Data for: Discovery of kyanite in typical cordierite/sillimanite-bearing low- to medium-pressure pelitic granulites: constraint on Paleoproterozoic plate tectonics

Major metaperidotite bodies of the Central and Western Alps and of Liguria are former subcontinental Adriatic lithosphere (Piccardo et al., 1992; Lemoine et al., 1987; Trommsdorff et al., 1993). One of the largest masses of metaperidotite occurs at Val Malenco, Eastern Central Alps, with a surface area of over 130 km2. It is composed dominantly of fertile and depleted spinel lherzolites and of subordinate amounts of dunite; corundum bearing garnet clinopyroxenite and phlogopite hornblendite (Muntener, 1997). There is clear geological and petrological evidence for a pre-oceanic subcontinental setting of the Malenco mantle and for Jurassic emplacement and denudation within the Piemontese ocean basin. The evidence may be summarized as follows: The Malenco mantle is in part overlain by a lower crustal granulite complex consisting of kyanite-garnet rocks; migmatites; wollastonite bearing calc-silicate rocks and olivine-spinel marbles. Pelitic granulites and mantle rocks are crosscut and welded together by a gabbro complex, the Braccia Gabbro (Hermann, 1997), which is of Lower Permian age (Hansmann et al., 1996). After the gabbro intrusion the complex underwent granulite facies equilibration. This crust mantle transition was stable at 25-30 km depth for a period of over 50 million years (Hermann et al., 1997), and then was rapidly exhumed during Jurassic rifting. During this process large parts of the Malenco mantle were emplaced in the Piemontese ocean basin and denuded. Proof of this is provided by ophicarbonate rocks that were deposited on top of the Malenco mantle as fracture fillings and as debris flows containing blocks of serpentinized lherzolite and, at some localities, of platform carbonate sediments. The western parts of the Malenco mantle rocks are intruded and overlain by MOR-type basalts which form the basis of a Jurassic to Cretaceous, oceanic sedimentary sequence, the Forno unit. During its oceanic stage the Malenco mantle was partly serpentinized and, concomitantly, metarodingites formed from the Permian gabbro and Jurassic MORB dykes within the mantle rocks. It is suggested on the basis of structural geological arguments that the Malenco mantle was exhumed along a lithosphere- scale shear zone that dipped towards the Adriatic continent. This shear zone is preserved in exposures extending several kilometers. The shear zone contains in its brittle part components of crustal and mantle rocks (Ur-breccia, Trommsdorff et al., 1993). The fossil Malenco margin thus resembles in all its properties the modern Galicia margin of the Atlantic ocean described by Boillot et al. (1995).

Discovery of pelitic high-pressure granulite from Manjinggou of the Huai’an Complex, North China Craton: Metamorphic P–T evolution and geological implications

Introduction Iran hosts numerous types of Volcanogenic massive sulfide (VMS) deposits that occur within different tectonic assemblages and have formed at discrete time periods (Mousivand et al. 2008). The Sabzevar zone hosts several VMS deposits including the Nudeh Cu-Ag deposit (Maghfouri, 2012) and some deposits in the Kharturan area (Tashi et al., 2014), and the Kharturan area locates in the Sabzevar subzone of the Central East Iranian Microcontinent. The Sabzevar subzone mainly involves Mesozoic and Cenozoic rock unites. The Late Cretaceous ophiolite mellanges and volcano-sedimentary sequences have high extension in the Subzone. Based on Rossetti (Rossetti et al. 2010), the Cretaceous rock units were formed in a back-arc setting due to subduction of the Neo-Tethyan oceanic crust beneath the Iranian plate. The exposed rock units of the Kharturan area from bottom to top are dominated by Early Cretaceous, orbitolina-bearing massive limestone, dacitic-andesitic volcanics and related volcaniclastic rocks٫ chert and radiolarite and Late Cretaceous globotrunkana- bearing limestone, paleocene polygenic conglomerate consisting of the Cretaceous volcanics and limestone pebbles (equal to the Kerman conglomerate), and Pliocene weakly-cemented polygenic conglomerate horizon. The Garmabe Paein copper-silver deposit and the Asbkeshan deposit and a few occurrences, are located at 290 km southeast of Shahrood and they have occurred within the Upper Cretaceous volcano-sedimentary sequence in the Sabzevar subzone. The aim of this study is to discuss the genesis of the Garmabe Paein deposit based on geological, textural and structural, mineralogical and geochemical evidence. Materials and methods A field study and sampling was performed during the year 2013. During the field observations, 94 rock samples were collected from the study area, and 45 thin sections were prepared and studied using a polarizing microscope. Also, 5 samples for the XRD method, 21 samples for the XRF and ICP-OES methods were analyzed in the Iranian Mines and Mining Industries Development and Renovation (IMIDRO) Company labs. Results The Garmabe Paein copper-silver deposit is located in the Sabzevar subzone of the Late Cretaceous Volcanio-sedimentary sequence. This mineralization occurred as stratiform and stratabound in a specific stratigraphic horizon. The host rocks of mineralization are andesitic-dacitic volcanic rocks and their related volcaniclastics. The mineralization occurred as four ore facies, from footwall to hanging wall: vein-veinlet-s (stringer), massive, bedded and exhalites. Ore textures and structures involve massive, semi-massive, laminated, banded, vein-veinlets, replacement and open space fillings. Minerlogically, the deposit contains primary minerals such as pyrite, chalcopyrite and magnetite, and secondary minerals such as native copper, cuprite, covellite, malachite and Fe-Mn oxides. Wallrock alterations are dominated by chloritic and minor siliceous and argillic. The highest grades of gold and silver in the deposit are 1 and 19 grams per ton, respectively. The amounts of Zn, Pb, Au, As, Ag and Mn increase from the stringer to the upper part of the deposit. It seems that the occurrence of submarine volcanic activity in the Late Cretaceous back- arc basin have resulted in the deposition of this Besshi type massive sulfide deposit. Discussion Most of characteristics of the Garmabe Paein Cu-Ag deposit including tectonic setting, geological environment, host rocks, geometry, textural and structural, mineralogical and geochemical features, are very similar to those of the Besshi- or pelitic mafic-type (Franklin et al., 2005) volcanogenic massive sulfide (VMS) deposits. Acknowledgements The authors are grateful to the University of Shahrood Grant Commission for research funding and the IMIDRO Company. References Franklin, J.M., Gibson, H.L., Galley, A.G. and Jonasson, I.R., 2005. Volcanogenic massive sulfide deposits. In: J.W. Hedenquist, J.F.H. Thompson, R.J. Goldfarb and J.P. Richads (Editors), Economic Geology 100th Anniversary Volume. Society of Economic Geologists, Littleton, Colorado, pp.523-560. Maghfouri, S., 2012. Geology, mineralogy, geochemistry and genesis of Cu mineralization Within Late Cretaceous Volcano- sedimentary sequence in southwest of Sabzevar, with emphasis on the Nudeh deposit. M.Sc. Thesis, Tarbit Modares University, Tehran, Iran, 312 pp. (In Persian with English abstract) Mousivand, F., Rastad, E. and Peter, J.M., 2008. An overview of volcanogenic massive sulfide deposits of Iran. 33rd International Geology Congress Oslo, Oslo, Norway. Rossetti, F., Nasrabady, M., Vignaroli, G., Theye, T., Gerdes, A., Razavi, M. and MoinVaziri, H., 2010. Early Cretaceous migmatitic mafic granulites from the Sabzevar range (NE Iran): implications for the closure of the Mesozoic peri- Tethyan oceans in central Iran. Journal of Terra Nova, 22(1): 26-34. Tashi, M., Mousivand, F. and Ghasemi, H., 2014. Volcanogenic massive sulfide Cu-Ag mineralization in the Kharturan area, southeast of Shahrood. 1th International Workshop on Tethyan Orogenesis and Metallogeny in Asia and Silk Road Higher Education Cooperation Forum, China University of Geosciences (Wuhan), Wuhan, China.

Structural evolution in the Palaeoproterozoic Banded Iron Formation of SW Egypt The exposed basement of the Western Desert of Egypt is part of the pre-Pan-African East Sahara Craton. The Gabel Uweinat-Bir Safsaf Aswan Uplift is situated at the eastern fringe of this craton, and its high-grade metamorphic and granitoid rock associations are markedly distinct from the metavolcanic-metasedimentary-ophiolitic sequences of the Eastern Desert of Egypt (Nubian Shield). Crystalline basement rocks cover an area of some 40,000 km2 in SW Egypt. The fieldwork and mapping of the basement rocks in the present area were carried out during the winters 1998, 1999 and at last in 2001 for altogether about 10 months of fieldwork. A detailed field geologic-structural map to the scale of 1:60,000 and two cross sections, perpendicular to the regional structural trend for the whole area, are prepared using vertical aerial photographs and Landsat images. Detailed petrographic studies of the different rock units were carried out to determine their compositional character and the effect of deformation on each rock unit. Some 125 rock specimens representing the different rock units were collected and more than 130 thin sections were examined petrographically using the polarizing microscope. Microstructure studies and (analyses) attempted to determine the structural evolution and possible transport direction from about 40 oriented thin sections parallel and perpendicular to the foliation. Further structural data, from the anisotropy of the magnetic susceptibility (AMS) was determined from 31 oriented samples, which were cored and cut (200 cylinders). The magnetic susceptibility measurements were analyzed with the Kappa bridge. The BIF is exposed as an upper unit, while anatexite forms a middle one, underlain by ultramafic-mafic units. The BIF shows large quartz crystals with wavy extinction and undeformed recrystallized quartz. The Anatexite sequences were affected by granulite facies metamorphism, followed by a retrograde metamorphism. The petrographic study shows some orthopyroxene crystals altered to hornblende, biotite and chlorite. The structural analysis of the area indicated that it was subjected to major tectonic deformation including folding, overthrusting, shearing and faulting. The area is built up of thrust slices of the BIF and Anatexite, which extend for more than 25 km in N15°E direction, dipping to the west with angles between 30° to 70°. The thickness of slices horses is up to 4 km. The thrust sequence in this area has about 20 km width. Thrust Faults have been derived from overturned folds, the shear surface replacing one of the limbs of the fold. The structure is dominated by a series of nearly parallel, minor thrust faults, or high angle reverse faults, which dissect the rock into slices, sheets, plates, blocks or wedges that are approximately equidistant and have the same displacement and are all steeply inclined to the WNW (285°). Restoration of this thrust sequence shows that the anatexite forms a basement to the overlying BIF. Both metamorphic banding in the anatexite and the layering in the BIF restore to a horizontal primary orientation. The Deformational Evolution Three major deformation phases can be discerned in the study area (D1, D2 and D3), the three phases D1, D2 and D3 affected only the basement rocks and are followed by Phanerozoic brittle deformation affecting both the basement and the overlying sedimentary rocks in the investigated area. The D1 structures indicate a crustal thickening followed by crustal thinning and developed the melano- and leucosome in the Anatexite sequences. A foliation (S1) observed in the thin section of the BIF as simple shear mylonitization zones. Generally in (D1) the Anatexite bands are parallel with the mylonitic shear zones in the BIF. The D2 structures dominate in the BIF as a micro and macro folding (F2) associated with low angle thrust or shear zones (S2). In the Anatexite and the Ultramafic-mafic sequences minor folds with the same characters as in the BIF are observed. Generally in (D2) the BIF and Anatexite bands had E-W strike and dipped shallowly to the south (S2), and contain minor folds (F2) with E-W axial surfaces. The D1 and D2 deformations are both of them overprinted by the D3 structures, which refolded the F2 at a perpendicular direction of the fold axes by F3. The D3 affected refolding and thrusting at the BIF, Anatexite sequences and Ultramfic-mafic bands as F3 and S3. The F3 has NNE trend and plunge with an angle of 15°. The foliation S3, is parallel to the fold axial surfaces and thrust surfaces. The dip angle ranges between 30° and 70° to the WWN (285°).

The Late Cretaceous sedimentary melanges from the External Liguride Units of Northern Apennines include large slide-blocks of subcontinental mantle peridotites, MORbasalts and lower and upper continental crust rocks. The slide-block association has been interpreted as representative of a continent-ocean transition between the Internal Liguride oceanic domain (Late Jurassic Western Tethys) and the thinned continental margin of the Adria plate (Marroni et al., 1998). The slide-blocks of lower continental crust consist of mafic and felsic granulites, which locally preserve primary contacts. The mafic granulites commonly display a metamorphic layering, but undeformed rocks preserving a gabbroic fabric are locally found. Undeformed mafic granulites are mostly represented by spinel-bearing gabbronorites, usually containing significant amounts of either olivine or Fe-Ti-oxides. Olivine- and Fe-Ti oxide-bearing rocks locally show spinel-pyroxene symplectites and garnet coronas, respectively. The felsic granulites are mainly quartzo- feldspathic rocks consisting of mesoperthitic to perthitic feldspar, quartz and garnet. The gabbroic protoliths of the granulites were emplaced at about 290 Ma at deep crustal levels, where they underwent slow cooling and recrystallisation under granulite-facies conditions (P = 0.7-0.8 GPa, T = 800-900°C). They were exhumed to upper levels, in association with the felsic granulites, in late Triassic-middle Jurassic times. The gabbro-derived granulites can be recognized as cumulus rocks with negligible amounts of residual trapped liquid, on the basis of low SiO2/Al2O3 ratios and overall low contents of incompatible trace elements. The Mg# value ranges from 80 to 52, and point to negative correlations with TiO2 and MnO, thus indicating a tholeiitic differentiation trend. Most gabbro-derived granulites have slightly LREEenriched patterns showing decreasing Eu positive anomaly with increasing total REE abundances. Chondrite normalization of incompatible trace elements reveals spikes at Ba and Sr, and a slight Zr depletion. The quartzo-feldspathic granulites have LREE enriched patterns, with nearly flat HREE and no or slightly positive Eu anomaly; Ba is abruptly enriched relative to REE, whereas Nb and Ti are depleted. The gabbro-derived granulites show a wide range in Sr and Nd isotopic compositions. The Sr isotopic ratio recalculated at 290 Ma varies between 0.7031 and 0.7077, and the initial eNd ranges between +6.8 and -4.5. Two samples of quartzo-feldspathic granulite yield age-corrected Sr isotopic ratios of 0.7107 and 0.7109, and eNd of -8.0 and -5.7. As a whole, the Nd and Sr isotopic data at 290 Ma form a hyperbolic array, in which the olivine-bearing gabbronorites have the highest eNd values and the lowest Sr isotopic ratios. Clinopyroxenes have been analyzed for trace elements by ion microprobe. Clinopyroxene from olivine-bearing gabbronorites shows peculiar compositions that indicate a metamorphic origin through olivine-plagioclase reaction, i.e. the igneous protoliths of the olivine-bearing gabbronorites were most likely troctolite-type cumulates. Clinopyroxenes from Fe-Ti oxide bearing gabbronorites show igneous geochemical trends, thus suggesting that these rocks contained clinopyroxene as original igneous phase. Petrography, bulk-rock and mineral composition indicate that the gabbro-derived granulites can be related to a fractional crystallization process, with early separation of olivine and plagioclase, followed by the replacement of olivine by pyroxene at the liquidus. Trace element modelization of the parental liquid compositions applied to the olivine-bearing rocks yields LREE- and LILE-enriched liquids, with absence of negative Nb anomaly, similar to plume-type MOR-basalts and continental tholeiites. However, a P-MORB origin seems to contrast with the initial Nd and Sr isotopic compositions, which are close to depleted mantle values at the time of emplacement. AFC modelization was successfully applied to obtain the isotopic compositions of the most contaminated samples, starting from the trace element and isotopic compositions of the parental liquids of the olivine gabbronorites and assuming a crustal contaminant with low Sr/Nd and isotopic composition comparable to that of the quartzo-feldspathic granulites. AFC calculations also indicate that the parental liquids of the olivine-bearing gabbronorites cannot be ascribed to N-MORB primary liquids. The primary mantle magma was necessarily characterized by moderate LILE enrichment, although an increase in LILE concentrations could have been enhanced by a small crustal contribution. The LILE enrichment in the parental liquids of the gabbro-derived granulites may be explained with a low degree partial melting of a rather fertile lithospheric mantle source. Alternatively, the primary liquids of the gabbro-derived granulites were related to a mantle source enriched in LILE as a result of the Variscan subduction event.

This paper deals with the metamorphic evolution of the Bacariza Fm that outcrops in the two uppermost structural units of the Cabo Ortegal Complex (NW Iberian Massif). This formation includes ultramafic and mafic granulites, garnet amphibolites and garnet trondhjemitic gneisses. Although mineral associations characteristic of high pressure granulites predominate in the least retrogressed of these rocks, the presence of relic kyanite along with the fact that plagioclase only appears in symplectitic textures resulting from de-jadeitization of pyroxenes point to an earlier eclogite facies metamorphism. Thermobarometric estimations indicate higher P-T conditions for the rocks in the uppermost structural unit.

There is a typical assemblage of garnet + kyanite + microperthite + quartz + rutile in high-pressure (HP) felsic granulite of Qinling complex in Songshugou area. East Qinling. The HP granulite was formed at 800 -900℃ and 1.3 -1.6GPa and has experienced two stages of retrograde metamorphism at 600- 650 ℃, 0.8-1.0GPa and 500-600℃, 0.3-0.6GPa, forming two retrograde metamorphic assemblages of margarite + plagiodase (PlI)+quartz and sillimanite + biotite + plagioclase(PlII) + microdine+quartz, respectively. They construct a two-stage clockwise P-T path which shows down-pressure cooling in both early and late stage.

The inner zone of the Sardinia Variscan segment consists of two metamorphic complexes: I) A polymetamorphic Migmatite Complex, with migmatites showing polyphase anatectic processes, in the presence of kyanite or sillimanite. The Migmatite complex preserved decametric lenses of eclogite relicts (eclogites A) affected by high T, high- to intermediate P recrystallization under granulite facies conditions The decompressional garnet + Ca-clinopyroxene + amphibole ± orthopyroxene-bearing assemblages developed in granoblastic textures generally in no stress conditions. In most cases, only symplectite textures provide evidence for the eclogitic event. II) A medium grade, mostly metapelitic complex consisting of Grt, Ky, Stau-bearing micaschists and paragneisses includes quartzites and garnet-bearing amphibolite boudins with N-MORB chemical affinity. Relicts of eclogite assemblages were locally found in the metabasite (eclogites B). In eclogites A, the geothermobarometric parameters yield temperatures in the range 690°-760°C for minimum pressure A1.3 GPa. Pyroxene compositions accord with temperatures in excess of 700°C. In eclogites B, the thermometric calibrations provide temperatures in the range 610°-700°C for pressures 1.3-1.5 GPa, based on the jadeite content. The temperatures are consistent with the biotite+muscovite+garnet+kyanite+staurolite assemblage in the host paragneisses, and with lack of anatectic processes. The age of 457±2 Ma, obtained by U/Pb dating on one sample of Type A eclogite is interpreted as a minimum estimate for the magmatism of the eclogite protolith. A second zircon population defined an age of 403±4 Ma interpreted as dating the zircon crystallization during the high-grade event. The relationships between Types A and B eclogites, and their bearing on the regional framework (Sardinia, Ligurian Alps) are discussed.

Nitrogen-bearing fluids, brines and carbonate liquids in Variscan migmatites of the Tatra Mountains, Western Carpathians - heritage of high-pressure metamorphism

The granulites of the Juiz de Fora Complex (JFC) integrate the pre-1.8 Ga basement of the Intermediate Thrust Sheet of the Ribeira Belt's central segment. This tectonic domain is characterized by intense tectonic imbrication of the JFC granulites with Meso- to Neoproterozoic metasedimentary units. In the Rio Preto (MG)-Vassouras (RJ) region, the JFC comprises three lithological associations: orthogranulites, orthogneisses and paragranulites which crop out as several thrust sheets formed by intense shortening during the Brasiliano Orogeny. The main contacts are characterized by the transformation of the granulites into amphibolite facies mylonites. The geochemistry of the orthogranulites leads to the identification of two tectonic associations. One comprises two calc-alkaline series compositionally similar to rocks of modern magmatic arcs, while the other contains two groups of basic rocks, respectively the tholeiitic series and alkaline to transitional basalts, both of intraplate extensional tectonic setting. The relationships between these distinct tectonic environments need further geochronological background, as the Brasiliano shortening obliterated the original paleogeography of this important Paleoproterozoic segment of the Ribeira belt.

For the first time, an unusual assemblage of talc-phengite-chlorite-K-feldspar was found in quartz schists from the Sanandaj-Sirjan zone in the Nahavand area in western Iran. The talc-bearing quartz schists occur as small bodies or lenses within pelitic schist layers and contain talc, phengite, chlorite, K-feldspar and quartz as major mineral constituents with subordinate amounts of calcite and graphite. Textural analysis revealed that talc, phengite, chlorite and K-feldspar are in sharp contact and no reaction rims between them were observed. Constructed petrogenetic gird in the K 2O-FeO-MgO-Al2O3-SiO2-H2O (KFMASH) model system containing talc, phengite, chlorite, K-feldspar, phlogopite and kyanite with excess quartz and H 2O shows that divariant assemblage of talcphengite- chlorite-K-feldspar is stable over a wide P-T range defined by the following two univariant reactions: phengite + talc + quartz = chlorite + K-feldspar + kyanite + H 2O and chlorite + phlogopite + quartz = talc + phengite + K-feldspar + H 2O. Constructed Al2O3-KAlO2-MgO+FeO (AKM) compatibility diagrams predict that phengite (X Ph = 0.280, YPh = 0.860), chlorite (XChl = 0.570, YChl = 0.640), talc (XTlc = 0.160, YTlc = 0.02) and Kfeldspar are stable at P = 11 kbar and T = 400°C. This relatively high-pressure assemblage could be formed during the subduction of the Neo-Tethys oceanic plate under Iranian microcontinent.

Role of the overriding plate in the subduction process

The Dam Feliciano Belt is a Pan-African mobile belt from the Ribeira orogen of southern Brazil. A detailed field and geochemical traverse along the BR392 road section between Pelotas and Caҫapava do Sul identifies two major tectonic domains; the Pelotas Batholith and the Santana Metamorphic Belt, striking NNE-SSW parallel to the major foliation of the belts. The two belts are separated by a Triassic basin with flat lying red beds and interbedded andesites and rhyolites. The Santana Metamorphic Belt is a NW-verging fold belt with a metamorphosed shelf sequence of quartzites, marbles and graphitic schists and a polydeformed Lower Proterozic gneissic basement deformed during the Pan-African orogeny. Detailed mapping recognized four phases of deformation in the basement gneisses, three of which are recorded in the basement schists and cover sequence. There is also evidence of late NE-verging thrusting post-dating the formation unmetamorphosed Paleozoic sediments. Late extension caused NW-SE and NE-SW normal faulting. Metamorphism occurred contemporaneously with D2 and 03, and PT conditions for peak: metamorphism have been calculated as 8.6Kb and 600°C within the basement schists corresponding to garnet growth during D3 deformation. Three phases of granite intrusion are recognized in the Santana Metamorphic Belt The Santana Granite (8oom.y.) represents the first phase intruding the basement and it is folded by 02 and 03. The Campinas Granite (500m.y.) has a D3 foliation and the Caҫapava Granite (474m.y.) is post-tectonic and intrudes the NW portion of the Santana Metamorphic Belt The Pelotas Batholith is almost entirely composed of granitoids of Pan-African age (600- 4S0m.y.). Both D2 and D3 are recognized in the batholith. A two fold subdivision based on geochemical and field criteria distinguishes the following categories of granitoid; foliated granitoids and unfoliated granites. Geochemically all granitoids of the two belts have a strong crustal signature. The foliated granitoids of the Pelotas Batholith (600-550m.y.) are metaluminous, calkalkaline granodiorites, and have volcanic arc characteristics with Sr initial ratios between 0.708 and 0.710 and model ages in the range of 1.6-1.4b.y. The unfoliated granites (500-450m.y.) of the Pelotas Batholith are slightly peraluminous and their field relations, trace element and isotopic data suggest a post-collision setting for their formation. Their higher Sr initial ratios (0.710-0.770), Nd model ages of 1.2-1.1b.y. and high source Rb/Sr, support the proposal that they are melts of the migmatized granodiorites. The Canguҫu Red Granite and the Capao do Leao Granite are also unfoliated but appear to be geochemically distinct from the other unfoliated granites. They have high Fe/Mg, Rb/Sr and Rb/Ba ratios, flat rare earth element patterns and negative europium anomalies, all suggestive of A-type granites. From isotopic studies, the Canguҫu Granite has very high Sr initial ratios of 0.750 to 0.81 and old model ages of 2.0-3.0b.y. In the Santana Metamorphic Belt, the foliated Santana Granite has a more depleted trace element chemistry than foliated granites of the Pelotas Batholith and an earlier emplacement age of 8oom.y. Trace element and isotope modelling suggest it to be a melt of the basement gneisses. The Campinas Granite is strongly peraluminous with high Rb/Sr, Rb/Ba and Sm/Nd and initial ratios between 0.780 and 0.820 and model ages of 2.0 b.y. suggesting that it is a crustal melt from a pelitic source. The unfoliated Caҫapava Granite of the Santana Metamorphic Belt has low Rb/Ba, a low Sr initial ratio (0.705) and high model age (2.5b.y.) suggesting it is a lower crustal melt. The unfoliated Encruzilhada Granite is fault bounded and outcrops between the two belts. It is distinctive from granitoids of both belts in terms of its trace element and isotopic characteristics which suggest that it formed from a basaltic source in a within plate tectonic setting. There appears to be no systematic change in geochemistry with distance along the cross-section and any changes appear to be temporal. Combined Sr and Nd isotope studies suggest that the Pan-African Ribeira orogen represents a period of crustal reworking rather than crustal growth and in this respect resembles the Damara orogen of Namibia which is dominated by crustal reworking, in contrast to the rapid crustal growth observed in the Arabian shield.

Paleoproterozoic metamorphism of high-grade granulite facies rocks in the North China Craton: Study advances, questions and new issues

This thesis presents new geological, structural and metamorphic maps for the Palaeoproterozoic Sefwi Greenstone Belt of SW Ghana in the West African Craton. It explores characteristics unique to new crustal material made two billion years ago and elucidates the contrasting mechanisms and processes of crustal growth and mountain building early in the Earth's history. With this research, we are better able to understand evolutionary changes in the plate tectonic processes that have shaped the Earth as we know it today.