U–Pb SHRIMP II age and origin of zircon from lhertzolite of the bug Paleoarchean complex,Ukrainian Shield

Complex study of the U–Pb and Lu–Hf systems of zircon from a lhertzolite lens of Archean gneiss enderbites of the Bug complex, Ukrainian Shield, showed that ultramafic magma was contaminated by the material of the country gneiss enderbites. The age of the zircons of 2.81 ± 0.05 Ga corresponds to the period of ultramafic magmatism within the Bug complex. Previously, this peak of endogenic activity was considered the stage of manifestation of metamorphism and magmatism of mafic composition.     

Paleoarchean orthopyroxenites of the Bug granulite–gneiss domain at the Ukrainian shield

This report presents data on the geological structure and location of the orthopyroxenite inclusion in gneissic enderbites of the Bug granulite–gneiss domain. Three stages of orthopyroxenite formation were identified on the basis of studies of the mineral composition along with the U–Pb and Lu–Hf isotope systems of zircons.     

First Data on the Age (U–Pb,SHRIMP-II) and Composition of Zircon from the Unique Yarega Oil–Titanium Deposit,South Timan

Doklady Earth Sciences - Isotope–geochemical study of zircon from leucoxene–quartz sandstone of the Yarega deposit in South Timan was conducted for the first time using the Sensitive...     

The U–Pb LA-SF-ICP-MS Age of Zircon from Metaplagiogranite of the Kharbei Metamorphic Complex (Polar Urals)

Doklady Earth Sciences - For timing of endogenous events in the Kharbei metamorphic complex (Polar Urals), U–Pb isotopic dating of zircons from garnet–clinozoisite–twomica...     

U–Pb Age and Geochemical Characteristics of Ultramafic–Mafic Rocks of the Dzhida Zone Ophiolite Association (Southwestern Transbaikalia)

This article presents new geochronological and isotope-geochemical data on ultramafic–mafic rocks of the banded complex of the Dzhida zone of the Caledonides ophiolite association.     

An Ordovician Age of the Dunite–Wehrlite–Clinopyroxenite Banded Complex of the Nurali Massif (Southern Urals,Russia): U–Pb (SHRIMP) Zircon Age Data

The data on the geochemistry and geochronology of zircons from wehrlites and clinopyroxenites of the dunite–wehrlite–clinopyroxenite banded complex that lies at the base of the crustal section of the ophiolite complex of the Nurali massif are presented. The obtained U–Pb age of the banded complex of 450 ± 4 Ma differs markedly from the previous age data. According to REE distribution patterns zircons from ultramafic rocks are attributed to the magmatic type and they indicate the age and supposed genetic similarity of the above rocks with lherzolites and dunites from the mantle section of the Nurali massif.     

Age of granitoids in the Pripechora fault zone of the basement of Pechora Basin: First U–Pb (SIMS) data

Upper Precambrian basement of the Pechora Basin that is located between the Urals and Timan and is a part of the Pechora plate lies beneath 1–7 km of Ordovician-Cenozoic sediment cover. On the base of geophysical data and drilling the basement of the Pechora plate is subdivided into the Timan crustal block and the Bolshezemel crustal block which differ by composition and the character of magmatism. The boundary between the crustal blocks is a system of deep faults called the Pripechora and Ilych-Chikshino faults that strike in a northwestern direction, extending from the Urals to the Pechora Sea. Granitoids of Charkayu complex which were penetrated by several deep boreholes in Pripechora fault zone are interpreted as suprasubduction (island arc and collision) magmas associated with the Timan orogeny. First U–Pb dating (SIMS, using SHRIMP-II and SHRIMP-RG) of zircons from granitoids indicate that granitoid magmatism which accompanied the final stages of the Timanide orogeny occurred in the Late Vendian about 555–544 Ma. The age of zircons from granites of the 1-Charkayu borehole is 544 ± 6 Ma, from granites of 1-East Charkayu borehole is 545 ± 5 Ma, and from granodiorites of 1-South Charkayu borehole is 555 ± 2 Ma.     

Zircon geochemistry and U–Pb age at rare metal deposits of syenite in the Ukrainian Shield

The distribution of rare and rare earth elements in zircon at the Yastrebets, Azov (Zr–REE–Y), and Perzhan (Be) rare metal deposits of the Ukrainian Shield was studied. Additional evidence for magmatic genesis of these deposits is obtained: unaltered zircon is characterized by a magmatic REE distribution spectrum with a somewhat higher δ¹⁸O value than that of the mantle (6.6‰ on average). The final formation stage of the deposit was marked by predominance of fluids enriched in Y, REE, Nb, and heavy oxygen, resulting in anomalous geochemical characteristics of zircon rims and alteration zones (up to 81500 Y ppm, over 10300 ppm Nb, and 13.9‰ δ¹⁸O). The age of zircon formed in ore-bearing Yastrebets and Azov nonnepheline syenite deposits was estimated at ~1770 Ma (U–Pb, SHRIMP-II).     

Three successive Proterozoic island arcs in the Northern Arabian–Nubian Shield: Evidence from SIMS U–Pb dating of zircon

Four isolated metamorphic complexes located within post-collisional granitoids occupying up to 70% of the total area, were distinguished in Sinai (Egypt) and Elat area (southern Israel), the northernmost part of the Arabian–Nubian Shield. The metamorphic rocks include metasediments, felsic and mafic metavolcanic rocks intruded by granitic, dioritic, and gabbroic plutons, all subjected to penetrative deformation.We present new SIMS U–Pb dating of zircons from 13 rock units comprising metasediments, volcanic rocks, gneisses and plutons from three metamorphic complexes (Sa'al, Feiran–Solaf, and Kid). In addition we present a SIMS U–Pb titanite age of a granitic gneiss previously dated using zircon. On the basis of the new and published U–Pb data, three successive Meso- to Neoproterozoic island arcs formed during a period of ca. 500 My are recognized. The Sa'al arc (represented by the oldest arc rocks in the ANS) evolved from 1.03 to 0.93 Ga (100 My); the Feiran–Elat arc developed from ca. 870 to 740 Ma (130 My), and the Kid arc formed from ca. 640 to 620 Ma (20 My). Evidence for an older, ca. 1.1 Ga, pre-Sa'al island arc was established from the zircon xenocryst population, though no exposures of rocks of this age were found. In the Sa'al and Kid arcs both volcanic and sedimentary rocks are preserved, whereas in the Elat–Feiran arc volcanic rocks are missing. We suggest that at ~ 700 Ma the Elat−Feiran arc was subjected to rifting that resulted in separating of the Qenaia block and its movement to the SE.     

Garnet U–Pb Age of Skarns from Dashkesan Deposit (Lesser Caucasus)

Doklady Earth Sciences - The results of the U–Pb geochronological study of garnet from scarns of the Dashkesan deposit are reported. The first “direct” estimate of the age of the...     

Age of island-arc granites in the Shchuch’ya zone,Polar Urals: First U–Pb (SIMS) results

The granitic magmatism occurred at the precollisional stage of the continentalization of the mafic basement of the Shchuch’ya island arc system. The first U–Pb (SIMS, SHRIMP II) data on zircons indicate three pulses of transformation of the oceanic crust into a continental crust: in the Silurian and Middle and Late Devonian. The age of the Yanganape granite is 429 ± 4 Ma, which corresponds to the Late Wenlockian; that of the Yurmeneku massif is 385 ± 2 Ma (Givetian); and that of the Canyon Massif is 368 ± 3 Ma (Famennian). The zircons from the Yanganape granite yielded an age of 335 ± 4 Ma, which corresponds to the Early Carboniferous (Visean). Similar ages were noted in uranium-rich zircons from the Canyon Massif granite. They correlate with the collision time of the island arc with the eastern edge of the Eastern European paleocontinent, and it is possible that this event caused disturbance of the U–Pb system of zircons in the islandarc granites of the Shchuch’ya zone.     

The Late Neoproterozoic Age of Differentiated Volcanic Complexes of the Ulutau Massif: Results of U–Th–Pb (SIMS) Dating

Doklady Earth Sciences - The metamorphosed differentiated volcanogenic strata of the Aralbai Group have been studied in the eastern part of the Precambrian Ulutau massif of Central Kazakhstan. The...     

The Upper Age Boundary of the Formation of the Olondo Fragment of the Tokko–Khani Greenstone Belt,Aldan Shield: U–Pb (ID-TIMS) Geochronological Data

Doklady Earth Sciences - This work presents new U–Pb ID-TIMS geochronological data obtained for the rocks of the metagabbro–diorite–tonalite complex of the Olondo fragment of the...     

Early Ordovician Age of Suprasubduction Ophiolites in the Northeastern Part of Central Kazakhstan: U–Th–Pb (SIMS) Dating of Plagiogranites

Doklady Earth Sciences - Suprasubduction zone ophiolites in the Bayanaul and Maikain–Kyzyltas zones in the northeastern part of Central Kazakhstan were studied. U–Pb dating of...     

An Archaean Tonalite–Trondhjemite–Granodiorite Association of the Kursk Block (Voronezh Massif): Composition,Age, and Correlation with the Ukrainian Shield

Doklady Earth Sciences - Framing of the Archaean greenstone belts of the Kursk Block (KB) of the East Sarmatia preserves rocks of the TTG association: those do not form massifs with distinct...     

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

Doklady Earth Sciences - 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,...     

Genesis of a Magnetite Layer in the Gabbro-10 Intrusion,Monchegorsk Complex,Kola Region: U–Pb SHRIMP-II Dating of Metadiorites

Geology of Ore Deposits - The Gabbro-10 intrusion is located in the southeastern part of the Early Proterozoic Monchegorsk layered complex of the Kola region. The intrusion, 1.4 × 0.7 km in...     

Middle Devonian Age of Metamorphism of Garnet Amphibolite at the Sole of the Kempirsai Ophiolite Allochthon (Southern Urals): Results of U–Th–Pb (SIMS) Dating

Doklady Earth Sciences - Metagabbroid garnet amphibolite formed after high-pressure granulite with an estimated P–T peak of 12–16 kbar at 700–790°C occurs at the sole of the...     

U–Pb (SHRIMP) Zircon Age of Granitoid Pebbles from the Kukkarauk Conglomerates of the Vendian Asha Group (Alatau Anticlinorium,Southern Urals)

Doklady Earth Sciences - The lack of reliable geochronological data for the Vendian deposits of the Urals and other regions is one reason why there is still uncertainty in the age estimates of the...     

The U–Pb System in Schorlomite from Calcite–Amphobole–Pyroxene Pegmatite of the Afrikanda Complex (Kola Peninsula)

The geochronological U–Pb study of shorlomite from igneous rocks of the alkali–ultramafic Afrikanda massif (Kola Peninsula) was performed. The results demonstrate the reliability of calcium garnet as a mineral for the U–Pb geochronology of a wide range of igneous rocks, i.e., carbonatite, syenite, foidolite, foidite, melilitolite, melilitite, lamprophyres, micaceous kimberlites, etc., and associated rare earth and trace elements (REE, Nb, Zr) mineralization.