Biotite Syenogranite Research Articles

Petrogenesis and metallogenic significance of late Mesozoic granites in the Akjilga mining area, Tajikistan: constraints from geochronology and geochemistry

The Akjilga (Акджилга) mining area in Tajikistan sits in the central part of the Pamir syntaxis in the western part of the Indo–Eurasia collisional orogenic belt. Recently, the mineralization phenomena of skarn-type tin polymetallic ore bodies and dolomite-type rare-earth metals in the copper polymetallic mining area have been reported. However, the limited knowledge on the genesis of granite and its relationship with mineralization in this area hinders further research. Here, the Late Mesozoic granite rocks in the mining area were studied by petrology, geochemistry, and zircon U–Pb dating. The results showed that the rocks comprise majorly porphyric biotite syenogranite and minorly porphyric biotite monzogranite. The zircon U–Pb age of the porphyric biotite syenogranite was 108.3 ± 2.0 Ma, highlighting the Early Cretaceous period. The porphyric biotite syenogranite features high silicon and potassium contents and low iron, magnesium, calcium, sodium, titanium, and phosphorus contents. Furthermore, their aluminum saturation indexes were 1.11–1.21. Therefore, they were classified as high-potassium calc-alkaline strong peraluminous rocks. Trace-element analysis showed the enrichment of large ionic lithophile elements and light rare-earth elements (REEs); the deficiency of high-field-strength elements and heavy REEs; and the negative anomalies of Nb, P, and Ti. Compared with ordinary granites, the porphyric biotite syenogranite exhibits a higher differentiation index (91.20–93.96) and strong negative Eu anomaly (0.05–0.26), as well as a low Zr content and abnormally low Nb/Ta, Zr/Hf, Y/Ho, ∑LREE/∑HREE ratios. Therefore, the rocks are considered highly differentiated I-type granites with good Sn polymetallic and rare-metal prospecting potentials, and it resulted in the subduction-collision of the Rushan-Pshart ocean between the Middle Pamir block and the South Pamir block during the northward subduction process of the Late Mesozoic New Tethys ocean (Shyok ocean).

The Amaros and Dois Córregos plutons: Mesoarchean and Orosirian magmatism in the northern Guanhães basement inlier, Araçuaí orogen, Brazil

In this paper we present new field, geophysical, petrographic, geochemical and geochronological data from granitic rocks newly recognized at the northern Guanhães block, one of the basement inliers of the Araçuaí orogen, eastern South America. Our data allowed the identification of two granitic units, namely Amaros and Dois Córregos plutons, intrusive in the Archean orthogneisses of the Guanhães Complex. In the studied area, the Guanhães Complex comprises muscovite-biotite gneisses, hornblende-biotite gneisses and clinopyroxene-hornblende-biotite gneisses. These rocks have distinct chemical characteristics, which range from TTG series to Late Archean hybrid granitoids. The Amaros pluton is composed of muscovite-bearing biotite metasyenogranites. These rocks are high-K calc-alkaline, magnesian and peraluminous, and were interpreted as a product of partial melting of an older TTG crust. U–Pb ICP-MS dating of zircons yielded a crystallization age of 2916 ± 19 Ma for Amaros pluton, which makes it the first Mesoarchean granite pluton delimited and detailed within the Guanhães block. Mesoarchean magmatism (ca. 2.9 Ga) similar in composition to the Amaros pluton is well known at the Porteirinha block, another basement inlier to the north of the Guanhães block, which raises questions about a connection between the two domains. The Dois Córregos pluton, firstly identified through geophysical analysis, is composed of hornblende-bearing biotite syenogranite crystallized at 2045.5 ± 24 Ma Ma (U–Pb in zircons, ICP-MS). These rocks are alkali-calcic to alkalic, magnesian to ferroan, ranging from per-to metaluminous and were interpreted as a product of the partial melting of continental crust, in a late-collisional stage of the Minas-Bahia orogeny, during the amalgamation of São Francisco-Congo paleocontinent.

Crucial control on magmatic-hydrothermal Sn deposit in the Tengchong block, SW China: Evidence from magma differentiation and zircon geochemistry

Magmatic-hydrothermal Sn deposits are commonly associated with high silica magmas, but why most global high silica granites do not bear economic Sn ore grades remains unclear. Two crucial factors controlling magmatic-hydrothermal Sn mineralization, including advanced fractionation and depressurization-induced rapid cooling, were revealed in the case study of the Guyong granitic pluton linked with the Xiaolonghe Sn deposit, in the Tengchong block, SW China. The Guyong granitic pluton comprises three petrological facies: less evolved biotite syenogranite, evolved alkali granite and leucogranite, and highly evolved facies (the protolith of greisenized granite). Similar crystallization ages (∼77 Ma) and gradual contact between different petrological facies indicate the Guyong granitic pluton records a continuous fractionation process. Monte Carlo-revised Rayleigh fractionation model suggests the fractionation degree of the Guyong pluton is markedly high (>87 wt.%) that can only be achieved by a high initial water (≥4 wt.%) content in the parent granitic magma revealed by rhyolite-MELTS calculation. Advanced degree fractionation causes the first Sn enrichment but it also significantly increases the viscosity of evolved magmas, suppressing the exsolution and transport of hydrothermal fluids. Hence, it must be compensated by the second critical factor: depressurization-induced rapid cooling, reflected by the occurrence of highly metamict zircons in the greisenized granite. The highly metamict feature, indicated by the large full width at half maximum (FWHM) values of zircon ν3(SiO4) peak (>19.5 cm−1), suggests these zircons do not experience thermal annealing but rapidly ascend into a shallow cooling environment. Depressurization-induced rapid cooling facilitates exsolution and transport of hydrothermal fluids, interacting with wall rocks and resulting in Sn mineralization.

Geochemical and REE mineralogical characteristics of the Zhaibei Granite in Jiangxi Province, southern China, and a model for the genesis of ion-adsorption REE deposits

The Zhaibei Granite in Jiangxi Province, southern China, hosts an ion-adsorption light rare earth element (LREE) deposit. Recently, heavy REE (HREE) ores have also been reported from weathered crusts of the granitic rocks. In this study, petrological, geochemical, and mineralogical characteristics of the Zhaibei pluton were analysed to establish the genesis of this REE deposit. The pluton contains coarse-grained biotite syenogranite and minor hornblende–biotite–quartz monzonite in its central zone, medium-grained biotite syenogranite in its transitional zone, and fine-grained muscovitic alkali-feldspar granite and porphyritic muscovitic biotite–alkali-feldspar granite together with monzogranite porphyry intrusions in its marginal zone. The REE minerals include titanite, allanite, monazite, bastnasite, and thorite-(Y) in the central zone, allanite, monazite, xenotime, bastnasite, and thorite-(Y) in the transitional zone, and synchysite-(Y), thorite-(Y), and xenotime in the marginal zone. The SiO2 content increases from 62 to 77 wt% from the centre to the margin, whereas the Al2O3, TiO2, MgO, FeO, and CaO contents decrease. In addition, the size of the negative Eu anomaly and HREE content increase, accompanied by decreases in Co, Zr, Hf, Sr, and Ba and increases in Rb, Cs, Nb, and Sn. These observations indicate that the Zhaibei Granite might have been formed by crystallisation differentiation of magma. The granitic pluton was also influenced by reactions with late-magmatic F-, CO2–, and REE-rich fluids that altered magmatic minerals and crystallised as REE-fluorocarbonates and thorite. The hydrothermal REE minerals constitute ∼ 40% of the total REEs in the bedrock and are the major supplier of ion-exchangeable REEs in the ores of the Zhaibei deposit. LREE-rich ores may have been derived from the LREE-rich granitic rocks, which contain bastnasite, titanite, and allanite, whereas HREE-rich ores were sourced mainly from the HREE-rich granites, which contain synchysite-(Y) and thorite-(Y). Furthermore, REE ores with enrichment in both HREEs and LREEs were probably sourced from the monzogranite porphyry bedrock, which contains bastnasite-(Y), bastnasite, allanite, and thorite-(Y).

Early Cretaceous A‐type Granites in the Dandong Area, NE China and its Geodynamical Implications

AbstractA‐type granites, as an important petrologic sign to build up environmental recognition, were mainly formed in extensional tectonic settings. A biotite syenogranite from the Fenghuangshan pluton in Dandong, Liaoning Province gave SHRIMP zircon U‐Pb ages of 122.5 ± 1.6 Ma, 124.9 ± 1.7 Ma and 126.9 ± 1.1 Ma. The monzogranites have SHRIMP zircon U‐Pb ages of 118.2 ± 1.6 Ma, 128.1 ± 1.7 Ma and 131.6 ± 1.9 Ma, giving an emplacement age for the pluton in the Early Cretaceous. SiO2 is 65.48–74.49 wt%, whereas that of K2O is 4.16–6.44 wt%, and that of Na2O is 2.99–4.70 wt%. They also contain 13.24–15.76 wt% of Al2O3, with an A/CNK ratio of 0.92–1.10, averaging 1.02. The alkalinity rate (AR) ranges from 2.68 to 5.12, and this range is within the AR of peraluminous type rocks. The granites of Fenghuangshan pluton are characterized by high contents of Na and K and low contents of Ca (thermophile element) and Mg, which are features of A‐type granites. The (Na2O + K2O) – Fe2O3∗ × 5 – (CaO + MgO) × 5 discrimination diagram also shows that Fenghuangshan pluton is an A2‐type granite. The above granite has zircon ∊Hf(t) values ranging from –17.06 to –9.09, with single‐stage Hf model ages (TDM) of 1141 Ma to 1498 Ma and two‐stage Hf crustal model ages (TDMC) of 1762 Ma to 2263 Ma. A comprehensive analysis suggests that the Fenghuangshan pluton might have been formed from the lithospheric‐plate sliding during the late stages of evolution of hot rift structures and might have been closely associated with the tectonic settings of Mesozoic Eurasia and the ancient Pacific Plate.

A newly Found Biotite Syenogranite in the Huangshaping Polymetallic Deposit, South China: Insights into Cu Mineralization

The W-Sn-Mo-Cu-Pb-Zn polymetallic mineralization in the Huangshaping Deposit is associated with different types of Jurassic granitic intrusions such as quartz porphyry, granophyre and granite porphyry. In this study, we carried out detailed mineralogical, petrological, geochemical, zircon U-Pb geochronological and Hf isotopic studies on a newly found, Cu-mineralization-related fine-grained biotite syenogranite at Huangshaping. This syenogranite is mainly composed of quartz (40%), K-feldspar (30%), plagioclase (15%) and biotite (5%), enriching in SiO2 (75.58 wt.%–76.02 wt.%), K2O (5.24 wt.%–5.78 wt.%), Al2O3 (12.23 wt.%–12.46 wt.%), Rb (405 ppm–504 ppm), U (18.5 ppm–40.7 ppm), Th (47 ppm–52.3 ppm), Nb (49.6 ppm–57.5 ppm), and Cu (54 ppm–288 ppm) whereas depleting in P2O5 (0.01 wt.%), TiO2 (0.05 wt.%–0.06 wt.%), Ba (5 ppm–13.1 ppm), Sr (6.8 ppm–23.9 ppm) and Eu (0.04 ppm–0.05 ppm), with A1-type alkaline granite characteristics. Magmatic and hydrothermal zircons were separated from a Cu-mineralized syenogranite sample and yielded the 206Pb/238U concordant ages of 156.5±1.8 and 154.4±2.9 Ma, representing the intrusive age of the pluton and probable Cu-mineralization time at the Huangshaping Deposit, respectively. Zircon Hf isotopes suggest a crust-derived (partial melting of Paleoproterozoic basement) magma for the syenogranite, with some degree of crust-mantle interaction. We infer that the syenogranite is a transitional phase between the granophyre and the granite porphyry, not only contributed greatly to the Cu mineralization but also provided W-Sn polymetallic ore-forming metals for the Huangshaping Deposit.

Highly differentiated magmas linked with polymetallic mineralization: A case study from the Cuihongshan granitic intrusions, Lesser Xing'an Range, NE China

The genetic link between granitoids and polymetallic skarn mineralization has remained equivocal. The Cuihongshan skarn-porphyry W-Mo-Pb-Zn-(Fe-Cu) deposit in the eastern part of the Central Asian Orogenic Belt provides a unique example to address this issue. The major rock types in the mine area are Early Paleozoic intrusions composed of biotite syenogranite and biotite porphyritic granite and Early Mesozoic intrusions represented by porphyritic quartz monzonite, biotite monzogranite, and porphyritic granite. The diagnostic mineralogical and geochemical features indicate that the rocks belong to A2-type granites. The Early Paleozoic suite shows zircon U-Pb ages of ~501Ma, and εHf(t) values of −4.4 to +2.7 and +2.4 to +7.6, respectively. In combination with their coherent geochemical trends, these rocks are inferred to be products of in-situ differentiation. Although the Mesozoic suite shows crystallization ages of 194–196Ma, εHf(t) values are in the range of −2.5 to +7.5 for the porphyritic quartz monzonite, the −1.8 to +4.5 values for the monzogranite and the +2.3 to +8.0 range for the porphyritic granite. The porphyritic quartz monzonite displays distinct mineral assemblage and shows significant compositional gap with the other two lithofacies. In contrast, the monzogranite and porphyritic granite have similar geochemical features, and are thus inferred to be co-magmatic. Considering the high SiO2 contents, variable εHf(t) (−4.4 to +8.0) and εNd(t) values (−8.4 to +0.28) for the two suites, we infer that both episodes of granitoid magmatism resulted from partial melting of crustal materials with a mixed source containing varying proportions of juvenile and Precambrian crustal components. The Early Mesozoic porphyritic granite shows a highly evolved F-rich geochemical affinity, and experienced magma-fluid interaction. Cassiterite from the calcic skarn and the magnesian skarn that coexists with magnetite orebodies shows a mean U-Pb age of 195.4±1.9Ma and 191.2±7.5Ma respectively, indicating that the mineralization is genetically related to the Mesozoic granitic rocks. We infer that halogen-rich magmatic-hydrothermal fluids were derived from the Early Mesozoic highly fractionated magma, and the spatial association of the metallic elements with different geochemical behavior in the Cuihongshan deposit is correlated to multiple stages of evolution of halogen-rich magmatic-hydrothermal fluids.

Geochemistry and zircon U–Pb–Hf isotopes of the granitoids of Qianjinchang pluton in the Xi Ujimqi, Inner Mongolia: Implications for petrogenesis and geodynamic setting

We conducted zircon U–Pb dating and geochemical analyses for the Qianjinchang (QJC) pluton in the Xi Ujimqi, Northeast China, with an aim to determine their ages, petrogenesis, and sources. The QJC pluton consists of coarse/medium‐grained biotite monzogranite in the core and fine‐grained biotite granodiorite in the rim; those rocks intrude into quartz diorite but are intruded by minor intrusive phases, including small biotite syenogranite, diorite bodies, late diorite, granodiorite, granite, and pegmatite dykes. Our new laser ablation inductively coupled plasma mass spectrometry zircon U–Pb data indicate that the QJC composite pluton composed of 2 phases of magmatic activities, with the ages of 301~313 Ma for the quartz diorite, 283 ± 1 Ma for the biotite granodiorite, 280 ± 1 Ma for the biotite syenogranite, and 280 ± 2 Ma for the diorite dyke. Hf isotopic analyses for the quartz diorite sample show εHf(t) = 3.75 to 11.72, with 2‐stage Hf model age (TDM2) ranging 568–1,078 Ma. The biotite syenogranite sample also shows a depleted εHf(t) = 4.47 to 8.71, withTDM2ranging 745–1,015 Ma, suggesting the major involvement of juvenile crustal components. The various εHfvalues of the QJC pluton indicate a hybrid magma source of juvenile material with old crustal component, and theTDM2values increase from the Carboniferous to Permian, which suggests an increasing proportion of old continental material during this period. Petrological and geochemical characteristics of the biotite granodiorite and biotite monzogranite samples suggest that they are S‐type granites and derived from partial melting of the clay‐poor, plagioclase‐rich psammitic source, produced at low‐medium pressure. The biotite syenogranite sample belongs to alkaline and shoshonitic series and probably formed by a hybridization process between basaltic magma and old continental components. Combined with previous studies on the contemporaneous magma‐tectonic activities in the Xilinhot microcontinent, we suggest that the QJC pluton formed in a postcollisional setting.

Rhyacian A-type tholeiitic granites in southern Brazil: Geochemistry, U–Pb zircon ages and Nd model ages

In the southern South American platform, 2.5 to 2.0Ga terranes, probably related to the Atlantica supercontinent, occur mainly as minor reworked inliers within Neoproterozoic, Brasiliano/Pan-African orogenic belts, as the Ribeira Belt in southern Brazil. The dispersion of such fragments has generated uncertainties about their geotectonic reconstruction, and their study has been supported mainly by elemental and isotope geochemistry. The southern Ribeira Belt lies between the Paranapanema and Luiz Alves cratons and contains reworked Neoarquean and Paleoproterozoic terranes which outcrop as basement nuclei in supracrustal sequences, as the Setuva Complex. The Água Comprida Suite, situated in the northern part of the Setuva Complex, consists of Amphibole-Biotite Syenogranite (ABS), Porphyritic Biotite Syenogranite (PBS), and Equigranular Biotite Syenogranite (EBS). All granites are foliated and intensively deformed. The oldest foliation (Sn) is marked by augen feldspars set in a recrystallized matrix, followed by a crenulation cleavage (Sn+1) which evolves to discrete shear zones. ABS is a metaluminous, reduced A-type granite with FeOt/(FeOt+MgO)>0.9, with high HFSE and REE contents, corresponding to magmas related to continental medium to high-K tholeiitic series. PBS and specially EBS are highly differentiated, metaluminous to peraluminous (EBS), oxidized granites. The increase of Al2O3 and Rb, and decrease of HFS and RE elements relative to ABS indicate their evolution from tholeiitic magmas. The Água Comprida Suite granites are cogenetic rocks evolved from a within-plate mantle source, marked by high Nb, Ta, and Y. The influence of previously metasomatised mantle sources is evidenced by negative Nb, Ti, and P anomalies. The age of ABS is 2187±26Ma, and that of PBS is between 2180±13 to 2186±22Ma. The Nd model age of 2.4Ga, and εNd(2.18Ga) between −0.23 and −0.27 support the interpretation of ABS being formed from juvenile material with a minor crustal component. The deviation of εNd(2.18Ga) for PBS and EBS (−0.69 to −2.65), plus the higher Nd model ages (2.4 to 2.5Ga) suggest crustal contamination. A post-collisional environment for the interaction of the mafic tholeiitic and felsic crustal magmas is suggested for the formation of the Água Comprida Suite, based mainly on geochemical features of these magmas. Post-collisional environments are still not described in the Rhyacian orogenies of southern Brazil, and this proposition may be an important contribution for the study of the final period of amalgamation of the Paleoproterozoic supercontinent in southern South America.

Petrogenesis and Mo mineralization of a granitic complex, Da Hinggan Mountains, NE China: insights from zircon U-Pb dating, major and trace element geochemistry, and Sr-Nd-Pb isotopes

Abundant Cu and Mo deposits are spatially related to granitic complexes in the Nuomin area, eastern Da Hinggan Mountains, China. The petrogenesis of these deposits is investigated using data from zircon U–Pb dating, whole-rock major and trace element geochemistry, and Sr–Nd–Pb isotopic compositions. The results show that the fine-grained biotite monzogranite and medium-grained biotite syenogranite formed in a Late Jurassic (155.7 ± 3.6 Ma) collision environment, characterized by fluid–melt interaction and plagioclase differentiation. These rocks belong to the high-K calc-alkaline, K-peraluminous series, indicating that the parent magma evolved from the low-temperature partial melting of lower crust, with geochemistry consistent with Neoproterozoic oceanic crust. The monzonitic diorite porphyrite, monzonite porphyry (with a crystallization age of 130.64 ± 0.74 Ma) and quartz monzonite porphyry belong to the high-K calc-alkaline, sodic, quasi-aluminous series. The results indicate petrogenesis in a post-collisional or late-orogenic tectonic environment, characterized by interactions with CO2-rich fluid and the fractional crystallization of amphibole, biotite and apatite. The parent magma formed from the partial melting of residual Neoproterozoic oceanic crust. The circulation of mineralized fluids was related to the petrogenesis of the monzonitic diorite porphyrite, monzonite porphyry and quartz monzonite porphyry. Copyright © 2015 John Wiley & Sons, Ltd.

Petrology and geochronology of the Bom Jardim de Goiás copper deposit (GO)

The Bom Jardim de Goias copper deposit is a remarkable example of a deposit formed in a Neoproterozoic juvenile arc in the South American Platform during the assembly of Gondwana. The deposit is inserted in the western margin of the Arenopolis Magmatic Arc, in the Tocantins Province. The host rocks comprise a volcanosedimentary sequence of intermediate to acid composition interpreted as crystal and ash tuffs. The tuffs represent calc-alkaline volcanism of rhyodacitic to dacitic composition, with lithogeochemical and biotite chemistry characteristic of magmas from intra-oceanic arcs. The tuffs are commonly cut by veins and veinlets with no preferential orientation and show eNd(t) values between +3.5 and +7.4 and T DM model ages ranging from 0.8 to 1.1 Ga, consistent with juvenile magmas generated in magmatic arc settings. Intrusive bodies in the volcanosedimentary sequence are represented by hornblende-biotite monzogranite, interpreted as Serra Negra Granite, and biotite syenogranite defined as Macacos Granite. The granites have geochemical characteristics of type I calc-alkaline granites, generated in a post-collision setting. Tholeiitic basalts intercalated with tuffs, interpreted as flows, show geochemical affinity with volcanic arc basalts, whereas the dikes that crosscut the granites have compositions characteristic of intra-plate tholeiitic basalts. The petrological data of the host and country rocks of the Bom Jardim de Goias area reveal an important production of calc-alkaline magma in a magmatic arc setting in western Goias around 750 Ma, genetically related to copper mineralization, and the generation of a non-mineralized post-collisional magmatism at 540 Ma.

Geochronology and geochemistry of the Early Cretaceous Jigongshan and Qijianfeng batholiths in the Tongbai orogen, central China: implications for lower crustal delamination

The Jigongshan and Qijianfeng batholiths in the Tongbai orogen consist mainly of porphyritic hornblende-biotite monzogranite, biotite monzogranite, and biotite syenogranite, which are variably intruded by lamprophyre, diorite, and syenogranite dykes. Mafic microgranular enclaves commonly occur in the hornblende-biotite monzogranite, whereas surmicaceous enclaves are found in the biotite monzogranite. Both batholiths have zircon U–Pb ages ranging from ca. 139 to 120 Ma, indicating their emplacement in the Early Cretaceous. The hornblende-biotite monzogranite has an adakitic affinity marked by relatively high Sr/Y and (La/Yb)N ratios, lack of Eu anomalies, low MgO and Ni contents, and Na2O > K2O. Its chemical compositions, combined with enriched Sr–Nd isotopic signatures, suggest formation by dehydration melting of mafic rocks in a thickened lower crust. This thickened crust resulted from the Permo-Triassic subduction-collision between the North China and South China blocks and persisted until the Early Cretaceous. The biotite monzogranite and biotite syenogranite have low Al2O3, CaO, and Sr contents, low Rb/Sr, FeOt/MgO, and (Na2O + K2O)/CaO ratios, and flat HREE patterns with moderate to weak Eu anomalies. They were produced by partial melting of crustal materials under relatively low pressure. Partial melting at different crustal levels could have significantly contributed to mechanical weakening of the crust. The diorite and lamprophyre dykes show linear trends between SiO2 and major or trace elements on Harker diagrams, with two lamprophyre samples containing normative nepheline and olivine. These rocks have high La/Yb and Dy/Yb ratios, both displaying co-variation with contents of Yb. They were originated from relatively deep lithospheric mantle followed by fractionation of olivine + clinopyroxene + apatite + Fe–Ti oxides. Extensive partial melting in the lithospheric mantle indicates relatively high temperatures at this level. We suggest that the presence of adakitic magmas, thickened but weakened crust and high temperatures in the lithosphere mantle point to lower crustal delamination in the Early Cretaceous in the Tongbai orogen.

Petrology and geochronology of the Bom Jardim de Goiás copper deposit (GO)

The Bom Jardim de Goiás copper deposit is a remarkable example of a deposit formed in a Neoproterozoic juvenile arc in the South American Platform during the assembly of Gondwana. The deposit is inserted in the western margin of the Arenópolis Magmatic Arc, in the Tocantins Province. The host rocks comprise a volcanosedimentary sequence of intermediate to acid composition interpreted as crystal and ash tuffs. The tuffs represent calc-alkaline volcanism of rhyodacitic to dacitic composition, with lithogeochemical and biotite chemistry characteristic of magmas from intra-oceanic arcs. The tuffs are commonly cut by veins and veinlets with no preferential orientation and show εNd(t) values between +3.5 and +7.4 and T DM model ages ranging from 0.8 to 1.1 Ga, consistent with juvenile magmas generated in magmatic arc settings. Intrusive bodies in the volcanosedimentary sequence are represented by hornblende-biotite monzogranite, interpreted as Serra Negra Granite, and biotite syenogranite defined as Macacos Granite. The granites have geochemical characteristics of type I calc-alkaline granites, generated in a post-collision setting. Tholeiitic basalts intercalated with tuffs, interpreted as flows, show geochemical affinity with volcanic arc basalts, whereas the dikes that crosscut the granites have compositions characteristic of intra-plate tholeiitic basalts. The petrological data of the host and country rocks of the Bom Jardim de Goiás area reveal an important production of calc-alkaline magma in a magmatic arc setting in western Goiás around 750 Ma, genetically related to copper mineralization, and the generation of a non-mineralized post-collisional magmatism at 540 Ma.

Geochemistry and geodynamic significance of the rare-earth mineralized Paleoproterozoic Longwangzhuang granite on the southern margin of the North China Craton

The Longwangzhuang granite pluton occurs on the southern margin of the North China Craton and consists mainly of biotite syenogranite with aegirine granite being locally distributed. The granites are characterized by high silicon and alkaline contents (SiO2=72.17%–76.82%, K2O+Na2O=8.28%–10.22%, K2O/Na2O≫1), AI (agpaitic index) =0.84–0.95, DI=95–97, ASI (aluminum saturation index)=0.96–1.13, and very high Fe* number (FeO*/(FeO*+Mg)=0.90–0.99), thus the granites are assigned to the metaluminous to weakly peraluminous, alkalic to calc-alkalic ferroan A-type granites. The granites are rich in large ion lithophile elements (LILE), especially high in REE concentrations (REE+Y=854×10−6–1572×10−6); whereas the enrichment of high strength field elements (Nb, Ta, Zr, Hf) is obviously less than that of LILEs, exhibiting mild depletions on trace element spider plots; and the rocks are significantly depleted in Ba, Sr, Ti, and Pb. The low ɛNd(t) values (−4.5–−7.2) and high model ages (2.3–2.5 Ga) of the granites as well as the low ɛHf(t) values (−1.11–−5.26) and high Hf model ages (THf1= 2.1–2.3 Ga, THf2=2.4–2.6 Ga) of zircons from the biotite syenogranite suggest that the granites were probably derived from an enriched mantle source. The zircons from the biotite syenogranite are mainly colorless transparent crystals exhibiting well-developed oscillatory zoning on the cathodoluminescence images with a LA-ICPMS zircon U-Pb age of 1602.1±6.6 Ma (MSWD=0.48). Petrochemical, trace elements, as well as Nd and Hf isotopic compositions of the rocks demonstrate that the granites were formed in a within-plate extensional tectonic regime possibly related to the breakup of the Columbia supercontinent. The granites were most likely formed through extreme fractional crystallization of alkali basaltic magma resulted from partial melting of the mantle, which was fertilized by recycling crustal rocks triggered by the delamination of lithospheric mantle and lower crust following the ∼1.8 Ga collision and amalgamation of the North China Craton which is part of the Columbia supercontinent. However, contamination of neo-Archean to Paleoproterozoic crustal rocks during the ascent and emplacement of the magma could not be excluded. Being the youngest known anorogenic magmatism on the southern margin of the North China Craton related to Columbia breakup, it might represent the break off of the North China Craton from Columbia supercontinent at the end of Paleoproterozoic.

Aspectos tectônicos das intrusões dos granitos do cerne, passa três e Rio Abaixo, sudeste do Pré-cambriano Paranaense. Estudo baseado em datações 39Ar-40Ar em Micas

The Cerne, Passa Três and Rio Abaixo granitic stocks are NE-SW-striking elliptic bodies intrusive in the metavolcano-sedimentary sequences of the southeastern portion of the Ribeira Belt (Paraná State, Brazil). These stocks are mainly biotite syenogranite, monzogranite and quartz-syenite with porphyritic textures containing microcline megacrystals. They are usually isotropic, but may also contain magmatic flow foliation and deformation restricted to the contact with the host rocks. These granites present petrological, geochemistries and geocchronological similarities, with many A-type characteristics, but they are enriched in Ba Sr and Zr. 40Ar-39Ar analyses of the Cerne Granite biotites indicate an integrated age of 557 ± 2 Ma, which is quite close to the lower Concordia intercept age interpreted as the crystallization age of about 563 Ma obtained by TIMS analysis of zircon from the Cerne and Rio Abaixo intrusions by Cury (2003). The 40Ar-39Ar determinations in the host muscovite schists from the vicinity of the Cerne granite are older (800-1200 Ma) than crystallization ages, indicating that the temperatures of the granite intrusion and of the regional metamorphic event that took place during the Brasiliano Cycle (c.a. 600 Ma) were not high enough to erase the isotopic record from these muscovites (T < 300ºC). These granitic stocks represent a late-orogenic magmatism (~560 Ma) in the context of the deformations phases registered in the Apiaí Domain, being different and subsequent to the event of Três Córregos - Cunhaporanga magmatic arc (c.a. 630-590 Ma). Their emplacement was closely associated with transcurrent shear zones and the development of the major antiforms and synforms during the Upper Proterozoic/Cambrian, associated with the final adjustments of the agglutination of the Gondwana Supercontinent.

The Temaguessine Fe-cordierite orbicular granite (Central Hoggar, Algeria): U–Pb SHRIMP age, petrology, origin and geodynamical consequences for the late Pan-African magmatism of the Tuareg shield

The Temaguessine high-level subcircular pluton is intrusive into the LATEA metacraton (Central Hoggar) Eburnian (2 Ga) basement and in the Pan-African (615 Ma) granitic batholiths along a major NW–SE oriented major shear zone. It is dated here (SHRIMP U–Pb on zircon) at 582 ± 5 Ma. Composed of amphibole–biotite granite and biotite syenogranite, it comprises abundant enclaves: mafic magmatic enclaves, country-rock xenoliths and remarkable Fe-cordierite (#Fe = 0.87) orbicules. The orbicules have a core rich in cordierite (40%) and a leucocratic quartz–feldspar rim. They are interpreted as resulting from the incongruent melting of the meta-wacke xenoliths collapsed into the magma: the breakdown of the biotite + quartz assemblage produced the cordierite and a quartz–feldspar minimum melt that is expelled, forming the leucocratic rim. The orbicule generation occurred at T < 850° and P < 0.3 GPa. The Fe-rich character of the cordierite resulted from the Fe-rich protolith (wacke with 4% Fe 2O 3 for 72% SiO 2). Strongly negative ε Nd (−9.6 to −11.2), Nd T DM model ages between 1.64 and 1.92 Ga, inherited zircons between 1.76 and 2.04 Ga and low to moderately high I Sr (0.704–0.710) indicate a Rb-depleted lower continental crust source for the Temaguessine pluton; regional considerations impose however also the participation of asthenospheric material. The Temaguessine pluton, together with other high-level subcircular pluton, is considered as marking the end of the Pan-African magma generation in the LATEA metacraton, resulting from the linear delamination along mega-shear zones, allowing asthenospheric uprise and melting of the lower continental crust. This implies that the younger Taourirt granitic province (535–520 Ma) should be considered as a Cambrian intraplate anorogenic event and not as a very late Pan-African event.

Geology and Pb-Pb Geochronology of Paleoproterozoic Volcanic and Granitic Rocks of Pitinga Province, Amazonian Craton, Northern Brazil

Pitinga Province is one of the main tin provinces of the Amazonian craton. The oldest unit in the studied area is the Iricoumé Group, which consists of rhyolites and rhyodacites with a 207Pb/206Pb zircon age of 1888 ± 3 Ma. This volcanic sequence is intruded by five A-type granite plutons. The studied portion of the Europa pluton is homogeneous, and composed of a peralkaline alkali-amphibole hypersolvus granite that yielded a 207Pb/206Pb zircon age of 1829 ± 1 Ma. The early facies of the Madeira pluton consists of a metaluminous amphibole-biotite syenogranite (rapakivi facies) with a 207Pb/206Pb zircon age of 1824 ± 2 Ma. It is intruded by a 1822 ± 1 Ma, mildly peraluminous biotite syenogranite. The later facies of this pluton consist of a porphyritic, hypersolvus, alkali-feldspar granite and an albite granite. Field relationships and an extensive drilling survey indicate that these two facies are sheet-shaped and were emplaced almost simultaneously. The hypersolvus alkali-feldspar granite has a 207Pb/206Pb zircon age of 1818 ± 2 Ma. Taking in account its field relationships with the albite granite, a similar age is assumed for the latter. The albite granite intrudes the biotite granite and rapakivi granite facies of the Madeira pluton, which was emplaced by shallow-level cauldron subsidence. The albite granite is sheet shaped and consists of a magmatic peralkaline cryolite-bearing core facies partially surrounded by an autometa-somatic peraluminous fluorile-bearing border facies. Both albite granite facies are strongly tin-mineralized and display anomalous contents of Nb, Rb, Zr, and REE. A massive body of cryolite and pegmatitic rocks is associated with the albite granite. The contrast in age between the Iricoume Group and the Europa + Madeira granites demonstrates that the plutons are not subvolcanic intrusions related to the extrusives. The ages of 1824 ± 2 Ma, 1822 ± 2 Ma, and 1818 ± 2 Ma obtained, respectively, for the amphibole + biotite syenogranite, biotite granite, and porphyritic hypersolvus granite of the Madeira pluton are consistent with the emplacement sequence inferred for these facies. These ages indicate that the Madeira pluton was emplaced in a relatively short time. Its facies are a little younger than the peralkaline granite of the Europa pluton, suggesting that the latter is not coeval with the Madeira peralkaline albite granite.

French Creek Granite and Hohonu Dyke Swarm, South Island, New Zealand: Late Cretaceous alkaline magmatism and the opening of the Tasman Sea*

The Hohonu Dyke Swarm and French Creek Granite represent contemporaneous and cogenetic alkaline magmatism generated during crustal extension in the Western Province of New Zealand. The age of 82 Ma for French Creek Granite coincides with the oldest oceanic crust in the Tasman Sea and suggests emplacement during the separation of New Zealand and Australia. The French Creek Granite is a composite A‐type granitoid, dominated by a subsolvus biotite syenogranite with high silica, low CaO, MgO, Cr, Ni, V and Sr and elevated high‐field‐strength elements (Zr, Nb, Ga, Y). Subordinate varieties of French Creek Granite include a hypersolvus alkali amphibole monzogranite and a quartz‐alkali feldspar syenite. Spatially associated rhyolitic dykes are considered to represent hypabyssal equivalents of French Creek Granite. The Hohonu Dyke Swarm represents mafic magmatism which preceded, overlapped with, and followed emplacement of French Creek Granite. Lamprophyric and doleritic varieties dominate the swarm, with rare phonolite dykes also present. Geochemical compositions of French Creek Granite indicate it is an A1‐subtype granitoid and suggest derivation by fractionation of a mantle‐derived melt with oceanic island basalt ‐ like characteristics. The hypothesis that the French Creek Granite represents fractionation of a Hohonu Dyke Swarm composition, or a mantle melt derived from the same source, is tested. Major‐ and trace‐element data are compatible with derivation of the French Creek Granite by fractionation of amphibole, clinopyroxene and plagioclase from mafic magmas, followed by fractionation of alkali and plagioclase feldspar at more felsic compositions. Although some variants of the French Creek Granite have Sr and Nd isotopic compositions overlapping those of the Hohonu Dyke Swarm, most of the French Creek Granite is more radiogenic than the Hohonu Dyke Swarm, indicating the involvement of a radiogenic crustal component. Assimilation‐fractional crystallisation modelling suggests isotopic compositions of French Creek Granite are consistent with extreme fractionation of Hohonu Dyke Swarm magmas with minor assimilation of the Greenland Group metasediments.