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In principle, potentially economic (fertile) granites can be distinguished from uneconomic (barren) granites based on the composition of their magmas. Ideally, this composition would be evaluated by analysing melt inclusions, but such inclusions are rarely preserved and difficult to analyse. Information on the composition of magmas can also be obtained from the composition of the minerals crystallising from these magmas, if the mineral-melt partition coefficients are known. In some cases, where these partition coefficients are not known, they have been calculated from lattice strain theory. Here we report arfvedsonite-melt partition coefficients for the rare earth elements (REE) calculated from the results of analyses of arfvedsonite, bulk rock and melt inclusions in granites and pegmatites in the Strange Lake peralkaline rare metal pluton. These coefficients were fitted to the lattice strain model from which values of the ideal partition coefficient (D 0), the ideal radius (r 0) and the elastic response (E M) were determined. The light REE were shown to partition preferentially into the M4 site and the heavy REE into the M2 site, requiring that partition coefficients be calculated for each site. The partition coefficients for both sites were shown to decrease systematically with increasing evolution of the magma, i.e., from the early hypersolvus granite to the late pegmatites. In the case of the M4 site, D 0 , r 0 and E M vary linearly with the Ca content of the arfvedsonite. By contrast, these parameters for the M2 site vary linearly with temperature. The two relationships form the basis of a predictive model, in which the arfvedsonite-melt REE partition coefficients for other peralkaline granites can be estimated, provided that the Ca content of the amphibole and its crystallisation temperature are known. This model was applied to a peralkaline granitic pegmatite from the Amis complex (Namibia) for which data on the composition of the amphibole and corresponding magma (melt inclusions) have been reported. The model successfully predicts the concentrations of the various REE in this magma, thereby providing confidence that it can be used to discriminate between granites that are potentially fertile and those that are barren in respect to the REE. • Arfvedsonite-melt REE partition coefficients are used to predict the evolving REE chemistry of the Strange Lake magma. • The arfvedsonite-melt REE partition coefficients are reliably fitted to a two-site amphibole lattice strain model. • The lattice strain parameters, r 0 , E M and D 0 , vary linearly with temperature (M2 site of arfvedsonite) and Ca (M4 site). • A model based on lattice strain theory is developed that predicts the REE distribution in peralkaline granitic magmas. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Ca-enriched silicates and carbonates in the endo and exocontact of granites. • Carbonate and calcsilicate minerals are very much responsive. • Physical-chemical regime of Ca-enriched mineral assemblages. • Marker mineral assemblages for crustal and subcrustal impact. • Ca-enriched silicates and carbonates and the geodynamic setting. Abstract Metacarbonate rocks (marble, calcsilicate rock, skarn) hosting strata- and structurebound Fe-, As-Sb, Bi-, Ni-Co, Cu-Pb-Zn, U-, W- ore minerals as well as talc, clay minerals, barite and fluorite are widespread in the country rocks south of the collisional calc-alkaline felsic to intermediate intrusive rocks of the Fichtelgebirge Pluton, Germany. At its western rim, thrustbound and vein-type mineral assemblages with Au-As-Sb and F-Ba minerals associated with carbonate gangue minerals developed. Only recently, a calcite-hosted Sb mineralization was encountered in a deep-seated lineamentary fault zone cutting through metaultrabasic rocks along the northern edge of the granites. The same structure zone forms the loci of calcite-bearing U episyenite situated within this pluton. A composite geological, mineralogical and chemical (major and trace elements, REE, C- and O isotopes) study has been conducted to distinguish the heat and element source in subcrustal or deep-seated crustal areas and in the largely exposed granite complex. Only Sn-W skarn deposits are genetically related to the highly fractionated granitic members of the Variscan pluton. Pegmatite skarn has a strong subcrustal component as to the heat source and the provenance of rare elements and a moderate crustal one as far as the silicates are concerned. Deep-seated fault zones were active over a rather long period of time and acted as conduits venting magmas and hydrothermal fluids from the waning stages of the Variscan deformation through the Neogene. Calcsilicate and carbonate mineral assemblages are an efficacious tool to constrain the physico-chemical regime in this mineral province, covering the temperature range from 745 °C down to 53 °C in a medium to low pressure regime at strongly varying redox conditions. The major and trace elements, the REE variation, the Ce and Eu anomalies as well as carbon and oxygen isotopes of the various mineral assemblages enable us to identify the fluid sources and depict the element concentration processes, e.g., mixing of fluids, connate fluid and meteoric fluid interaction. From the economic point of view, the mineralizing system is most prospective for rare element deposits, talc, kaolinite-group minerals, iron, and uranium. Accumulations of fluorite and barite are subeconomic in mineral assemblages inside as well as outside the granites, while base metals and precious metals are only of mineralogical interest. [ABSTRACT FROM AUTHOR]

In the Tavşanlı Zone, the Eocene magmatism led to NW-SE trending plutons located just south of the İzmir-Ankara-Erzincan Suture Zone in Turkey. The Middle Eocene-aged Günyüzü Intrusive Complex (Karacaören, Tekören, Dinek, Kadıncık) is one of these plutonic rocks and has metaluminous to peraluminous, medium-K calc-alkaline to shoshonitic and mainly I-type granite characteristics. The plutonic rocks consist of mainly granodiorite and granite, and their mafic microgranular enclaves are widespread in these rocks. Mineral assemblages in the host rocks and enclaves also are quite similar (quartz, plagioclase, K-feldspar, biotite, and hornblende), but the latter are more enriched in mafic minerals. The enclaves have disequilibrium textures such as oscillatory zoning and resorbed rims, indicating magma mixing/mingling. In the chondrite-normalized REEs patterns of the plutonic rocks are moderately fractionated and have small negative Eu anomalies. They are enriched in LILEs and LREEs relative to HFSEs, showing characteristics of subductionrelated granitoids. The enclaves also have similar geochemical characteristics, indicating equilibration between the mafic and felsic magmas. Whole-rock geochemical data show that the parental magmas in the Günyüzü area were produced by partial melting from mafic crustal rocks and also magma mixing/mingling from enriched lithospheric mantle. Slab break-off is the likely mechanism for the initiation of the postcollisional magmatism in the Tavşanlı Zone. [ABSTRACT FROM AUTHOR]

Abstract The Sukari granitoid pluton is situated in the southern central Eastern Desert of Egypt and is considered as one of the best examples of the gold–bearing granites in the Arabian Nubian Shield (ANS). It consists of coarse– to medium–grained alkali–feldspar granite, syenogranite and monzogranite intruded the volcano–sedimentary sequences and metagabbro–diorite complex. Geochemically, these granitoids are metaluminous to peraluminous in character. They are characterized by positive Rb, K, Zr and Pb and negative Ba, Sr, P, Nb and Ti anomalies and exhibit similar trace element patterns. Moreover, they show pronounced LREE–enriched patterns and negative Eu anomalies that indicate plagioclase fractionation. The studied rocks are typical of within plate granites generated in tensional environment. They belong to ferroan/A–type granites, particularly A 2 –type suggesting post-collisional setting. Their high SiO 2 , Al 2 O 3 and low MgO contents along with the low Ce/Pb ratios reflect derivation from melting crustal source. The major structures of the Sukari area encompass Akbar Wahid, Golden Boy, Buthinae and Kaolinitic Faults. The area is characterized by NNE-NE trending shear zone and WNW-EW stress orientation. The mineralized structures contain quartz veins trending mostly EW, NS and NNW; joints with NS, EW, NNE and NNW trends; faults with NNW, NNE, NS and EW trends; and breccia with NNW trend. The kinematic indicators are represented by mylonites, quartz fish and augen structures. Mineralization in Sukari area found as quartz veins, stockworks and brecciated veins. Highlights • Studied rocks comprise alkali–feldspar granite, syenogranite and monzogranite. • They classified as ferroan/A–type granites, particularly A 2 –type indicating post-collisional setting. • Geochemical characteristics suggest derivation from melting crustal source. • Kinematic indicators are mylonites, quartz fish and augen structures. • Mineralization occurs as quartz veins, stockworks and brecciated veins. [ABSTRACT FROM AUTHOR]

Granitic melt inclusions were found in layers of garnet clinopyroxenites from orogenic peridotites hosted in high-pressure felsic granulites of the Granulitgebirge, central Europe. The inclusions are both glassy and crystallized, and occur as clusters in the garnet. Microstructural features suggest that the inclusions formed while garnet was growing as a peritectic phase, likely alongside clinopyroxene. The chemistry of the melt, in particular its trace element signature, shows a crustal contribution, probably due to the involvement of phengite in the melt-producing reaction, most likely in the presence of a fluid. The presence of a granitoid melt in mantle rocks may be the result of localized melting of a phengite-bearing protolith either already present in the peridotites or, more likely, within the local deeply subducted crustal units. In the latter case, the melt would have infiltrated the peridotites and generated pyroxenite via metasomatism. In either case, the presence of granitoid inclusions in orogenic peridotite provides direct evidence for a genetic connection between a high-pressure crustal melt and garnet pyroxenites. The in situ characterization of these remnants of natural melt provides direct quantitative constraints on (one of) the agents responsible for the interaction between crust and mantle. [ABSTRACT FROM AUTHOR]

Anatectic magmas form plutons or accumulate in the core of anatectic domes. Both scenarios have distinct implications on the behaviour of the continental crust during orogenic evolution from collision to collapse. Considering a stepwise extraction of melt, we simulate the evolution of anatectic melt and of solid residues produced in the crust from collision to collapse using thermodynamic modelling. We also simulate the effect of entrainment of source material (restite-unmixing and peritectic assemblage entrainment) on the compositional range of the resulting magmas. The results are then compared to the compositions of lower crustal xenoliths and of peraluminous granites in both plutons and anatectic dome in the southeastern French Massif Central (SE-FMC). From our calculations, we identify two type of anatectic melts (1) cool-and-wet produced at low-temperature (< 800 °C) which release fluids during crystallisation and (2) hot-and-dry produced at high-temperature (> 750 °C) which only release fluids at the end of crystallisation. When emplaced around 0.4 GPa, cold-and-wet melts are produced by muscovite-dehydration melting reactions; hot-and-dry are produced by biotite-dehydration melting. In the SE-FMC, the Velay dome is cored by the Velay granite, intruded by small bodies of Velay leucogranite and surrounded by plutons made of either two mica leucogranite (MPG) or cordierite-bearing granite (CPG). MPG and Velay leucogranite compositions are best reproduced by cool-and-wet magmas. CPG and Velay granite compositions are best reproduced by hot-and-dry magmas. Melt extraction after biotite dehydration melting leaves residues that are similar in composition to lower-crustal xenoliths. Magmas forming plutons migrate freely toward the upper crust forming plutons with distinct compositions. On the contrary, to form a dome, magmas are retained on the way up. The emplacement and accumulation of magma at deeper level enhances (or trigger) melting due to the addition of heat (from hot-and-dry) and fluids (from cool-and-wet). The accumulation of magma and the in situ melting increases melt fraction and has consequence to weaken the middle crust and leads to the formation of an anatectic dome. We suggest that magmas are retained due to lithological heterogeneities in the crust. In the case of the Velay dome, a large orthogneiss formation similar to the Velay orthogneiss formation may have played that role. [ABSTRACT FROM AUTHOR]

Studies on the magmatic enclaves, pelitic xenoliths and host Jaspa granite pluton outcropped in the Lahaul area, NW Himalaya, India illustrate that the rocks have undergone garnet-grade metamorphism. The P-T pseudosection modelling shows that the metamorphic mineral assemblage is stable in the P-T range ~4.5-7.3 kbar and ~440-500°C, matching quite well with the results obtained from the conventional geothermobarometers (5.7-8.6 kbar and 409-531°C). The observed garnet-grade metamorphism in and around the Jaspa pluton is proposed to be due to localized perturbation of high-temperature isotherms in the Tethys Himalaya, as a consequence of the Cenozoic tectono-thermal event during Himalayan orogeny. Further, the Haimanta group of Tethys Himalayan rocks in the Lahaul area has been interpreted to have attained right-way-up metamorphic field gradient. [ABSTRACT FROM AUTHOR]

Abstract The Paleoproterozoic Central Lapland Granitoid Complex (CLGC) forms the northern core of the Fennoscandian Shield. We present here new U-Pb age data and review the existing ones from plutonic and metasedimentary rocks of the CLGC, and integrate the results with the structural field observations to decipher the tectonic history of this region. Granitoids vary in age from 2.43 Ga to 1.78 Ga, whereas metamorphic zircon overgrowths, both in granites and metasedimentary rocks, vary between 1.90 Ga and 1.76 Ga with several age peaks indicating prominent metamorphic pulses. The almost continuous growth of metamorphic zircon domains favors that the central part of the CLGC was near solidus for 100–120 Ma. A succession of five deformations and associated foliation-producing events, which were near-orthogonal to each other, have been identified. East-vergent thrusting and stacking (D1) commenced at ca. 1.92 Ga, and led to the onset of Barrovian-type metamorphism followed by a radical tectonic shift that yielded E-W trending D2 structures. Exhumation at 1.88–1.87 Ga caused decompression melting of thermally evolved thickened crust and led to the emplacement of large volumes of granites and triggering of Buchan-type metamorphic conditions. NE-SW collision (D3) at the southwestern margin of Fennoscandia heterogeneously overprinted the S3 fabric on D2 structures. Orogen parallel (NNW-SSE) buckling at 1.87–1.85 Ga formed oroclines in the hot linear arc segments. Renewed NNW-SSE shortening (D4) at 1.84–1.81 Ga produced long wavelength folds and caused the formation of domal structure in the CLGC. The final 1.78–1.76 Ga far-field collision (D5) in the west overprinted all the pre-existing structures. This complex multi- directional tectonic scenario provoked the intermittent exhumation phases between different contraction events of the CLGC. Highlights • Central part of the Lapland Granitoid Complex (CLGC) was near solidus for 100–120 Ma. • Five major deformation events (D1-D5) occurred between 1.92 Ga and 1.76 Ga. • Barrovian- to Buchan-type metamorphism at 1.88–1.87 Ga. • Migmatitic core was transformed to long wavelength folds during D4. [ABSTRACT FROM AUTHOR]

The central portion of the Canaã dos Carajás domain, located in the northern part of the Carajás province was originally marked by the occurrence of undifferentiated rocks belonging to the Xingu complex and Plaque suite, as well as greenstone belts, mafic rocks of the Pium diopside-norite and high K calc-alkaline leucogranites (Boa Sorte and Cruzadão granites). A semi-detailed geological mapping (1:100.000) was carried out in the Vila União area and allowed the identification of several deformed granite bodies intrusive in the Mesoarchean units. They correspond to the most expressive unit of the studied area and are composed predominantly of monzogranites with chemical and mineralogical affinity with the Neoarchean A-type granites of the Planalto and Vila Jussara suites. The variable felsic and ferromagnesian minerals contents, as well as the different proportions between them, allowed to distinguish four major groups of granitoids: (i) biotite-hornblende monzogranites (BtHblMzG); (ii) biotite granites and leucogranites (BtLG); (iii) biotite-hornblende tonalites (BtHblTn); and (iv) quartz diorites (QD). The tectonic foliation of these rocks follows the regional E-W trend and exhibits high angles (70–85°). Well-developed core and mantle structures in quartz and feldspar crystals, as well as the presence of serrated and irregular contacts between these crystals suggest that dynamic recrystallization occurred at relatively high temperatures (>500 °C). These rocks exhibit a wide variation in silica content (57.20–75.91 wt%), are metaluminous to slightly peraluminous and show affinity with A-type (high HFSE) and ferroan granites. Based on magnetic petrology studies it was possible to distinguish two groups of rocks: (1) granites containing only ilmenite with low magnetic susceptibility values (MS; <0.570 × 10 −3 SI), and (2) granites with magnetite as the main iron and titanium oxide mineral and higher MS values (>1.437 × 10 −3 SI). Textural and compositional evidences indicate that magnetite and ilmenite are early-crystallized phases and titanite has magmatic origin. Amphiboles are calcic and classified as hastingsite, whereas biotites are magnesian to ferroan. The relatively high Fe/(Fe + Mg) ratios found in the amphiboles of the BtHblMzG and BtHblTn varieties indicate that these granitoids were formed under low to moderate f O 2 conditions, whereas in the BtLG the lower values of this ratio suggest more oxidizing conditions. Geothermometers point to crystallization temperatures between 830 and 930 °C in the different facies. The high total Al content in the amphibole crystals suggests crystallization at pressures between 400 and 800 MPa, indicating that these granitoids were emplaced at different crustal depths. [ABSTRACT FROM AUTHOR]

Granites and pegmatites in the Strange Lake pluton underwent extreme enrichment in high field strength elements (HFSE), including the rare earth elements (REE). Much of this enrichment took place in the most altered rocks, and is expressed as secondary minerals, showing that hydrothermal fluids played an important role in HFSE concentration. Vasyukova et al. (2016) reconstructed a P-T-X path for the evolution of these fluids and provided evidence that hydrothermal activity was initiated by exsolution of fluid during crystallisation of border zone pegmatites (at ~450–500 °C and 1.1 kbar). This early fluid comprised a high salinity (25 wt% NaCl) aqueous phase and a CH 4  + H 2 gas. During cooling, the gas was gradually oxidised, first to higher hydrocarbons (e.g., C 2 H 6 , C 3 H 8 ), and then to CO 2 , and the salinity decreased to 4 wt% (~250–300 °C), before increasing to 19 wt%, due to fluid-rock interaction (~150 °C). Here, we present crush-leach fluid inclusion data on the concentrations of the REE and major ligands at different stages of the evolution of the fluid. The chondrite-normalised REE profile of the fluid evolved from light REE (La-Nd)-enriched at high temperature (~400 °C, Stages 1–2a) to middle REE (Sm-Er)-enriched at 360 to 250 °C (Stages 2b–3) and strongly heavy REE (Tm-Lu)-enriched at low temperature (150 °C, Stage 5). These changes in the REE distribution were accompanied by changes in the concentrations of major ligands, i.e., Cl − was the dominant ligand in Stages 1, 2, 4 and 5, whereas HCO 3 − was dominant in Stage 3. Alteration of arfvedsonite to aegirine and/or hematite contributed strongly to the mobilisation of the REE. This alteration released middle REE (MREE) and heavy REE (HREE), which either partitioned into the fluid or precipitated directly as bastnäsite-(Ce), ferri-allanite-(Ce) or gadolinite-(Y). Replacement of primary fluorbritholite-(Ce), which crystallised from an immiscible fluoride melt and altered to bastnäsite-(Ce), was also important in mobilising the REE (MREE). This paper presents the first report of the distribution of the REE in an evolving hydrothermal fluid. Using this distribution, in conjunction with information on the changing physicochemical conditions, the study identifies the sources of REE enrichment, reconstructs the path of REE concentration, and evaluates the REE mineralising capacity of the fluid. Finally, this information is integrated into a predictive model for REE mobilisation applicable not only to Strange Lake but any REE ore-forming system, in which hydrothermal processes were important. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

ABSTRACT Suprasolidus continental crust is prone to loss and redistribution of anatectic melt to shallow crustal levels. These processes ultimately lead to differentiation of the continental crust. The majority of granulite facies rocks worldwide has experienced melt loss and the reintegration of melt is becoming an increasingly popular approach to reconstruct the prograde history of melt-depleted rocks by means of phase equilibria modelling. It involves the stepwise down-temperature reintegration of a certain amount of melt into the residual bulk composition along an inferred P-T path, and various ways of calculating and reintegrating melt compositions have been developed and applied. Here different melt-reintegration approaches are tested using El Hoyazo granulitic enclaves (SE Spain), and Mt. Stafford residual migmatites (central Australia). Various sets of P-T pseudosections were constructed progressing step by step, to lower temperatures along the inferred P-T paths. Melt-reintegration was done following one-step and multi-step procedures proposed in the literature. For El Hoyazo granulites, modelling was also performed reintegrating the measured melt inclusions and matrix glass compositions and considering the melt amounts inferred by mass-balance calculations. The overall topology of phase diagrams is pretty similar, suggesting that, in spite of the different methods adopted, reintegrating a certain amount of melt can be sufficient to reconstruct a plausible prograde history (i.e. melting conditions and reactions, and melt productivity) of residual migmatites and granulites. However, significant underestimations of melt productivity may occur and have to be taken into account when a melt-reintegration approach is applied to highly residual (SiO2 <55 wt%) rocks, or to rocks for which H2O retention from subsolidus conditions is high (such as in the case of rapid crustal melting triggered by mafic magma underplating). [ABSTRACT FROM AUTHOR]

The Variscan Braszowice-Brzeźnica Massif (SW Poland) consists of gabbros and serpentinized peridotites with gabbro veins. Antigorite serpentinites form the western part of the Massif, whereas tremolite peridotites, tremolite serpentinites and lizardite-chrysotile serpentinites are found at the contact with granite intrusion in the east. Sparse relics of clinopyroxene, olivine and chromite were studied within the antigorite serpentinites. Clinopyroxene I (Mg# 90.9-93.47, 1.92-3.80 wt. % A2O3) occurs in the neighbourhood of gabbro veins. Its REE patterns are similar to those of clinopyroxene from the mid-ocean ridge gabbros. Clinopyroxene II (Mg# 96.0-97.0) is Al-poor (≤ 0.10 wt. % A2O3). Olivine I (Fo = 90.1-92.3) contains 0.32-0.50 wt. % NiO, whereas olivine II (Fo = 86.0-91.2) is Ni-poor (0.01-0.25 wt. % NiO) and contains micrometric magnetite intergrowths. Chromite I (Cr# 44.9-54.0, Mg# 45.0-52.1, < 0.17 wt. % TiO2) is associated with olivine I and clinopyroxene I, whereas chromite II (Cr# 43.2-51.4, Mg# = 34.6-47.7, 0.49-0.74 wt. % TiO2) occurs in serpentinites penetrated by gabbro veins. The serpentinites of the Braszowice-Brzeźnica Massif were formed supposedly immediately below the paleo-Moho in the ocean-spreading setting. Chemistry of clinopyroxene I from antigorite serpentinites resembles, in terms of major elements and REE, clinopyroxenes that originate due to MORB-like melt percolation through abyssal peridotites. The coexisting olivine I with both chromite I and II supposedly shared a similar origin. Composition of chromite suggests the back-arc setting of the Braszowice-Brzeźnica Massif. Clinopyroxene II and olivine II have major-element compositions indicative of metamorphic origin at expense of serpentine ± magnetite (deserpentinization). The deserpentinization assemblage occurring in serpentinites (antigorite-olivine-clinopyroxene) was formed probably under low-grade metamorphic conditions. The tremolite-bearing rocks record the thermal metamorphism by granite intrusion. [ABSTRACT FROM AUTHOR]

The textural relationships and geochemistry of feldspars from least-altered to sericite-hematite altered and mineralised ~ 1.595 Ga Roxby Downs Granite (RDG) at Olympic Dam, South Australia, were examined. The sample suite is representative of RDG both distal (> 5 km) and proximal (< 1 km) to the hydrothermal breccias of the Olympic Dam Breccia Complex (ODBC), which host Fe-oxide Cu-Au-(U) mineralisation at Olympic Dam. Microscopic observations and quantitative analyses indicate that a range of feldspar reactions have taken place within the RDG hosting the Olympic Dam deposit. An early phase of igneous plagioclase (~ An 27–34 ) is recognised, along with a more abundant, less-calcic plagioclase (~ An 12–20 ) both displaying rapakivi and anti-rapakivi textures with alkali feldspar. Alkali feldspars (~ Or 55 Ab 43 An 2 ) record post-magmatic evolution from cryptoperthite to patch perthite. Subsequent patch perthite is overprinted by highly porous, near end-member albite and K-feldspar, while plagioclase undergoes replacement by albite + sericite ± Ba-rich K-feldspar. In sericite-hematite altered and mineralised RDG along the margin of the ODBC, sericite replaces all plagioclase, whereas red-stained, Fe-rich K-feldspar persists. Sulphide-uranium-rare earth element mineralisation is observed in association with hydrothermal feldspars, and increases in abundance with proximity to the orebody. Petrographic observations and whole-rock geochemistry illustrate the transformation of plagioclase and alkali feldspar from igneous to hydrothermal processes, and indicate that hydrothermal albite and K-feldspar formed within the RDG without the need for an external source of alkalis. Feldspar geothermometry indicates a minimum crystallisation temperature of 765 °C at 2.2 kbar for alkali feldspar (pressure estimate obtained using plagioclase-amphibole geobarometry) followed by a range of lower temperature transformations. Late-stage magma mixing/contamination is postulated from supportive temperature and pressure estimates along with feldspar and mafic mineral relationships. [ABSTRACT FROM AUTHOR]

Recent studies have documented marine turbidites with syn-sedimentary deformation features in the central Sulu orogenic belt of eastern China. These units preserve essential information on the Late Mesozoic evolution of the Sulu orogenic belt. Referred to as the Baxiandun Formation, the turbidites exhibit similar lithologic characteristics to nearby units such as the Lingshandao Formation that have been well studied even though precise geochronologic constraints are lacking for a more precise correlation. This study reports detrital zircon U Pb age data that correlate the Baxiandun Formation turbidites of the central Sulu orogenic belt to the Early Cretaceous Lingshandao Formation. We also report Al-in-hornblende emplacement depth estimates for granitic intrusions of the Sulu orogenic belt's Laoshan mountain. A sharp contact between the Laoshan granites and the marine Baxiandun Formation indicates that the Baxiandun basin rapidly subsided to the emplacement depth of the Laoshan plutons. Lateral correlation among the marine turbidites, the Lingshandao and Baxiandun Formations, combined with information established by previous studies indicates initiation of transpressional tectonics at 122–121 Ma. Transpression ceased with the emplacement of the Laoshan granites, whose A1-type composition indicates a return to extensional tectonics at ca. 111 Ma. [ABSTRACT FROM AUTHOR]

Melt inclusions were studied by various methods, including electron and ion microprobe analysis, to determine the compositions of melts and mechanisms of formation of rare-metal peralkaline granites of the Khaldzan Buregtey massif in Mongolia. Primary crystalline and coexisting melt inclusions were found in quartz from the rare-metal granites of intrusive phase V. Among the crystalline inclusions, we identified potassium feldspar, albite, tuhualite, titanite, fluorite, and diverse rare-metal phases, including minerals of zirconium (zircon and gittinsite), niobium (pyrochlore), and rare earth elements (parisite). The observed crystalline inclusions reproduce almost the whole suite of major and accessory minerals of the rare-metal granites, which supports the possibility of their crystallization from a magmatic melt. Melt inclusions in quartz from these rocks are completely crystallized. Their daughter mineral assemblage includes quartz, microcline, aegirine, arfvedsonite, polylithionite, a zirconosilicate, pyrochlore, and a rare-earth fluorocarbonate. The melt inclusions were homogenized in an internally heated gas vessel at a temperature of 850°C and a pressure of 3 kbar. After the experiments, many inclusions were homogeneous and consisted of silicate glass. In addition to silicate glass, some inclusions contained tiny quench zircon crystals confined to the boundary of inclusions, which indicates that the melts were saturated in zircon. In a few inclusions, glass coexisted with a CO phase. This allowed us to estimate the content of CO in the inclusion as 1.5 wt %. The composition of glasses from the homogeneous melt inclusions is similar to the composition of the rare-metal granites, in particular, with respect to SiO (68-74 wt %), TiO (0.5-0.9 wt %), FeO (2.2-4.6 wt %), MgO (0.02 wt %), and NaO + KO (up to 8.5 wt %). On the other hand, the glasses of melt inclusions appeared to be strongly depleted compared with the rocks in CaO (0.22 and 4 wt %, respectively) and AlO (5.5-7.0 and 9.6 wt %, respectively). The agpaitic index is 1.1-1.7. The melts contain up to 3 wt % HO and 2-4 wt % F. The trace element analysis of glasses from homogenized melt inclusions in quartz showed that the rare-metal granites were formed from extensively evolved rare-metal alkaline melts with high contents of Zr, Nb, Th, U, Ta, Hf, Rb, Pb, Y, and REE, which reflects the metallogenic signature of the Khaldzan Buregtey deposit. The development of unique rare metal Zr-Nb-REE mineralization in these rocks is related to the prolonged crystallization differentiation of melts and assimilation of enclosing carbonate rocks. [ABSTRACT FROM AUTHOR]

The Pan-African NE-SW elongated Bandja granitic pluton, located at the western part of the Pan-African belt in Cameroon, is a K-feldspar megacryst granite. It is emplaced in banded gneiss and its NW border underwent mylonitization. The magmatic foliation shows NE-SW and NNE-SSW strike directions with moderate to strong dip respectively in its northern and central parts. This mostly, ferromagnetic granite displays magnetic fabrics carried by magnetite and characterized by (i) magnetic foliation with best poles at 295/34, 283/33 and 35/59 respectively in its northern, central and southern parts and (ii) a subhorizontal magnetic lineation with best line at 37/8, 191/9 and 267/22 respectively in the northern, central and southern parts. Magnetic lineation shows an 'S' shape trend that allows to (1) consider the complete emplacement and deformation of the pluton during the Pan-African D and D events which occurred in the Pan-African belt in Cameroon and (2) reorganize Pan-African ages from Nguiessi Tchakam et al. () compared with those of the other granitic plutons in the belt as: 686 ±17 Ma (Rb/Sr) for D age of metamorphism recorded in gneiss; and the period between 604-557 Ma for D -D emplacement and deformation age of the granitic pluton in a dextral ENE-WSW shear movement. [ABSTRACT FROM AUTHOR]

The U-Pb SIMS age dating of zircons from different-age granitoid assemblages varying in composition of the Verkhisetsk batholith shows that it comprises rocks of three age groups, formed at different stages of the Ural Mobile Belt. The first age group is represented by quartz diorites (396 ± 5 Ma) with insignificant distribution in area. Their formation was synchronous to island arc volcanism, manifested in the area of study from the second half of the Emsian to late Givetian-early Frasnian. According to this, we could consider these granitoides as comagmatic to island arc volcanites. The second age group includes tonalites and trondhjemites (367 ± 4 Ma), comprising the western part of the batholith. On the basis of similarity between these rocks and granitoides of modern active continental margins in material composition, it is assumed that they formed throughout the island arc-continental stage of development of the Ural Mobile Belt. Granitoides of the third age group, dominating in the Verkhisetsk batholith, formed as a result of several homodrome rhythms of granodiorite-granite intrusions of moderate-potassium composition during a short period of time (315-300 Ma). Their formation is related to the initial stage of the collision stage of development of the region, lasting from the early Bashkirian to Late Permian in the Middle Urals, which is fixed by deposition of flysch and molasse sediments in the Ural Foredeep. The data obtained change our understanding significantly of the character of evolution of granitoid magmatism and the place of rock assemblages studied in the geological history of the Urals. [ABSTRACT FROM AUTHOR]

Mafic and felsic igneous rocks in the Karacaali Magmatic Complex (KMC) in the northwestern margin of the Central Anatolian Crystalline Complex (CACC) are classified into 4 groups: i) granitoid pluton including granite, granodiorite, and monzonite; ii) a few meter-scale porphyritic microgranite enclaves within the hybrid rocks; iii) hybrid rocks formed by mixing/mingling of mafic lavas (basaltic/diabasic/lamprophyric), anorthositic, and/or rhyolitic lavas; iv) diabasic dykes/veins within the granitoid pluton. Major element composition of the granitoid pluton and porphyritic microgranite enclaves within the hybrid rocks indicate subalkaline, calc-alkaline, and mostly I-type characteristics. These rocks are mainly peraluminous with aluminum saturation index > 1, but mainly between 1 and 1.1, indicating transitional peraluminous. On the tectonomagmatic discrimination diagrams (Y vs. Nb and (Y+Nb) vs. Rb diagrams), all the granitic and monzonitic rock suites from the complex fall mostly in the VAG+Syn-COLG and VAG fields respectively, suggesting arc-related origin. On the R1 vs. R2 tectonic diagram, the granitic rocks display distribution from preplate collision to syncollision field, but quartz-monzonitic samples plot within the postcollision uplift field. Based on limited geological, petrographic, and geochemical results, the tectonomagmatic evolution of the KMC can be summarized as follow: i) initiation of subduction of the Inner Tauride oceanic lithosphere beneath the CACC during the Late Cretaceous time; ii) underplating of partial melts derived from subducted slab and/or mantle wedge, which provided enough heat for partial melting of the mafic lower crust and generation of granitic magma; iii) slab detachment following the continent-continent collision that resulted in tensional forces within the overlying continental crust, which allowed the intrusion of the granitic magma to the upper crust, also cutting the central Anatolian ophiolites, from the Late Cretaceous to most likely the Paleocene time. The hybrid rocks formed by mixing/mingling of the mafic, anorthositic, and/or rhyolitic magmas most likely indicate their injection into a partly crystalline granitic magmatic system just after crystallization of granitic magma in the upper crust. However, this model is open to discussion and needs to be investigated using isotope data in future studies. [ABSTRACT FROM AUTHOR]

A Triassic granodioritic pluton with mafic microgranular enclaves (MMEs) in central South China provides an important insight into crust-mantle interaction. Here we present a comprehensive study of fieldwork, geochronology, geochemistry, and Sr-Nd-Hf isotopes for the Taojiang granodioritic host and the MMEs in central South China. The host granodiorites (218 ± 3 Ma) are high-K calc-alkaline I-type granites (SiO2: 66.17-69.47 wt%; ANCK < 1.0) that show light rare earth element (REE) enrichment and flat heavy REE patterns with weakly negative Eu anomalies. They exhibit strongly negative Ba, Sr, Nb, P, and Ti anomalies and positive Rb and Pb anomalies and have high initial 87Sr/86Sr ratios (0.712783 to 0.714799), negative εNd(t) values (-8.3 to -7.8), and negative zircon εHf(t) values (-6.4 to -3.1). The coeval MMEs (225 ± 3 Ma) have compositions ranging from mafic to intermediate (SiO2: 49.2-60.8 wt%) with high MgO (2.8-6.3 wt%), FeOT (6.7-15.2 wt%), CaO (4.3-7.1 wt%), TiO2 (0.8-2.0 wt%), Ni (18.2-61.4 ppm), and Cr (17.2-125.4 ppm) contents. They are enriched in light REE, Rb, Pb, and Th and depleted in Ba, Nb, Ta, Sr, Eu, and Ti. The MMEs have lower whole-rock initial 87Sr/86Sr ratios (0.708052-0.713413) and higher whole-rock εNd(t) (-6.3 to -4.3) and zircon εHf(t) (-4.6 to -0.6) values than those of the granodioritic host. Our results suggest that the Taojiang granodioritic host and the MMEs were likely produced by mixing of mantle- and crust-derived magmas. Combined with previous paleomagnetic and magnetostratigraphic results, we propose that the Triassic magmatism in central South China might be related to underplating of mantle-derived magma induced by mantle plume or asthenosphere upwelling. [ABSTRACT FROM AUTHOR]

In this contribution we provide evidence for the extraction of volatile and incompatible element enriched melts from common granites. This provides a mechanism showing that at least a large proportion of granitic pegmatites could be genetically directly connected to a main granite body. In granites there are often two principal types of melt inclusions: (i) those that represent the bulk chemistry of the granite and (ii) those with very different compositions. In the Variscan Erzgebirge granites, the second type is characterized by the abundance of fluorine. However, in other geodynamic settings inclusions in granites can contain high concentrations of other elements which may take over the function of fluorine. From textural relationships the second inclusion type represents intergranular melts enriched in all elements incompatible with the ideal haplogranite system. Due to the high volatile content of such melts, the viscosity can be several orders of magnitude lower than the quasi-solid bulk system and can therefore move rapidly through the partially or totally crystallized host, and flow together into a separate system forming pegmatite bodies inside or outside the granite body. Another important effect of the high volatile content is the phase separation resulting from the speciation changes OH- → H2O or CO32- → CO2, due to temperature and/or pressure changes at different locations within the granite-intergranular melt system. Since melt inclusions provide a means of conserving original un-degassed compositions, they yield important evidence for closing the gap between granites and granitic pegmatites. The paper is dedicated to two Czech colleagues - Petr Černý and Milan Novák - who have devoted their lives to the study of granitic pegmatites. [ABSTRACT FROM AUTHOR]

The Darreh Bagh granitoid pluton (DGP), with middle Jurassic age (178 Ma), located in the northwest of Aligudarz city. The pluton is mainly granodioritic composition which emplaced in metapelitic rocks of Sanandaj-Sirjan structural zone. For the first time, the emplacement mechanism of this pluton, investigated by anisotropy of magnetic susceptibility (AMS) method. Based on the present investigations, the mean magnetic susceptibility, in terms of µSI for the studied rock groups are as follow: granodiorites (257), leucogranites (47), high tourmaline leucogranites (148), low tourmaline leucogranites (48), migmatites (437), surmicaceous enclaves (386). Considering the obtained values, the felsic part of the DGP belongs to the paramagnetic granitoids (500>km>0 in µSI) (equal to ilmenite series or S-type). Based on the magnetic parameters and their interpretations it is possible to divide DGP into the A and B domains and A1, A2 subdomains. The magnetic lineations in the subdomains oriented to the north. Whereas in the middle part of the pluton (B domain) it oriented dominantly to the east and southeast. Based on distribution patterns of magnetic lineations these domains were emplaced with a short delay compared to each other. Meanwhile, A domain was emplaced prior to B domain. With attention to distribution patterns of magnetic lineations and foliations, the principles of interpretation of magnetic parameters and regional geological characteristics, the Darreh Bagh granitoid pluton was emplaced in the form of a relatively large sill in a dextral shear zone (related to a transpression regime). [ABSTRACT FROM AUTHOR]

The Zhongchuan district is an important component of the metallogenic belt in the Western Qinling. The Zhongchuan granite pluton occurring in the centre of the Zhongchuan metallogenic area has been poorly constrained, though the Triassic granite in Western Qinling has been well documented. In-situ zircon U-Pb ages, Hf isotopic compositions and whole-rock geochemical data are presented for host granite and mafic microgranular enclaves (MMES) from the Zhongchuan pluton, in order to constrain its sources, petrogenesis and tectonic setting of the pluton. The distribution of major, trace and rare earth elements apparently reflect exchange between the MMES and the host granitic rocks mainly due to interactions between coeval felsic host magma and mafic magma. The zircon U-Pb age of host granite (231.6 ± 1.5 to 235.8 ± 2.3 Ma) has overlapping uncertainty with that of the MMES (236.6 ± 1.3 Ma), establishing that the mafic and felsic magmas were coeval. The Hf isotopic composition of the MMES ( εHf( t) = −13.4 to 4.0) is distinct from the host granite ( εHf( t) = −15.7 to 0.0), indicating that both enriched subcontinental lithosphere mantle (SCLM) and crustal sources contributed to their origin. The zircons have two-stage Hf model ages of 1064 to 1798 Ma for the host granite and 858 to 1747 Ma for the MMES. This suggests that the granitic pluton was likely derived from partial melting of a Late Mesoproterozoic crust, with subsequent interaction with the SCLM-derived mafic magmas in tectonic affinity to the South China Block. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Geochronological, geochemical, whole-rock Sr-Nd, and zircon Hf isotopic analyses were carried out on the Jiasha Gabbro, mafic microgranular enclaves (MME) and host Longchahe Granite samples from the Gejiu area in the southeast Yunnan province, SW China, with the aim of characterizing their petrogenesis. Compositional zoning is evident in the gabbro body as the cumulate textures and mineral proportions in the gabbro interior are distinct from the gabbro margin. The Longchahe Granite largely comprises metaluminous quartz monzonite with distinctive K-feldspar megacrysts, but also contains a minor component of peraluminous leucogranite. The MME have spheroidal to elongated/lenticular shapes with sharp, crenulated and occasionally diffuse contacts with the host granite, which we attribute to the undercooling and disaggregation of mafic magma globules within the cooler host felsic magma. Field observations, geochronology, geochemistry, Sr-Nd and zircon Hf isotopic compositions point to a complex petrogenesis for this granite-MME-gabbro association. Zircon Pb/U ages determined by LA-ICP-MS for a mafic enclave, its host granite and the gabbro body are 83.1 ± 0.9 Ma, 83.1 ± 0.4 Ma and 83.2 ± 0.4 Ma, respectively, indicating coeval crystallization of these igneous rock units. Crystal fractionation processes can explain much of the compositional diversity of the Jiasha Gabbro. The geochemical features of the gabbro, such as high Mg (up to 70) and Cr (up to 327 ppm), enrichment in LILEs (e.g., Rb, Ba, KO) and LREEs, and depletion in HFSE (e.g., Nb, Ta, Ti), together with initial Sr/Sr ratios of 0.708-0.709 and negative εNd(t) values (−5.23 to −6.45), indicate they were derived from a mantle source that had undergone previous enrichment, possibly by subduction components. The Longchahe Granite has a large range of SiO (59.87-74.94 wt%), is distinctly alkaline in composition, and has Sr-Nd-Hf isotopic compositions ((Sr/Sr) > 0.712, εNd(t) = −6.93 to −7.62 and εHf(t) = −5.8 to −9.9) that are indicative of derivation from a crustal source. However, the most primitive rocks of Longchahe Granite are compositionally distinct from any feasible crustal melt. We interpret the spectrum of rock types of the Longchahe Granite to have formed via mixing between crustally derived peraluminous leucogranite magma and mantle-derived magma of similar heritage to the Jiasha Gabbro. We speculate that this mixing event occurred early in the magmatic history of these rocks at relatively high temperature and/or deep in the crust to allow efficient physical mixing of magmas. Saturation and accumulation of K-feldspar and zircon in the mixed magma is invoked to explain the megacrystic K-feldspar and elevated KO and Zr content of some of the granitic rocks. A later episode of magma mixing/mingling is preserved as the MME that have geochemical and isotopic compositions that, for the most part, are intermediate between the granite and the gabbro. The MME are interpreted to be fractionated melts of mafic magma related to gabbro that were subsequently injected into the cooler, partly crystalline granitic magma. Mingling and mixing processes within the convectively dynamic upper crustal magma chamber resulting in a hybrid (MME) magma. During this second mixing episode, element interdiffusion, rather than bulk physical mixing, is interpreted to be the dominant mixing process. [ABSTRACT FROM AUTHOR]

Abstract: Metasedimentary granulite enclaves hosted in the Indo-Sinian Darongshan–Shiwandashan granite belt from the southeastern Guangxi province, South China, experienced a three-stage metamorphic evolution: (1) the early prograde metamorphism in the stability field of sillimanite at ~800°C; (2) the peak metamorphism with a mineral assemblage of spinel+quartz at 7.5–8.0kbar and 950–1000°C (260–250Ma); and (3) a near-isothermal decompression stage with orthopyroxene+plagioclase and orthopyroxene+cordierite symplectic textures at 3.2–3.7kbar and 790–820°C (240–230Ma). The clockwise P–T–t path suggested that the granulite enclaves have undergone initial crustal thickening and subsequent rapid exhumation and cooling history. The granulite enclaves show peraluminous affinities (A/CNK=1.11–3.14, A/CNK=Al2O3/(CaO+Na2O+K2O) in molecular ratio) with Al2O3 up to 25.31%; chondrite-normalized REE patterns similar to those of upper continental crust; relative Rb, Ba, Th, LREE, K, Zr and Hf enrichment and Sr, Nb, Ta, P and Ti depletion in primitive mantle-normalized spidergrams; and highly radiogenic Sr (87Sr/86Sr(i)=0.71295–0.74273 ) and nonradiogenic Nd (εNd(t)=−14.8 to −11.2). Systematic elemental variation trends from the granulite enclaves to the host granites, and similar Sr–Nd isotope compositions in the enclaves and the host granites, indicate that the two have a coherent origin — the granulites were restites of the host granites. The granulite enclaves can also be subdivided into two groups: high-87Sr/86Sr(i) (>0.7303) and low-87Sr/86Sr(i) groups (<0.7135). The estimated magma source for the host granites may contain 10–40% low-87Sr/86Sr(i) and 60–90% high-87Sr/86Sr(i) granulites. P–T–t path and geochemical features of the granulite enclaves, temperature estimation for the host granites, and previous geochronological data, indicate limited dehydration melting of the metasedimentary protoliths during the prograde and peak metamorphic stages. Instead, large scale crustal melting may have occurred during the stage of exhumation and uplifting of the lower-middle crust. [Copyright &y& Elsevier]

Abstract: Early Cretaceous granodioritic host rocks with mafic microgranular enclaves (MME) in the Dabie orogen provide important insights into magma mixing between melts from delaminated eclogitic lower continental crust and mantle-derived magma. The Meichuan host granodiorites (132±1Ma) from the eastern margin of the Dabie orogen, adjacent to the Tan–Lu fault, are high-Mg adakitic rocks containing 63.5–69.6wt.% SiO2 and 2.2–4.5wt.% MgO with high Mg# values (Mg# =molar 100×Mg/(Mg+Fe)) from 50.4 to 63.0. Whole-rock geochemical features include high Cr (56.0–281.3ppm), Ni (49.3–140.0ppm), and Sr (745–1373ppm) concentrations, low Y (7.6–12.4ppm) and heavy rare earth elements (HREE; e.g., Yb: 0.64–1.14ppm), resulting in high Sr/Y (67.2–130.5) and (La/Yb)N (22.2–68.7) ratios. The host granodiorites also have moderately enriched initial 87Sr/86Sr ratios (0.7056–0.7059), low εNd(t=130Ma) values (−18.8 to −15.0), enrichment of large ion lithophile elements, and depletion of high field strength elements. These geochemical features indicate that the host granodiorites were derived from partial melting of delaminated lower continental crust and subsequently hybridized by mantle melts. The MMEs have a wide range SiO2 contents from 47.7 to 61.0wt.%. MMEs with low SiO2 contents (<51.0wt.%) have extremely high MgO, Ni, Cr, Y, and Yb, and low Sr contents, resulting in high Mg# values and low Sr/Y and (La/Yb)N ratios, similar to Early Cretaceous mafic–ultramafic rocks in the Dabie orogen. MMEs with high-SiO2 (>51.0wt.%) have relatively low MgO (but Mg# values are still more than 50, 55.2–61.3), Y, and Yb, and high Sr concentrations, resulting in high Sr/Y and (La/Yb)N ratios, analogous to high-Mg adakitic rocks. Evidence from fieldwork and geochemistry clearly points to magma mixing during magma evolution, e.g., the contact relationships between coeval MMEs and their host; excellent linear trends on Harker diagrams from low-SiO2 MMEs via high-SiO2 MMEs to granodioritic host without interruption. Thus, the Meichuan granodioritic host and MMEs can be interpreted as a mixture between a mantle-derived magma having high Mg# values and low Sr/Y and (La/Yb)N ratios, and a delaminated eclogitic lower continental crust-derived adakitic melt, e.g., low Mg# values and high Sr/Y and (La/Yb)N ratios. The distribution of the late Mesozoic high-Mg adakites in eastern China generally forms a high-Mg adakite belt along the southern Tan–Lu fault. Our results suggest that the large strike–slip motion of the Tan–Lu fault might have triggered the foundering of the over-thickened lithosphere which caused orogenic collapse and subsequent crust–mantle interaction. Generation of the Meichuan granodioritic host and MMEs requires both delamination of eclogitic lower crust and magma mixing in the mantle. [Copyright &y& Elsevier]

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 Alaçamdağ (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 Na2O, Ba, Rb, Rb/La and lower Al2O3, CaO, MgO, TiO2, Zr/Y values than those of the SG host rocks. AG and SG host rocks differ from those of MMEs, with their lower Al2O3, CaO, MgO, Fe2O3, TiO2, Sr, V, Mg# and higher SiO2 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 87Sr/86Sr (AG host)=0.708835–0.710206 and εNd(t) (AG host)=(−5.36 to −7.36); 87Sr/86Sr (AG MME)=0.709107–0.709801 and εNd(t) (AG MME)=−5.36 to −7.36; 87Sr/86Sr (AG MME)=0.709107–0.709801 and εNd(t) (AG MME)=−5.55 to −6.51; 87Sr/86Sr (SG host)=0.712200–0.712408 and εNd(t) (SG host)=−8.03 to −8.61; 87Sr/86Sr (SG MME)=0.712028–0.712351 and εNd(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. [Copyright &y& Elsevier]

The Hadean (before 4.0 Ga) crust has long been considered to comprise mainly primitive mafic and ultramafic rocks. However, mineral inclusions in detrital zircons as old as 4.4 Ga from Jack Hills, Australia, have been interpreted to be magmatic and to provide evidence for extensive granitic crust. In situ U-Pb dating of monazite and xenotime inclusions in 4.25-3.35 Ga detrital zircons from Jack Hills shows that these inclusions are not magmatic, but formed during metamorphism at either 2.68 Ga or 0.8 Ga. Monazite-xenotime thermometry of intergrowths in the inclusions and the quartz-muscovite rock matrix constrain temperatures to between 420-475 °C, corresponding with conditions during peak regional metamorphism. Petrography and U-Pb geochronology of zircon inclusions from other localities show that the replacement of primary inclusions may commence in the igneous host rock and continue through weathering, sedimentation, and diagenesis. With increasing metamorphic grade, the inclusion assemblage increasingly reflects the composition of the rock matrix. In Jack Hills, most of the inclusions have the same composition and abundances as the metamorphic matrix, consistent with their formation during metamorphism. The titanium content of quartz inclusions indicates formation temperatures of 350-490 °C, supporting a metamorphic origin. Several lines of evidence indicate that at least some of the muscovite inclusions are also secondary. The lack of apatite inclusions in zircons from Jack Hills, relative to zircon in common granitic rocks, suggests that secondary minerals may have replaced primary apatite. Thus, detrital zircon may not be impermeable to post-depositional fluids, raising doubts about the use of the mineral inclusions they contain to infer initial magma chemistry. These results call for a reassessment of the source melts of the Hadean zircons and the composition of the earliest crust. [ABSTRACT FROM AUTHOR]

The article discusses the isotopic data of the first Neodymium (Nd)-Strontium (Sr) of microgranitoid inclusions in the granitoides of Eastern Sikhote-Alin in Japan Sea coast, as well as their genetic significance. It says that the isotope data of Samarium (Sm) and Nd for inclusion rock pairs possess isotope characteristics that are typical for acid rocks. It states that the inclusions occur in various types of rocks and are characterized to have higher magnetic susceptibility and porosity compared to their host rocks. Moreover, data analysis of rubidium (Rb)-Sr and Sm-Nd isotopes reveals a simultaneous increase of 87Sr/86Sr and 87Rb/86Sr ratios in the series of diorites to granites.

Abstract: Experimental glasses and naturally quenched melts from pelitic and psammitic protoliths both contain markedly less (FeO*+MgO) than typical S-type granites. The entrainment of residual (peritectic) phases and contamination by country rock material are two mechanisms commonly proposed to account for their higher abundance in granites. This study examines the origin of the ferromagnesian minerals, specifically biotite, contained in the Wuluma Pluton, a heterogeneous granite body in central Australia that lies within its granulite facies pelitic and psammitic source rocks. Heterogeneity at the margins of the Wuluma Pluton arises from abundant enclaves and innumerable dykes of granite separated by screens of country rock. Towards its center heterogeneity arises from abundant biotite-rich, enclaves, schlieren and aggregates. Based on field observations, the microstructural relationships between minerals and the composition of minerals obtained by electron microprobe and LA-ICP-MS analysis, the origin of three of the most common types of schlieren were determined. Enclave-related schlieren are the remains of isolated enclaves that interacted with the host granite; long schlieren developed from screens of country rocks trapped between sheets of granite, and wispy schlieren are derived from porphyroblasts of garnet, cordierite and orthoproxene in the granite. Once incorporated in the granite, all the enclaves, schlieren, porphyroblasts of garnet and cordierite are progressively replaced by biotite. Most of the newly formed biotite and the magmatic biotite subsequently re-equilibrate with the host granite and acquires the same composition. Very little of the biotite retains the compositional traits of the minerals it has replaced. Disaggregation of the enclaves and schlieren that have been replaced by biotite adds biotite to the granite, and this constitutes the major source of biotite in the Wuluma Pluton, that can reach 15 modal%. [Copyright &y& Elsevier]

Abstract: The influence of tempering on the mechanical performance of pottery is assessed. Emphasis is placed on the examination of the impact of temper shape (low vs. high sphericity) and extent of vitrification on the strength and toughness of the ceramic material. Measurements on experimental briquettes show that the replacement of platy phyllitic temper with bulky granitic temper results in a reduction in strength but, at least at very high firing temperatures, in an increase in toughness. The observed differences in strength reduction with different temper shapes is semi-quantitatively assessed by adapting the damaged zone model, developed previously to disk-shaped particles. The effect of temper shape on toughness is particularly pronounced at high firing temperatures, where platy temper results in significantly lower fracture toughness of the corresponding material. [Copyright &y& Elsevier]

Abstract: Microgranular enclaves are common within intermediate to felsic granitic rocks that have I- and S-type affinity however they are rare within alkaline anorogenic granitoids of A-type affinity. The Permian (~260Ma) Emeishan large igneous province (ELIP) of southwest China contains two peralkaline silica saturated A-type granitic plutons that host microgranular enclaves. The enclaves from the Baima pluton are intermediate in composition and have lower SiO2 and higher TiO2, CaO and Mg# (SiO2 =57.2 to 63.0wt.%; TiO2 =0.8 to 1.8wt.%; CaO=1.7 to 3.3wt.%; Mg#=28 to 44) than their host (SiO2 =62.6 to 67.8wt.%; TiO2 =0.5 to 1.4wt.%; CaO=0.4 to 1.8wt.%; Mg#=15 to 31). The enclaves from the Taihe pluton are more felsic (SiO2 =63.8 to 71.3wt.%; TiO2 =0.3 to 0.6wt.%; CaO=0.6 to 2.3wt.%; Mg#=8 to 22) but are still less evolved than their host (SiO2 =69.8 to 75.1wt.%; TiO2 =0.2 to 0.6wt.%; CaO=0.4 to 0.8wt.%; Mg#=3 to 12). In both cases, the enclaves have very similar εNd(T) values (Baima εNd(T) =+2.8 to +3.2; Taihe εNd(T) =+1.0 to +2.0) as their hosts (Baima εNd(T) =+3.0 to +3.2; Taihe εNd(T) =+1.5 to +1.9). The major and trace element trends of the enclave-host pairs suggest that fractional crystallization occurred and that element diffusion was likely minimal. The enclaves are interpreted as entrained accumulations of early formed crystals of a silicic magma which was originally produced by fractional crystallization of a mafic magma. [Copyright &y& Elsevier]

Turkestanite, a rare Th- and REE-bearing cyclosilicate in the ekanite–steacyite group was found in evolved peralkaline granites from the Morro Redondo Complex, south Brazil. It occurs with quartz, alkali feldspar and an unnamed Y-bearing silicate. Electron microprobe analysis indicates relatively homogeneous compositions with maximum ThO2, Na2O and K2O contents of 22.4%, 2.93% and 3.15 wt.%, respectively, and significant REE2O3abundances(5.21 to 11.04 wt.%). The REEpatterns show enrichment of LREEover HREE, a strong negative Eu anomaly and positive Ce anomaly, the latter in the most transformed crystals. Laser ablation inductively coupled plasma mass spectrometry trace element patterns display considerable depletions in Nb, Zr, Hf, Ti and Li relative to whole-rock sample compositions. Observed compositional variations suggest the influence of coupled substitution mechanisms involving steacyite, a Na-dominant analogue of turkestanite, iraqite, a REE-bearing end-member in the ekanite–steacyite group, ekanite and some theoretical end-members. Turkestanite crystals were interpreted as having precipitated during post-magmatic stages in the presence of residual HFSE-rich fluids carrying Ca, the circulation of which was enhanced by deformational events. [ABSTRACT FROM AUTHOR]

The article presents a study on the composition and age structure of granitoid plutons found at the megabasin of Western Siberia, Russia. It states that granitoids are considered as the most perspective rocks used for researches on hydrocarbon raw materials in sedimentary basins. It mentions the materials used in the study which include granite plutons with oval form, isotopic and chemical dating of the granosyenite samples, and isometric rounded grains of uraninite. It says that the chemical dating presents the total lead content in the mineral which means that uraninite still has lead content. Moreover, it adds that the age structure and temperature of the granitoid plutons are viewed to be shown by the difference between the chemical age and absolute age of the uraninite.

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Abstract: The Early Cretaceous Baijuhuajian pluton is an A-type granitic intrusion, emplaced along the Jiangshan-Shaoxing (JSSX) fault zone in western Zhejiang Province, SE South China. It intruded into a Late Jurassic volcanic basin bounded by Proterozoic sandstone and siltstone. The granite has a coarse-grained, porphyritic texture and is composed of alkali feldspar phenocrysts in a matrix of K-feldspar, quartz, plagioclase and biotite. The pluton has a clear A-type geochemical signature, e.g. it is metaluminous (A/CNK~1.0) and has high SiO2 (75 to 78 wt.%), total alkalis (Na2O+K2O=4.8 to 8.5 wt.%), rare earth elements (total REE=228 to 438 ppm), HFSE and Fe⁎ [FeOt/(FeOt +MgO)=0.87 to 0.97]. On the other hand, it is characterized by low CaO (0.51 to 1.01 wt.%), TiO2 (0.06 to 0.13 wt.%), P2O5 (below detection) and Sr (7.0 to 9.5 ppm). The hypersolvus texture and fine-grained groundmass indicate emplacement at a shallow-depth. SHRIMP U–Pb zircon dating yielded a weighted mean 206Pb/238U age of 126±3 Ma and zircons from this pluton give εHf(T) values between −0.52 and +4.24, suggesting the importance of juvenile material in the magma source. Most of the plutonic rocks in southeast China are calc-alkaline, subduction-related intrusions of Jurassic and Cretaceous age. Previous studies suggested that the sparse A-type granites in South China were emplaced in two episodes: 190–155 Ma in the inland area and ~100 Ma along the coastal area in SE South China. Our study of the Baijuhuajian granite, together with the coeval Suzhou A-type granite (123 Ma) in Jiangsu Province, defines an important extensional event between 125 and 100 Ma. Considering the available data for the Mesozoic igneous rocks in South China, we suggest that subduction of the Pacific plate in the Mesozoic produced voluminous calc-alkaline granitoids and volcanic rocks with a younging trend from west to east. The A-type granites were generated during periods of local extension at 190–155 Ma and 125–100 Ma, perhaps corresponding to localized rollback of the Pacific plate. [Copyright &y& Elsevier]

Abstract: Whole-rock major-trace elements and Sr–Nd isotopes, mineral chemistry, and zircon U–Pb and Lu–Hf isotope compositions are reported for I-type monzogranite and its mafic microgranular enclaves from the Triassic Mishuling granite in the Qinling orogen, central China. Zircon U–Pb dating yields an age of 212±5 Ma for the mafic enclaves and 213±3 Ma for the host monzogranite. Whole-rock major-trace elements, Sr–Nd isotopes and zircon Hf isotopes preclude simple crystal fractionation or restite unmixing for a genetic link between the enclaves and the monzogranite. Mixing between mafic and felsic magmas is compatible with the geochemical data. The monzogranite displays an enriched LILE and LREE pattern, high (87Sr/86Sr)i ratios of 0.7068 to 0.7071 and low ε Nd(t) values of −9.2 to −5.7, suggesting a crustal origin. Its high Mg# (47.6 to 50.7), Cr and Ni contents clearly indicate its derivation from mafic refractory lower crust. Most of the zircons in the monzogranite have negative ε Hf(t) values of −12.5 to −0.1 and two-stage Hf model ages of 1049 to 1683 Ma, and some zircons in the host monzogranite have positive ε Hf(t) values of 0.3 to 4.8 and single-stage Hf model ages of 665 to 845 Ma. This indicates that the monzogranite is most likely to be formed by partial melting of a Proterozoic lower continental crust. The mafic enclaves have fine-grained igneous textures and contain abundant acicular apatite that indicates rapid cooling. They also have a high (87Sr/86Sr)i ratio of 0.7071 and a low ε Nd(t) value of −6.5, suggesting a derivation from ancient subcontinental lithosphere mantle (SCLM). Zircons in the mafic microgranular enclaves have ε Hf(t) values of −1.6 to 5.1 and single-stage Hf model ages of 700 to 910 Ma, suggesting a possible origin from partial melting of the Neoproterozoic SCLM that may form in association with contemporaneously supercontinental rifting in the South China Block. Therefore, the Mishuling I-type granite may form by anatexis of Meso-Neoproterozoic lower crust, with mixing between the mafic and felsic magmas. In particular, we interpret the positive ε Hf(t) values as being derived from reworking of Neoproterozoic juvenile lithosphere in response to tectonic extension in the late stage of the Triassic continental collision between the South China Block and the North China Block. [Copyright &y& Elsevier]

Abstract: The Chinese Altai orogen is a typical domain of the Central Asian Orogenic Belt and in previous syntheses was divided into six tectonic units (or terranes). In this paper, 41 new and 36 published whole-rock Nd and Sr isotopic data for granitoid intrusions and mafic dykes within units 2 and 3 of the central Altai and units 4 to 6 of the southern Altai were used for isotopic mapping. The age of the samples used is known from U–Pb zircon dating. ε Nd(t) values range from −4 to +2 in the central Altai units 2 and 3, and from +1.4 to +6 in the southern Altai units 4 and 5 and up to +8.4 in unit 6. Correspondingly, Nd model ages (T DM) decrease from 1.6–1.1 Ga in the central Altai to 1.0–0.5 Ga in the southern Altai, except for a continental fragment in unit 4. I Sr is elevated in the central units, decreasing to <0.705 in the southern units 5 and 6. These results demonstrate that the central Altai contains widespread old crustal components in its basement, whereas the southern Altai comprises a higher proportion of juvenile crust. When integrated with published U–Pb zircon ages, our data show that new crust grew southwards in the Chinese Altai. In addition, our data suggest that units 2 and 3 are a single tectonic unit, whereas the southern Altai (unit 4), which previously was regarded as a single young accretionary terrane, should be subdivided into two units: a younger arc and an older continental fragment. The granitoids in the Chinese Altai can be divided into syn- and post-/non-orogenic groups. The syn-orogenic granitoids have ca. 50–80% mantle-derived component, whereas the post/non-orogenic granitoids contain ca. 70–90%. The generation of syn- and post-/non-orogenic granitoids represents horizontal (lateral) and vertical crustal growth, which contributed ca. 18–28% and 7–8% respectively to the area of the Chinese Altai. This work shows that isotopic mapping is an effective approach to elucidate terrane composition in the Central Asian Orogenic Belt and thereby better constrain Palaeozoic crustal growth. [Copyright &y& Elsevier]

Abstract: The origin of mafic enclaves in intermediate and felsic granitoids has long been debated. In this paper, petrological and geochemical analyses (whole-rock geochemistry, Nd–Sr and zircon in-situ Hf isotopic compositions) are used to address this controversial issue. Mafic enclaves in the Taihang felsic plutons (north China craton) are fine-grained and show typical magmatic textures. They occur as rounded to ellipsoidal globules, and are sometimes highly elongated (without solid state deformation) due to stretching within the partially crystallized, convective felsic magma. Such occurrence suggests that the mafic enclaves and host rocks represent two co-existing, compositionally distinct magmas. The mafic enclaves contain abundant hydrous phases (hornblende and biotite) and show the reaction relationship of clinopyroxene being rimmed by hornblende. They also contain plagioclase xenocrysts showing compositional and textural disequilibrium. In terms of Nd–Hf isotopes, mafic enclaves have ε Nd(t) values of −10 to −15, and host rocks have lower values as a whole (−13 to −18). Zircons from a single enclave show a large variation in Hf isotopic compositions (ε Hf(t)=−5 to −20). A model is proposed whereby an evolved basaltic magma first mixed with a granitic magma of crustal origin at depth; and then the mixed magma broke up into discrete globules upon entering the felsic magma chamber, forming enclaves by convective motion, or forceful injection in the host felsic magma. This was followed by a double mechanical transfer of plagioclase crystals at the contact of the two magmas, and by the diffusion of mobile elements (e.g., Si, alkalis, P, Y, Yb, Pb) from felsic magma to enclave-forming magma. [Copyright &y& Elsevier]

Abstract: Lithium concentrations and isotopic compositions of 39 A-type granites and mafic enclaves from 11 plutons in Northeast China and the North China craton are used to constrain their genesis and to characterize further the average composition of the continental crust. Lithium concentrations (2.8 to 80 ppm) in 29 A-type granites are slightly higher than those of average I-type granites and lower than those of average S-type granites, reflecting source differences. Lithium isotopic compositions (δ 7Li=−1.8 to +6.9) of A-type granites fall within the range of worldwide I-type and S-type granites. By contrast, 10 mafic enclaves have significantly higher Li concentrations (32 to 179 ppm) and less variation in Li isotopic compositions (δ 7Li=−3.2 to +3.1) than their corresponding granites, due to the high modal abundance of amphiboles and biotites. Overall, the weighted mean δ 7Li for A-type granites, as well as I-type and S-type granites is lighter than that of the mantle. Lithium concentrations in granites vary as a function of fractional crystallization and are mainly controlled by modal mineralogy. Lithium mostly behaves as an incompatible element during granite differentiation, although Li is compatible in hornblende and biotite during crystallization of mafic enclaves. By contrast, Li isotopic compositions of A-type granites and mafic enclaves are not controlled by fractional crystallization, comparable to that for I- and S-type granites, indicating negligible Li isotope fractionation during granite differentiation. Instead, they reflect source heterogeneity produced by mixing of isotopically heterogeneous lower crust and/or variable amounts of re-equilibration between enclaves and host granites. The Li isotopic compositions of A-, I- and S-type granites can be used to derive an independent estimate of the average Li isotopic composition of the continental crust (i.e., δ 7Li=+1.7, weighted mean of all granites), comparable to our previous estimate (δ 7Li=+1.2) that relies on large-scale sampling of upper, middle and lower continental crust. Compared to the mantle, the continental crust has lower δ 7Li, indicating the influence of weathering and recycling in controlling the Li isotopic composition of the continents. [Copyright &y& Elsevier]

The sizes, distributions and shapes of zircon grains within variably deformed granite gneiss from the western Alps have been studied. Zircon shows numerous indicators of a metamorphic response in both the host gneiss and a 5 cm wide continuous ductile shear zone, within which the zircon grain sizes range from <1 μm to >50 μm. However, the very fine grain sizes are virtually absent from grain boundaries. Within this zone, zircons consistently have more rounded and embayed margins, which are interpreted as evidence of dissolution in response to fluid influx during shearing. Zircons are preferentially located near metamorphic muscovite in both the host gneiss and the shear zone and tend to show the poorest crystal shape, indicating that fluids linked to the formation and presence of muscovite may enhance both the crystallization of zircon and its subsequent dissolution. Larger zircon crystals typically show a brittle response to deformation when adjacent to phyllosilicates, with fractures consistently perpendicular to the (001) mica cleavage. The variety of metamorphic behaviour observed for zircon indicates that it may be highly reactive in sub-solidus mid-crustal metamorphic environments. [ABSTRACT FROM AUTHOR]

A detailed field study to determine quantitatively the distribution of K-feldspar megacrysts, mafic microgranular enclaves (MME) and metasedimentary xenoliths has been carried out in the Monte Capanne pluton (Elba, Italy) with a view to evaluating the utility of this approach to petrogenetic investigations. Mafic microgranular enclaves are inferred to result from interactions between mafic and felsic magmas, while xenoliths attest to crustal assimilation occurring in the Monte Capanne magma chamber. In particular, we emphasize, based on our field data, that both processes are intimately linked, such that xenolith dissolution during assimilation was triggered by replenishment with hot mafic magma. It is suggested that the previously defined 'San Piero' and 'San Francesco' facies do not differ substantially, and are thus amalgamated and renamed as the 'Pomonte' facies. Results also indicate that the abundance of K-feldspar megacrysts is positively correlated with the volumetric abundance of MME in the Sant' Andrea facies, which we link to a recharging, mingling and textural coarsening event that occurred at a rather late stage of magma-chamber evolution prior to emplacement. This study demonstrates how petrogenetic processes can be deciphered by detailed field quantitative analyses of granite-forming components, thus complementing geochemical investigations. [ABSTRACT FROM AUTHOR]

Schlieren that form above the solidus are potentially diagnostic of the rheology of crystallizing granitic magmas and could provide insights into magma chamber structure. Here we focus on steep schlieren associated with comagmatic enclaves in the Vinalhaven granite. Steep schlieren extend 1–3 m upward from the sides of enclaves and appear to have steep cylindrical shapes in 3D. Analyses of schlieren widths and the sizes of associated enclaves suggest that granitic crystal mush in which they occur had a plastic rheology probably characterized by a yield strength. The enclaves, now enclosed in coarse-grained granite, must have existed at higher levels in a crystal-poor part of a magma chamber and settled downward until reaching material with a yield strength exceeding the buoyancy of the enclaves. In addition to constraining the local rheology of the granite, their relative positions may indicate vertical rheological variations and possibly the chamber floor. [ABSTRACT FROM AUTHOR]

Focuses on the Xihuashan granitic complex, which is characterized by rare-earth elements (REE). Enrichment of the second-stage granite (G-b) with yttrium; The complex associations of Y-bearing minerals; Specific yttrium zoning with an Y-rich core and a ‘clean’ rim in the garnet of this granite; Small inclusions of Y-bearing minerals; Discovery of a striking amount of Y and HREE in the magmatic fractionation; Suggestion that the ‘clean’ rim could be from the accumulation of fluid phases in the magma; Implication for REE in the garnet structure.

Summary ¶Mafic microgranular enclaves occur in most calc-alkaline granitoids, and it is widely accepted that they represent the remnants of basic magmas that interacted with more acid magmas. In this work we present new data on mafic microgranular enclaves occurring in the granodiorites of the Sithonia Plutonic Complex (Northern Greece). Enclave properties have been studied using different methods. Quantitative textural analysis has been carried out in order to decipher the crystallization history of enclaves once they have been entrained in the more acid and cooler host magma. In particular, the nucleation density (C), the mode (M) and the crystal index (n) of enclaves has been measured. Along with textural analysis, the size of enclaves has also been estimated using a method that, based on two-dimensional sections of enclaves, allows the estimation of volume of enclaves. Geochemical analyses have been performed to investigate the degree of chemical interaction that enclaves suffered from the host acid magma. The different data sets have been utilized to furnish a general evolutionary model of the magmatic interaction process between the basic and the acid magmas that led to the formation of the granodioritic host rock and related mafic microgranular enclaves. It is concluded that, as the magmatic interaction process proceeded, the crystallization of enclaves involved the nucleation of apatite and epidote (first stage of crystallization) followed by biotite, ± hornblende, plagioclase, and titanite (second stage of crystallization); the last minerals that nucleate were quartz and K-feldspar. During crystallization enclaves underwent contamination by the host acid magma through flow channels opened during the transfer of mineral phases from the host magma to the enclaves. When the two magmas attained similar rheological behaviour a two-end member mixing process was favoured inducing progressively more vigorous mixing dynamics. Volumetric analysis of enclaves indicates that the smaller ones suffered a more intense geochemical interaction compared to the larger ones. We interpret this evidence as being strictly related to the kinematics of the mixing process, the latter governed by chaotic dynamics. Enclaves are viewed as portions of the basic magma that did not mix completely with the acid host magma and survived the mixing process. Host rocks are considered as volumes of the magmatic system where the more efficient mixing dynamics produced different, generally higher, degrees of hybridisation. [ABSTRACT FROM AUTHOR]

Presents information on a study pertaining to the felsic enclaves which occur at the highest exposed levels of the Gouldsboro granite along the coast of Maine while focusing on their characteristics. Objectives of the paper; Where does magmatic microgramular enclaves (MME) occur; Information on the Gouldsboro granite.

Describes an alternative method of determining the age of the Manaslu pluton in Nepal by establishing the minimum age and cooling history of its contact aureole with 40 Ar/ 39 Ar incremental-heating and laser-microprobe techniques. Manaslu geologic setting; Description of the Manaslu granite; Cooling history of the Manaslu pluton.

Determines the ages of the Gaborone and Kanye rapakivi granite sequences in the Witwatersrand basin hinterland in southern Africa by using the Uranium-Lead zircon dating methods of T.E. Krogh. Sampling and geologic relations; Geochemistry of dated samples; Isotope results.

The Cadillac Mountain intrusive complex is dominated by the Cadillac Mountain granite and a 2–3 km thick section of interlayered gabbroic, dioritic and granitic rocks which occurs near the base of the granite. The layered rocks record hundreds of injections of basaltic magma that ponded on the chamber floor and variably interacted with the overlying silicic magma. Magmatic enclaves, ranging in composition from 55 to 78 wt % SiO2, are abundant in granite above the layered mafic rocks. The most mafic enclaves are highly enriched in incompatible elements and depleted in compatible elements. Their compositions can be best explained by periodic replenishment, mixing and fractional crystallization of basaltic magma at the base of the chamber. The intermediate to silicic enclaves formed by hybridization between the evolved basaltic magma and resident silicic magma. There is little evidence for significant exchange between enclaves and the enclosing granite. Instead, hybridization apparently occurred between stratified mafic and silicic magmas at the base of the chamber. Enclaves in a restricted area commonly show distinctive compositional characteristics, suggesting they were derived from a discrete batch of hybrid magma. Enclaves were probably dispersed into a localized portion of the granitic magma when replenishment or eruption disrupted the intermediate layer. [ABSTRACT FROM AUTHOR]