 while time averaged frontal currents varied from 11 2 to 17 6 cm s 1 in the shallowest bin in one out of three cases c which implied that there were faster currents than the rate of advance of the front and which implied that the origin of surface frontal material is behind the front not in front of it three invertebrate larval taxa were found at all sites across fronts but only two intertidal barnacles pollicipes polymerus and chthamalus spp were concentrated at the front s surface while the subtidal bryozoan membranipora spp was not frontal pollicipes were more concentrated than were chthamalus the frontal downwelling currents observed suggested that concentrated larvae would have to swim upward in order to maintain depth pollicipes were abundant on the offshore warm side of the fronts but were absent or rare on the onshore colder side suggesting that the origin of frontal pollicipes was behind the front although an alternative cannot be ruled out conclusively chthamalus were more abundant at depth than at the surface at all sites except at the front where this pattern was reversed the origin of frontal chthamalus is uncertain membranipora were more abundant on the onshore colder side of the fronts and abundances were usually higher at depth than at surface lack of accumulation in this species may be due to its limited swimming capability

exploration of crustal mantle material for the earth and moon using reflectance spectroscopy abstract near infrared reflectance spectra have been acquired a for moses rock diatreme in se utah using an airborne imaging spectrometer ais and b for small areas in and around the large lunar impact crater copernicus using a spectrometer on earth based telescopes the high spectral resolution and precision of these data allow several mineral components of surface material to be identified and analyzed in a spatial context the derived mineralogical information is used to address specific geological problems for the terrestrial study the distribution of the measured abundance of mantle derived ultramafic microbreccia across moses rock dike indicates that flow stabilized into a few channels during the violent eruption for the lunar study the variety of rock types identified in crustal material of deep seated origin is distinct from the dominant rock types sampled from the upper lunar crust and suggests a complex crustal evolution

garnetite xenoliths and mantle water interactions below the colorado plateau southwestern united states garnetite xenoliths from ultramafic diatremes in northeastern arizona provide insights into hydration and metasomatism in the mantle the garnetites contain more than 95 garnet some of which has complex compositional zonation related to growth in fractures within grains accessory minerals include rutile ilmenite chlorite clinopyroxene and zircon zircon grains in one rock were analyzed in situ to determine u pb ages and hf isotopic compositions most u pb analyses plot on or near concordia in the range 60 85ma but a few are discordant the range in 176 hf 177 hf is about 0 2818 0 2828 with grains zoned to more radiogenic hf from interiors to rims the garnetite protolith contained zircons at least 1 8ga in age and garnet and additional zircon crystallized episodically during the interval 85 60ma the garnetites are interpreted as mantle analogues of rodingites formed in metasomatic reaction zones caused by water rock interactions in proterozoic mantle during late cretaceous and cenozoic subduction of the farallon plate associated eclogite xenoliths may have been parts of these same reaction zones the rodingite hypothesis requires serpentinization in the mantle wedge 700km from the trench beginning 5 10myr before tectonism related to low angle subduction

tectonic implications of the age composition and orientation of lamprophyre dikes navajo volcanic field arizona abstract fifty one lamprophyre dikes of the navajo volcanic field are randomly oriented in contrast to dikes of similar age from adjacent tectonic provinces k ar ages obtained on nine of these dikes indicate that they were emplaced between 28 and 19 m y ago initiation of dike emplacement was approximately coeval with the initial demarcation of the colorado plateau in the mid tertiary chemical analyses obtained on nine dike samples show a wide range in composition silica contents range from 33 6 in a phlogopite katungite to 55 9 in a felsic minette two of the samples have na 2 o k 2 o indicating that sodic volcanism was occurring concurrently with the dominant potassic volcanism published results of high pressure experimental studies of katungite suggest that this magma was derived from k metasomatised mantle because this potassium metasomatism produces a positive volume change we propose a model that relates uplift of the colorado plateau to metasomatism magma genesis and dike emplacement

gravity currents facilitate formation of high frequency internal solitons and bores at the base of the fraser delta in the southern strait of georgia

origin of lamprophyres by the mixing of basic and alkaline melts in magma chamber in beiya area western yunnan china abstract lamprophyres consisting mainly of diopside phlogopite and k feldspar formed in the early tertiary around 60 ma in the beiya area and are characterized by low sio 2 46 50 wt rb 31 45 ppm and sr 225 262 ppm high al 2 o 3 11 2 13 1 wt cao 8 0 8 7 wt mgo 11 5 12 1 wt k 2 o 4 9 5 5 wt tio 2 2 9 3 3 wt and ree 174 177 ppm and compatible elements e g sc cr and ni and hsf elements e g th u zr nb ta ti and y and low 143 nd 144 nd 0 512372 0 512536 middle 87 sr 86 sr 0 707322 0 707395 middle 206 pb 204 pb 18 50 18 59 207 pb 204 pb 15 60 15 65 and 208 pb 204 pb 38 75 38 8 these rocks developed peculiar quartz megacrysts with poly layer reaction zones melt inclusions and partial melted k feldspar and plagioclase inclusions and plastic shapes important features of these rocks include 1 hybrid composition of elements 2 abrupt increase of sio 2 content of the melt recorded by zoned diopside 3 development of sanidine and aegirine augite reaction zones 4 alkaline melt and partial melted k feldspar and plagioclase inclusions 5 deformed quartz inclusions associated with quartz megacrysts 6 the presence of quartz megacrysts in plastic shape with their parent melts 7 the occurrence of olivine high mgo ilmenite and spinel inclusions within earlier formed diopside phlogopite and magnetite median 87 sr 86 sr values between tertiary alkaline porphyries in the beiya area and the western yunnan and tertiary basalt in the western yunnan indicate that the beiya lamprophyre melts were derivative and resulted from the mixing between basic melts that were related to the partial melting of phenocrysts of spinel iherzolite from a mantle source the alkaline melts originated from partial melting along the jinshajiang subduction ductile shear zone at the contact between the buried palaeo tethyan oceanic lithosphere and the upper mantle lithosphere the alkaline melts are composed of 65 sanidine or 70 ab 28 an 2 and 35 sio 2 the melt mixing occurred in magma chambers in the middle shallow crust at 8 10 km before the derivative lamprophyre melts intruded into the shallow cover in beiya area this mixing of basic and alkaline melts might represent a general process for the formation of lamprophyre in the western yunnan

comments on tectonic implications of the age composition and orientation of lamprophyre dikes navajo volcanic field arizona by a w laughlin m j aldrich jr m shafiqullah and j husler commentaire sur l article de a w laughlin m j aldrich jr m shifiqullah et j husler paru dans earth planet sci le hers nld 1979 43 279 284

ti phlogopites of the shaw s cove minette a comparison with micas of other lamprophyres potassic rocks kimberlites and mantle xenoliths the two generations of micas in the shaw s cove minette mica potash feldspar lamprophyre of northern new brunswick canada are tio2 rich phlogopites with variable but low silica and potash contents low soda and efectively all their aluminum in tetrahedral sites a majority of the micas have an excess of y cations and a deficiency of x cations there are positive correlations between excess y ions and number of al ions in z sites between k2o and sio2 contents and between k2o and volatile free totals yet the micas optically appear fresh do not respond to hydration or glycolation and x ray diffraction patterns show none of the peaks of talc montmorillonites vermiculite or 7 or l4 a chlorites this suggests that some normally octahedrally coordinated cations and water or hydronium ions are located in the interlayer x sites phenocryst micas are sharply zoned cores are paler colored and have high mg atomic ratio mg mg fe 2 0 810 88 cr2o3 i 0 88 wt vo and nio i 0 08 wt but relatively low tio2 2 93 wt and negligible bao phenocryst rims and groundmass micas are darker reddish brown and have lower mg 0 68 0 79 nil crzor and nio but high tio2 x 5 40 wt and bao x 0 38 wt micas in minettes from other localities 62 analyses are frequently richer in silica and potash than the shaw s cove samples but otherwise are generally chemically comparable chemical zoning or bimodalism is nearly universal in minette micas though the boundary between high zg low tioz phenocryst and low mghigh tioz groundmass groups varies from province to province and even from minette to minette within a swarm comparison of analyses of minette micas with 353 analyses of micas from other mafic largely potassic rocks indicates that micas chemically indistinguishable from those of minettes can be found within some other lamprophyres ultra potassic rocks kimberlites and high pressure xenoliths in alkaline volcanic rocks and kimberlites though each ofthese groups also contains micas unlike those in minettes those kimberlite phlogopites that match minette micas are predominantly secondary rims of phenocrysts or megacrysts or groundmass crystals mainly type ii but some are unzoned pre fluidization phenocrysts while primary primary metasomatic and uaruo suite phlogopites of mantle xenoliths are unlike minette micas higher mg and sioz lower tio2 and alzor some of the secondary metasomatic phlogopites in sheared garnetiferous mantle xenoliths are wholly minettelike the chemical identity of minette mica phenocryst cores and some phenocrysts of diverse mantle derived rocks implies crystallization under similar conditions by analogy with the chemistry of phlogopites produced experimentally in potassic systems at high pressures and studies of equilibration conditions of natural phlogopites it is concluded that phenocrystic phlogopites in minettes may form at temperatures and pressures up to at least 1250 c and 40 kbar and probably under o conditions between the nno and hm buffers higher o than for primary primary metasomatic and uanto suite micas in kimberlites and their included xenoliths

eruptive conditions and depositional processes of narbona pass maar volcano navajo volcanic field navajo nation new mexico usa phreatomagmatic deposits at narbona pass a mid tertiary maar in the navajo volcanic field nvf new mexico usa were characterized in order to reconstruct the evolution and dynamic conditions of the eruption our findings shed light on the temporal evolution of the eruption dominant depositional mechanisms influence of liquid water on deposit characteristics geometry and evolution of the vent efficiency of fragmentation and the relative importance of magmatic and external volatiles the basal deposits form a thick 5 20 m massive lapilli tuff to tuff breccia deposit this is overlain by alternating bedded sequences of symmetrical to antidune cross stratified tuff and lapilli tuff and diffusely stratified clast supported reversely graded lapilli tuffs that pinch and swell laterally this sequence is interpreted to reflect an initial vent clearing phase that produced concentrated pyroclastic density currents followed by a pulsating eruption that produced multiple density currents with varying particle concentrations and flow conditions to yield the well stratified deposits only minor localized soft sediment deformation was observed no accretionary lapilli were found and grain accretion occurs on the lee side of dunes this suggests that little to no liquid water existed in the density currents during deposition juvenile material is dominantly present as blocky fine ash and finely vesiculated fine to coarse lapilli pumice this indicates that phreatomagmatic fragmentation was predominant but also that the magma was volatile rich and vesiculating at the time of eruption this is the first study to document a significant magmatic volatile component in an nvf maar diatreme eruption the top of the phreatomagmatic sequence abruptly contacts the overlying minette lava flows indicating no gradual drying out period between the explosive and effusive phases the lithology of the accidental clasts is consistent throughout the vertical pyroclastic stratigraphy suggesting that the diatreme eruption did not penetrate below the base of the uppermost country rock unit a sandstone aquifer 360 m thick by comparison other nvf diatremes several tens of kilometers away were excavated to depths of 1 000 m beneath the paleosurface e g delaney pt ship rock new mexico the vent of a violent volcanic eruption in beus ss ed geological society of america centennial field guide rocky mountain section 2 411 415 1987 this can be accounted for by structurally controlled variations in aquifer thickness beneath different regions of the volcanic field variations in accidental clast composition and bedding style around the edifice are indicative of a laterally migrating or widening vent that encountered lateral variations in subsurface geology we offer reasonable evidence that this subsurface lithology controlled the availability of external water to the magma which in turn controlled characteristics of deposits and their distribution around the vent

the origin of the high k latites from camp creek arizona constraints from experiments with variable fo2 and a_ text h _ text 2 text o near liquidus melting experiments were performed on a high k latite at fo2 s ranging from iron wustite graphite iwg to nickel nickel oxide nno in the presence of a c o h fluid phase clinopyroxene is a liquidus phase under all conditions at iwg a text h text 2 text o 0 17 the liquidus at 10 kb is about 1 150 c but is depressed to 1 025 c at nno and a text h text 2 text o 1 phlogopite and apatite are near liquidus phases with apatite crystallizing first at pressures below 10 kb phlogopite is a liquidus phase only at nno and high a text h text 2 text o under all conditions the high k latites show a large crystallization interval with phlogopite becoming the dominant crystalline phase with decreasing temperature increasing fo2 affects phlogopite crystallization but the liquidus temperature is essentially a function of a text h text 2 text o the chemical compositions of the near liquidus phases support formation of the high k latites under oxidizing conditions nno or higher and high a text h text 2 text o it is concluded from the temperature of the h2o saturated liquidus at 10 kb the groundmass crystal ratio and presence of chilled latite margins around some xenoliths that the camp creek high k latite magma passed thru the lower crust at temperatures of 1 000 c or more

xenolithic evidence for proterozoic crustal evolution beneath the colorado plateau tertiary diatremes of the navajo volcanic field brought a wide variety of proterozoic xenoliths to the surface of the colorado plateau examination of crustal xenoliths from the navajo volcanic field diatremes permits reconstruction of proterozoic pressure temperature p t histories beneath the colorado plateau diatremes from the northwest part of the navajo volcanic field carry the greatest variety of xenoliths including metasedimentary rocks amphibolites felsic gneisses mafic granulites and crustally derived eclogites these rock types show variable degrees of hydrous alteration and evidence for complex reaction histories in contrast diatremes from the southeast part of the navajo volcanic field contain primarily mafic and felsic granulites that show fewer reaction textures and less alteration metasedimentary and eclogitic xenoliths are absent in these diatremes the p t paths from the northwest xenoliths are counterclockwise and reach temperatures as high as 850 c and pressures equal to or greater than 10 kbar later hydrous alteration occurred around 500 c and 8 12 kbar xenoliths from the southeast diatremes preserve little evidence of their p t evolution but paths involve heating and or decompression the differing rock types p t paths and alteration histories of the northwest and southeast populations suggest that proterozoic tectonism juxtaposed two distinct crustal blocks beneath the colorado plateau previous workers have postulated that the boundary between the proterozoic yavapai and mazatzal provinces occurs in the region our data support the existence of a northeast trending boundary beneath the four corners area if the eclogitic metamorphism and hydrous alteration are proterozoic in age their restricted occurrence beneath the northwest part of the plateau suggests that subduction was northwest dipping during proterozoic accretion of the mazatzal province onto north america

lamprophyric lavas in the colima graben sw mexico the colima graben located in sw mexico is one of three grabens which intersect about 50 km ssw of guadalajara forming a triple junction the 90 km long 20 60 km wide colima graben represents a n s rift of the e w trending mexican volcanic belt since the early pliocene the colima graben has served as a locus for the eruption of alkaline lavas the most recent of which are basanites and minettes erupted from late pleistocene cinder cones luhr and carmichael 1981 in this paper we report on older alkaline lavas which crop out in the graben s walls these rocks include phlogopite and hornblende bearing lamprophyres a phlogopite kalsilite ankaratrite and high k andesites these lavas crop out throughout the colima graben area and are intimately associated with calc alkaline lavas in the field compared to these the alkaline rocks are strikingly enriched in the incompatible elements particularly ba sr p and the lree unlike the younger late pleistocene alkaline cinder cone lavas most of the graben wall lamprophyres and the high k andesites represent magmas that appear to have undergone significant evolution since their generation including fractionation crustal contamination and possible magma mixing least squares modeling indicates that the cinder cone minettes represent reasonable parental magmas for the graben lamprophyres the occurrence of these alkaline lavas in an active calc alkaline volcanic arc is unusual and we suggest that they are a manifestation of the rifting processes which produced the colima graben

observations of polarity reversal in shoaling nonlinear internal waves observations off the new jersey coast document the shoaling of three groups of nonlinear internal waves of depression over 35 km across the shelf each wave group experienced changing background conditions along its shoreward transit despite different wave environments a clear pattern emerges nearly symmetric waves propagating into shallow water develop an asymmetric shape in the wave reference frame the leading edge accelerates causing the front face to broaden while the trailing face remains steep this trend continues until the front edge and face of the leading depression wave become unidentifiable and a near bottom elevation wave emerges formed from the trailing face of the initial depression wave and the leading face of the following wave the transition from depression to elevation waves is diagnosed by the integrated wave vorticity which changes sign as the wave s polarity changes sign this transition is predicted by the sign change of the coefficient of the nonlinear term in the kdv equation when evaluated using observed profiles of stratification and velocity

origin of coexisting minette and ultramafic breccia navajo volcanic field trace element evidence indicates that at the buell park diatreme navajo volcanic field the felsic minette can be best explained by crystal fractionation from a potassic magma similar in composition to the mafic minettes compatible trace element cr ni sc abundances decrease while concentrations of most incompatible elements ce yb rb ba sr remain constant or increase from mafic to felsic minette in particular the nearly constant ce yb ratio of the minettes combined with the decrease in cr ni and sc abundances from mafic to felsic minette is inconsistent with a model of varying amounts of partial melting as the process to explain minette compositions the uniformity of rare earth element ree abundances in all the minettes requires that an accessory mineral apatite dominated the geochemistry of the ree during fractionation a decrease in p2o5 from mafic to felsic minette and the presence of apatite in cognate inclusions are also consistent with apatite fractionation higher initial87sr 86sr ratios in the felsic minettes relative to the proposed parental mafic minettes however is inconsistent with a simple fractionation model also a separated phlogopite has a higher initial87sr 86sr ratio than host minette these anomalous isotopic features probably reflect interaction of minette magma with crust the associated ultramafic breccia at buell park is one of the navajo kimberlites but ree concentrations of the matrix do not support the kimberlite classification although the matrix of the breccia is enriched in the light ree relative to chondrites and has high la rb ba and sr concentrations relative to peridotites the concentrations of these elements are significantly lower than in south african kimberlites a high initial87sr 86sr ratio combined with petrographic evidence of ubiquitous crustal xenoliths in the navajo kimberlites suggests that the relatively high incompatible element concentrations are due to a crustal component apparently navajo kimberlites are most likely a mixture of comminuted mantle wall rock and crustal material there is no evidence for an incompatible element rich magma which is characteristic of south african kimberlites if the mafic minettes are primary magmas derived from a garnet peridotite source with chondritic ree abundances then ree geochemistry requires very small less than 1 degrees of melting to explain the minettes alternatively the minettes could have formed by a larger degree of melting of a metasomatized relatively light ree enriched garnet peridotite the important role of phlogopite and apatite in the differentiation of the minettes supports this latter hypothesis

orthopyroxene minettes and lamproites their status and genetic significance orthopyroxene is a normal if rare constituent of some minettes and lamproites it is sometimes partly xenocrystic but mostly authigenic i e separated directly from lamprophyric magmas as can be shown when orthopyroxene lamprophyres are compared with the experimental phase diagrams of appropriate systems the orthopyroxene bearing lamprophyres represent modified mantle derived magmas characterized by a high mgo high sio2 speciation which was acquired in different ways in individual regions the crystallization of orthopyroxene lamprophyres was not controlled by particular pressure temperature conditions compared with clinopyroxene potassic lamprophyres the orthopyroxene lamprophyres represent more primitive magmas orthopyroxene minettes can also be altered by a post magmatic hydrothermal inflow which occasionally increases their cao content to the level normal in clinopyroxene minettes if this had happened before magma consolidation clinopyroxene instead of orthopyroxene would have crystallized orthopyroxene minettes are well defined mineralogically and chemically and may be related to other types in the minette series

magma serpentinite interaction as the origin of diatremes a case study from the hyblean plateau southeastern sicily some diatremes formed in the hyblean plateau in a time span from 6 5 to 9 4 ma producing volcaniclastic deposits which host deep seated xenoliths the origin of the explosive activity that has brecciated the magma and the country rocks is controversial two are the prevalent models phreatomagmatic and magmatic brecciation we propose an alternative explanation based on the thermal and mechanical interaction of a rising basaltic magma with serpentinized mantle rocks representing the main lithologies in the permo triassic hyblean basement we suggest that magma serpentinite interaction could have remobilized fluids from serpentinites that reached the overpressure necessary for the brecciation of country rocks the possible depth of this interaction has been estimated considering variations of porosity and permeability at different depths in the hyblean lithosphere these properties have been taken into account in the dimensionless parameter v e jamtveit et al in physical geology of high level magmatic systems vol 234 geological society london special publications london pp 233 241 2004 which reflects the relative rates of heat and fluid transport since a high fluid flux is enhanced by a high boiling temperature of pore water raised by magma rock heat exchange v e remains less than 1 up to a depth of 7 km corresponding to the average thickness of the sedimentary volcanic sequence characterized by a high permeability k 10 12 10 14 m2 that inhibits fluid overpressure built up in contrast to both phreatomagmatic and magmatic models at deeper levels k 10 19 m2 from 8 km downward the value of v e is greater than 1 therefore we propose that the dehydration of serpentinites upon heating by hot basaltic magma would have liberated huge amounts of fluids whose accumulation at an average depth of 8 km beneath the impermeable serpentinized level induced supercritical fluid overpressure strong enough to exceed the lithospheric pressure fluid overpressure caused the opening of fractures in the overlying permeable upper crust triggering the energetic fluid expansion and hence the brecciation of country rocks finally we suppose that aforementioned conditions for supercritical fluid overpressure could have been gained in other areas of the hyblean region in coincidence with various mesozoic volcanic events even though older diatremes may have been obliterated by subsequent sedimentary cycles and volcanic events as well as in serpentinite diatremes in the navajo volcanic field colorado plateau sw usa

geochemistry nd and sr isotopes and u pb zircon ages of granitoid and metasedimentary xenoliths from the navajo volcanic field four corners area southwestern united states abstract proterozoic granitoid xenoliths from the navajo volcanic field nvf in the southwestern united states range in composition from tonalite diorite to granite with the latter greatly dominating there is no apparent relationship between chemical or isotopic composition and age geographic location or degree of alteration or deformation of the xenoliths two of the major ages of proterozoic plutonism recognized in the southwest 1 75 1 70 yavapai and 1 45 1 41 ga anorogenic are represented by the nvf xenoliths in some instances within a single diatreme we did not find any xenoliths in the 1 65 1 62 ma mazatzal range the xenoliths are dominantly i types and both nd and sr isotopes and trace element distributions indicate juvenile arc sources approximately 1 8 ga the granite magmas may have been produced by either vapor absent partial melting or fractional crystallization of a tonalite parent juvenile sources must have been available for melting in each of the three periods of magma production and hence some juvenile 1 8 ga crust in this region must have escaped melting in the first two episodes of magmatism and deformation metasedimentary xenoliths are chiefly biotite sillimanite schists garnet biotite schists and garnet paragneisses these three groups are strikingly similar in chemical and isotopic composition suggesting similar graywacke pelite protoliths the schists appear to be limited to the far northern part of the volcanic field consistent with a possible crustal boundary in the basement compositional and thermobarometric results suggest that the biotite schist xenoliths are not restites but that the paragneisses may be mixtures of melt and restite sedimentary protoliths may have been deposited in a forearc basin and later tectonically transported to the deep crust during one or more arc continent collisions in the late paleoproterozoic

petrological significance of mineral chemistry in the agathla peak and the thumb minettes navajo volcanic field the agathla peak and the thumb minettes from the navajo province southwestern usa are characterized by macrocrysts of phlogopite and diopside plus rare olivine sim fo 84 set in a crystalline to glassy groundmass containing diopside phlogopite sanidine apatite ti magnetite and analcime the diopside has low al ti and na like late stage diopside in kimberlite groundmass ti rich phlogopite is zoned with increasing fe ti and ba from a cr ni bearing core high sr in the minettes is expressed in groundmass sanidine up to 1 2 wt sro apatite 0 5 0 9 and diopside 0 03 0 11 xenocrystal apatite is chemically distinct from phenocrystal apatite in the thumb minette in having low sro 0 04 wt and a distinct ree distribution which matches apatites in garaet granulite xenoliths all chemical properties of the minerals are consistent with derivation of the minette magmas from a region of the upper mantle containing olivine clinopyroxene phlogopite and ilmenite and enriched in k ti b

evolution of a shoaling internal solitary wavetrain 1 field observations of an internal solitary wavetrain impacting a shoaling bottom are presented measurements of the spatio temporal characteristics of the shoaling waves are given as well as estimations of the mixing they may have caused upon impact the observations are discussed in the context of numerical simulations laboratory experiments and hypotheses recently raised on the origin and evolution of internal solitary waves in coastal environments

lower crustal evolution under central arizona sr nd and pb isotopic and geochemical evidence from the mafic xenoliths of camp creek abstract oligocene potassic volcanism at the camp creek area arizona has sampled the lower crust by bringing mafic granulite amphibolite and garnet bearing pyroxenite eclogite xenoliths to the surface xenolith geobarometry records metamorphic pressures of approximately 10 kbar and temperatures of 650 900 c whole rock sr and nd isotopic compositions correlate roughly with xenolith metamorphic mineral assemblages higher temperature eclogites have 87sr 86sr ranging from 0 7066 to 0 7080 and end of 2 to 5 8 while lower temperature amphibolites have 87sr 86sr of 0 7074 to 0 7082 and end of 6 to 9 sr and nd isotopic compositions of mineral separates reflect in some xenoliths intermineral diffusion up to the time of latite eruption and limited exchange with the host latite pb isotopic compositions of the xenoliths show little mineralogical dependence and overlap the field for normal morb these data suggest that lower crustal metamorphism has significantly affected the sr and nd isotope evolution of the eclogites but has had little effect on their pb isotope systematics for xenoliths closer to igneous bulk compositions i e not enriched in metamorphic garnet and pyroxene nd depleted mantle model ages range from 1 2 to 1 9 ga in agreement with the pb pb array age of 1 1 0 6ga this is interpreted as dating the separation of the lower crust from the mantle during the proterozoic crust building event in this area similar nd model ages for nearby cenozoic and mesozoic granitoids suggest that the type of mafic lower crust represented by the camp creek xenoliths may be a suitable source for younger plutonics in the area

a refined method for trace element modelling of nonmodal batch partial melting processes the cenozoic continental volcanism of calatrava central spain abstract a refined method for quantitative trace element modelling of partial melting processes is proposed here this method is based on a two part approach 1 from binary diagrams and a minimal number of assumptions a set of constrained values of the parameters f d 0 i p l i c 0 i are constrained for selected trace elements 2 a simultaneous best fit solution is obtained for those elements which is then used to calculate the parameters for the remaining trace elements this approach eliminates much of the mathematical complexity of other inversion techniques as well as the necessity of assuming values for poorly constrained parameters e g mineral liquid distribution coefficients this method was succesfully applied to the primary melilitites nephelinites and olivine basalts from calatrava central spain the results of this calculation suggest that this basaltic suite was generated from a homogeneous garnet lherzolite with phlogopite that was enriched relative to chondrites up to 18 times for the highly incompatible elements and about 3 times for the moderately incompatible this source underwent progressively higher melting degrees between 5 melilitites and 17 olivine basalts

abundance and distribution of ultramafic microbreccia in moses rock dike quantitative application of mapping spectroscopy moses rock dike is a tertiary diatreme containing serpentinized ultramafic microbreccia sum located on the colorado plateau in utah field evidence indicates that sum was emplaced first followed by breccias derived from the permian strata exposed in the walls of the diatreme and finally by complex breccias containing basement and mantle derived rocks sum is primarily found dispersed throughout the matrix of the diatreme we examined the nature of sum abundance and spatial distribution using data collected remotely by the airborne imaging spectometer ais the minerals serpentine gypsum and illite as well as desert varnish and the lithologies sum and various sandstones were identified from the ais data six end members sum two types of sandstone gypsiferous soil clay rich soil desert varnish were chosen to represent the dominant lithologies of the surface in moses rock dike region spectra of these end members were used in an intimate mixing model to deconvolve the ais spectral data into surface abundance coefficients for each component using a nonnegative least squares inverse algorithm the results of this calculation of surface composition are consistent with field observations and investigations sum distribution and abundance in the matrix of the diatreme were examined in detail and two distinct styles of sum dispersion were observed one style is characterized by high to moderate sum abundance surrounded by halos of lesser sum abundance the dispersion halos grade steeply into regions of the matrix with little to no sum the second style is characterized by moderate sum abundances and broad dispersion halos with sum distributed across the entire width of the diatreme these dispersion styles are consistent with emplacement of the dike as a fluidized solid volatile system where sum which is emplaced early becomes reincorporated into the turbulent flow of the diatreme by abrasion and comminution by paniculate matter carried along in the eruption this eroded material is then dispersed throughout the matrix by eddy diffusion the first style represents an early arrested phase of the eruption sequence while the second style represents a more mature phase distributions of the second style probably indicate the location of channels where flow was concentrated during later stages of eruption since both styles are observed at the same level of erosion this indicates that the duration of eruption varied along strike at moses rock dike

minette lavas and associated leucitites from the western front of the mexican volcanic belt petrology chemistry and origin during the late pliocene k rich minette and leucitite lavas erupted in the western mexican volcanic belt near the town of los volcanes a region which is located much closer to the middle america trench than the main line of currently active andesite stratovolcanoes during this period the tectonic regime in western mexico was highly complex due to the simultaneous occurrence of active subduction of the young rivera plate and rifting caused by crustal extension most of these basic lavas contain phenocrysts of phlogopite augite and apatite along with microphenocrysts of leucite and fe ti oxide olivine is absent from all but two of the flows one an olivine leucitite and the other a felsic minette the phlogopite phenocrysts and high whole rock fe2o3 feo ratios which are characteristic of this suite record evidence of high magmatic water contents and oxygen fugacities all of these rock types are highly enriched in the large ion lithophile and light rare earth elements with sr 5100 ppm ba 4800 ppm and ce 330 ppm they are also mildly enriched in the high field strength elements e g zr 260 700 ppm and display the strong relative enrichment of the lile over the hfse that is characteristic of magmas erupted in convergent margins consideration of high pressure phase equilibria in the mg2sio4 camgsi2o6 kalsio4 sio2 system shows that the minettes from this region are not related through fractional crystallization to the more mgo rich olivinebearing minettes which have erupted in other parts of the western mexican volcanic belt during the quaternary this conclusion is consistent with both the trace element geochemistry of these lavas and with the results of fractional crystallization models instead the data suggests that these high k magmas were derived from a source region which consists predominantly of phlogopite clinopyroxene and apatite and which has formed through hydrous enrichment of the subarc mantle in response to subduction

rare earth abundances in mesozoic undersaturated alkaline rocks from west greenland abstract rare earth element analyses from a series of mesozoic undersaturated lamprophyre dykes from southern west greenland show concentration levels comparable to similar rock types elsewhere an earlier published simple fractionation model describing their evolution must be modified a primitive olivine nephelinitic parent magma similar to the most primitive lamprophyre coexisted in the mantle with a fluid phase and evolved possibly at a higher level mainly through crystal fractionation and liquid immiscibility crustal contamination may have had minor importance for their evolution

internal solitary waves with subsurface cores large internal solitary waves with subsurface cores have recently been observed in the south china sea here fully nonlinear solutions of the dubreil jacotin long equation are used to study the conditions under which such cores exist we find that the location of the cores either at the surface or below the surface is largely determined by the sign of the vorticity of the near surface background current the results of a numerical simulation of a two dimensional shoaling internal solitary wave are presented which illustrate the formation of a subsurface core

petrological evolution of the crust and mantle in its simplest form crust mantle evolution can be thought of as a study of the processes by which material is lost from the mantle and forms new crust the overall goal is achievement of mass balance between the average composition of material known to have been added to the crust and the estimated average composition of the entire crust attainment of this goal for the earth has been elusive primarily because the materials available for study have generally been involved in several stages of evolution including fractionation within both the crust and mantle and recycling of material from crust to mantle thereby complicating the interpretation of available data although the overall composition of the continental crust generally has been modelled as andesitic taylor and mclennan 1981a the present upper continental crust is granodioritic and requires a more mafic lower crust it has been proposed taylor and mclennan 1981a that originally the archean crust had an andesitic composition throughout its volume and that partial melting in the lower crust developed more felsic melts that rose to enrich the upper crust leaving a more mafic residuum of lower crust this concept has been challenged by weaver and tarney 1981a who argue that the granulites of presumed lower crustal origin do not have the correct compositions for this model if one considers more recent additions to the crust from the mantle over the past several hundred million years it appears that these latest additions are basaltic with very little if any granitic additions in fact barker 1981 in his introduction to a special issue of jgr on granites and rhyolites states to date no one has demonstrated that such magmas may form in the mantle indeed much experimental and geochemical work indicates that such siliceous liquids cannot originate there therefore such magmas must be generated in the crust in island arc environments where the average composition of added material normally is thought to be andesitic a anderson 1982 has shown that the parent melt is basaltic not andesitic in addition kay 1980 has shown that the k content of the newly added material is less than the average k content of the previously existing crust in the oceanic crust the additions from the mantle are basaltic and according to o hara 1982 probably are derived from very mafic picritic melts as parents continental flood basalts which have also added material from mantle to crust also are clearly derived from basaltic parental melts basaltic volcanism study project 1981 thus the evidence for the nature of material subtracted from the mantle and added to the crust for the past several hundred million or perhaps a billion years points to very mafic melts this contrasts significantly with the overall andesitic composition of continental crust it implies furthermore that if the overall archean crustal composition was andesitic as estimated by taylor and mclennan 1981a then additions to the crust have become more mafic with time a concept in direct conflict with most models in which secular trends are from mafic to felsic with time veizer and jansen 1979 and mclennan et al 198o a question which is beginning to appear either explicitly or implicitly is whether crustal volcanic rocks or the crust as a whole really represents the parent melt that formed in the mantle a anderson 1982 o hara 1982 and nisbet and walker 1982

three dimensional seismic analysis of sediment waves and related geomorphological features on a carbonate shelf exposed to large amplitude internal waves browse basin region australia this study analyses the three dimensional geometry of sedimentary features recorded on the modern sea floor and in the shallow subsurface of a shelf to upper slope region offshore australia that is characterized by a pronounced internal wave regime the data interpreted comprise an extensive 12 500 km2 industrial three dimensional seismic reflection survey that images the northern part of the browse basin australian north west shelf the most prominent seismic morphological features on the modern sea floor are submarine terrace escarpments fault scarps and incised channels as well as restricted areas of seismic distortion interpreted as mass wasting deposits besides these kilometre scale sea floor irregularities smaller bedforms were discovered also including a multitude of sediment waves with a lateral extent of several kilometres and heights up to 10 m these sedimentological features generally occur in extensive fields in water depths below 250 m mostly at the foot of submerged terraces along the scarps of modern faults and along the shelf break between the outer shelf and the upper continental rise additional bedforms that characterize the more planar regions of the outer shelf are elongate north west south east oriented furrows and ridges the formation of both sediment waves and furrow ridge systems requires flow velocities between 0 3 m sec 1 and 1 5 m sec 1 which could be generated by oceanic currents gravity currents or internal waves in the studied setting these velocities can be best explained as being generated by bottom currents induced by internal waves an interpretation that is discussed against oceanographic background data and modelling results in addition to the documentation of three dimensional seismic geomorphological features of the modern sea floor it was also possible to map kilometre scale buried sediment wave fields in the seismic volume down to ca 500 ms two way time below the present sea floor indicating the general potential for the preservation of such bedforms in the sedimentary record

geochemistry and petrogenesis of lamproites late cretaceous age woodson county kansas u s a abstract lamproite sills and their associated sedimentary and contact metamorphic rocks from woodson county kansas have been analyzed for major elements selected trace elements and strontium isotopic composition these lamproites like lamproites elsewhere are alkalic molecular k 2 o na 2 o al 2 o 3 1 6 2 6 are ultrapotassic k 2 o na 2 o 9 6 150 are enriched in incompatible elements lree or light rare earth elements ba th hf ta sr rb and have moderate to high initial strontium isotopic compositions 0 7042 and 0 7102 the silica saturated magma olivine hypersthene normative of the silver city lamproite could have formed by about 2 percent melting of a phlogopite garnet lherzolite under high h 2 o co 2 ratios in which the iherzolite was enriched before melting in the incompatible elements by metasomatism the rose dome lamproite probably formed in a similar fashion although the extreme alteration due to addition of carbonate presumably from the underlying limestone makes its origin less certain significant fractional crystallization of phases that occur as phenocrysts diopside olivine k richterite and phlogopite in the silver city magma and that concentrate co cr and sc are precluded as the magma moved from the source toward the surface due to the high abundances of co cr and sc in the magma similar to that predicted by direct melting of the metasomatized iherzolite ba and to a lesser extent k and rb and have been transported from the intrusions at shallow depth into the surrounding contact metamorphic zone the silver city lamproite has vertical fractionation of some elements due either to volatile transport or to variations in the abundance of phenocrysts relative to groundmass most probably due to flow differentiation although multiple injection or fractional crystallization cannot be conclusively rejected

alkaline and calc alkaline lavas near los volcanes jalisco mexico geochemical diversity and its significance in volcanic arcs a remarkably diverse suite of lavas erupted during the late pliocene at the volcanic front of the western mexican volcanic belt near the town of los volcanes jalisco this region is much closer to the middle america trench than the main axis of quaternary andesite dacite stratovolcanoes and volcanism occurred in a complex tectonic regime involving both subduction of the young rivera plate and transverse crustal extension of the jalisco structural block the variety of lava types covers a wide spectrum from highly potassic minettes and leucitites to calc alkaline basalts and andesites which are compositionally similar to those erupted elsewhere in the mexican volcanic belt other alkaline varieties intermediate between these extremes include absarokites trachybasalts and trachyandesites phlogopite amphibole and apatite are common phenocryst phases whole rock compositions show a wide range of alkali contents e g k2o of 1 0 8 6 wt and typically contain 5 wt mgo mgo ni v and cr show little systematic decrease with increasing sio2 suggesting that these lavas have evolved from primitive mantle derived magmas with a wide range of sio2 contents strong enrichments in incompatible trace elements are observed in all of the lavas sr 700 5100 ppm ba 470 4800 ce 22 325 ppm zr 90 700 ppm as is the relative enrichment of large ion lithophile ba sr rb and light rare earth elements la ce over the high field strength elements ti zr which is typical of magmas in volcanic arcs this enrichment pattern suggests that these magmas come from source regions which contain incompatible element rich phases such as phlogopite amphibole and apatite the petrological and geochemical features of the lavas which occur in the los volcanes region provide direct evidence of the extreme heterogeneity which may exist in magma source regions at convergent margins the complex tectonic regime in western mexico further suggests that rifting and crustal extension play an important role in the generation and successful ascent of melts from enriched regions of the sub arc mantle

shoaling of nonlinear internal waves in massachusetts bay 1 the shoaling of the nonlinear internal tide in massachusetts bay is studied with a fully nonlinear and nonhydrostatic model the results are compared with current and temperature observations obtained during the august 1998 massachusetts bay internal wave experiment and observations from a shorter experiment which took place in september 2001 the model shows how the approaching nonlinear undular bore interacts strongly with a shoaling bottom offshore of where kdv theory predicts polarity switching should occur it is shown that the shoaling process is dominated by nonlinearity and the model results are interpreted with the aid of a two layer nonlinear but hydrostatic model after interacting with the shoaling bottom the undular bore emerges on the shallow shelf inshore of the 30 m isobath as a nonlinear internal tide with a range of possible shapes all of which are found in the available observational record

evolution of navajo eclogites and hydration of the mantle wedge below the colorado plateau southwestern united states 1 eclogite and pyroxenite xenoliths from ultramafic diatremes of the navajo province on the colorado plateau have been analyzed to investigate hydration of continental mantle and effects of low angle subduction on the mantle wedge xenoliths have been characterized by petrographic and electron probe analysis and by sm nd rb sr k ar and o isotopic analysis of mineral separates from one eclogite and by u pb isotopic analysis of zircons from three samples k ar analysis of phengite establishes eruption of a garnet ridge arizona diatreme at 30 ma sm nd and rb sr analyses of clinopyroxene and garnet from that eclogite document recrystallization shortly preceding eruption three zircon fractions have been analyzed from that eclogite and from two others representing the nearby moses rock and mule ear diatremes seven of nine small multigrain fractions scatter about a poorly fit discordia between ca 35 ma and 1515 ma fractions range from overlapping concordia at the lower intercept to a 207pb 206pb age of ca 1220 ma the discordant fractions establish a mid proterozoic zircon component in each eclogite inconsistent with an origin from basalt of the farallon plate the pressure recorded by one of these eclogites 3 3 gpa exceeds that of an eclogite previously attributed to the farallon plate nonetheless each of the eclogites contains a fraction of nearly concordant zircons with ages in the range 35 to 41 ma and one rock also contains a fraction that is nearly concordant at 70 ma these concordant ages are interpreted to record episodic zircon growth during recrystallization of proterozoic mantle the concordant zircon ages are consistent with published data that establish recrystallization of navajo eclogites from 81 to 33 ma a time interval similar to that of the laramide orogeny the eclogite facies recrystallization and growth of new zircon are attributed to the catalytic effects of water introduced into the mantle from the farallon slab water penetrated fracture zones extending for at least tens of kilometers into the mantle wedge above the farallon slab during low angle subduction magmatism in the san juan volcanic field to the northeast of the diatremes may be related to similar hydration

rare earth element geochemistry of garnet lherzolite and megacrystalline nodules from minette of the colorado plateau province abstract mineral and whole rock ree abundances in garnet lherzolite and megacrystalline nodules from the thumb display broad correlations with major element compositions lherzolites with 12 modal clinopyroxene plus garnet high ca al lherzolites have relatively flat chondrite normalized whole rock ree patterns lherzolites poor in clinopyroxene and garnet low ca al lherzolites have lower hree in clinopyroxenes and garnets and higher whole rock lree hree it is concluded that the low ca al lherzolites may have undergone lree metasomatism after depletion of the major element compositions by partial melting and that much of the garnet now present was originally dissolved in aluminous orthopyroxene the high ca al lherzolites may be interpreted either as primordial mantle samples or as products of equilibration with very lree enriched liquids the megacrystalline nodules are medium to ultracoarse grained intergrowths and megacrysts with mineral compositions similar to discrete nodule suites in kimberlites the ree abundances of the megacrystalline minerals are consistent with an origin as cumulates from magma with extremely fractionated ree similar to minette or kimberlite the patterns of correlation of ree and major elements in this inclusion suite are similar to the patterns observed in the garnet lherzolite and discrete nodule suites of southern african kimberlites both of the subcontinental mantle provinces represented by these suites contain three distinct petrogenetic components refractory garnet lherzolite enriched in lree and depleted in hree fertile garnet lherzolite with generally chondritic ree abundances and a suite of ultracoarse minerals precipitated from magma with extremely fractionated ree generally similar to the host magmas

transport by breaking internal gravity waves on slopes we use the results of a direct numerical simulation dns with a particle tracking model to investigate three dimensional transport by breaking internal gravity waves on slopes onshore transport occurs within an upslope surge of dense fluid after breaking offshore transport occurs due to an intrusion of mixed fluid that propagates offshore and resembles an intermediate nepheloid layer inl entrainment of particles into the inl is related to irreversible mixing of the density field during wave breaking maximum onshore and offshore transport are calculated as a function of initial particle position and can be of the order of the initial wave length scale for particles initialized within the breaking region an effective cross shore dispersion coefficient is also calculated and is roughly three orders of magnitude larger than the molecular diffusivity within the breaking region particles are transported laterally due to turbulence that develops during wave breaking and this lateral spreading is quantified with a lateral turbulent diffusivity lateral turbulent diffusivity values calculated using particles are elevated by more than one order of magnitude above the molecular diffusivity and are shown to agree well with turbulent diffusivities estimated using a generic length scale turbulence closure model based on a favourable comparison of dns results with those of a similar two dimensional case we use two dimensional simulations to extend our cross shore transport results to additional wave amplitude and bathymetric slope conditions

generation of internal waves in massachusetts bay observations of stratified tidal flow over a submarine ridge indicate that the large amplitude and asymmetry of the topography are critical in determining the type of flow response the observations consist of hydrographic current meter and echo sounding data and are used as a basis for inferring the generation mechanism of previously observed trains of internal waves the flow response on ebb and flood tide is categorized according to the froude number classification of sill flows proposed by farmer and smith 1980a the calculated froude numbers response length scale and duration differ markedly between the two phases of the tide due to the asymmetry of the bank the development of two features in the acoustic imagery related to wave formation is followed

massive fluid influx beneath the colorado plateau usa related to slab removal and diatreme emplacement evidence from oxygen isotope zoning in eclogite xenoliths

submesoscale impacts on horizontal and vertical transport in the gulf of mexico 1 impacts of submesoscale processes on transport are investigated numerically in an energetic mesoscale flow with an ocean model run at two horizontal resolutions 1 and 5 km the focus is the northwestern gulf of mexico where the loop current eddies are surrounded by smaller vortices by increasing the horizontal resolution the number and strength of submesoscale eddies and vorticity filaments within the mixed layer increase dramatically and with them the vertical velocities inside the coherent eddies and at their peripheries increased vertical velocities for increasing resolution are associated to near inertial motions and they are not limited to the mixed layer but are found at all depths horizontal velocities on the contrary are similar lagrangian isobaric tracers are deployed close to the surface and at 100 m and three dimensional neutrally buoyant particles are released close to the surface at the base of the mixed layer and at 100 m the modeled horizontal dispersion curves for each deployment depth are independent of the kind of particles and of horizontal resolution close to the ocean surface however convergence zones generated by submesoscale ageostrophic motions and resolved at 1 km resolution influence the details of the tracer distributions vertical dispersion increases by several folds for increasing resolution at all depths explored with the largest differences found close to the surface therefore submesoscales processes play a fundamental role in driving vertical transport in eddy dominated flows both within and below the mixed layer for times comparable to the eulerian time scale

mode 2 waves on the continental shelf ephemeral components of the nonlinear internal wavefield 1 shoreward propagating mode 2 nonlinear waves appear sporadically in mooring records obtained off the coast of new jersey in the summer of 2006 individual mode 2 packets were tracked between two moorings separated by 1 km however packets could not be tracked between moorings separated by greater distances from one another 10 km the inability to track individual packets large distances through the mooring array combined with detailed observations from a ship suggest that these waves are short lived the evolution of the ship tracked wave group was recorded using acoustic backscatter acoustic doppler current profilers and turbulence profiling the leading mode 2 wave quickly changed form and developed a tail of short small amplitude mode 1 waves the wavelength of the mode 1 oscillations agreed with that expected for a copropagating tail on the basis of linear theory turbulent dissipation in the mixed layer and radiation of the short mode 1 waves contributed to rapid energy loss in the leading mode 2 wave consistent with the observed decay rate and short life span of only a few hours the energy in the leading mode 2 wave was 10 100 times smaller than the energy of mode 1 nonlinear internal waves observed during the experiment however the magnitudes of wave localized turbulent dissipation were similar

mineralogical and geochemical spatial analyses of a waste rock dump at the libiola fe cu sulphide mine eastern liguria italy in this work we investigated a 3 ha sulphide bearing waste rock dump libiola mine italy using mineralogical geochemical and geostatistical analyses the dumped materials were highly heterogeneous in grain size and lithology and varied both laterally and vertically other than the host rock of the ore basalts and serpentinites the dumped materials contained high amounts of low grade chalcopyrite and pyrite rich mineralisations due to these characteristics and to the absence of minerals able to neutralise acidity this waste rock dump can be classified as an acid mine drainage amd producer the study confirms that amd is still active and in the best scenario can persist for up to 6 17 103 years the consequences of this process are of serious environmental concern as it involves strong acidification of the circulating waters the release of potentially toxic metals into the soil streams and rivers and the precipitation of huge quantities of secondary fe oxides and fe oxyhydroxides

horizontal variability of high frequency nonlinear internal waves in massachusetts bay detected by an array of seafloor pressure sensors a two dimensional array of fourteen seafloor pressure sensors was deployed to measure properties of tidally generated nonlinear high frequency internal waves over a 14 km by 12 km area west of stellwagen bank in massachusetts bay during summer 2009 thirteen high frequency internal wave packets propagated through the region over 6 5 days one packet every semidiurnal cycle propagation speed and direction of wave packets were determined by triangulation using arrival times and distances between triads of sensor locations wavefront curvature ranged from straight to radially spreading with wave speeds generally faster to the south waves propagated to the southwest rotating to more westward with shoreward propagation linear theory predicts a relationship between kinetic energy and bottom pressure variance of internal waves that is sensitive to sheared background currents water depth and stratification by comparison to seafloor acoustic doppler current profiler measurements observations nonetheless show a strong relationship between kinetic energy and bottom pressure variance this is presumably due to phase locking of the wave packets to the internal tide that dominates background currents and to horizontally uniform and relatively constant stratification throughout the study this relationship was used to qualitatively describe variations in kinetic energy of the high frequency wave packets in general high frequency internal wave kinetic energy was greater near the southern extent of wavefronts and greatly decreased upon propagating shoreward of the 40 m isobath this article is protected by copyright all rights reserved

detection of massachusetts bay internal waves by the synthetic aperture radar sar on seasat we have examined all eight seasat passes over massachusetts bay that yielded synthetic aperture radar sar imagery four of the passes showed banded surface features that suggested a group of internal waves propagating southwestward from stellwagen bank comparison of the positions of the sar features with predictions of internal wave locations derived from earlier in situ work at massachusetts bay confirms that the sar features are indeed rough and smooth bands of water caused by a propagating packet of internal waves the packet is caused by tidal currents interacting with the stratification over and the topography of stellwagen bank even the four passes that do not show internal waves are consistent with the above conclusions since the predicted packet positions occur outside the region covered by those four passes these comparisons are presented to show that the seasat sar is indeed capable of detecting internal waves in massachusetts bay even though these waves are considerably less intense than in some other reported areas of the world

tertiary minette and melanephelinite dikes wasatch plateau utah records of mantle heterogeneities and changing tectonics a swarm of minette and melanephelinite dikes is exposed over 2500 km2 in and near the wasatch plateau central utah along the western margin of the colorado plateaus in the transition zone with the basin and range province to date 110 vertical dikes in 25 dike sets have been recognized strikes shift from about n80 w for 24 ma dikes to about n60 w for 18 ma to due north for 8 7 m y these orientations are consistent with a shift from east west oligocene compression associated with subduction to east west late miocene crustal extension minettes are the most common rock type mica rich minette and mica bearing melanephelinite occurs in 24 ma dikes whereas more ordinary minette is found in 8 7 ma dikes one melanephelinite dike is 18 ma these mafic alkaline rocks are transitional to one another in modal and major element composition but have distinctive trace element patterns and isotopic compositions they appear to have crystallized from primitive magmas major trace element and nd sr isotopic data indicate that melanephelinite which has similarities to ocean island basalt was derived from small degree melts of mantle with a chondritic sm nd ratio probably located in the asthenosphere but it is difficult to rule out a lithospheric source in contrast mica bearing rocks mica melanephelinite and both types of minette are more potassic and have trace element patterns with strong nb ta depletions and sr nd isotopic compositions caused by involvement with a component from heterogeneously enriched lithospheric mantle with long term enrichment of rb or light rare earth elements ree epsilon nd as low as 15 in minette light ree enrichment must have occurred anciently in the mid proterozoic when the lithosphere was formed and is not a result of cenozoic subduction processes after about 25 ma foundering of the subducting farallon plate may have triggered upwelling of warm asthenospheric mantle to the base of the lithosphere melanephelinite magma may have separated from the asthenosphere and while rising through the lithosphere provided heat for lithospheric magma generation varying degrees of interaction between melanephelinite and small potassic melt fractions derived from the lithospheric mantle can explain the gradational character of the melanephelinite to minette suite

observations of highly nonlinear internal solitons over the continental shelf surface disturbances caused by strong near surface internal waves are widely seen in coastal regions as bands of slick and rough water propagating shoreward these surface slicks are typically manifestations of optical and radar backscatter properties above internal solitons and have strong surface current pulses associated with them during a recent experiment studying coastal internal waves extremely strong solitary internal wave packets were observed over a three week period on a very shallow and strongly stratified pycnocline off northern oregon during periods of strongest tidal forcing solitons were consistently observed on the leading edge of a semidiurnal internal tide bore with pycnocline displacements up to 25m downward from a 7m initial depth in the first few solitons the extreme nonlinearity of these internal waves is believed to be unique in ocean observations this note characterizes these highly nonlinear solitary internal waves siw and presents a second order kdv model which reproduces the form of the displacements and the small change in soliton width with amplitude predicted by this model

reef building and carbonate production modes in the west central tethys during the cenozoic abstract changing components rock textures lithofacies platform types and architecture throughout time are unique characteristics of carbonate rocks characterizing these attributes has been approached by 1 building reference models for specific phanerozoic intervals 2 recognizing the climatic impact in modulating carbonate production and 3 analyzing the influence of changing bio geochemical conditions the reference model approach is mostly based on biological evolution the climatic impact approach emphasizes temperature and the bio geochemical approach considers the changes in mg ca ratios and ca concentrations in the oceans to date however an analysis integrating all of these factors is still missing the analysis presented here includes all these factors but also co 2 which is fundamental for both photosynthesis and caco 3 precipitation here we analyze the waxing and waning of cenozoic reef limestones from the central tethys region through several steps 1 on the basis of rock volume rock textures associated sediments and light dependent skeletal components as records of light penetration and wave energy depth 2 on global environmental conditions 13 c 18 o p co 2 temperature and 3 on the basis of functionality nutritional requirements and available resources through the cenozoic water motion whether induced by surface or internal waves or by currents increased as the thermal gradients strengthened both with depth and with latitude active water motion is essential for plankton catchers such as corals but less so for many larger benthic foraminifers lbf pycnoclines in the meso oligophotic zone would then favor the benthic plankton catchers such as corals but would be detrimental for many lbf warm temperatures favored lbf the eocene lbf families predominated during lowering of atmospheric p co 2 by using respiratory co 2 to enhance the symbiont production of photosynthates under oligotrophic conditions and limited turbulence whereas the miocene families had to adapt to a progressive increase in turbulence the eurythermal coralline red algae however became preponderant producers in the mesophotic zone during times when the 13 c was relatively high this explains two apparent paradoxes 1 corals thrive best when the earth s high latitudes cool and 2 the dominance of corals and lbf is inversely correlated despite they both require tropical conditions and have similar trophic strategies mixotrophy

whales and waves humpback whale foraging response and the shoaling of internal waves at stellwagen bank we tested the hypothesis that humpback whales aggregate at the southern flank of stellwagen bank sb in response to internal waves iws generated semidiurnally at race point rp channel because of the presence of their preferred prey planktivorous fish which in turn respond to zooplankton concentrated by the predictable iws analysis of synthetic aperture radar sar images indicates that rp iws approach the southern flank of sb frequently 62 of the images published reports of whale sighting data and archived sar images point to a coarse spatial coincidence between whales and race point iws at sb s southern flank the responses of whales to iws were evaluated via sightings and behavior of humpback whales and iws were observed in situ by acoustic backscatter and temperature measurements modeling of iws complemented the observations and results indicate a change of 0 4 m s in current velocity and 1 5 pa in dynamic pressure near the bottom which may be sufficient for bottom fish to detect the iws however fish were rare in our acoustic observations and fish response to the iws could not be evaluated rp iws do not represent the leading edge of the internal tide and they may have less mass transport potential than typical coastal iws there was large interannual variability in whale sightings at sb s southern flank with decreases in both numbers of sightings and proportion of sightings where feeding was observed from 2008 to 2013 coincidence of whales and iws was inconsistent and results do not support the hypothesis

breaking of internal kelvin waves shoaling on a slope in stratified flow breaking of internal waves over slopes induces resuspension of bottom sediments and transport of mass when internal waves shoal and break flow dynamics and mass transport diff

garnet peridotite from colorado plateau ultramafic diatremes hydrates carbonates and comparative geothermometry crystal fragments of pyrope from diatremes of ultramafic microbreccia in the navajo province of the colorado plateau contain inclusions of olivine pyroxene spinel chlorite amphibole chlorapatite and dolomite the included suite supports earlier hypotheses that hydrous phases and carbonates were primary parts of some garnet peridotite assemblages in the plateau lithosphere garnets with spinel and orthopyroxene inclusions likely all were sampled at pressures less than 36 kb and perhaps as low as 15 20 kb no evidence was found for inclusions from greater depths temperature estimates are 800 900 c for garnet clinopyroxene equilibration but only 500 700 c for garnetolivine equilibration inherent differences between geothermometry methods account for only part of the discrepancy pronounced fe mg zoning in garnet at olivine contacts and the lack of such zoning at clinopyroxene contacts are evidence that the difference in part relates to relative reequilibration rates with cooling the garnet olivine temperature estimates may be the best approximations to mantle temperatures before eruption our data are compatible both with the hypothesis that the garnet peridotite was emplaced in the mantle by large scale horizontal transport in the lithosphere and with the hypothesis that rocks were sampled from precambrian lithosphere cooled to temperatures like those along a low heat flow geotherm discordances between the geothermometers here and in other lherzolite localities may be keys to evaluating tectonic histories of lherzolite masses

origin of nonbedded pyroclastic rocks in the cathedral cliff diatreme navajo volcanic field new mexico cathedral cliff is a well exposed mid tertiary phreatomagmatic diatreme in the navajo volcanic field new mexico post eruptive erosion estimated between 500 and 1000 m exposes the deep part of the diatreme cathedral cliff provides an opportunity to examine the transition between the bedded pyroclastic rocks of an upper diatreme and the nonbedded pyroclastic rocks of the subjacent lower diatreme bedded pyroclastic rocks occupy 49 of the mapped diatreme area nonbedded pyroclastic rocks occupy 45 and the remaining 6 consist of sedimentary megablocks the bedded pyroclastic rocks range from coarse tuff to medium lapilli tuff and from lithic to juvenile rich they were emplaced during eruption at the bottom of the crater by pyroclastic density currents pyroclastic fallout and as ballistic bombs and blocks as the eruption continued they subsided into the diatreme to their current location bedding ranges from well preserved continuous beds to partially destroyed broken beds syn eruptive subsidence the passage of debris jets through the broken beds as well as a concentration of explosions nearby explains the partial destruction of the bedding the nonbedded pyroclastic rocks are massive and poorly sorted and consist of coarse tuff lapilli tuff and tuff breccia on average they are coarser grained and more juvenile rich than the bedded rocks nonbedded rocks form zones with steep contacts that cross cut each other and the bedded rocks in places they have gradual transitions into broken beds we interpret the nonbedded rocks as formed by the passage of debris jets through existing diatreme infill and from the destruction and recycling of the bedded deposits with juvenile clast enrichment due to dike fragmentation

geochemical comparison between minettes and kersantites from the western european hercynian orogen trace element and pbsrnd isotope constraints on their origin trace element and isotopic characteristics of late carboniferous to early permian minettes and kersantites have been determined these lamprophyres have been sampled throughout the western european hercynian orogen from brittany to the west to schwarzwald to the east in spite of sharp petrological differences reflected by mineralogy and major element geochemistry minettes and kersantites exhibit close identity with respect to trace element and isotopic features these features comprise enrichment in incompatible elements highcs rb and lowce pb ratios ta and ti relative depletion high abundance in transition elements and highni mg ratios pb isotope ratios are undistinguishable from those measured on hercynian continental crust initial143nd 144nd ratios are between0 5120 ei 5 and0 5122 ei 1 for minettes and kersantites whereas initial87sr 86sr ratios vary between 0 7055 0 710 for minettes and 0 707 0 708 for kersantites no simple mixing relations are visible on rbsr and smnd isochron diagrams the exceptional homogeneity of these geochemical characteristics along a 1000 km traverse does not allow for an hypothesis of enrichment through upper level assimilation and thus leads to propose that these rocks originated through melting of a mantle enriched by recycling of crustal material

the role of apatite in mantle enrichment processes and in the petrogenesis of some alkali basalt suites analyses of sr and ree in apatites from a variety of mantle derived parageneses are used in conjunction with trace element data from the literature to investigate relationships between alkali basalts and apatite rich materials in upper mantle source regions despite difficulties in interpretation positive p anomalies in the hygromagmatophile element abundance patterns of some continental primary alkali basalts suggest either p enrichment of their source or assimilation of p rich material or both amphibole and apatite rich xenoliths occur in several alkali basalt provinces and by virtue of the p and lree enrichment represent a probable source of the p anomalies and part of the other trace element enrichments of these magmas incorporation of such apatite rich materials by later primary magmas would be enhanced by the high p2o5 concentrations required to achieve apatite saturation in basaltic liquids in the early stages of mantle diapirism an undersaturated magma produced by slight partial melting of garnet peridotite might fractionate as it rises to the range of amphibole stability hygromagmatophile element patterns of clinopyroxenite xenoliths indicate that clinopyroxene fractionation could produce p enriched liquids which might subsequently crystallize amphibole and apatite rich materials now represented by xenoliths during generation of later primary magma apatite rich materials might preferentially contaminate the liquids to yield positive p anomalies this model requires that magmas undergo prolonged fractionation at considerable depth 100 km a process which is apparently most probable in subcontinental environments an apatite and zircon bearing mica clinopyroxenite xenolith from matsoku provides a link between the s african marid suite and amphibole and apatite rich xenoliths from various alkali basalt provinces unusual ree patterns lan cen ndn cen yn 10 of apatites in this xenolith suggest a link between the marid suite xenoliths and postulated pre karroo mantle metasomatism

petrology of an unusual orthopyroxene bearing minette suite from southeastern peru eastern andean cordillera al rich lamproites contaminated by peraluminous granites abstract the puno minettes eastern andean cordillera southern peru are phlogopite phyric rocks with a groundmass consisting mainly of phlogopite alkali feldspar and apatite microphenocrysts and or microlites they display the strong large ion lithophile element enrichments that characterize potassic to ultrapotassic rocks of the lamprophyre clan rb ba sr up to 103 primordial mantle ree up to 6 102 ci chondrites in addition to their close association with granitoids the rocks of this series show many features of minettes occurring in arc related collisional zones i e absence of mantle xenoliths up to 30 vol felsic xenocrysts and strong negative nb and ti anomalies however they are distinguished by unusual phenocryst phases whole rock compositions and groundmass mineralogy some minettes contain only a few per cent of biotite quartz plagioclase xenocrysts immersed in a typical minette groundmass whereas those richer in xenocrysts display the complete liquidus paragenesis of the coexisting peraluminous granite biotite quartz plagioclase alkali feldspar cordierite zircon pyrite in a high k latitic to trachydacitic groundmass field relations radiometric ages whole rock data and felsic xenocrysts all indicate that the puno minettes result from a mixing process involving al rich lamproites and peraluminous monzogranites the most common phenocryst assemblage highly magnesian phlogopite olivine titanian cr spinel ca rich enstatite magnesian ilmenite al and ti poor diopside is similar to that reported in al rich phlogopite lamproites from southeastern spain likewise the host rocks have diagnostic features of spanish phlogopite lamproites e g k2o al2o3 ratios 9 cao contents

observations of internal wave packets propagating along shelf in northern monterey bay internal waves of depression were observed propagating along shelf and into northern monterey bay california ca on the inner shelf these waves had amplitudes approximately equal to the thermocline depth 4 m and were unstable to shear and mix the thermocline isopycnal gradient spectra showed that the wave packets lead to an elevated mean dissipation rate of 2 63 10 5 m3 s 2 for up to 2 hours after wave passage the proximity to the surface created strong surface convergences that can actively transport buoyant material such as plankton back into the bay the wave packets were observed regularly over the upwelling season across multiple years suggesting they may have large effects on the documented spatial variation of phytoplankton and larvae on the inner shelf the timing of the waves suggests they are not formed by tides interacting with bathymetry but are generated by buoyant plume propagation

primitive calc alkaline and alkaline rock types from the western mexican volcanic belt since the early pliocene small volumes of alkaline magmas have erupted in the western mexican volcanic belt mvb in close association with the volumetrically dominant calc alkaline magmas both suites include relatively rare primitive types characterized by high mg cr and ni contents primitive hypersthene normative basalts parental to the calc alkaline suite are found along the volcanic front but are absent at greater distances from the trench the volcanic front calc alkaline suites are typically hornblende bearing indicating relatively high water contents associated primitive alkaline magmas at volcanic front locations also contain hydrous minerals these nepheline normative suites include basanites phlogopite bearing minettes and other hornblende bearing lamprophyres these are probably the youngest and freshest lamprophyres yet discovered on earth and ideal samples for addressing the origin of this exotic class of rocks on extended morb normalized elemental plots all lamprophyres show patterns similar to the calc alkaline basalts but have overall enrichments of 2 to 25x in ti k p ba sr light rare earth elements and other incompatible elements the lamprophyres show the same strong relative enrichments of ba k and sr and depletions in ti and nb that characterize the calc alkaline rocks of western mexico and all subduction zones these similarities in relative element abundances support a common source region for all primitive magmas of the western mvb the primitive calc alkaline and alkaline rocks of western mexico show narrow overlapping ranges in sr nd and pb isotopic ratios also consistent with derivation of all magmas from a common source the presence of the relatively cold subducted cocos and rivera plates below the volcanic front demands that all primitive magmas originated in the depth range 30 to 75 km these magmas are enriched in ba k sr and other elements probably transported by hydrous fluids rising from the subducted slab several lines of evidence support the presence of phlogopite in the source region of western mvb magmas probably in the form of phlogopite rich veins cutting asthenospheric peridotite the first liquids formed upon partial melting of this veined source region will concentrate the vein component and generate the lamprophyres these lamprophyric melts rarely erupt in arc settings more commonly forming dikes in the arc crust eruption of lamprophyric magmas in the western mvb is favored by through crustal extensional fracture systems related to active rifting of the jalisco block from the n american plate larger volumes of calc alkaline basalt are generated by melting of the same source which dilutes the vein component with larger proportions of peridotitic wall rock

peridotite xenoliths in silica rich potassic latite from the transition zone of the colorado plateau in north central arizona potassic latite in the transition zone of the colorado plateau near chino valley arizona contains abundant eclogite and amphibolite xenoliths and minor websterite and pyroxenite xenoliths one unit contains peridotite xenoliths analyzed samples have mg ratios of 68 and 71 58 and 63 wt sio2 and are enriched in potassium and other large ion lithophile lil elements rare earth element ree patterns are light ree enriched with la greater than 100 times chondritic abundance the peridotite xenoliths are partly to totally altered but contain remnant olivine orthopyroxene and clinopyroxene one harzburgite nodule also contains spinel mineral compositions from the xenoliths are relatively refractory and similar to those in other spinel peridotite xenoliths from the colorado plateau geothermometry on olivine spinel and two pyroxene pairs indicates equilibration temperatures of less than 800 c for the peridotite nodules the relatively low temperatures calculated from mineral equilibria are consistent with temperature estimates for other mantle nodules from under the colorado plateau

footprints of obliquely incident internal solitary waves and internal tides near the shelf break in the northern south china sea a mooring system and two sites of bottom currents were deployed over the slope and near the shelf break on the propagating paths of internal solitary waves isws west off dongsha atoll in the northern south china sea data indicated that energetic isws obliquely shoaled onto the shelf west off dongsha atoll in an approximately 290 degrees direction causing strong reversing currents some exceeding 80 cm s near the bottom two types of sandwaves and short scour channels are discernible on the seafloor near the shelf break which have reasonable correlations with the obliquely incident isws and internal tides type 1 sandwaves featured by isws at the depths of 130 150 m have flat crests interacting with the isobaths at an angle of nearly 45 degrees which slightly incline and migrate upslope type 2 sandwaves are associated with internal tides which have crests parallel to the isobaths and distinctly incline and migrate downslope short channels are parallel to the depth contours and truncate the strata which could be formed and maintained by along slope currents that are probably produced by the obliquely isws on a large gradient gamma 0 8 degrees the isws can move coarse grains or suspend fine grains but do not change the long term trend of sediment transport on the seabed with larger gradients gamma c 1 which is dominated by internal tides these features are likely widespread near the shelf break in the northern south china sea and other seas but are limited on mild slopes where isws do not break

the transition from density driven to wave dominated isolated flows an isolated fluid mass travelling horizontally in a stratified layer is a phenomenon described alternatively as a detached gravity current head or a strongly nonlinear solitary wave a key feature of this flow is the transport of mass laboratory experiments examine the transition in time from a regime in which the flow is density driven to one in which it is wave dominated a simple means of creating this transitional regime an isolated flow that exhibits both density and wave effects is achieved by dropping a thermal into a linearly stratified layer this transitional regime is called an isolated propagating flow parameters for which the transitional regime occurs are identified particle tracking studies reveal the vertical flow structure there is an upper zone that is wave dynamical and a lower zone in which transport of mass occurs the transported mass slowly leaks out until the phenomenon resembles a weakly nonlinear solitary wave the experiments mimic a thunderstorm microburst impacting a temperature inversion which has aviation safety implications in the ocean cracks in the ice cap polar leads cause similar flows impacting the thermocline

jurassic intraplate magmatism in southern hunan eastern guangxi 40ar 39ar dating geochemistry sr nd isotopes and implications for the tectonic evolution of se china the mesozoic geology of se china is characterized by intensive and widespread magmatism however the tectonic regime that accounted for the mesozoic magmatism has been an issue with little consensus a comprehensive study of ar 40 ar 39 dating geochemistry and sr nd isotopes has been conducted on basalts from southern hunan and syenite intrusions from eastern guangxi three episodes of jurassic magmatism i e alkaline basalts of c 175 ma in age syenitic intrusions of c 160 ma and high mg basalts of c 150 ma are identified the older c 175 ma alkaline basalts are characterized by low sr i sr 0 7035 0 7040 and high nd epsilon nd t 5 to 6 isotopic compositions and oib like trace element patterns e g nb la 1 in contrast the younger c 150 ma high mg basalts have high sr i sr c 0 7054 and low nd epsilon nd t c 2 isotopic compositions and incompatible trace element patterns of arc affinity the c 160 ma syenitic intrusions display a relatively large range of sr and nd isotopic compositions i sr 0 7032 0 7082 epsilon nd t 5 5 to 4 1 with the qinghu syenites having the lowest i sr highest epsilon nd t and oib type incompatible trace element patterns analogous to the c 175 ma alkaline basalts such a secular variation in rock types and geochemical and isotopic characteristics reveals changes in melt segregation depth and mantle sources which are inferred to have resulted from the post indosinian orogenic lithosphere extension and thinning the c 175 ma alkaline basalts are suggested to have formed by small degrees of decompression melting of the astheno sphere or an enriched lithospheric mantle source accreted by asthenosphere derived melts during the initial extension the c 160 ma syenitic and c 150 ma high mg basaltic rocks mainly originated from the enriched lithospheric mantle that melted owing to a raised geotherm caused by lithosphere thinning this interpretation is at odds with the active continental margin related to the subduction of palaeo pacific plate but consistent with continental rifting and extension for the mesozoic of se china

observation of internal wave polarity conversion generated by a rising tide the observations reported here are based on time series of in situ observation data in laoshan bay off the qingdao coast a chain of thermistors t chain at a fixed location recorded a sequence of elevation internal waves followed by depression internal waves passing by over an elapsed time of about 1 h this observed polarity conversion at a fixed location is caused by the vertical stratification variation mainly induced by the rising tide which is believed to be the first reported observation of this kind the process of an elevation internal wave train converting to a depression wave train is simulated using the variable coefficient extended korteweg de vries vekdv equation which also provides a further comparison between theory and the reported observations

geochemistry of a transitional ne trachybasalt q trachyte lava series from patmos dodecanesos greece further evidence for fractionation mixing and assimilation trace element and preliminary sr and o isotopic data are reported for a transitional alkaline sub alkaline lava series mvs from patmos greece the lava types belonging to this series are ne trachybasalt hy trachybasalt hy trachyandesite and q trachyte rb sr and ba contents as well as k rb ratios of the ne trachybasalts differ from those of alkali basalts of oceanic islands and those of k rich alkaline lavas of continental regions and are consistent with the occurrence of these volcanics in a destructive plate margin environment qualitatively the variations shown by many trace elements throughout the mvs are explicable in terms of magma evolution via fractional crystallization involving removal of the observed phenocryst phases cross cutting ree patterns can be explained by removal of small amounts of apatite however certain features of the data cannot be reconciled with the operation of fractional crystallization alone these are a the compatible behavior of ba throughout the mvs b the moderately as opposed to highly incompatible behavior of zr rb and nb relative to th and c the significant decrease of k th rb th zr th zr nb nb th yb th ta th u th and zr ta ratios especially but not exclusively in the mafic part of the series quantitative modeling indicates that the hy trachybasalts are anomalously enriched in both highly incompatible and highly compatible elements and these lavas are shown to be hybrids formed by mixing of ne trachybasalt and hy trachyandesite mixing proportions of the end members calculated from incompatible element abundances 19 ne trachybasalt differ from those calculated from compatible element abundances 62 ne trachybasalt and are inconsistent with proportions calculated from published mineral chemical data in addition mixing cannot account for the observed variations in incompatible element ratios and this is taken as evidence for the simultaneous operation of assimilation isotopic variations 87sr 86sr from 0 7049 to 0 7076 and 18o 16o from 4 7 to 8 6 and the positive correlation of isotope ratios with sio2 and th contents provide conclusive proof that assimilation occurred calculations show that the isotopic characteristics and the concentrations of many trace elements in the q trachytes can be explained by fractional crystallization of ne trachybasalt combined with assimilation of average continental crust 87sr 86sr 0 710 and that large amounts of assimilation are not necessary ma mc 0 55 ree data are not well explained by this model and suggest a crustal end member enriched in lree relative to the average crust zr and hf data are also not well explained and indicate that the assimilant was depleted in hfse relative to average crust or that hfse are held back in relatively insoluble phases such as zircon in the restite during assimilation nevertheless the results of the modeling demonstrate that ba concentrations may decrease during afc processes and that high sr contents 1500 ppm in the mvs ne trachybasalts do not render mafic parental magmas immune to the effects of assimilation in terms of their 87sr 86sr ratios the results of this study confirm conclusions based upon major oxide and mineral chemical data for the mvs lavas but more importantly show that careful analysis of trace element data allows the various processes involved in magma evolution to be identified and quantified even in the absence of major oxide and isotopic data finally it is reiterated that magma mixing and assimilation may be coupled processes in the magma chambers beneath many volcanic centers and recognition of this fact has profound implications for studies of magmas erupted at continental margins and through continental crust

large amplitude internal solitary waves observed in the northern south china sea properties and energetics abstractfive large amplitude internal solitary waves isws propagating westward on the upper continental slope in the northern south china sea were observed in may june 2011 with nearly full depth measurements of velocity temperature salinity and density as they shoaled at least three waves reached the convective breaking limit along wave current velocity exceeded the wave propagation speed c vertical overturns of 100 m were observed within the wave cores estimated turbulent kinetic energy was up to 1 5 10 4 w kg 1 in the cores and at the pycnocline the gradient richardson number was mostly 0 25 the maximum isw vertical displacement was 173 m 38 of the water depth the normalized maximum vertical displacement was 0 4 for three convective breaking isws in agreement with laboratory results for shoaling isws observed isws had greater available potential energy ape than kinetic energy ke for one of the largest observed isws the total wave energy per unit meter along the wave crest e