Amphibole-biotite Granites Research Articles

Nyatygran intrusive suite, Bureya massif: Petrography, geochemistry, and age

The proposed review and analytical article provides updated information on the geology, petrography, mineralogy, and chemical composition of rocks of the Precambrian Nyatygran intrusive suite. The article provides a geochemical interpretation of the chemical and trace element compositions and presents the most actual data on the uranium-lead isotopic age of the rocks. The igneous formations of the Nyatygran gabbro-granodiorite-granite complex make up small intrusive massifs of gabbroids and granitoids, located near the ore-bearing Mel’gin trough, in the basins of the Verkhny Mel’gin, Chepkan, and Bureya rivers and their tributaries. In the gabbroids, the main rock-forming minerals are labradorite, andesine, bluish-green hornblende, and biotite. The gneissic granitoids are dominated by cataclastic quartz and feldspars (andesine, oligoclase, microcline) and contain abundant micas (biotite, sericite). The subalkaline leucogranites are dominated by oligoclase, quartz, orthoclase, and microcline; they also contain significant amounts of biotite and aegirine and rare amphibole (hornblende). The gabbro and gabbrodiorites of normal and elevated alkalinity are assigned to the high-aluminous high-magnesian rocks. The gabbroids represent I-type igneous rocks. The gneissic granitoids of normal and elevated alkalinity are predominantly high-aluminous, more ferroan than magnesian rocks, and are represented by S- and I-type granitoids. The determined isotopic ages of the Nyatygran suite formations are confined to the three main ranges: 933 ± 12–916,3 ± 7,2 Ma (1st magmatic phase: gabbro, gabbrodiorites, amphibole-biotite granites), 909,0 ± 6,6–907,3 ± 5,5 Ma (2nd phase: granodiorites and granites), and 806,8 ± 6,6–789 ± 4,0 Ma (3rd phase: biotite granites and granite-porphyry dikes). The Nyatygran suite age is established as Neoproterozoic and corresponds to the early Neoproterozoic, or Tonian (1000–720 Ma), according to the International Chronostratigraphic Scale, 2018. On the 3rd generation 1:1 000 000-scale State geological maps of the Russian Federation, it is presented as Early Proterozoic.

Geochronology, geochemistry, and mineral chemistry of the Lingshan-Huangshan complex, South China: Insights into Nb and Ta enrichment

The Huangshan Nb-Ta deposit, located at the northern segment of the Qin-Hang metallogenic belt of South China, is closely associated with the Lingshan-Huangshan complex. As a large Nb-Ta deposit, with the Nb-Ta mineralization hosted by the late two phases of the Lingshan-Huangshan complex, the factors that led to Nb and Ta enrichment in the Huangshan deposit remain unclear. Therefore, we conducted a comprehensive investigation of petrography, geochronology, whole-rock geochemistry, and mineral compositions (zircon and mica) of the Lingshan-Huangshan complex. The Lingshan-Huangshan complex comprises the Lingshan coarse-grained porphyritic amphibole-biotite granite, the Huangshan coarse-grained biotite granite, the fine-grained albite-biotite granite, and the pegmatite from the center outwards. Zircon U-Pb dating shows that the different phases within this complex formed at 133.4–132.7 Ma. They are characterized by high SiO2 (66.46–79.11 wt%), total alkali (7.38–10.39 wt%) contents, moderate A/CNK values (average of 1.01), and high Ga/Al and Zr + Nb + Ce + Y values, presenting geochemical affinities to A-type granites. Combined with the pre-existing Nd-Hf isotopic data, they originated from the Proterozoic crust of South China with some input of juvenile crustal or mantle-derived materials. The whole-rock Al2O3, TiO2, and Fe2O3 contents and Nb/Ta and Zr/Hf ratios decrease with increasing SiO2 contents from the Huangshan coarse-grained biotite granite, the fine-grained albite-biotite granite to the pegmatite. These variations, together with the increasing Hf and Th + U + Y in zircon and increasing Rb, Nb, and Ta in mica, indicate that these phases (especially the late two) underwent highly fractional crystallization. The Lingshan coarse-grained porphyritic amphibole-biotite granite shares part of the whole-rock geochemical variations with the other phases, but its Nb/Ta ratios varied discordantly, which may be attributed to the solidified residual crystal-rich mush. The increasing F and Li in micas from the early to late phases of the Lingshan-Huangshan complex reflect enrichment of F and Li content during the magmatic evolution process, which is conducive to enhancing the solubilities of Nb and Ta in the melt. Accordingly, we suggest that the Nb-Ta enrichment in the Huangshan deposit is closely associated with highly fractionated magma and elevated volatile elements F and Li in melts.

Trace element composition of quartz from alkaline granites – A factor supporting genetic considerations: Case study of the Pitinga Sn–Nb–Ta–Th-cryolite deposit

The Madeira pluton, bearing the world-class tin-cryolite deposit of Pitinga, and the closely associated Europa pluton lie in the central part of the Amazon craton, Brazil. The Madeira pluton consists of four principal rock types: early metaluminous porphyritic amphibole-biotite granite with rapakivi texture, metaluminous biotite granite, metaluminous hypersolvus porphyritic granite, and peralkaline albite granite, while the Europa pluton consists of peralkaline riebeckite-biotite alkali feldspar granite. Texture and chemical composition of quartz from all mentioned rock types was evaluated in order: (i) to estimate the contents of trace elements in quartz from peralkaline granites, (ii) to define major differences in the uptake of trace elements into quartz in peraluminous vs. peralkaline conditions, (iii) to better constrain the evolution of the composite Madeira pluton. The contents of Li, Be, B, Na, Al, P, K, Sc, Ti, Mn, Fe, Ga, Ge, Rb, Sr, Zr, Nb, Sn, Sb, Ce, Yb, Hf, Ta, Th, and U in quartz were analyzed using laser-ablation ICP-MS. Quartz from the studied metaluminous and peralkaline granites of the Madeira and Europa plutons is poor in Al (<150 ppm Al) and Li (mostly <20 ppm Li) but enriched in Ge (max. 10 ppm), Sc (max. 6 ppm), and Ga (max. 13 ppm). As suggested by the TitaniQ thermobarometer, the Madeira biotite granite crystallized between ca. 700 and 650 °C at a nearly constant pressure of 3 kbar, while the hypersolvus granite crystallized between 800 and 700 °C at 15–20 to 2 kbar. Textural and chemical data on quartz are in agreement with previous geochronological data: the Madeira pluton comprises two older pulses of less evolved, mostly metaluminous biotite-hornblende and biotite granites, and two younger pulses of mutually mingled metaluminous hypersolvus granite and rare metal-enriched peralkaline albite granite. Differences in texture and composition of quartz do not support direct relations between the hypersolvus granite and the albite granite via magmatic fractionation, but exposure to similar metasomatic processes after their mingling is highly probable. Typical chemical features of quartz from peralkaline granites are relative high contents of Ti and Ge accompanied by low contents of Al and Li, forming an array along the Ti–Ge join in the Ti–Al–Ge ternary diagram.

Petrology and Geochemical Characteristic of Granitoids From Guéra Massif in the Central Part of Chad: An Example of Mixing Magmas

The granitoids of Gu&amp;eacute;ra Massif are composed of biotite-granite, amphibole-biotite granite and gabbro-diorite and commonly contain micro granular mafic enclaves which vary from monzogabbro to syenite composition. They are metaluminous, high-K calc-alkaline to shoshonitic series. Gabbro-diorite rocks are magnesian while amphibole-biotite granites are magnesian to ferroan, and biotite granites are ferroan. They are enriched in LREEs relative to HREE and display negative anomalies in Nb, Ta and Ti. Fields relationships, petrology and geochemistry indicate that mixing and mingling processes could be more relevant for the genesis of granitoids associated to fractional crystallization. Thus, the presence of mafic enclaves of gabbro-diorite composition in the granites, the resumption of alkaline feldspar xenocrystals in the gabbro-diorites, as well as the linear correlation between the granites and the gabbro-diorites and the intermediate position of the mafic enclaves between the two formations, enable us to propose magmatic mixing as the major process that presided over the evolution of the Gu&amp;eacute;ra granitoids. The delamination of the continental lithosphere during the post-collisional phase of the Pan-African orogeny would have caused the partial melting of the subduction-modofied mantle and lower continental crust and thus produced the magmas of the Gu&amp;eacute;ra granitoids.

Свойства и минералогический состав темногумусовой квазиглеевой солончаковой солонцеватой криотурбированной мерзлотной почвы Баргузинской котловины (Бурятия)

Morphological, physical-chemical properties, texture, salt composition mineralogical composition of the particle-size fractions 5 mkm of dark-humus quasigleyic solonchakous solonetzic cryoturbated deeply permafrost loamy-sandy soil developed from alluvial sediments (Salic Mollic Reductaquic Turbic Cryosol (Eutric, Loamic, Calcaric, Fluvic, Sodic)) are presented. The soil is situated at the northern-eastern part of Barguzin Depression in the impact zone of dumping of nitrogen siliceous thermal underground waters of Kuldur type (Kuchiger springs). The soil forms from materials of disintegration of high-content-potassium calcareous-alkali granites of Barguzin complex of Angara-Vitim Batholith. It was found soil salinity of weak to very strong degree, presumably sulfate-sodium with gypsum. There is a net of gypsum filaments in the solum that is observed by morphological analysis. Low amount of rectorite was found in clay fraction of undisturbed layers of alluvium at the depth of 54-145 cm in the studied soil profile. Regular structure of rectorite comprised mica (A) and smectite (B) packets with alternation motive ABAB… is transformed into irregular structure of mica-smectite interstratifications by impact of soluble sodium salts and cryoturbation of soil material in soil horizons at the depth of 0-54 cm formed from the alluvium. Regional peculiarity of studied soil is small shear of quartz in silt and sand fractions that is a result of mineral composition of biotite and amphibole-biotite granites and granitoids. Irregular mica-smectite interstratifications with high shear (>50%) of smectite packets are destroyed by impact of sodium sulfate and hydrocarbonates hydrogenic accumulation in the solum and are partially illuviated into middle part of soil profile with formation of humus-clay cutans on the lateral sides of aggregates by infiltration of rain waters. Existence of humus-clay cutans is an evidence of weak degree of solonetzic process.

The Pan-African Biotite-Muscovite Granite and Amphibole-Biotite Granite of Doua (Central Cameroon): Zircon Features, LA-MC-ICP-MS U-Pb Dating and Implication on Their Tectonic Setting

The Doua area belongs to the Adamawa-Yadé domain (AYD) of the Central African Fold Belt (CAFB) in Cameroon. It is crossed by the Central Cameroonian Shear Zone (CCSZ). The purpose of this research is to determine the tectonic setting of granites of the studied area, based on their petrography, zircons feature and their ages. Petrographicaly, the Doua area is made up of plutonic rocks hosted in an ortho or paraderivative metamorphic basement. Amphibole-biotite granite (ABG) and biotite-muscovite granite form hills and crop out on the hill side, as flagstones in the valley or river bed, and as huge blocks. Amphibole-biotite granite is granular in texture and made up of amphibole, biotite, feldspar, accessory minerals (Sphene, zircon, and apatite) and secondary minerals (sericite). Biotite-muscovite granite (BMG) is granular to granular porphyritic in texture, made up of biotite, muscovite, plagioclase, K-feldspar, quartz, accessory minerals (zircon, opaques minerals) and secondary minerals (chlorite, sericite). ABG show elongated zircon grains with well-developed magmatic oscillatory zonation. LA-ICP-MS U-Pb data from these zircons define a concordia age of 607 ± 3 Ma and considered as crystallization age of the granite. BMG shows zircon with various shape and various internal structures (oscillatory zonation, sector zonation, blurred oscillatory zonation …) which are divided into two sets. The first set regarded as xenocryst from Paleoproterozoic granitoids emplaced at 2126 ±36 Ma or from sediments which detritus comes from such granitoids. The second set of zircons shows effects of recent lead lost and a subconcordant U-Pb age of 646 ± 39 Ma . ABG was emplaced during the D3 deformational phase, date at 607 ± 3 Ma , while BMG was trigger because of syn-D1 activity of the CCSZ at 647 ±46 Ma in association with the collisional process.

Petrography and Geochemistry of the Mbip Granitic Massif, SW Tchollir&amp;#233; (Central North Cameroon): Petrogenetic and Geodynamic Implication

In this article, we discussed about the petrography and geochemistry of magmatic rocks of the Mbip massif located SW of Tcholliré, in Central North Cameroon (Central African Fold Belt). Petrographic study shows that this massif is made of granodiorite, amphibole-biotite granite, and biotite granite which often contain enclave of mafic rocks (gabbro). Granodiorites and granites show porphyritic texture and consist dominantly of plagioclase and alkaline feldspar phenocrysts, quartz, biotite and often few amphibole. The gabbro enclaves are characterized by a granular porphyroid texture constituted of amphibole, plagioclase and olivine phenocrysts, all in a matrix of small crystals of plagioclase, olivine, amphibole, pyroxene and opaque minerals. All the analyzed rocks provide geochemical features of sublkaline serie and have nothing to do with the alkaline nature previously signaled in the former works. Granodiorites and granites are shoshonitic to calc-alkaline strongly potassic affinity consistent with emplacement in the continental collision setting. They present positive anomalies in Rb, Th, U; negative anomalies in Sr, P, Ti, Nb, Ta and some facies contain hydrated minerals such as amphibole. These characters are consistent with crustal and mantle contribution in their genesis. The mafic rocks (gabbro) have geochemical characteristics conferring a mantle origin, as confirmed by the high Mg# value (49.9). On the whole, the fractional crystallization of the magma formed by melting of crustal material and the magmatic mixing are the main petrogenetic process in the Mbip massif. Petrographic studies and geochemical data shows that the Mbip massif was emplaced in an active continental margin, into transitional regime from the end of maximum compression to the beginning of relaxation.

ZONALIDADE REVERSA DOS GRANITOS DO COMPLEXO INTRUSIVO LAVRAS DO SUL, RS: PETROGRAFIA, SUSCETIBILIDADE MAGNÉTICA E ÓXIDOS DE FE-TI

We evaluate the magma redox conditions of granites from the Lavras do Sul intrusive complex - LSIC (ca. 606-586 Ma). The main goal is to explain the zoning of magnetic susceptibility-k that shows a concentric pattern revealing the reverse zoning of petrographic facies. The granite pluton includes: (a) alkali-calcic, biotite granodiorite and hybrid amphibole-biotite granites in the core (k of 4.0-7.5 10 -3 SI), and (b) alkaline, biotite-amphibole syenogranite and perthite granite that occur around the core (k of 9-10 10 -3 SI). All facies are ferromagnetic, and the differences in k-values are due to the distinct nature of parental magmas and to the variations in redox path shown by mafic phases (amphiboles, biotite and Fe-Ti oxides). Divergent Fe/Mg ratios between mafic silicates and rock imply an oxidizing environment for the crystallization of core types, in which the two Fe-Ti oxides are common (Ti-Mt:Ilm of 3:1 to 10:1). Such conditions were ascribed to the magmatic fluid phase on distinct situations, of crystal-volatile equilibrium (monzogranite) and of volatile exsolution (granodiorite). This reinforces that the core-granites represent distinct pulses of a hydrous magma (3-4 wt. % H 2 O) evolving at different pressure (4-2 kbar). The parental magma of alkaline granites had lower H 2 O content (~2 wt. %), and would be intrinsically oxidizing as suggested abundant Ti-magnetite (Ti-mt:Ilm ≥ 20:1) and primary titanite. Convergent Fe/Mg ratios for mafic phases and rock imply the mineralogical control in the redox path also marked by the decrease of pressure with differentiation (2-1 kbar). We conclude that the pluton formed during two major episodes of resurgence in a magma chamber related to the volcano-plutonic subsidence system-LSIC: a central event responsible for the alkali-calcic granites, and a circumferential one for the alkaline types. So, petrographic and magnetic zoning, strengthened by magnetic and gravity data, show such differences. Despite the low k-values in the core granites, a magmatic environment with varied fO 2 , allows the genetic link with the Au-Cu ore occurrences.

Geological Characteristics of the Furong Tin Orefield, Hunan, 40Ar‐39Ar Dating of Tin Ores and Related Granite and Its Geodynamic Significance for Rock and Ore Formation

Abstract Furong, Hunan, is a large tin orefield discovered in China in recent years, which is mainly of the skarn‐greisen‐chlorite type. On the basis of the geological characteristics of the orefield, 40Ar‐39Ar dating was performed on muscovite from greisen‐type tin ore and biotite from related amphibole‐biotite granite, which yielded three sets of age data, i.e., a plateau age of 157.5±0.3 Ma and an isochron age of 156.9±3 Ma for amphibole‐biotite granite; a plateau age of 156.1±0.4 Ma and an isochron age of 155.7±1.7 Ma for the Sanmen greisen‐type tin ore; and a plateau age of 160.1±0.9 Ma and an isochron age of 157.5±1.5 Ma for the Taoxiwo greisen‐type tin ore. The three sets of age data coincide well with each other. They not only accurately reflect the timing of rock and ore formation but also indicate close relations between granite and tin deposits. In addition, the plateau ages of all three sets suggest that no subsequent thermal perturbation event occurred after the formation of granite and tin deposits. The Furong tin orefield is a component part of the southern Hunan large tungsten‐tin polymetallic deposit concentration area and also a representative deposit formed in the time interval of 160–135 Ma in four peaks of Mesozoic tungsten‐tin mineralization in the South China region. They might still correspond to the middle and late stages of the major geodynamic transition from a N‐S‐ to an E‐W‐direction in eastern China.

Petrography and Geochemistry of the Carapé Granitic Complex (Southeastern Uruguay)

The southern sector of Uruguay was intruded by numerous granitic plutons during the Brasiliano Cycle. The granites and granodiorites of the Carapé Complex comprise a large part of the Neoproterozoic terrain exposed in southern Uruguay. Typological and age relationships show that the characteristic of the granitic rocks changed during the Brasiliano Cycle. Four groups of granitoids can be distinguished according to their emplacement. The first group corresponds to the Campanero Unit, interpreted as a pre-Brasiliano basement, which includes mainly preorogenic granites. The second group, Pan de Azúcar and related granitoids, includes synorogenic granites and granodiorites. The third granitoid group, Dos Hermanos Granite and related plutons, is classified as late- to postorogenic granites. Finally, the fourth group, consisting of the Águila Granite and related plutons, is represented by alkaline amphibole-biotite granites and are considered as post-collisional alkaline granites, which we assign to an extensional event associated with post-collisional slab-break off marking the end of the late Proterozoic Brasiliano orogenic cycle. Most of the granitic plutons in this area (2, 300 km 2) are relatively well exposed and have well-defined intrusive relationships with the metamorphic country-rocks. These granitic rocks are the result of successive magma pulses from similar magma chambers through the late Proterozoic to early Paleozoic times.

Absolute (U–Pb) and relative age determinations of intrusive rocks in the Ragunda rapakivi complex, central Sweden

The Ragunda complex (ca 550 km 2) is one of the two major rapakivi occurrences in central Sweden and forms, together with seven smaller complexes, the youngest group (1.53–1.47 Ga) of rapakivi complexes in the Fennoscandian Shield. In contrast to most of the classic Finnish rapakivi plutons the Ragunda complex consists of large amounts of mafic rocks and a substantial volume of syenite and quartz syenite. At the present erosion level, the Ragunda complex includes ca 30% gabbro, 5% syenite and quartz syenite and 65% amphibole–biotite and biotite granites. Minor amounts of hybrid rocks and a large number of acid and basic dykes are found as well. The complex consists of three massifs with distinctive aeromagnetic anomalies. The Western Massif is a centred complex in which magmatic activity began in the west and moved towards the east, forming a linear sequence of approximately circular gabbro, syenite and granite intrusions. The last intrusion, a amphibole–biotite granite, gave a U–Pb zircon age of 1514±5 Ma. The Central Massif is a large centred complex without any obvious linear intrusion sequence, and consists of several consecutively emplaced plutons including a late granite with a U–Pb zircon age of 1505±12 Ma. The Northeastern Massif is a small centred complex consisting of gabbro closely followed by granite. Magma mingling structures are observed throughout the complex, most commonly in contact zones between gabbro and granite. The generation of the Ragunda complex and the small complexes in central Sweden cannot be explained by a lithospheric plate moving over a stationary hot spot. Deep fractures formed in response to an extensional regime probably controlled the emplacement of the complexes. This is supported by the large number of subparallel mafic and acid dykes associated with them.

Pb-Nd-Sr isotopic and geochemical constraints on the origin of the 1.54–1.56 Ga Salmi rapakivi granite—Anorthosite batholith (Karelia, Russia)

The Salmi batholith is situated on the eastern edge of the EW-trending anorthositerapakivi granite belt of the Fennoscandian shield, at the contact between Proterozoic and Archean crustal domains. The tectonic setting and high K, Rb, Nb, Y, Zr, REE (except Eu), F, Sn, Be, and Li contents of.the Salmi batholith indicate that it represents typical subalkaline A-type and within plate granites. Gabbro-anorthosites of the batholith demonstrate a concordant U-Pb apatite age of 1563 ± 9 (2σ) Ma and a Sm-Nd internal isochron age of 1552 ± 69 Ma. Zircons from amphibole-biotite granites have an upper concordia intercept U-Pb age of 1543 ± 8 Ma. An older inherited zircon component with elevated Th/U ratio is found in zircons separated from K-feldspar ovoids. Rb-Sr internal errorchron for the granites yields an age of 1455 ± 17 Ma, probably the time of completion of postmagmatic processes within the batholith. The gabbro-anorthosites and granites show similar initial Nd, Sr, and feldspar Pb isotope compositions (ɛNd = - 6.5 to - 8.2;μ2 = 8.6 to 8.9;κ2 = 3.9 to 4.0; ISr = 0.7052 to 0.7057 for the basic rocks, andɛNd = -6.2 to -8.9;μ2 = 8.1 to 9.2;κ2 = 4.0 to 4.4; ISr = 0.7050 to 0.7072 for the granites). Two-stage neodymium TDM model ages for both assemblages range from 2.60 to 2.80 Ga. Old LREE-enriched sources with low time-integrated U/Pb and Rb/Sr and elevated Th/U ratios were involved in the formation of both the gabbroanorthosites and the granites. Bulk contamination with crustal materials cannot explain the data for the basic rocks. Selective incorporation of Pb, Sr, and Nd from Archean lower crust is needed, or else, the gabbro-anorthosites may have been derived from an isotopically anomalous subcontinental mantle source. The ascent of a mantle diapir resulted in anatexis of the lower crust and formation of the parent magma for the rapakivi granites.