Age Of Granitoids Research Articles

Geochronology and geochemistry of granitoids of the Yanghuidongzi porphyry Cu deposit, Heilongjiang Province: Implications for petrogenesis and metallogenic setting during the Early Jurassic in the Northeast of China

AbstractThe Yanghuidongzi Cu deposit is a newly discovered porphyry Cu deposit in the eastern segment of the Central Asian Orogenic Belt. The Cu mineralization is associated with granodiorite porphyry and granodiorite. This paper presents new zircon U–Pb dating, Hf–O isotopes, whole‐rock major and trace elements data for this deposit, to constrain the ore‐forming age and the magma source of the granitoids. LA–ICP–MS U–Pb dating of zircons from granodiorite porphyry and granodiorite samples yielded ages of 192.8 ± 1.7 Ma, and 198.1 ± 1.4 Ma, respectively, which are interpreted as the emplacement ages of granitoids. These age data confirm that the granodiorite porphyry is associated with the porphyry Cu deposit, and both granitic intrusion and Cu mineralization were associated with the Early Jurassic magmatism in NE China. The granodiorite porphyry has high SiO2, Al2O3, and Sr contents together with low concentrations of Y and Yb. It is enriched in LILE, and depleted in HFSE, classified as adakitic. The granodiorite has high SiO2 and K2O, enriched in LILE, depleted in HFSE, and is classified as high‐K calk‐alkaline I‐type granite. The granodiorite porphyry and granodiorite have variable εHf(t) values (5.2 to 9.5), Mesoproterozoic two‐stage Hf models (TDM2) of 629–905 Ma, and δ18O values (4.26‰ to 7.50‰). These geochemical data and zircon Hf–O isotopes suggest that the granodiorite porphyry originated from the partial melting of thickened juvenile crustal materials and granodiorite derived from the partial melting of juvenile crustal materials with an additional of mantle‐derived magmas input. Combining our new data with the regional tectonic setting, the Yanghuidongzi Cu deposit and the related granitoids formed in a compressional tectonic setting associated with the subduction of the Paleo–Pacific Plate beneath the Eurasian continent.

Origin of the internal basement massif of the Guatemala Suture Zone: evidence from U-Pb geochronology and Sm-Nd and Lu-Hf isotope systematics

Abstract The origin of eclogite-bearing granitoid gneisses and metapelites of the Chuacús Complex is investigated. This complex represents the internal basement massif of the Guatemala Suture Zone, a part of the western North America–Caribbean plate boundary. LA-ICP-MS U-Pb and trace element zircon data are combined with whole-rock Sm-Nd and Lu-Hf isotopes to re-evaluate granitoid petrogenesis and inquire into the sedimentary record. New granitoid ages of ca. 1030–1010 Ma are reported, adding to those already known of ca. 1100, 990 and 225 Ma. Stenian A-type granitoids within the bimodal Cubulco unit formed by mixing of magmas derived from late Palaeoproterozoic crust and mantle-derived melts produced in an extensional setting during Rodinia assembly. During the Tonian, an extended (or later) period of extensional tectonics produced peraluminous granitoids (Pachajob gneiss) by anatexis of rejuvenated late Mesoproterozoic crust. After a hiatus encompassing most of the Neoproterozoic, marine sedimentation occurred between the Ediacaran and the early Palaeozoic as recorded by the Palibatz schist, a sequence formed by detritus sourced from peri-Gondwanan continental areas. No evidence of middle to late Palaeozoic magmatism or sedimentation was found in the studied area. Late Triassic granitoids (Agua Caliente unit) were produced by mixing melts from late Mesoproterozoic crust with enriched mantle magmas in response to post-collisional thinning during the western Pangea breakup. This extensional stage led to considerable thinning of the Chuacús crust and its evolution into a passive margin that would be prone to subduct during the Cretaceous.

Monazite and titanite U[sbnd]Pb ages of granitoids from the North Qinling Terrane: Implications for the subduction of the Shangdan Ocean and accretionary processes

The early Paleozoic granitoids of the North Qinling Terrane have been widely viewed as the products of an Andean-type margin related to the long-lasting subduction of the Proto-Tethys (Shangdan) ocean. However, the spatial and temporal distributions of the arc granitoids coupled with subduction-accretion processes are still a subject of debate. Here, we report LA-ICP-MS UPb monazite and titanite ages and trace element concentrations for granites and a paragneiss from the North Qinling Terrane. The results, together with data in the literatures, are used to reconstruct the magmatic evolution related to the subduction of the Shangdan ocean during the early Paleozoic. As revealed by UPb geochronology, subduction-related magmatism in the southern belt of the North Qinling magmatic arc (NQMA) was most active between 423 and 404 Ma, and therefore younger and shorter than previously speculated. The ages are in agreement with a metamorphic monazite UPb age (415 Ma) obtained from the paragneiss, suggesting that crustal anatexis of the NQMA was contemporaneous with the magmatism. Overall, magmatism in the NQMA moved progressively from north to south. This southward propagation is consistent with roll-back of the Shangdan oceanic slab and transition from an oceanic arc into a back-arc basin setting. The timing of magmatism and migmatization as well as high-temperature granulite metamorphism in the NQMA signifies that the Shangdan ocean retreated to the North Qinling Unit before c. 423 Ma. Monazites from NQMA generally show HREE depletion and negative Eu anomalies, and some display the REE tetrad effect. These geochemical features indicated that the NQMA granites were highly fractionated. In addition, the abrupt changes in REE compositions displayed by titanites probably record a mixing event with a mafic magma along the Shangdan suture zone.

Geodynamic Formation Conditions and Age of Granitoids from Small Intrusions in the West of the Yana–Kolyma Gold Belt (Northeast Asia)

Abstract We report results of geological, mineralogical-petrographic, geochemical, isotope-geochemical (Sm–Nd, Rb–Sr), and geochronological (U–Pb, 40Ar/39Ar) studies of acid and intermediate intrusive rocks (granodiorites, leucocratic granites, subalkaline granites, and subalkaline leucocratic granites, diorites, and quartz diorites) of the Bukeschen and Samyr small plutons in the western part of the Yana–Kolyma gold belt (northeast Asia). These rocks are combined with Late Jurassic (151–145 Ma) dikes of basic, intermediate, and acid compositions into a single complex of small intrusions. They intrude the Upper Triassic–Middle Jurassic terrigenous deposits of continental margin blocks in the eastern part of the Verkhoyansk–Kolyma folded area. Our new U–Pb data for zircon (SHRIMP-II) indicate that the Bukeschen and Samyr pluton granitoids formed in the Berriasian, at 144.5 and 143 Ma, respectively. The small-intrusion granitoids have geochemical and isotope (Sm–Nd and Rb–Sr) characteristics similar to those of Late Jurassic dikes of varying composition. Therefore, they can be united into a single complex of small intrusions generated from a mixed source with the participation of mantle (OIB- and E-MORB type), lower crust, and subduction components and with Paleoproterozoic–Mesoproterozoic Sm–Nd model age estimates for the magma sources. Late Jurassic–Early Cretaceous magmatic and postmagmatic events and cooling of the intrusions played an important role in the processes of gold localization in the western part of the Yana–Kolyma gold belt. This is reflected in two tectonothermal stages (accounting for closing temperatures of the U–Pb, 40Ar/39Ar, and Re–Os isotope systems for different minerals) estimated at 151–141 and 138–137 Ma. These results for the small-intrusion complex agree with the tectonic model of the evolution of an active continental margin (northeastern Siberia) in the Mesozoic era, whose final development stage in the Berriasian age saw the formation of mostly small granitoid plutons.

Paleoarchean evolution of the Singhbhum Craton, eastern India: New constraints from geochemistry and geochronology of granitoids of Bonai and Champua area

The Singhbhum Craton, one of five major Archean cratons in the Indian subcontinent, contains abundant well-preserved Paleoarchean supracrustals and granitoids. This study presents zircon U-Pb ages and whole rock geochemistry of tonalite-trondhjemite-granodiorites (TTGs) and granites from the Bonai Granite Complex (BGC) and Older Metamorphic Tonalite Gneiss (OMTG), which are separated from each other by the Jamda-Koira-Noamundi Iron Ore Group (IOG) supracrustals. Emplacement ages obtained in this study indicate that a major episode of TTG magmatism took place in BGC around 3368 ± 8 Ma (1σ), followed by granitic magmatism around 3331 ± 33 Ma (1σ). In contrast, a TTG from the Deo Nala area representing OMTG yielded crystallization age of 3312 ± 8 Ma (1σ). The emplacement and evolution of the BGC were coeval with granitoid magmatism from the central part of the Singhbhum Craton. Whole rock geochemical data identify both high- and low-HREE TTGs in both the BGC and OMTG to the west and east of the IOG basin, respectively. The trace element systematics of high-HREE Bonai TTG are similar to those of Icelandic dacites, suggestive of their derivation from a garnet free, plagioclase rich amphibolite. The low-HREE TTGs of the BGC and OMTG were derived from an amphibolite source with varying amounts of garnet. The potassic granites of the BGC were sourced from the older TTGs which had undergone partial melting at a shallow depth. The evolution of the BGC and OMTG can be attributed to the partial melting under a thickened mafic crust. Dome and keel structures and emplacement ages of granitoids from the west and east of the Jamda-Koira-Noamundi IOG basin, support the origin of these Paleoarchean granitoids in a stagnant lid regime. High geothermal gradients induced by heat supplied by mantle upwelling appear to have induced the melting of the thickened crust, to form the TTG. Delamination induced mafic–ultramafic underplating resulted in melting of early formed TTGs, to form the younger potassic granites of the BGC at ∼ 3.33 Ga.

Deciphering crustal growth in the southernmost Arabian Shield through zircon U-Pb geochronology, whole rock chemistry and Nd isotopes

ABSTRACT New U-Pb zircon geochronology using high-spatial resolution secondary ion mass spectrometry fills a data gap and provides crystallization ages for granitoids from the Asir composite terrane in the southernmost Arabian Shield of Saudi Arabia. Ages of c. 810–685 Ma, c. 663–636 Ma, and 625–610 Ma reflect oceanic island arc genesis, subduction-related arc accretion (syn-collisional), and post-collisional stabilization, respectively. All samples have juvenile εNd(t) compositions with no evidence of older material being involved in their genesis, indicating that this part of the Arabian Shield grew through juvenile magmatic addition and that assimilation by syn- and post-tectonic magmatism involved an isotopically juvenile component(s). The crustal thickness derived from the (La/Yb)N proxy indicates significant thickening from 10–20 km to c. 70 km at c. 650 Ma, consistent with timing of orogenic uplift and increasing crustal thickness post-dating peak Nabitah orogeny. The age of an intrusion cross-cutting the Atura formation, when combined with other data, provides a well-constrained depositional age of c. 646–625 Ma for the Atura formation and indicates that erosion of the orogenic edifice in this part of the Arabian Shield began at latest by 625 Ma. Our new data indicate that denudation occurred 80–100 m.y. before the development of the prominent sub-Cambrian peneplain, consistent with previous assertions that major pulses of denudation occurred prior to the waning stages of Nabitah orogenesis.

Mesozoic Intracontinental Orogeny in the Tectonic History of the Kolyvan’– Tomsk Folded Zone (Southern Siberia): a Synthesis of Geological Data and results of Apatite Fission Track Analysis

Abstract —The Kolyvan’–Tomsk folded zone (KTFZ) is a late Permian collisional orogen in the northwestern section of the Central Asian Orogenic Belt. The Mesozoic history of the KTFZ area includes Late Triassic–Early Jurassic and Late Jurassic–Early Cretaceous orogenic events. The earlier event produced narrow deep half-ramp basins filled with Early–Middle Jurassic molasse south of the KTFZ, and the later activity rejuvenated the Tomsk thrust fault, whereby the KTFZ Paleozoic rocks were thrust over the Early–Middle Jurassic basin sediments. The Mesozoic orogenic events induced erosion and the ensuing exposure of granitoids (Barlak complex) that were emplaced in a within-plate context after the Permian collisional orogeny. Both events were most likely associated with ocean closure, i.e., the Paleothetys Ocean in the Late Triassic–Early Jurassic and the Mongol–Okhotsk Ocean in the Late Jurassic–Early Cretaceous. The apatite fission track (AFT) ages of granitoids from the Ob’ complex in the KTFZ range between ~120 and 100 Ma (the Aptian and the Albian). The rocks with Early Cretaceous AFT ages were exhumed as a result of denudation and peneplanation of the Early Cretaceous orogeny, which produced a vast Late Cretaceous–Paleogene planation surface. The tectonic pattern of the two orogenic events, although being different in details, generally inherited the late Paleozoic primary collisional structure of the Kolyvan’–Tomsk zone.

Металлогения Конгинской зоны Омолонского террейна (Северо-Восток Азии)

The article presents new data on geology, mineralogy, and geochemistry of porphyry-copper, gold-silver, and silver-polymetallic ore occurrences in the Kongin magmatic zone of the Omolon terrane and granitoids, associated with it. It has been demonstrated that petrology and the age of granitoids are similar to those in the OCVB Penzhina segment. Mineralization of the Kongin zone is very close to that of the OCVB, differing in relatively high Mo in porphyry-copper ores and prevalence of silver-polymetallic mineralization over gold-silver.

Zircon U-Pb Age of Granitoids from the Mamu Pb-Zn Skarn Mineralized Area in Western Gangdese and Its Geological Significance

Zircon U-Pb Age of Granitoids from the Mamu Pb-Zn Skarn Mineralized Area in Western Gangdese and Its Geological Significance

THE U-Pb AGE AND Lu-Hf ISOTOPE SYSTEMATICS OF ZIRCON FROM THE HULIAIPOLE MET AVOLCANICS, THE AZOV DOMAIN OF THE UKRAINIAN SHIELD: EVIDENCE FOR THE PALEOARCHEAN-HADEAN CRUST

The Azov Domain occurs as a part of a larger Mesoarchean (3.2-3.0 Ga) craton, fragments of which are preserved in the eastern part of the Ukrainian Shield and as a block of the Kursk Magnetic Anomaly (KMA). In the Neoarchean-Palaeoproterozoic time, it was fragmented into several tectonic blocks: Vovcha, Remivka, Huliaipole, Bilotserkivka, and Saltych. The northern part of the Huliaipole Block is composed of tonalite-trondhjemite-granodiorite (TTG) rock association, that hosts the Kosivtsevo greenstone structure. It is composed of metamorphosed rocks of the jaspilite-komatiite-tholeiite association (the Kosivtsevo unit), which corresponds to the Sura Suite of the Konka Series of the Middle Dnieper Domain. The Neoarchean-Paleoproterozoic formations are represented by volcano-sedimentary rocks of the Huliaipole Suite and granitoids of the Dobropillya and Anadol complexes. Granitoids of the Dobropillya complex host numerous pyroxenite, gneiss, and plagioclase granite xenoliths. The U-Pb zircon age of granitoids of the Dobropillya Complex is 2040 Ma and inherited zircon has an age up to 3400 Ma. Small intrusions of two-feldspar granites of the Anadol Complex are widespread in the Ternuvate structure. Their U-Pb monazite age is 2190 Ma. In the central part of the Huliaipole Block, the NW-striking Huliaipole syncline (3.5 × 9 km) occurs. This structure is composed of volcano-sedimentary rocks of the Huliaipole Suite, which unconformably overlie Archean TTG. Felsic and intermediate metavolcanics are confined mainly to ferruginous quartzites of the middle Subsuites. To a limited extent, meta-andesites and felsic metavolcanics are also found in the lower and upper Huliaipole Subsuites. Zircons from meta-andesites and felsic metavolcanics of the Huliaipole Suite are very heterogeneous, indicating their crustal derivation. The U-Pb age of zircon populations from metadacite of the Huliaipole Suite was determined using the LA-ICP-MS method at 3085-2850 and 3700-3360 Ma. In addition, the age of the two crystals exceeded 3800 Ma. According to geological and geochronological data, the Huliaipole Block, 30 × 50 km in size, is composed of rocks and relicts of the Hadean, Archean, and Palaeoproterozoic eons. The oldest nucleoid of the Azov Domain.

Early Neoproterozoic (~920 Ma) Granite–Gneiss of the Junggar Alataw, South Kazakhstan: Age Substantiation Based on the Results of U–Th–Pb (SIMS) Dating

Based on the results of U–Th–Pb (SIMS) dating, an Early Neoproterozoic (924 ± 4 Ma) age was obtained for granite–gneiss of the Sarychabyn Complex, which is one of the oldest complexes in the Junggar Alataw Range. This value constrains the minimum age of the metasedimentary rocks of the Sarychabyn Group hosting granite–gneiss as well. The most likely age of metasediments is Late Mesoproterozoic–Early Neoproterozoic, which is consistent with the age of lithologically similar complexes in the adjacent regions of Kazakhstan and China. The age of the gneiss of the Sarychabyn Complex coincides with the ages of anorogenic granitoids and felsic volcanic rocks from the Aktau-Mointy massif of Central Kazakhstan and the ages of granitoids in the Wenquan Complex in China. An episode of granitoid magmatism at ~920 Ma, widespread in the Aktau-Junggar microcontinent, is a characteristic feature that distinguishes it from other Precambrian crustal blocks of Kazakhstan and the Northern Tianshan.

Chemical composition and age of monazite-(Ce) in granitoids of the crystalline basement from the South Yamal

The relevance of the work is due to the need to improve the method of chemical dating as applied to high-thorium accessory minerals, which are difficult to date by isotope research methods. Purpose of the work: study of the chemical composition of accessory monazite from granitoids of the crystalline basement of the South Yamal and determination of its age. Research methodology: quantitative analysis of the chemical composition of monazite was carried out using X-ray spectral electron probe microanalyzer CAMECA SX 100 (electron beam diameter from 1 μm, BSE, SE, Cat modes, determination of elements from beryllium to uranium). The spectra were obtained with the help of inclined wave spectrometers, the intensity was measured using analytical lines: Th Ma, U Mb, Pb Ma, Y La, Si Ka, Ca Ka, P Ka, Ce La, La La, Pr Lb, Nd La, Sm Lb, Dy La, Gd Lb. The age calculation was carried out according to the well-known methods of foreign authors in addition to some developments of the author. Results. The chemical composition of monazite makes it possible to classify it as a cerium variety, the content of radiogenic components varies greatly (in wt.%): ThO2 – 5.37–16.31, UO2 – 0.40–0.81, PbO – 0.08–0,19. There are significant concentrations of SiO2 (up to 3.5 wt.%), Y2 O3 (up to 1.8 wt.%) and CaO (up to 1.2 wt.%). It turns out that monazite implements hattonite (Th4+(U4+)+Si4+ → REE3++P5+) and cheralite (Th4+(U4+)+Ca2+(Sr2+,Ba2+,Pb2+) → 2REE3+) isomorphism types. The decent content of lead and high crystallinity of the substance makes it possible to use this mineral as a geochronometer mineral. Conclusions. New data on the chemical composition of monazite have been obtained, and the late Permian age of granitoids has been determined by microprobe dating. The values of the point U–Th–Pb ages of monazite together give a weighted average age of 256 ± 10 Ma (MSWD = 0.15) and an isochron of 254 ± 19 Ma (MSWD = 0.28), which almost ideally coincides with the results of isotopic U–Pb zircon dating from the same rock, 254 ± 3 Ma.

The Zirconometry and Thermochronology of Migmatized Gneisses of the Gondaray Metamorphic Complex (Greater Caucasus)

The results of the isotope dating of the crystalline basement of the Greater Caucasus (the Elbrus subzone of the Main Caucasus Range) within of the high-temperature gneiss–migmatite area of the Gondaray metamorphic complex is discussed. The relationships between regional metamorphism, migmatization, and heat flows in the lithosphere are considered. The measurements of the zircon isotope compositions were performed on a SHRIMP-II ion microprobe at the CIR VSEGEI (St. Petersburg). All zircon crystals from gneiss sample 526 have a zonal structure with ancient detrital cores. Almost all U–Pb isotope dating points lie on the concordant line and show a wide age range from 320–1000 Ма, partially inherited from detrital zircon grains from primary pelitic sediments. The youngest ages (320 Ма) were measured in the regeneration zones of zircon grains recrystallized during stage of the anatexis and migmatization. The other points of detrital zircons form an age cluster of 540–1000 Ма, which indicates their origin from different magmatic sources that existed during the formation of the protometamorphic protolith. Several detrital zircon grains yielded a Cambrian age; this is evidence for an Early Paleozoic age of the metamorphic protolith, which was traditionally suggested to be Precambrian or even Archean. The ages of the rims of recrystallized zircons (320 Ма) have a direct correlation with the postmetamorphic granitoid ages of the Greater Caucasus. The thermochronological modeling of the transformation of the Gondaray metamorphic complex during the retrogressive stage of metamorphism demonstrates that its cooling from the temperature of migmatite crystallization (650°С) to the closure of the temperature of the K–Ar biotite isotope system (350°С) was relatively rapid (the rate of cooling was 8–10°С/Ma) under subisobaric conditions and during a time range approximately 30–40 Ма.

The age of mineralization of Mayskoe gold ore deposit (Central Chukotka): results of Re-Os isotopic dating

The article presents the results of the sulfide mineralization dating of the Mayskoe gold ore deposit using the Re-Os isotope system and isochron age estimation method of the main sulfide minerals: arsenopyrite, pyrite, and antimonite. The complex multistage formation of the studied sulfides, as well as the close intergrowths of genetically different mineral phases, did not allow obtaining a single rhenium-osmium isochron corresponding to the formation time of sulfide mineralization. Isochrones for single minerals, collected from each sulfide sample, turned out to be the result of isotopically distinct components mixture (radiogenic crustal and non-radiogenic mantle) and do not make sense from the geochronological point of view. In terms of geology, the most significant result of the study is an age estimation of 128.8 ± 4.4 Ma, obtained for the sulfide mineralization of Mayskoe deposit using Re-Os isotope dating of single fractions of pyrite and antimonite of the ore mineralization stage. While arsenopyrite is most closely associated with gold mineralization, one of the arsenopyrite varieties corrodes framboidal pyrite of the pre-ore stage, has a maximum of the crust component in the osmium isotopic composition and forms a mixing line in the isochron diagram with an apparent formation age of 458 ± 18 Ma. The initial osmium isotopic composition of the studied sulfides indicates a mixed mantle-crust source of sulfide mineralization. The issue of simultaneous ore genesis and granitoid magmatism in the Mayskoe deposit remained unresolved (the age of granitoids according to the U-Pb zircon system is 108 Ma). However, a possible solution could be the further determination of the Re-Os isochron age of the ore mineralization sulphides from the single paragenesis of a specific sample containing both arsenopyrite and pyrite (+ antimonite) with gold.

Volcanic Rocks and Granitoids from Cape Svyatoy Nos (Eastern Arctic): Their Age, Composition, and Paleotectonic Reconstructions

For the first time, geochemical and geochronological (U–Pb SIMS, zircon) data are obtained for volcanic rocks and tuffs of the volcanic–sedimentary sequence and for granitoids intruding them in the Cape Svyatoy Nos area (eastern Arctic). The concordant U–Pb age of basalts is 146 ± 2. The ages of granitoids are 114 ± 1, 112 ± 1, and 114 ± 2 Ma. These ages correspond to the Late Jurassic (Tithonian) and the Aptian–Albian boundary. The section structure and the geochemical characteristics of the volcanic rocks and tuffs, as well as their similarities with the Mariana arc volcanics, indicate their formation in the settings of an intraoceanic subduction zone. The data obtained allow us to suggest that the volcanogenic–sedimentary rocks of Cape Svyatoy Nos represent a continuation of the Kul’pol’nei oceanic arc, which marked the northeastern convergent boundary between the Siberian continent and the South Anyui Basin in the Late Jurassic. In terms of their petrographic composition and petrogeochemical characteristics, the Aptian–Albian granitoids correspond to type I granites. The time of their intrusion coincides with the extension after the ending of the collision between the Siberian continent and the Chukotka–Arctic Alaska microplate as a result of the South Anyui Basin consumption.

U–Pb ages of granitoids around the Kofu basin: Implications for the Neogene geotectonic evolution of the South Fossa Magna region, central Japan

AbstractThe Japanese archipelago underwent two arc–arc collisions during the Neogene. Southwest Honshu arc collided with the Izu‐Bonin‐Mariana arc and the northeast Honshu arc collided with the Chishima arc. The complicated geological structure of the South Fossa Magna region has been attributed to the collision between the Izu‐Bonin‐Mariana arc and the southwest Honshu arc. Understanding the geotectonic evolution of this tectonically active region is crucial for delineating the Neogene tectonics of the Japanese archipelago. Many intrusive granitoids occur around the Kofu basin, in the South Fossa Magna region. Although the igneous ages of these granitoids have been mainly estimated through biotite and hornblende K–Ar dating, here, we perform U–Pb dating of zircon to determine the igneous ages more precisely. In most cases, the secondary post‐magmatic overprint on the zircon U–Pb system was minor. Based on our results, we identify four groups of U–Pb ages: ca 15.5 Ma, ca 13 Ma, ca 10.5 Ma, and ca 4 Ma. The Tsuburai pluton belongs to the first group, and its age suggests that the granite formation within the Izu‐Bonin‐Mariana arc dates back to at least 15.5 Ma. The granitoids of the second group intruded into the boundary between the Honshu arc and the ancient Izu‐Bonin‐Mariana arc, suggesting that the arc–arc collision started by ca 13 Ma. As in the case of the Kaikomagatake pluton, the Chino pluton likely corresponds to a granodiorite formed in a rear‐arc setting in parallel with the other granodiorites of the third group. The U–Pb age of the Kogarasu pluton, which belongs to the fourth group, is the same as those of the Tanzawa tonalitic plutons. This might support a syncollisional rapid granitic magma formation in the South Fossa Magna region.

Ediacaran, Early Ordovician and early Silurian arcs in the South Tianshan orogen of Kyrgyzstan

The oldest magmatic rocks from the South Tianshan orogen of Kyrgyzstan (STS) are important for better understanding of the Neoproterozoic and early Palaeozoic evolution of the southwestern Central Asian Orogenic Belt. Bulk rock major and trace element and Sm-Nd isotopic composition and zircon U-Pb ages of granitoids from mélange blocks reveal two previously unknown episodes of arc magmatism in the STS orogen of Kyrgyzstan, namely, the Ediacaran (ca. 624 Ma) and Early Ordovician (ca. 472 Ma) episodes. Moderately positive ɛNd(t) value of + 5.8 of the Ediacaran granodiorite indicates a mainly juvenile source for this rock. Negative ɛNd(t) value of −9.1 for the Early Ordovician granodiorite indicates melting of the predominantly Precambrian crustal material. The latter is also supported by the inherited zircon cores with an age range of 1.04–2.7 Ga. The geochemical signature of the Silurian (late Llandovery and Wenlock) basalts suggests formation in arc settings. Arc-related origin of the Ediacaran granodiorite suggests that mature oceanic basin with subduction system existed in the western STS since the late Neoproterozoic. The arc also evolved in the Ordovician and Silurian and was inactive in the middle Cambrian to the earliest Ordovician. Ediacaran granodiorite, old zircon cores and negative ɛNd(t) values of the Ordovician granodiorite suggest the existence of Precambrian microcontinents in the Kyrgyz STS. These crustal fragments were likely rifted off the Tarim and / or Karakum-Tajik microcontinents, where the rocks with similar ages occur. In the Palaeozoic, they traveled north and were incorporated in the STS orogen in the late Carboniferous.

Geochemical Features and Geological Processes Timescale of the Achaean TTG Complexes of the Ingozero Massif and the Pechenga Frame (NE Baltic Shield)

This article provides a geological review and results of the structural, metamorphic, and geochronological studies of the Pechenga frame outcrops located in the NW part of the Central-Kola terrain and the Ingozero massif outcrops situated in the northeastern part of the Belomorian mobile belt of the Kola Region (NW Baltic Shield). As a result of the work, the deformation scales and ages of the geological processes at the Neo-Archaean–Paleoproterozoic stage of the area’s development were compiled, and the reference rocks were dated. The petrochemical and geochemical characteristics of the Ingozero rocks are similar to those of tonalite–trondhjemite–granodiorite (TTG) complexes established on other Archaean shields. The isotope U–Pb dating of individual zircon grains from the biotite gneisses provided the oldest age for magmatic protolith of the Ingozero gneisses, which is 3149 ± 46 Ma. Sm–Nd model ages showed that the gneisses protolite initial melt formed at 3.1–2.8 Ga. Ages of metamorphic processes were determined by using isotope U–Pb dating ID TIMS (isotope dilution thermal ionization mass spectrometry): Biotite gneisses—2697 ± 9 Ma; amphibole–biotite gneisses—2725 ± 2 Ma and 2667 ± 7 Ma; and biotite–amphibole gneisses 2727 ± 5 Ma. Ages of granitoids, which cut the deformed gneisses, are 2615 ± 8 Ma and 2549 ± 31 Ma for plagiogranites and pegmatoid veins in gneisses, respectively. The following age sequence of geological processes was established by using U–Pb zircon dating: 2.8 Ga—The time of the garnet–biotite gneiss metamorphism; 2722 ± 9 Ma—The granodiorite crystallization time; 2636 ± 41 Ma—The aplite emplacement age and 2620 ± 16 Ma—The age of pegmatites origin, which marked final stages of the Archaean evolution; 2587 ± 5 Ma—The age of gabbros emplacement and 2507 ± 7 Ma—The age of gabbros metamorphism; 2522–2503 Ma—The origin time of the iron quartzite interpreted as the age of gabbros and biotite gneiss metamorphism.

Age, composition and sources of rocks and ores of the Okunevskoe fluorite-leucophanite deposit, Western Sayan: assessment of the contribution of magmatism to ore mineralization

The paper presents data on the structure of the Okunevskoe fluorite-Leucophanite deposit, located within the Early Paleozoic rare-metal East Sayan rare metal metallogenic zone. The deposit is controlled by alkali granitoids, with ore mineralization concentrated at the contact of granitoids and host carbonates. It is represented by leucophanite-fluorite and pyroxene-fluorite ore types. The Ar-Ar age of granitoids is established at ~485Ma. Geochemical characteristics of igneous rocks, ores, and host carbonates are determined. It is shown that in geochemical parameters leucophanite-fluorite ores are close to alkaline granites, while pyroxene-fluorite ores are close to alkaline syenites. The characteristics of the Nd isotop composition in rocks and ores of the deposit are given. Igneous rocks (granitoids and basite dikes) are characterized byNd (t) values from +4 to +5.5. TheNd (t) values in ores range from +1.2 to+4.2, in skarns itis +4.8. The host carbonates have abruptly contrasting valuesNd (t) = 4.2. Based on these data, which demonstrate a high compositional similarity between granitoids and ores, aconclusion is drawn about the leading contribution from magmatic processes to the ore mineralization of the Okunevskoe deposit.

Sr-Nd-Pb-Hf isotopic composition of late paleozoic granitoids of Central Chukotka

Results of the study of Sr–Nd–Pb–Hf isotopic composition of Late Paleozoic granitoids of Central Chukotka are represented on the example of Kibera and Kuekvun plutons. The age of granitoids of these plutons and granites from pebbles in conglomerates in the base of overlying Lower Carboniferous deposits is 351–363 Ma (U–Pb zircon, TIMS, SIMS, LA–ICP–MS). Thus, granitoid magmatism corresponds in time to tectonic events of Elsmerian orogeny in Arctic region. Sr–Nd–Pb–Hf isotopic composition of granitoids indicate participation of mantle and crustal components in the source of granite melts. Granitoids formation probably occurred in geodynamic setting of Andean type continental margin during the interaction between mantle melts, forming at the mantle wedge melting in suprasubduction conditions, and continental crust.