time scales of hybridisation of magmatic enclaves in regular and chaotic flow fields petrologic and volcanologic implications this paper describes numerical models of advection diffusion between enclaves and host magmas applied with the aim of estimating time scales during which enclaves can be homogenised in particular advection was simulated using a numerical system consisting of regular and chaotic regions results indicate that the homogenisation time of enclaves in chaotic regions is several orders of magnitude faster than in regular regions for instance an enclave with a diameter of 100 cm may be homogenised in the chaotic region in 380 years assuming an advection velocity of 10 cm year whereas in the regular region it would require 6 5 105 years for complete homogenisation this implies that in the same magmatic system large differences in the degree of homogenisation may co exist generating magmatic masses with large spatial and temporal inhomogeneities

evidence of isotopic equilibration between microgranitoid enclaves and host granodiorite warburton granodiorite lachlan fold belt australia abstract microgranitoid enclaves in the s type warburton granodiorite lachlan fold belt australia display a range in mineralogical and isotopic compositions many show obvious similarities to the host granodiorite they contain biotite as the sole ferromagnesian phase and have isotopic signatures similar to the host other enclaves contain cummingtonite actinolite and rare orthopyroxene mainly in the core of the enclaves these enclaves typically have higher nd i and lower sol 87 sr 86 sr i than the host rocks reversely zoned plagioclase megacrysts in some enclaves contain anhedral cores which are similar in composition to an poor plagioclase crystals in the host rock an45 these megacrysts are jacketed by an rich plagioclase an70 an80 the enclaves are interpreted to be globules of a more mafic magma which mingled with the host while it was still partially liquid megacrysts within the enclaves are thought to have been derived from the granodioritic magma the mafic enclave magma is likely to have been derived from a mantle source but equilibration between enclaves and host rock has changed the mineralogy and isotope geochemistry of all enclaves the equilibration process was incomplete for some enclaves resulting in mineralogical zoning and distinctions in isotopic signature between these enclaves and the host rock this equilibration process is likely to have been arrested as a result of rapid cooling of the pluton due to its small size and shallow emplacement level it is uncertain whether the compositions of the least equilibrated enclaves are truly representative of the original mafic enclave magma or whether their trace element signature has been affected by diffusional processes within a stratified magma chamber

the jeffers brook diorite granodiorite pluton style of emplacement and role of volatiles at various crustal levels in avalonian appinites canadian appalachians small appinite plutons ca 610 ma outcrop in the peri gondwanan avalon terrane of northern nova scotia with different structural levels exposed field mapping shows that the jeffers brook pluton is a laccolith emplaced along an upper crustal thrust zone likely in a dilational jog in a regional dextral strike slip system the oldest rocks are probably mafic sills which heated the area facilitating emplacement of intermediate magmas cross cutting relationships show that both mafic and intermediate magmas were supplied throughout the history of pluton emplacement the modal composition mineral chemistry and bulk chemistry of gabbro diorite tonalite granodiorite and granite have been studied in the main plutonic phases dykes and sills and mafic microgranular enclaves as with the type appinites in the scottish caledonides the pluton shows evidence of high water content the dominance of hornblende locally within pegmatitic texture vesicles and irregular felsic patches in enclaves and late aplite dykes analyzed mafic microgranular enclaves are geochemically similar to larger diorite bodies in the pluton tonalite granodiorite is distinct from the diorite in trace element geochemistry and radiogenic isotopes elsewhere to the east similar rocks of the same age form vertically sheeted complexes in major shear zones hornblende chemistry shows that they were emplaced at a deeper upper crustal level this implies that little of the observed geochemical variability in the jeffers brook pluton was developed within the pluton the general requirements to form appinites are proposed to be small magma volumes of subduction related magmas that reach the upper crust because of continual heating by mafic magmas moving through strike slip fault pathways and trapping of aqueous fluids rather than venting through volcanic activity

geology and geochemistry of archaean granites in the kalgoorlie region of the eastern goldfields western australia a syn collisional tectonic setting abstract granites in the kalgoorlie region of the archaean yilgarn craton are predominantly biotite granodiorite and monzogranite with some hornblende bearing varieties granites are divided on the basis of field relationships petrography and chemical composition into five supersuites an older supersuite containing four suites pre dates regional folding and four supersuites post date regional folding the potassic composition of the mainly silica rich granites 68 sio2 suggest that the most appropriate source for the majority of supersuites is continental crust with a composition in the range tonalite to granodiorite most supersuites evolved by fractional crystallization mainly of biotite and plagioclase some suites contain synplutonic dykes and microgranite xenoliths that crystallized from enriched mantle derived magmas there was only limited and local chemical interaction between granite and mantle derived magmas geometric and temporal relationships between regional structures and granites indicate that the granites were emplaced during a major orogenic event however s type granites which are widespread in some modern syn collision settings are absent in the kalgoorlie region the predominance of high fo2 i type granites in the study area probably reflects the absence of large graphite bearing metasedimentary accumulations in the lower crustal source regions the distribution of suites and supersuites implies a common source region beneath the kalgoorlie and gindalbie granite greenstone terranes suggesting that they shared a common geological history dating back to late greenstone deposition

petrogenetic and tectonic inferences from the study of the mt cer pluton west serbia the mt cer pluton serbia is a complex laccolith like intrusion 60 km 2 situated along the junction between the southern pannonian basin and northern dinarides it intrudes palaeozoic metamorphic rocks causing weak to strong thermal effects based on modal and chemical compositions four rock types can be distinguished 1 metaluminous i type quartz monzonite quartz monzodiorite qmzd 2 peraluminous s type two mica granite tmg which intrudes qmzd 3 stra anica granodiorite quartz monzonite gds and 4 isolated mafic enclaves me found only in qmzd 40 k 39 ar dating and geological constraints indicate that the main quartz monzonite quartz monzodiorite body of mt cer was emplaced not later than 21 ma whereas the emplacement ages of the stra anica granodiorite quartz monzonite and two mica granites are estimated at around 18 and 16 ma respectively the mt cer pluton is similar to the mt bukulja pluton some 80 km southwestwards genesis of qmzd cannot be interpreted by fractional crystallization coupled with mixing or assimilation it is best explained by a convection diffusion process between mantle derived minette leucominette magmas and gds like magmas followed by two end member magma mixing the composition of gds rocks suggests that gds like magmas could have formed by melting of lower crustal lithologies similar to amphibolite metabasalts the geochemistry of tmg is reproduced by an assimilation fractional crystallization model with a ratio of rate of assimilation to rate of fractional crystallization of 0 4 using the compositions of the least evolved tmg of the bukulja pluton and adjacent metamorphic rocks as proxies for the parental magma and contaminant respectively the origin and evolution of the mt cer and adjacent mt bukulja plutons provide new constraints on the tertiary geodynamics of the northern dinarides southern pannonian region the quartz monzonite quartz monzodiorite is interpreted as a result of the oligocene post collisional dinaride orogen collapse which included a limited lithosphere delamination small scale mantle upwelling and melting of the lower crust by contrast the two mica granite magmas formed through melting in shallower crustal levels during the extensional collapse in the pannonian area

genesis of post collisional calc alkaline and alkaline granitoids in qiman tagh east kunlun china abstract the post collisional magmatism of qiman tagh is characterized by the intrusion of voluminous intermediate to felsic granitoids including syenogranite monzogranite granodiorite tonalite and diorite the granitoids can be divided into two magmatic suites calc alkaline ca and alkaline alk which were emplaced from 236 ma to 204 ma the ca suite contains metaluminous granodiorites and monzogranites typical qiman tagh ca granodiorites show moderately fractionated ree patterns la yb n 4 35 25 11 with significant negative eu anomalies eu eu 0 54 1 34 and the primitive mantle normalized spidergrams show strong depletion of nb and sr the qiman tagh ca monzogranites show similar fractionated ree patterns la yb n 2 70 13 5 with less prominent negative eu anomalies and the chondrite normalized spidergrams show strongly depleted ba nb and sr the alk suite including syenogranite is highly potassic k 2 o na 2 o 1 09 3 56 and peraluminous a cnk 0 91 1 06 compared to typical qiman tagh ca granodiorites the qiman tagh alk granitoids can be distinguished by their higher rb nb ga al feo mgo y sr and rb sr as well as their lower mg mgo cao al 2 o 3 sr co v eu eu ba nb la nb ba la and ce nb the qiman tagh ca rocks were most likely to be derived from the partial melting of garnet amphibolite facies rocks in the lower crust leaving behind anhydrous granulite facies rocks with plagioclase and garnet in the residue the alk rocks may have formed by the continued partial melting of granulite facies rocks at elevated temperatures 830 c

fractal analysis of mingled mixed magmas an example from the upper pollara eruption salina island southern tyrrhenian sea italy abstract upper pollara eruption products 13 ka salina island italy include both homogeneous and heterogeneous pumices resulting from mixing mingling processes between an hk andesite and a high sio2 rhyolite representative samples of heterogeneous pumices are collected and analyzed in order to check the correspondence between glass composition and morphological features of the mingling mixing structures image analysis techniques are applied and eight grey color ranges classes are extracted from high resolution scans of pumice class 1 lighter colors and class 8 darker colors show end member glass compositions i e hk andesite and high sio2 rhyolite respectively these two classes show spot to cluster like morphological structures intermediate classes show an hk dacitic to rhyolitic composition and a banding to fold like morphology fractal analysis by box counting of the boundary pattern of eight grey classified images is performed over a length scale of 0 028 1 8 cm fractal dimension d is between 1 01 and 1 84 coupled fractal analysis and geochemical data reveal that d increases as the degree of magma interaction homogenization increases this feature well fits the results from numerical models on the convective mixing of fluids driven by thermal convection we conclude that the increase of d observed in the upper pollara samples reflects the transition from fractal mixing to homogenization end member magmas hk andesite and high sio2 rhyolite represent isolated mixing regions while homogenized magmas represent active mixing regions in the analyzed pumices isolated and active mixing regions coexist at scales between 10 4 and 10 2 m morphological and compositional features of the upper pollara pumices result from turbulence

morphometric analysis of magmatic enclaves a tool for understanding magma vesiculation and ascent abstract the extent of deformation of magmatic enclaves that occur in different portions of the khaggiar endogenous lava dome island of pantelleria italy has been quantified using two morphometric techniques thin plate splines and fractals deformation of enclaves decreases from the outer portions of the dome to the more internal portions defining two exponential trends the amount and distribution of vesicles have also been quantified using image analysis of digital images obtained by a scanning electron microscope the variation of deformation of enclaves correlates with the variation of their vesicle content suggesting that deformation and vesiculation are related we envisaged a continuous feedback system between vesiculation of enclaves and radial forces exerted by the surrounding host magma during the growth of the dome these relationships are used as dynamic markers to infer the eruptive style of the endogenous dome in particular it is suggested that the variation of vesicularity of enclaves is related to the pressure exerted by magma on the extrusion vent this resulted in enclaves being more vesicular and more deformed in the outer portions of the dome that emplaced first and at lower pressure and less vesicular and less deformed in the more internal portions that emplaced later and at higher pressure we interpret the occurrence of the two trends in the variation of deformation and porosity as related to two main eruptive pulses of dome growth

ambiguous isotopic and geochemical signatures resulting from limited melt interactions in a seemingly composite pluton a case study from the strzegom sobotka massif sudetes poland the western part of the late variscan strzegom sobotka massif exemplifies an intrusion that formed in a multi component system the system shows ambiguous isotopic and geochemical signatures and presents a seemingly composite character biotite granite with negligible amount of hornblende hbg and microgranular mafic enclaves mmes the melts responsible for forming granitic rock and its mmes were not derived from contrasting crustal and mantle sources but from different crustal domains these melts exhibit hybrid characteristics due to subsequent contamination processes the data suggest two different stages of hybridization of two geochemically distinct magmas corresponding to granite and enclaves the processes were temporally and spatially distinct heterogeneous protoliths and hybridization made these magma isotopic signatures and trace element patterns ambiguous the main mechanism involved in developing granitic rocks was fractional crystallization fc the mechanism responsible for mme composition was mixing but other local processes were also involved in rock formation generally the fc signature was not obscured by the hybrid mafic melt input this felsic mafic melt interaction was a limited one sided process granitic melt was changed by the presence of small mafic magma blobs but their influence on granite crystallization was negligible the massif is thus an ideal example of an environment where mmes coexist with a granitic body although mmes do not determine the actual composite character of the pluton the early stage of variscan pluton formation within the bohemian massif and adjacent areas was shaped by interacting mantle and crust derived melts the pluton described in this paper belongs to the late stage of variscan magmatism it is a multi component system shaped by the participation of melts derived from heterogeneous crustal domains the presence of enclaves does not explicitly indicate their dominant role in the formation of composite plutons of crust mantle origin it is decisive to determine whether the ambiguous signatures appearing in such cases truly indicate both of these sources

mafic enclaves in granitoid intrusions a catastrophic model of rheological behaviour the significance of mafic enclaves as indicators of magma mixing processes between juxtaposed felsic and mafic magmas is evaluated from a rheological point of view a qualitative model for explaining strain and morphological changes in the enclaves has been developed on the basis of the catastrophe theory mafic enclaves in intrusive granitoids commonly behave as physical systems that can be described using a cusp catastrophe model their behaviour is characterized by bimodality divergence and sudden changes which are properties typical of this model accordingly the presence of mafic enclaves showing variable strain and morphology within the same granitoid intrusion would be indicarive of mutual interaction and mingling between mafic and felsic magmas due to the characteristics of these processes it is not possible to establish unambiguous age relationships between the two magmatic components

microchemical and sr isotopic investigation of zoned k feldspar megacrysts insights into the petrogenesis of a granitic system and disequilibrium crystal growth k feldspar megacrysts kfm are used to investigate the magmatic evolution of the 7ma monte capanne mc monzogranite elba italy dissolution and regrowth of kfm during magma mixing or mingling events produce indented resorption surfaces associated with high ba contents diffusion calculations demonstrate that kfm chemical zoning is primary core to rim variations in ba rb sr li and p support magma mixing i e high ba and p and low rb sr at rims but more complex variations require other mechanisms in particular we show that disequilibrium growth related to variations in diffusion rates in the melt may have occurred as a result of thermal disturbance following influx of mafic magma in the magma chamber initial 87 sr 86 sr ratios isr obtained by microdrilling decrease from core to rim inner core analyses define a mixing trend extending towards a high isr rb sr melt component whereas the outer cores and rims display a more restricted range of isr but a larger range of rb sr lower isr at the rim of one megacryst suggests mixing with high k calc alkaline mantle derived volcanics of similar age on capraia trace element and isotopic profiles suggest 1 early megacryst growth in magmas contaminated by crust and refreshed by high isr silicic melts as seen in the inner cores and 2 later recharge with mafic magmas as seen in the outer cores followed by 3 crystal fractionation with possible interaction with hydrothermal fluids as seen in the rim the model is compatible with the field occurrence of mafic enclaves and xenoliths

u pb ages and morphologies of zircon in microgranitoid enclaves and peraluminous host granite evidence for magma mingling granites of the s type wilson s promontory batholith lachlan fold belt australia contain zircons which are euhedral and relatively large their age is 395 ma which can be considered as the best available estimate of the crystallysation age of the granites contrary to their dominance in other s type granites of the lachlan fold belt very few zircon cores give inherited ages varying between 500 and 1700 ma microgranitoid enclaves contained within the granites contain a zircon population that is dominated by relatively small anhedral or elongated crystals these give ages that are indistinguishable from the crystallisation age of the granite some enclaves which are characterised by the presence of megacrysts contain a proportion of larger euhedral zircons these zircons give inherited ages similar to the zircons from the granitic host rocks the data are in agreement with a magma mingling origin for the microgranitoid enclaves the large euhedral zircons are interpreted to have been introduced into the enclave magma during a hybridisation event which also introduced quartz and plagioclase megacrysts into the magma the relatively high proportion of inherited cores within the large zircon population of the enclaves is related to the timing of mixing between enclave and host magma this mixing event took place before the majority of the magmatic zircons crystallised in the granitic magma the small anhedral zircons within the enclaves crystallised during quenching of the globules of enclave magma against the cooler granitic magma

mineralogy and geochemistry of microgranular enclaves in palaeoproterozoic malanjkhand granitoids central india evidence of magma mixing mingling and chemical equilibration palaeoproterozoic ca 2 480 ma felsic magmatism of malanjkhand region of central indian precambrian shield referred to as malanjkhand granitoids mg contain xenoliths of country rocks and mesocratic to melanocratic fine grained porphyritic microgranular enclaves me the shape of me is spheroidal ellipsoidal discoidal elongated and lenticular varying in size from a few centimeters to about 2 m across the contact of me with the host mg is commonly sharp crenulate and occasionally diffuse which we attribute to the undercooling and disaggregation of me globules within the cooler host mg the me as well as mg show hypidiomorphic texture with common mineral hbl bt kfs pl qtz assemblage but differ in modal proportions the variation in minerals composition presence of apatite needles elongated biotites resorbed plagiclase ocellar quartz and other mafic felsic xenocrysts strongly oppose the restite and cognate origins of me compositions of plagioclases an3 an29 amphiboles mg mg fe2 0 55 0 69 and biotites mg mg fe2 0 46 0 60 of me are slightly distinct or similar to those of mg which suggest partial to complete equilibration during mafic felsic magma interactions al in amphibole estimates the mg pluton emplacement at ca 3 4 0 5 kbar and therefore magma mixing and mingling must have occurred at or below this level the hbox fe rightleftharpoons hbox mg substitution in biotites of me and mg largely suggests subduction related calc alkaline metaluminous i type nature of felsic melts most major and trace elements against sio2 produce near linear variation trends for me and mg probably generated by the mixing of mafic and felsic magmas in various proportions trace including rare earth elements patterns of me mg pairs however show partial to complete equilibration most likely governed by different degrees of elemental diffusion the available evidence supports the model of me origin that coeval mafic enclave and felsic mg magmas produced a hybrid me magma layer which injected into cooler partly crystalline mg and dispersed mingled and undercooled as me globules in a convectively dynamic magma chamber

geochemistry of tuscan archipelago granitoids central italy the role of hybridization processes in their genesis this paper reports major trace and rare earth element data for selected samples from the elba giglio and monte cristo plutons which lie in the tuscan archipelago italy on the basis of field and petrologic constraints all the rocks can be divided into five facies and range in composition from granodioritic to alkali granitic with a strong predominance of monzogranites tuscan archipelago granitoids are clearly collision related rocks and they straddle the i and s types of chappell and white however mineralogical and chemical characteristics indicate that the more basic rocks are broadly i type while the high silica rocks are s type genetic models that relate these magmas through the segregation of their major and accessory mineral phases are inconsistent with major trace and ree element abundant data geological petrographical and geochemical constraints show that the microgranular mafic enclaves found within the rocks are blobs of mafic high temperature magma chilled within a cooler m

igneous and metamorphic enclaves in the s type deddick granodiorite lachlan fold belt se australia petrographic geochemical and nd sr isotopic evidence for crustal melting and magma mixing the deddick granodiorite a mafic s type pluton in the lachlan introduction fold belt contains abundant enclaves most are derived from enclaves in granites and volcanic rocks can provide high grade metasediments of pelitic psammitic composition and petrogenetic information not readily available from their migmatites are common among these discrete fragments of host rocks didier 1973 didier barbarin 1991 for melanosomes rich in cordierite and garnet are restites from partial example metasedimentary enclaves can place constraints melting however compositional and nd sr isotopic data indicate on the age composition and deformational history of they are not restite in equilibrium with the melt component of the magma source regions within continental crust fleming host magma but may have formed part of a spectrum of diverse 1991 steele et al 1991 enclaves formed by acmagma source lithologies alternatively they may be accidental cumulation of early phenocrysts autoliths document xenoliths regardless of their origin data for these enclaves suggest the early evolution of the host magma whereas others their precursors could represent deeply buried age equivalents of the may represent commingled magmas and illustrate the ubiquitous ordovician turbidites of the lachlan fold belt three possible role of hybridization didier 1987 types of microgranular enclaves with igneous textures are disenclave suites in the relatively mafic s type granitoids tinguished the most common type are small and rounded mafic of se australia are often diverse including abundant enclaves of tonalitic composition they carry xenocrysts derived from enclaves of metasedimentary origin and microgranular the host magma and some contain high mg pyroxene derived from enclaves phillips et al 1981 price 1983 chen et al a mafic magma isotopic data form an array with end from 6 to 1989 wyborn et al 1991 the metasedimentary en 12 and sr sr from 0 7130 to 0 7167 host rock 10 and claves are lithologically diverse including gneissic 0 715 respectively these enclaves formed as globules of hybrid migmatitic types and biotite rich surmicaceous types mafic magma commingled with and contaminated by the more apart from their potential as indicators of crustal structure felsic host magma other enclave types were derived from disrupted and composition they are of interest as possible fragments syn plutonic dykes having a distinct isotopic composition and from of source material and or refractory residue from which a cogenetic marginal facies of the host peraluminous melts were generated and extracted by

discussion on metallogenic setting and time difference between magmatism and mineralization of molybdenum deposits in east china east china was intensely affected by the marginal pacific metallogenic domain in mesozoic most molybdenum deposits along border areas of different tectonic units or regional deep faults are dominantly distributed in such metallogenic belts as east qinling yanshan liaoning middle lower reaches of the yangtze river nanling and da hinggan mountains combined with previous studies this paper discusses metallogenic settings of these regions exemplified by typical ore deposits and draws the conclusion that mo mineralization in these me tallogenic belts probably resulted from the extensional setting of post collision and or subduction of the pacific plate according to isotopic data of mineralization and ore related rocks collected from some typical mo deposits in east china the authors investigated in detail and quantitatively determined the characteristics of time diffe rence between magmatism and mineralization for mo deposits mo mineralization in east china occurred contemporaneously with or immediately after ore related granitoids time differences of the two peaking stages of mo mineralization are within 0 10 0 ma and 0 15 0 ma respectively for a single mo deposit the time differences are concentrated in 0 14 0 ma with a mean of 4 1 ma in order of porphyry type mo deposits porphyry skarn complex mo deposits skarn type mo deposits quartz vein type mo deposits the time differences seem gradually increase which is consistent with the observed geological facts of the magmatic hydrothermal ore formational process

linear relationship between heat flow and heat production in panxi paleorift zone southwestern china the panzhihua xichang panxi area of southwestern china approximately 26 00 n to 28 48 n and 101 00 e to 103 00 e is a paleorift zone of hercynian age the last major tectono thermal event occurred 200 to 250 ma ago with extensive basaltic eruptions regional surface heat flow values vary from 40 to 90 mw m with the average of 63 15 mw m the u th contents increase with the acidity of igneous rocks the highest contents u 9 57 ppm th 27 67 ppm are observed in biotite granite the u th contents are well correlated with each other and the correlation coefficient is 0 9646 indicating the poor migration of u in epimagmatic state on the basis of heat flow and heat production data a linear relationship was obtained for the region

a type granitoids from the eastern pontides ne turkey records for generation of hybrid a type rocks in a subduction related environment the eastern pontides is characterized by the many of intrusive bodies formed throughout the late mesozoic early cenozoic most of these are i type granitoids but here we present for the first time an a type pluton from the region to assess source characteristics and geodynamic implications the a type pirnalli pluton has a shrimp zircon u pb age of 81 2 1 ma it is composed of granite syenite and quartz monzonite and its enclaves are monzonitic in composition with elevated ga al ratios and low mg 42 the pluton is dominantly metaluminous a cnk 0 88 to 1 00 and belong to shoshonitic and ultra potassic series the samples are highly enriched in lree and show significant negative eu eu eu 0 33 to 0 92 ba nb sr and ti anomalies in the spidergrams the host rocks and their enclaves posses quite similar sr nd isotopic compositions isr 0 70693 to 0 70736 end 81 ma 2 6 to 2 0 tdm 0 94 to 1 12 ga pointing to a lower crustal parental magma with a minor contribution of lithospheric mantle we hypothesize that upwelling of asthenosphere triggered melting of chemically enriched upper mantle and basic magma formed melting of lower crust was provided by the underplating of this basic magma mixing between lower crust and mantle derived melts at depths of lower crust appears to be most reasonable petrogenetic process responsible for generation of the pluton sr nd isotope modeling suggests mixing of 82 90 of the lower crustal derived melt with 10 18 of the mantle derived melt then the hybrid melt ascended to shallower crustal level and underwent a limited fractionation process to generate a variety of rock types our data also suggest that the a type pirnalli pluton likely formed at an extensional environment of active continental margin throughout the late cretaceous ongoing extension then led to opening of black sea as a back arc basin further north of the eastern pontides

geochemistry geochronology and zircon hf isotopic study of peralkaline alkaline intrusions along the northern margin of the north china craton and its tectonic implication for the southeastern central asian orogenic belt abstract a giant permian alkaline magmatic belt has recently been identified in southern inner mongolia along the northern margin of the north china craton ncc this belt is mainly composed of syenite quartz syenite alkaline granite and mafic microgranular enclaves mme bearing granodiorite in order to study the petrogenesis and tectonic implications of these rocks we undertook zircon u pb dating and geochemical analysis of two permian alkaline plutons the first guangxingyuan pluton occurs in the hexigten area and is composed of mme bearing tonalite k feldspar granite and syenite the second durenwuliji pluton located in the xianghuangqi area comprises syenite quartz syenite and k feldspar granite zircon u pb dating on tonalite k feldspar granite syenite and quartz syenite from the two plutons yielded a tight range of ages from 259 to 267 ma the peralkaline alkaline rocks show high abundance of total alkalis k2o na2o 7 9 12 9 and k2o contents 3 9 8 0 enrichment in large ion lithophile elements lile and light rare earth element lree and depletion of high field strength elements hfse the associated tonalite and mmes display i type granitic geochemical affinity with less total abundance of trace elements than the peralkaline alkaline rocks zircon hf isotopic analysis of the guangxingyuan pluton yielded a large range of ehf t values from 15 5 to 6 7 and model ages tdmc from 781 to 2012 ma by contrast the hf isotopic data of the durenwuliji pluton shows a small range of ehf t from 6 2 to 8 9 and tdmc from 667 to 816 ma the geochemical and hf isotopic characteristics indicate that the parental magma was derived from a mixing of metasomatic mantle derived mafic magma with different amount of crust derived felsic magma and followed by fractional crystallization considering previous tectonic studies in inner mongolia a permian post orogenic extension was proposed to account for these peralkaline alkaline intrusions following the amalgamation of ncc and its northern blocks in the southeastern part of central asian orogenic belt

formation of composite dykes by contact remelting and magma mingling the shaluta pluton transbaikalia russia abstract a unique opportunity to study the source areas from which composite dykes were injected occurs in the shaluta pluton transbaikalia russia the major quartz syenite pluton was intruded by several synplutonic gabbro bodies of various sizes investigations of the contact zones between gabbro and host syenite showed that liquid basalt magma intruded the incompletely crystallized coarse grained quartz syenite with t 700 720 c and caused contact remelting of the silicic rock at about 900 950 c mechanical interaction between newly formed silicic melt and partially crystallized mafic magma resulted in extensive magma mingling chemical interaction was exhibited by migration of mgo cao feo sr h2o and cl from the basalt magma whereas silica alkalis rb and ba migrated from the silicic refusion zone into the crystallized gabbro presence of melt inclusions with homogenization temperature ranging from 640 to 790 c in quartz and attaining 850 900 c in late clinopyroxene indicates that at least part of newly formed minerals crystallized from the hybrid melt mingled magmatic material was squeezed out inwards into the host solid quartz syenite pluton and formed dyke like apophyses that can be traced for a distance of 60 70 m from the contact zone apophyses have the same dimensions structure and composition as typical composite dykes that are common in the roof pendant over the gabbro bodies and nearby the gabbro exposures

geochronology and isotopic geochemistry of the a type granites from the huanggang sn fe deposit southern great hinggan range ne china implication for their origin and tectonic setting abstract the huanggang sn fe deposit inner mongolia is located in southern great hinggan range metallogenic belt la icp ms zircon u pb dating show that the k feldspar granite and granite porphyry in the huanggang mine were formed at 136 7 1 1 ma and 136 8 0 57 ma respectively sr nd pb isotope of the rocks and in situ zircon hf isotopic systematics show that 87 sr 86 sr i values range from 0 70211 to 0 70729 close to the 87 sr 86 sr i of oceanic basalts and lower than those of continental crust the e nd t values and nd model ages t dm vary from 0 8 to 0 9 and 855 to 993 ma respectively the pb isotopic compositions are also variable with 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb values of 18 974 26 107 15 554 15 914 and 38 894 39 890 respectively suggesting that the lead is derived from a mixed source the 176 hf 177 hf values range from 0 282744 to 0 282922 with corresponding e hf t values ranging from 1 9 to 18 3 and two stage hf model ages t dm2 of between 561 and 888 ma the isotope composition shows that huanggang granites were derived from partial melting of juvenile lower crust that originated from depleted mantle perhaps contaminated by small amounts of ancient continental crust younger nd hf isotope model ages imply that an important crustal growth event took place in this area during the neoproterozoic integrating our data with previously published results and the late mesozoic regional tectonic setting we conclude that the huanggang granites were generated in an intraplate tectonic magmatic setting asthenospheric mantle upwelling due to lithospheric delamination and magma underplating caused the partial melting of a mantle wedge metasomatized by the fluids released from subducted oceanic crust or by decompression of depleted mantle this resulted in remelting differentiation and a continued evolution of the mafic juvenile crust producing a large quantity of granitic magma the tectonic setting for these processes may be linked to the nnw subduction of the pacific plate izanagi in the mesozoic which affected most of eastern china

geochemistry and u pb shrimp zircon chronology of granitoids and microgranular enclaves from jhirgadandi pluton of mahakoshal belt central india tectonic zone india abstract the northern part of central india tectonic zone citz is delineated by an arc shaped supracrustal belt commonly referred to as mahakoshal belt which is considered as a product of intense rifting of sialic crust that occurred at ca 2400 2600 ma several granitoid plutons intrude the parsoi formation of mahakoshal belt among these an elliptical small stock like granitoid body trending e w is exposed in and around jhirgadandi region of mahakoshal belt referred herein as jhirgadandi pluton it is composed of minor amount of mafic rocks diorite and predominant granitoids country rock pelitic xenoliths and microgranular enclaves me are commonly hosted in granitoids but are absent in diorite the me exhibit typical magmatic texture with a bt cpx hbl pl kf qtz mag ap assemblage similar to that in host granitoids but with contrasting mineral proportions whole rock molar al 2 o 3 cao na 2 o k 2 o a cnk ratios of diorite 0 63 0 72 me 0 69 1 21 and granitoids 0 83 1 05 suggest their nature largely metaluminous i type to rarely peraluminous s type granitoids on most binary plots involving silica two distinct compositional paths can be recognized one formed by an array of differentiating diorite and me and another by fractionating granitoids gradually depleting in compatible elements it is most likely that me were generated by progressive and concurrent mixing of coeval pristine mafic diorite and granitoid magmas and fractionation processes however coherent and identical trace elements except for sr th y and ni and ree patterns for me granitoid pairs most likely suggest partial to near complete chemical equilibration through varying degrees of diffusion process across the me partly crystalline host granitoid boundary high precision u pb shrimp zircon 206 pb 238 u ages for me 1758 19 ma and host granitoid 1753 9 1 ma from jhirgadandi pluton further support the notion that they were coeval the obtained age 1750 ma of jhirgadandi pluton also points to the existence and role of super columbian continental component in the evolution of mahakoshal belt of the citz

dynamics and time evolution of a shallow plumbing system the 1739 and 1888 90 eruptions vulcano island italy abstract in this work we analyze the morphology of latitic enclaves occurring in the rhyolitic lava flow of pietre cotte island of vulcano italy we show that enclave morphology is a feature inherited from the shallow plumbing system of the volcano during the invasion of the latitic magma into the rhyolitic magma the complexity of enclave morphology is quantified by fractal analyses using the empirical relationship given by perugini et al 2005 relating the fractal dimension and viscosity ratio the range of viscosity ratios that developed during the injection of the latitic magma into the rhyolitic one is estimated thermodynamical and rheological modeling indicates that the most plausible scenario to explain the variability of observed viscosity ratios is represented by a plumbing system where a large volume of latitic magma intruded a smaller volume of rhyolitic magma the comparison of volume proportions of magmas on the outcrop with those estimated by the modeling allows us to infer that most of the latitic magma remained in the plumbing system after the ending of the 1739 eruptive cycle the strong similarity of compositions from the pietre cotte lava flow and products erupted during the last volcanic activity of vulcano 1888 1890 is interpreted as the reactivation of the latitic magma that possibly evolved through fractional crystallization to produce trachy rhyolitic compositions during the 1888 1890 eruptive cycle we suggest that the methodological approach presented here can represent a further tool for hazard mitigation in volcanic areas in particular it allows obtaining information about the dynamics of plumbing systems of active volcanoes and their time evolution

composite dikes in four successive granitoid suites from transbaikalia russia the effect of silicic and mafic magma interaction on the chemical features of granitoids abstract in the study area of 60 by 15 km located south of lake baikal coeval mafic rocks form small intrusive bodies synplutonic dikes and composite mafic felsic dikes in four successive late paleozoic and early mesozoic syenite and granite suites mafic rocks in all suites are monzogabbro with similar mineral and chemical composition this attests that mantle derived mafic magmas produced at post collisional and within plate tectonic settings were not noticeably distinguished in chemical composition within a time interval of about 60 65 m y detailed study of the interaction zones between synplutonic mafic magma and host syenite at two key localities allowed recognition of syenite remelting stage at about 900 950 c remelting was accompanied by sr and ba enrichment by diffusion from the adjacent mafic magma diffusive transport of ba also caused enhanced bao content 0 37 0 54 wt in alkali feldspars of the newly formed syenite remelting of the host syenite was followed by mingling chemical interaction and mixing of mafic and silicic magmas within the contact zone the results of petrographic and geochemical study of the composite and synplutonic dikes are used to interpret the chemical features of the large about 1000 km2 essentially syenitic ust khilok pluton two varieties of syenite are recognized in the pluton one with ba

petrogenesis of the linxi granitoids northern inner mongolia of china constraints on basaltic underplating five representative granitoid plutons in the linxi area northern inner mongolia of china divided into two suites are mainly granodiorite and syenogranite and correspond to i and a type granites respectively zircon u pb dating yields an age of 230 ma but most ages range from 149 ma to 111 ma for intrusion of the five plutons suite 1 granitoids show lower sio2 66 1 72 51 and k2o higher al2o3 cao mgo feo and tio2 higher sr ba and eu and lower sm gd nb y and yb than suite 2 granitoids 71 73 78 14 sio2 modeling of major and trace elements shows that fractional crystallization of hornblende and lesser amounts of feldspars for suite 1 and plagioclase and alkali feldspar for suite 2 with overprint of magmatic hydrothermal fluids can explain the geochemical variations the linxi granitoids have initial end t values varying between 5 60 and 2 89 and initial 87 sr 86 sr t ratios ranging from 0 701764 to 0 707654 geochronology of inherited zircons coupled with the nd sr isotopic comparison between granitoids late jurassic basalts and proterozoic gneisses indicates that the linxi granitoids derive from a mixed source of dominantly underplated material or mafic magma with various amounts of the proterozoic gneiss basaltic underplating provides both material and heat to produce the late jurassic to early cretaceous granitoids variation of end t and 87 sr 86 sr t with age suggests involvement in the melting of increasingly greater amounts of the old lower crustal rock our refined equation yields less scattered nd isotope depleted mantle model ages the least fractionated granitoids from each suite have low ca sr rb sr rb ba and k ba ratios and hence represent parental magmas suite 1 parent magma is produced by dehydration melting or derives principally from the fluid metasomatized mantle melting of the underplated tholeiites and their differentiated products generates suite 2 parent magma d 2005 elsevier b v all rights reserved

fingerprinting feldspar phenocrysts using crystal isotopic composition stratigraphy implications for crystal transfer and magma mingling in s type granites microsampling of cm scale feldspar crystals within an s type granite from the lachlan fold belt of southeastern australia has revealed complex internal sr and nd isotopic variations the observed isotopic zonations are in part interpreted as recording feldspar crystallisation in a dynamically mixing magma system the isotopic composition of which was varying in response to the influx of more mafic and isotopically more mantle like magmas the latter stages of which are now represented in modified form by microgranular enclaves similar core to rim isotopic variations in feldspar megacrysts from a microgranular enclave and the adjacent host granite strongly suggest megacrysts in the enclave were transferred from the granitic magma during crystallisation feldspar rims have higher 87sr 86sri and lower nd i than adjacent whole rock analyses but match those of mineral separates from the surrounding enclave matrix this suggests that the final stages of megacryst growth occurred in the presence of a component that had previously interacted with a high 87sr 86sr low nd i component such as metasedimentary wall rocks isotopic heterogeneities are also presererved within different mineral phases in the enclave matrix suggesting that differing phases grew at differing stages of equilibration between the enclave magma and its host granitic magma our results reveal major isotopic heterogeneities on a single crystal and also inter mineral scale in a pluton which shows well constrained evidence for magma mingling these results indicate the suitability of feldspars as recorders of isotopic change in magmatic systems even those which have cooled slowly in the plutonic environment and suggest that much heterogeneity in plutonic systems may be overlooked on a whole rock scale

genetic significance of multiple enclave types in a peraluminous ignimbrite suite lachlan fold belt australia the violet town volcanics lachlan fold belt australia are an s type ignimbrite suite containing microgranitoid enclaves basaltic andesite enclaves and enclaves of high silica rhyolite the microgranitoid enclaves are similar to those in peraluminous granites they typically have lower initial sr sr and higher e i than the host and represent globules of a mafic mantle derived magma ivhich was hybridized by mixing and diffusional exchange with the host magma the basaltic andesite enclaves were incorporated into the ignimbrite as xenoliths but their parental magma may have been similar to that of the microgranitoid enclaves they are isotopically less depleted than other mantle derived rocks from the lachlan fold belt reflecting contamination by crustal material or derivation from less depleted mantle sources the high silica rhyolite enclaves previously interpreted to be related to the ignimbrite by crystal fractionation have ejw values up to 3 units higher than their host and cannot be related to their host by crystal fractionation or assimilation fractional crystallization afc processes the coexistence of s type magmas and mantle derived magmas suggests that the latter may have played a role in the palaeozoic magmatism of the lachlan fold belt acting as a heat source for melting and perhaps also contributing chemical components to the crustally derived magmas

three step continental crust growth from subduction accretion and underplating through intermediary differentiation to granitoid production sensitive high resolution ion microprobe shrimp u pb dating laser ablation multi collector icpms hf isotope and electron microprobe element analyses of inherited antecrystal and magmatic zircons from five granitoid intrusions of linxi area in the southern segment of the great xing an range of china were integrated to solve continental crustal growth mechanisms these intrusions were divided into two suites suites 1 and 2 are mainly granodiorite and syenogranite and correspond to magnesian and ferroan granites respectively shrimp dating establishes an early cretaceous 135 125 ma age for most linxi granitoids and a time of 146 ma when their source rocks were generated or re melted however some granitoids were generated in early triassic 241 ma and late jurassic 146 ma after their source rock experienced precursory melting episodes at 263 ma and 165 ma respectively all zircon 206pb 238u ages 300 ma n 100 and high positive zircon ehf t values n 175 suggest juvenile source materials with an absence of precambrian basement hf nd isotopic decoupling of linxi granitoids suggests a source component of pelagic sediments i e paleozoic subduction accretion complexes zircon ehf t values t 263 165 ma form a trend sub parallel to the depleted mantle hf isotope evolution curve whilst those with t 146 125 ma fall markedly below the latter the first trend indicates a provenance from essentially subducted oceanic slabs however the abrupt ehf t decrease together with extensive early cretaceous magmatism is interpreted as reflecting mantle upwelling and resultant underplating and exhumation of subducted oceanic slabs suite 1 granitoids derive mainly from subducted oceanic slabs or paleozoic subduction accretion complex whereas suite 2 from underplated mafic rock and subordinately paleozoic subduction accretion complex compositions of suites 1 and 2 depend on the hydrous oxidized or relatively anhydrous reduced nature of source rocks among each of these five intrusions magmatic zircons have systematically lower 176hf 177hf than inherited antecrystal zircons hf isotopic and substituting element profiles through inherited antecrystal zircons t 263 to 146 ma indicate repeated low melt fraction melting in the source region in contrast profiles through inherited antecrystal and magmatic zircons t 146 125 ma reveal melting region expansion with a widening range of source compositions and increasing melt fractions these results lead to the conclusion that continental growth in this region involved a three step process this included subduction accretion and repeated underplating intermediary differentiation of juvenile rocks and granitoid production from these differentiated rocks

mineralogy geochemistry and sr nd isotopes of the cretaceous leucogranite from karamadazi kayseri central turkey implications for their sources and geological setting the leucogranite is the major constituent of the bimodal late cretaceous karamadazi granitoid developed in relation with evolution of the inner tauride ocean along the northern margin of the taurides in central turkey new analyses of minerals major and trace elements including rare earth elements ree and of sr and nd isotopes are performed to determine the origin and geochemical characteristics of the leucogranites medium coarse grained leucogranite contains normally zoned plagioclase an12 20 mildly alkaline biotite and xenocrystic magneziohornblende actinolite and ferrohornblende it is characterized by concave up ree patterns with respect to middle heavy ree field relations mineral chemistry geochemical data and isotopic data suggest that the leucogranite could have originated from an amphibole bearing igneous source in lower to middle crust by low rate partial melting 40 under low pressure and low h2o activity conditions possibly coupled by mixing mingling with mafic magma and high level feldspar and minor biotite fractionation in contrast the quartz diorite and mafic microgranular enclave mme are probably developed from an enriched mantle with possible mingling mixing mme quartz diorite and leucogranite may represent a magmatic suite which formed in an extensional tectonic regime by bimodal magmatic activity probably because of lithospheric delamination or slab break off or after the alpine thicken within the gondwanan tauride anatolide platform initial sr data exhibit an age of 65 13 ma for the leucogranite but it does not indicate a true intrusion age of the magma due to isotopic modification of the magma

magma mixing in the genesis of hercynian calc alkaline granitoids an integrated petrographic and geochemical study of the sazava intrusion central bohemian pluton czech republic the devonian early carboniferous 354 1 3 5 ma conventional zircon u pb age sazava intrusion biotite amphibole quartz diorite tonalite and granodiorite of the central bohemian pluton cbp associated with bodies of olivine pyroxene amphibole gabbro gabbrodiorite quartz diorite and rare hornblendite gives an opportunity for a comparative study of a rather shallow calc alkaline magma mixing zone at two levels separated by a vertical difference of approximately 1 km the deeper section p ibram displays the direct evidence for the existence of a long lived periodically tapped and replenished floored magma chamber masli the contacts between the subhorizontal sheet like basic bodies and the surrounding commonly cumulus rich sazava granitoid are arcuate and cut by a series of veins and ascending pipes shallow dipping swarms of strongly elongated and flow aligned mafic microgranular enclaves mme concordant with the contacts of the basic bodies are commonplace the higher level teletin section shows relatively independent basic intrusions some of them distinctly hybrid in character and mainly of quartz dioritic composition surrounded by relatively homogeneous nearly cumulus free sazava tonalite rich in texturally variable mme larger quartz microdiorite bodies and the mme both interpreted as hybrids contain varying proportions of highly heterogeneous plagioclase megacrysts with complex zoning particularly well shown by cathodoluminescence cl most often the megacrysts have cores of labradorite anorthite partly resorbed and overgrown by andesine rims but some are strongly brecciated and fragments have been annealed by rim growth also characteristic are long prisms of apatite oikocrysts of quartz and k feldspar and zoned amphibole the latter has brown pargasite and magnesiohastingsite cores resorbed and overgrown by magnesiohornblende compositionally similar to the amphibole in the sazava tonalite the brown cores are probably relics of a higher p t stage with temperature exceeding 900 c plots of major element analyses of the teletin quartz microdiorite and the mme fall close to the line joining the compositions of the evolved sazava granodiorite tonalite and the associated gabbros the estimated minimal proportions of the acidic end member range from ca 15 to 20 for the quartz microdiorite and ca 40 to 60 for the enclaves field relationships macroscopic and mineralogical features and whole rock geochemistry are consistent with a hybrid origin of the quartz microdiorite masses and enclaves unzoned calcic plagioclase cores are interpreted as having crystallized from a basic magma prior to its injection into a high level acidic magma chamber the sudden decrease in ca activity and introduction of water due to magma mixing with tonalitic melt led to their resorption and brecciation quartz ocelli that are abundant locally in some basic bodies are most likely xenocrysts introduced from the felsic magma in the basic melt they were resorbed and became a substrate for heterogeneous nucleation of the amphibole or pyroxene coronas strong undercooling of the basic magma resulted in the growth of long prismatic apatite together with dendritic boxy cellular plagioclase both types of plagioclase cores were subsequently overgrown by more sodic mantles at the same time small unzoned plagioclase crystals nucleated in the groundmass following thermal re adjustment crystallization of the hybrid magma ended with considerably slower growth of quartz and k feldspar oikocrysts

petrogenesis and metallogenic potential of the wulanba granite southern great xing an range ne china constraints from whole rock and apatite geochemistry the wulanba granite consisting of biotite monzogranite and syenogranite is located in the southern part of the great xing an range ne china whole rock major and trace element geochemistry suggests the wulanba granite is a high k shoshonitic slightly peraluminous and highly differentiated i type granite the sr nd hf isotopes indicate that it originated from partial melting of juvenile crust derived from the depleted mantle with a minor input of old crust the relatively young t 2dm and t dm2 ages indicate it was most likely derived from a late neoproterozoic to early palaeozoic source we have demonstrated that the biotite monzogranite is the ore related intrusion of the haobugao zn fe mineralization based on the following geological geochronological and geochemical evidence 1 the chalcopyrite pyrite in the biotite monzogranite and the continuous mineralization of drill core zk2508 2 the consistence of the emplacement age of the biotite monzogranite 141 140 138 ma with the skarn mineralization age 142 ma and 3 the presence of rich ore forming elements fe zn cu in the biotite monzogranite and the similar pb compositions of the sulfides from the haobugao deposit and the biotite monzogranite compared to the barren syenogranite the fertile biotite monzogranite is more oxidized while the edges of the apatite grains in the biotite monzogranite are more oxidized than the centres the average f cl ratio of the fertile biotite monzogranite 123 45 is much higher than that of the barren syenogranite 73 98 we conclude that these differences reflect unique geochemical signatures and the geochemical composition of the apatite can be used to infer the economic potential of granites

petrogenesis of the middle triassic erenhot granitoid batholith in central inner mongolia northern china with tectonic implication for the triassic mo mineralization in the eastern central asian orogenic belt abstract voluminous post orogenic magmatism holds a key to monitoring important geodynamic processes and crustal evolution within an extensional accretionary orogen the middle triassic erenhot granitoid batholith from central inner mongolia northern china is tectonically located in the eastern central asian orogenic belt this batholith consists of monzogranite syenogranite alkali feldspar granite and albite granite with minor mafic to felsic enclaves and dykes the formation of this composite batholith involved distinct mafic and felsic magma end members concomitant episodic mafic felsic interaction and intra felsic magma evolution mafic diabasic and high mg intermediate dioritic dykes show enrichment in large ion lithophile elements depletion in high field strength elements and heterogeneous isotopic compositions indicative of a metasomatized lithospheric mantle source inherited from prior oceanic slab subduction the monzogranites and aplites have arc like elemental features and variable isotopic compositions isr t 0 706132 end t 0 4 zircon ehf t 2 8 to 7 4 zircon 18o 5 32 to 6 74 clearly suggesting that the felsic magma end member of a dual heritage was derived from dominant newly underplated mafic crust and subordinate ancient lower crust hybridization processes between mantle derived mafic magma and crust derived felsic magma result in the formation of monzonitic enclaves isr t 0 704850 end t 0 1 with an isotopic resemblance to the host granites fractional crystallization of the monzogranitic magmas endows the differentiated syenogranites and alkali feldspar granites with highly evolved elemental characteristics we further deduce that the magmatic immiscibility between k rich and na rich residual melts in a deep reservoir produces albite granites with distinct deformation imprints variable k2o contents and wide range of crystallization temperatures combining with coeval regional igneous episodes as well as concomitant sedimentary and structural events in the northern china mongolia tract the triassic erenhot composite batholith can be considered as post orogenic magmatic products possibly within a coupled geodynamic scenario between lithospheric dripping and concurrent gravitational collapse therefore the documentation of this large scale triassic post orogenic magmatism could not only lead to the characterization of the eventual closure of the paleo asian ocean but also capture a snapshot into the tectonic background for the widespread porphyry type mo mineralization in the eastern central asian orogenic belt during early mesozoic

crust mantle interaction and craton destruction evidence from late mesozoic plutons in the north china craton late mesozoic granitoids widely distributed in the yanshan belt of the north china craton ncc are important markers of cratonic destruction and lithospheric thinning we report new petrological geochemical zircon u pb and lu hf isotopic data on two late mesozoic granitic plutons from the central ncc near the trans north china orogen we report zircon u pb emplacement ages of 162 156 ma and 132 ma from the siganding and fangshan plutons respectively indicating late jurassic early cretaceous magmatism the presence of a dusty zone and discontinuous zoning in plagioclase phenocrysts and the occurrence of mafic microgranular enclaves in both granitoid plutons suggest mingling and mixing of felsic and basic magmas the rocks investigated in this study show high na 2 o k 2 o and high mg mg mg fe mg and are metaluminous with enrichment in light rare earth elements and large ion lithophile elements rb ba u and sr and depletion in high strength field elements th u nb ta p and ti they also display negative ehf t values and high sr y ratios comparable with adakitic rocks suggesting that the felsic magmas of these intrusions were probably derived from the partial melting of the palaeoproterozoic two stage zircon hf depleted model ages between 2 5 and 1 9 ga thickened lower crust of the ncc whereas the mafic magma was probably derived from subcontinental lithospheric mantle we correlate the magmatism with lithospheric thinning beneath the ncc and associated crust mantle interaction it is inferred that lithospheric thinning was of limited extent in late jurassic 162 156 ma times the magma flare up at around 130 ma was produced by large scale melting of the enriched subcontinental lithospheric mantle with development of extensive intracontinental adakitic magmatic rocks derived from thickened ancient lower continental crust with variable involvement of subcontinental lithospheric mantle supplementary material mineral assemblages and abundance representative electron microprobe analyses la icp ms zircon u pb age data and la mc icp ms lu hf isotopic data are available at https doi org 10 6084 m9 figshare c 3815308

chaotic dynamics and fractals in magmatic interaction processes a different approach to the interpretation of mafic microgranular enclaves abstract fractals have been used for describing a wide range of natural processes however applications of fractal geometry to the study of magma mingling mixing processes is almost completely lacking in spite of the fact that such an approach could give new insights into the nature of magmatic interactions fractal analyses of two geochemically linked groups of mafic microgranular enclaves mme from the sithonia plutonic complex northern greece have been performed because of the difficulties involved in using contours of enclaves to estimate their fractal dimensions a different approach is used in this paper fractal dimension is estimated using distribution maps of chemical elements inside enclaves the results obtained indicate that a clear correlation between fractal dimensions of enclaves and geochemical evidences of interaction exists and hence the two groups of enclaves reflect different degrees of interaction from a dynamical point of view stretching and folding processes between two magmas with different rheologies are considered representative of magmatic interaction this dynamic system can easily generate chaotic patterns recognized by the presence of fractal structures the contemporaneous occurrence of well mixed regions together with poorly mixed regions in the same system is thought to be similar to the host enclave system found in many granitoid plutons in particular mme are believed to represent islands of partially mixed mafic fluid subjected to different degrees of interaction with the host granitoid whereas host rocks are believed to represent mixed regions where the mixing process acted more efficiently producing almost completely hybrids it is shown that fractal geometry and chaotic dynamics can be considered suitable techniques in studying complex petrological phenomena and they can represent helpful methods in the development of petrogenetic models

the significance of mafic microgranular enclaves in the petrogenesis of the dehno complex sanandaj sirjan belt iran abstract quartz monzodioritic and granodioritic enclaves occur in the upper cretaceous paleocene dehno complex nw of isfahan iran they are hosted by hornblende granodiorite and granodiorite monzogranite respectively the presence of xenocrystic plagioclase biotite quartz magnesio hornblende occasionally with relics of clinopyroxene in quartz monzodiorites minor k feldspar and the lack of peraluminous minerals dominate the mineralogy of these rocks and suggest a metaluminous source the plagioclase in the quartz monzodioritic enclaves has higher an content than that of the respective plagioclase of their host hornblende granodiorite indicating crystallization from more mafic magma the quartz monzodioritic enclaves generally contain higher values of fe 2 o 3 mgo cao mno na 2 o transition elements ni cr co v ree and lower values of sio 2 k 2 o p 2 o 5 and zr than their host which are in consistent with occurrence of abundant ferromagnesian minerals in these rocks compare to their host the granodioritic enclaves have higher amount of fe 2 o 3 mgo mno tio 2 p 2 o 5 rb zr y ni cr co and lower concentration of sio 2 k 2 o and ba aside from hornblende granodiorite and granodiorite monzogranite the dehno complex comprises leucogranodiorite and tourmaline leuco granites geochemically the rocks of the complex are metaluminous to strongly peraluminous and are enriched in lile e g rb k sr ba and depleted in hfse e g nb ta p ti zr hf with medium to high k calc alkaline nature these geochemical features are proposed for the volcanic arc granites emplaced in an active continental margin whole rock and quartz 18 o values for all rocks are high 9 7 14 4 and 10 1 14 9 respectively suggesting the interaction of magma with crustal derived components the strongly peraluminous composition can be interpreted in terms of this hypothesis all these mineralogical and geochemical features support the idea that the granitoid rocks of the dehno complex developed through variable degrees of mixing mingling between a basic magma and a supracrustal melt during subduction of the neotethys oceanic crust beneath central iranian microcontenent the quartz monzodioritic enclaves most likely represent the nearest composition to the original more mafic magma the granodioritic enclaves result from the mixing mingling of globules basic magma with host granitic magma

geochemical and sr nd pb isotopic compositions of the eocene dolek and saricicek plutons eastern turkey implications for magma interaction in the genesis of high k calc alkaline granitoids in a post collision extensional setting abstract the major and trace elements and sr nd pb isotopes of the host rocks and the mafic microgranular enclaves mme gathered from the dolek and saricicek plutons eastern turkey were studied to understand the underlying petrogenesis and geodynamic setting the plutons were emplaced at 43 ma at shallow depths 5 to 9 km as estimated from al in hornblende geobarometry the host rocks consist of a variety of rock types ranging from diorite to granite sio 2 56 98 72 67 wt mg 36 8 50 0 populated by mmes of gabbroic diorite to monzodiorite in composition sio 2 53 21 60 94 wt mg 44 4 53 5 all the rocks show a high k calc alkaline differentiation trend chondrite normalized ree patterns are moderately fractionated and relatively flat la yb n 5 11 to 8 51 they display small negative eu anomalies eu eu 0 62 to 0 88 with enrichment of lile and depletion of hfse initial nd sr isotopic compositions for the host rocks are e nd 43 ma 0 6 to 0 8 and mostly i sr 0 70482 0 70548 the nd model ages t dm vary from 0 84 to 0 99 ga the pb isotopic ratios are 206 pb 204 pb 18 60 18 65 207 pb 204 pb 15 61 15 66 and 208 pb 204 pb 38 69 38 85 compared with the host rocks the mmes are relatively homogeneous in isotopic composition with i sr ranging from 0 70485 to 0 70517 e nd 43 ma 0 1 to 0 8 and with pb isotopic ratios of 206 pb 204 pb 18 58 18 64 207 pb 204 pb 15 60 15 66 and 208 pb 204 pb 38 64 38 77 the mmes have t dm ranging from 0 86 to 1 36 ga the geochemical and isotopic similarities between the mmes and their host rocks indicate that the enclaves are of mixed origin and are most probably formed by the interaction between the lower crust and mantle derived magmas all the geochemical data in conjunction with the geodynamic evidence suggest that a basic magma derived from an enriched subcontinental lithospheric mantle probably triggered by the upwelling of the asthenophere and interacted with a crustal melt that originated from the dehydration melting of the mafic lower crust at deep crustal levels modeling based on the sr nd isotope data indicates that 77 83 of the subcontinental lithospheric mantle involved in the genesis consequently the interaction process played an important role in the genesis of the hybrid granitoid bodies which subsequently underwent a fractional crystallization process along with minor amounts of crustal assimilation en route to the upper crustal levels generating a wide variety of rock types ranging from diorite to granite in an extensional regime

geochronology and geochemistry constraints of the early cretaceous taibudai porphyry cu deposit northeast china and its tectonic significance abstract the southern great xing an range sgxr located in the southeastern part of inner mongolia china shows intense mesozoic tectono magmatic activity and hosts economically important polymetallic cu pb zn sn fe ag au mo mineralization here we present new zircon u pb ages whole rock geochemical data nd sr hf isotopic data and re os ages for the taibudai deposit in the sgxr the taibudai granitoids show high sio2 70 62 72 13 wt and alkali na2o k2o 7 04 8 60 wt concentrations low mgo 0 89 1 37 wt and al2o3 14 wt asi ratios

petrology of the late carboniferous punta falcone gabbroic complex nothern sardinia italy the punta falcone gabbroic complex represents an evolved high alumina basalt which rose from the mantle through the lower crust and subsequently intruded a granite magma in middle crustal levels during the calc alkaline magmatic activity which took place in the sardinian and corsican islands in the carboniferous the gabbroic complex has a stratified sub vertical structure and consists of three zones developing from the bottom to the top of the magma chamber an interaction zone can be recognized along contacts with the surrounding granite stock and it is characterized by finer grained and more evolved rocks than the interior of the gabbroic complex processes occurring in its interior zone have been substantially different from those occurring in its marginal interaction zone petrographical and geochemical features indicate that the differentiation of the interior of the gabbroic complex can be accounted for by low pressure closed system in situ crystallization the different gabbroic units represent mixtures between cumulus phases and trapped liquid plagioclase pyroxenes and successively plagioclase calcic amphibole oxides nucleated and grew in situ on the floor and walls of the chamber floating of plagioclase towards the top of the magma chamber resulted in the accumulation of the denser liquid at the bottom compaction phenomena and convective fractionation processes permitted the development of the pile of cumulus crystals with their trapped liquid and the migration of part of this evolved liquid towards the top of the magma chamber on the basis of major and trace element modelling a mathematical artifice has been developed to evaluate cumulus intercumulus processes that occurred in the interior of the gabbroic complex accordingly the formation of the different units can be modelled by mixtures between the parental magma and different percentages of minerals formed during the first stages of crystallization contemporaneously with the differentiation of the interior zone the envelope of fine grained rocks enclosing and grading into the coarser inner part of the gabbroic complex experienced both chemical and physical processes chemical processes resulted in the evolution of the marginal interaction zone by crystal fractionation plus contamination by the acid magma physical processes were closely related to the thermodynamic instability of this marginal zone and consisted of mingling and back veining phenomena which developed interdigitations of granite veins along contacts in addition an increase of the melt fraction of the granite magma superheated by the latent heat of crystallization of the mafic magma caused the occurrence of tilting of the mafic magma chamber and resulted in the development of the sub vertical structure of the gabbroic complex

melt extraction and accumulation from partially molten rocks current models for melt segregation and ascent are not adequate to accurately describe transport and accumulation in combination we propose that transport is discontinuous and in batches and that accumulation occurs by stepwise merging of batches a simple numerical model of jostling spheres that merge when they touch was used to represent stepwise accumulation and transport of batches by propagation of hydrofractures results of the numerical model indicate that such a system may quickly develop into a self organised critical soc state in this state the distribution of melt batch volumes can be described by a power law with an exponent m that lies between 2 3 and 1 once a self organised critical state is established the system is capable of discharging any additional melt without further change to itself deformation aids melt extraction efficiency as it increases the mobility of hydrofractures enhances accumulation and hence lowers the exponent m full connectivity of melt needs never to be reached in the system and melt transport and extraction can occur at very low melt fractions the chemical evolution of melt from source to emplacement level will be governed by the discontinuous mixing and mingling of batches each with different histories and possibly different sources if no subsequent homogenisation occurs in a magma chamber or the final emplacement structure the process can be identified by chemical heterogeneity of plutons and volcanic rocks

geochemical modeling of acid basic magma interaction in the sardinia corsica batholith the case study of sarrabus southeastern sardinia italy abstract the hercynian intrusive rocks outcropping in the sarrabus area southeastern sardinia italy consist of microgranular mafic enclave mme bearing granites 95 associated with coeval stratified gabbroic complexes and basic septa bs

chaotic three dimensional distribution of ba rb and sr in feldspar megacrysts grown in an open magmatic system as has been demonstrated in recent years the heterogeneities of coeval magmas can be more successfully revealed by zoned megacrysts rather than by analysis of the whole rocks hosting them here the geochemical heterogeneities of feldspar megacrysts from the karkonosze granite poland are investigated by la icp ms the crystals are the product of migration and growth in regions of poorly mixed magmas 3d modeling of the ba sr and rb distributions emphasizes the importance of micro domain growth morphologies two models of element behavior a relative concentration model and a composition gradient model provide a potentially effective tool for tracking the mixing process on a microscale measured concentrations of elements of different mobilities do not agree with what might be expected from the mixing of two end member magmas if mixing was the only process occurring linear correlations between the concentrations of any two elements should be observed this however is not the case for combinations of any two of the three elements modeling reveals differing non linear correlations between concentrations the megacryst heterogeneities provide an insight into how mixing magmas are chaotically advected to growing crystals and the degree of inter magma element exchange between the magmas

field evidence of magma mixing from microgranular enclaves hosted in palaeoproterozoic malanjkhand granitoids central india abstract the malanjkhand granitoids mg pluton about 1500 sq km occurs in the balaghat district of madhya pradesh the mg 2400 ma represent an episode of palaeoproterozoic felsic magmatism in central india and hosts potential cu mo au deposits the enclaves hosted in mg can be broadly classified into two categories microgranular enclaves dark coloured fine grained magmatic and xenoliths of country rocks the microgranular enclaves me may be rounded ellipsoidal discoid elongated lenticular or tabular and their size commonly reaches up to 2 metres across the me have sharp and in places diffuse contacts with their host granitoids the shape and size of me indicate contemporaneous flow and mingling of partly crystalline felsic mafic magmas some me exhibit dark crenulated margins giving them a pillow like form that has been attributed to undercooling of a me magma as globules intruded into a granitoid magma the presence of corroded felsic and mafic minerals xenocrysts in me is interpreted as the result of mechanical transfer during the mafic felsic magma interaction and mixing event mafic minerals biotite rim the quartz xenocrysts giving rise to ocellar texture which exhibit signatures of resorption under hybrid enclave magma conditions all these features suggest an origin for the calc alkaline intermediate granitoid magma in malanjkhand involving a magma mixing process

geochronology fluid inclusions and isotopic characteristics of the chaganbulagen pb zn ag deposit inner mongolia china abstract the large chaganbulagen pb zn ag deposit is located in the derbugan metallogenic belt of the northern great xing an range the vein style orebodies of the deposit occur in the nww trending fault zones the ore forming process at the deposit can be divided into three stages an early quartz pyrite arsenopyrite pyrrhotite sphalerite galena chalcopyrite stage a middle quartz carbonate pyrite sphalerite galena silver bearing minerals stage and a late quartz carbonate pyrite stage the sericite sample yielded a 40 ar 39 ar plateau age of 138 1 ma and an isochron age of 137 3 ma and the zircon la icp ms u pb age of monzogranite porphyry was 143 2 ma indicating that the ages of mineralization and monzogranite porphyry in the chaganbulagen deposit should be the early cretaceous and that the mineralization should be slightly later than the intrusion of monzogranite porphyry there are only liquid inclusions in quartz veins of the chaganbulagen deposit homogenization temperatures densities and salinities of the fluid inclusions from the early stage are 261 340 c 0 65 0 81 g cm 3 and 0 7 6 3 wt nacl eqv respectively fluid inclusions of the middle stage have homogenization temperatures densities and salinities of 209 265 c 0 75 0 86 g cm 3 and 0 5 5 7 wt nacl eqv respectively for fluid inclusions of the late stage their homogenization temperatures densities and salinities are 173 219 c 0 85 0 91 g cm 3 and 0 4 2 7 wt nacl eqv respectively the ore forming fluids of the deposit are generally characterized by moderate temperature and low salinity and density and belong to an h 2 o nacl co 2 ch 4 system the 18 o water values calculated for ore bearing quartz vary from 17 9 to 10 8 and the d v smow values from bulk extraction of fluid inclusion waters vary from 166 to 127 suggesting that the ore forming fluids consist dominantly of meteoric water the 34 s v cdt values range from 1 4 to 4 1 the 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb values of the ore minerals are in the ranges of 18 302 19 037 15 473 15 593 and 38 110 38 945 respectively the data for the s and pb isotopic systems indicate that the ore forming metals and sulfur came from mesozoic magma the chaganbulagen deposit is a low sulfidation epithermal pb zn ag deposit and the temperature decrease is the dominant mechanism for the deposition of ore forming materials

magma interaction processes in syn extensional granitoids the tertiary menderes metamorphic core complex western turkey abstract western turkey which forms the eastern part of the aegean region was subjected to continental extension that led to formation of metamorphic core complexes and associated syn extensional granitoids this study deals with petrogenesis of the syn extensional early miocene alacamdag ag and middle miocene salihli sg granitoids and associated mafic microgranular enclaves mme in order to better understand the time progressive evolution of the mantle sources beneath the extended continental crust in western turkey ag and sg granitoids consist of undeformed and ductility deformed granitoids together with abundant mmes they are calc alkaline to high k calc alkaline rocks that are metaluminous to slightly peraluminous mg of ag host rocks is slightly lower than that of sg host rocks ag host rocks have higher na 2 o ba rb rb la and lower al 2 o 3 cao mgo tio 2 zr y values than those of the sg host rocks ag and sg host rocks differ from those of mmes with their lower al 2 o 3 cao mgo fe 2 o 3 tio 2 sr v mg and higher sio 2 values mmes are intermediate corresponding to monzonite monzodiorite in ag and diorite in sg compositions and are more mafic with respect to their host rocks in the primitive mantle pm normalized trace element patterns host rock and mme samples have similar trace element patterns all of these rocks are enriched in large ion lithophile elements liles cs rb ba th k and sr and strongly depleted high field strength elements hfses ta nb p ti compared to the primitive mantle the isotope ratios of the syn extensional ag and sg rocks display increasing radiogenic strontium and decreasing radiogenic neodymium isotopic values for the ag and sg host rocks and mme samples are 87 sr 86 sr ag host 0 708835 0 710206 and e nd t ag host 5 36 to 7 36 87 sr 86 sr ag mme 0 709107 0 709801 and e nd t ag mme 5 36 to 7 36 87 sr 86 sr ag mme 0 709107 0 709801 and e nd t ag mme 5 55 to 6 51 87 sr 86 sr sg host 0 712200 0 712408 and e nd t sg host 8 03 to 8 61 87 sr 86 sr sg mme 0 712028 0 712351 and e nd t sg mme 7 57 to 8 48 syn extensional granitoids in western turkey were mainly affected by crustal contamination fractional crystallization and magma mixing mingling mm processes magma mixing mingling partial mixing appear to have larger affects on the compositional range of the magmas than those generated by partial melting crustal contamination and fractional crystallization mafic and felsic magmas forming syn extensional granitoids have also undergone metasomatism chemical equilibrium and diffusional exchange processes during cooling syn extensional granitoids have been derived from a hybrid magma that originated from mixing of coeval lower crustal derived felsic magma and lithospheric mantle derived mafic magmas during extensional processes

age origin and cooling history of the coronel joao sa pluton bahia brazil received april 2 2002 accepted august 8 2004advance access publication october 22 2004in north east brazil archean and paleoproterozoic cratonic blocksare enclosed within a network of brasiliano age 0 7 0 55ga metasedimentary foldbelts the unfoliated coronel joa o sa grano diorite pluton which contains magmatic epidote and stronglyresorbed clinopyroxene intrudes the sergipano foldbelt zirconsyield a concordant u pb crystallization age of 625 2ma titanite ages are approximately 621ma discordant zircons suggestinheritance from at least two magma sources of ages 2 2ga model calculations based on diffusion parameters andrb sr isotope data from separated minerals indicate that the plutoncooled ata rate of 36 c myr whole rock element compositionsandinitialsr ndisotopic compositionsthat areheterogeneous onalllength scales suggest magma mixing trace element concentrationsand nd isotope data argue against a contribution from a contem poraneous mantle derived magma values of magmatic e

temporal evolution of granitic magmas in the luanchuan metallogenic belt east qinling orogen central china implications for mo metallogenesis abstract the luanchuan metallogenic belt located within the eastern part of the qinling orogen central china hosts a number of world class mo deposits that are closely related to small late mesozoic granitic plutons zircon u pb dating of distinct plutons in the luanchuan metallogenic belt has yielded ages of 153 1 154 2 152 2 and 148 1 ma molybdenite re os isotopic compositions of yuku ore district in the southern part of luanchuan metallogenic belt has yielded an isochron age of 146 1 ma which is consistent with the large scale mineralization ages in the northern part of the luanchuan metallogenic belt a combination of previous studies and new geochronological and isotopic data show a concordant temporal and genetic link between granitic magmatism and mo mineralization in the luanchuan metallogenic belt suggesting that this mineralization episode formed the most extensive mo mineralization belt in the east qinling orogen zircon grains from mo related granitic plutons show similar trace element distributions high precision multi collector inductively coupled plasma mass spectrometry mc icp ms pb isotope analysis of k feldspar megacrysts from mineralization related granites suggest that they were derived from the lower crust similarly the pb isotopic compositions of pyrite coprecipitated with molybdenite also suggest that the metals were derived form the lower crust with probably minor mantle contribution a continuum mineralization model that describes the sourcing of mo from an evolving granitic magma over successive differentiation events possibly in separate but connected magma chambers could explain the remarkable mo enrichment in the luanchuan metallogenic belt the volatile and mo bearing granitic magmas ascended as diapirs from the deep crust and were emplaced as dikes in the upper crust lithological differences between these mo bearing granites may relate to different stages in the evolution of individual magmas finally ore forming fluids were exsolved from the granitic melts in shallow crustal magma chambers resulting in the formation of the mo deposits of the luanchuan metallogenic belt this model may account for the widespread late mesozoic mo deposits of eastern china

zircon u pb geochronology geochemistry and sr nd hf isotopes of granitoids in the yulekenhalasu copper ore district northern junggar china petrogenesis and tectonic implications abstract the yulekenhalasu porphyry copper deposit is located in the kalaxiange er metallogenic belt in northern junggar china we present the results from zircon u pb geochronology and geochemical and sr nd hf isotope analyses of the granitoids associated with the ore deposits with a view to constrain their petrogenesis and tectonic setting the granitoids consist of quartz diorite diorite porphyry porphyritic monzonite and quartz porphyry emplaced at 382 379 375 374 and 348 ma respectively which span late devonian to early carboniferous ages the ore bearing intrusion is mainly diorite porphyry with subordinate porphyritic monzonite the late devonian intrusions are characterized by sio2 contents of 54 5 64 79 wt na2o contents of 3 82 8 24 wt enrichment in na light rare earth elements lrees and large ion lithophile elements they also display relative depletion in y ba p nb ta and ti and weak negative eu anomalies eu 0 6 0 87 the early carboniferous quartz porphyry is characterized by high sio2 content 72 26 73 35 wt enrichment in lrees k and sr and relative depletion in y 10 82 12 52 ppm and yb 1 06 1 15 ppm the late devonian and early carboniferous granitoids are characterized by positive end t values 5 2 10 1 one sample at 1 9 positive ehf t values 7 46 18 45 low 87sr 86sr i values 0 70363 0 70476 and young crustal residence ages these data indicate that the sources of the granitoids were mainly mantle derived juvenile rocks geochemical and nd sr hf isotopic data demonstrate that the late devonian granitoids formed in an oceanic island arc and they were formed from different sources among which the mineralized diorite porphyry might have originated from a mixed slab derived and mantle wedge melt source the early carboniferous quartz porphyry was likely emplaced in a mature island arc environment and was probably derived from juvenile crust

chaotic advection fractals and diffusion during mixing of magmas evidence from lava flows structures of magma mixing from three different lava flows have been analyzed and the degree of mingling has been quantified by measuring the contact perimeter between magmas and the fractal dimension of structures in each lava flow the values of these parameters suggest that the magma mixing structures were produced by chaotic dynamics induced by stretching and folding processes between the interacting magmas the mingling of magmas has been simulated using a chaotic dynamical system consisting of repeated stretching and folding processes the simulation shows the same patterns of variation of contact perimeter and fractal dimension as those observed in natural structures and indicates that magma interaction processes acted with different intensities in the three lava flows in response to different magmatic interaction regimes since physical dispersion of one magma inside another through stretching and folding processes and chemical exchanges are closely related we performed coupled numerical simulations of chaotic advection and chemical diffusion the results show a good agreement between the computed and natural structures in particular the occurrence in the same system of well and poorly mixed regions it is shown that magma interaction processes are able to generate magmatic masses having wide spatial heterogenity at many length scales this occurrence can account for the presence of magmatic enclaves inside host rocks showing a variable degree of hybridization in both plutonic and volcanic environments

interaction between felsic and mafic magmas in the salmas intrusive complex northwestern iran constraints from petrography and geochemistry abstract the salmas plutonic complex in the northernmost part of sanandaj sirjan zone of iran provides evidence for magma interaction processes the complex contains mafic intermediate hybrid and felsic rocks which intruded into the paleozoic metamorphic complex they show typical relationships described in many mafic felsic mingling and mixing zones worldwide such as mafic microgranular enclaves in felsic and hybrid rocks mafic sheets and hybrid rocks the mafic microgranular enclaves mmes are characterized by fine grained equigranular and hypidiomorphic texture and some special types of microscopic textures e g quartz xenocrysts oscillatory zoned plagioclase small lath shaped plagioclase in large plagioclase spike zones in plagioclase and spongy cellular plagioclase textures rounded plagioclase megacrysts blade shaped biotite acicular apatite the mafic sheets and mmes in granites mme gr which indicated magma mingling structures show isr values and end i similar to diorites the hybrid rocks and their mafic enclaves mme h show isotope signatures similar to each other granites have isotope signatures higher 87sr 86sr i 0 70788 0 71075 and lower end i 2 4 to 4 2 distinct to those of the all rock types and mmes major trace and ree modeling show that hybrid rocks are generated via 40 60 mixing of mafic dioritic and felsic granitic end members all the geochemical data suggest that underplating of dioritic magma which has been produced by fractional crystallization of gabbros under the lower crust caused its melting to make felsic granitic magma injection of dioritic magma into the base of the felsic magma chamber and a limited mixing of two end members the lower crust derived magma and mantle derived melts formed hybrid magma and their enclaves injections of new mafic magma pulses into hybrid magma generated mafic enclaves into them the injections of denser dioritic magma pulses into a felsic magma chamber and spreading of it at the level of rheological contrast have been formed mafic sheets and mmes in granites

crystallization of the shap granite evidence from zoned k feldspar megacrysts textural chemical and sr isotopic studies of feldspars from the subsolvus shap granite northern england demonstrate that a number of magma mixing events have dominated the evolution of this pluton k feldspar megacrysts are phenocrysts formed in the magma chamber they contain a number of ba rich zones that developed during periods of slight dissolution and regrowth linked to the hybridization of the granite by the intrusion of basic magmas diorite enclaves represent the relicts of these magmas and these also contain k feldspar megacrysts which show evidence of major dissolution they are xenocrysts picked up from the host granite and incorporated in the basic magma increasing h 2 o contents during fractional crystallization caused a late switch from growth of megacrysts to finer grained k feldspars in the matrix the chemically and isotopically zoned k feldspar megacrysts preserve an exceptional record of the evolution of the magma and the zones also had a significant influence on the development of exsolution microtextures during cooling