NEW DATA ABOUT AGE AND GEODYNAMIC NATURE OF HAMSARA TERRANE

On the basis of isotopic-geochemical studies and analysis of geological evidences heterogeneity of Hamsara terrane has been determined. Formation of stationed metamorphosed layers underlying the Hamsara formation occurred not earlier than 630 Ma, probably in the oceanic island arc system. Acidic effusive rocks of Hamsara formation were formed in intraplate condition in the range of 462–464 Ma. Sediments of Hamsara formation couldn’t be the part of island arc system and belong to completely other period of geological region development. This is the time of completion of accretion-collision events in the northern part of Altai-Sayan fragment of CAFB adjacent to the Siberian platform.On the basis of isotopic-geochemical studies and analysis of geological evidences heterogeneity of Hamsara terrane has been determined. Formation of stationed metamorphosed layers underlying the Hamsara formation occurred not earlier than 630 Ma, probably in the oceanic island arc system. Acidic effusive rocks of Hamsara formation were formed in intraplate condition in the range of 462–464 Ma. Sediments of Hamsara formation couldn’t be the part of island arc system and belong to completely other period of geological region development. This is the time of completion of accretion-collision events in the northern part of Altai-Sayan fragment of CAFB adjacent to the Siberian platform

PALEOARCHEAN MAFIC ROCKS OF THE SOUTHWESTERN SIBERIAN CRATON: PRELIMINARY GEOCHRONOLOGY AND GEOCHEMICAL CHARACTERIZATION

The Siberian craton consists of Archean blocks, which were welded up into the same large unit by ca 1.9 Ga [Gladkochub et al., 2006; Rojas-Agramonte et al., 2011]. The history of the constituent Archean blocks is mosaic because of limited number of outcrops, insufficient sampling coverage because of their location in remote regions and deep forest and difficulties with analytical studies of ancient rocks, which commonly underwent metamorphic modifications and secondary alterations. In this short note, we report data on discovery of unusual for Archean mafic rocks of ultimate fresh appearance. These rocks were discovered within southwestern Siberian craton in a region near a boundary between Kitoy granulites of the Sharyzhalgai highgrade metamorphic complex and Onot green-schist belt (Fig. 1). Here we present preliminary data on geochronology of these rocks and provide their geochemical characterization.The Siberian craton consists of Archean blocks, which were welded up into the same large unit by ca 1.9 Ga [Gladkochub et al., 2006; Rojas-Agramonte et al., 2011]. The history of the constituent Archean blocks is mosaic because of limited number of outcrops, insufficient sampling coverage because of their location in remote regions and deep forest and difficulties with analytical studies of ancient rocks, which commonly underwent metamorphic modifications and secondary alterations. In this short note, we report data on discovery of unusual for Archean mafic rocks of ultimate fresh appearance. These rocks were discovered within southwestern Siberian craton in a region near a boundary between Kitoy granulites of the Sharyzhalgai highgrade metamorphic complex and Onot green-schist belt (Fig. 1). Here we present preliminary data on geochronology of these rocks and provide their geochemical characterization

AN ACTIVE NEOPROTEROZOIC CONTINENTAL MARGIN OF THE ZAVKHAN MICROCONTINENT (MONGOLIA): ISOTOPIC-GEOCHRONOLOGICAL EVIDENCE

There have been presented the results of the study of a thick (no less than 2–3 km), extended (for more than 200 km) volcanogenic formation (Tsetsen-Uul or Yargait) in the south of the Zavkhan terrane of the Central Asian fold belt. The formation is an assemblage of frequently intercalating effusive rocks of the subalkaline basalt-andesite-dacite-rhyolite series, their tuffs, tuffites, ignimbrites, and terrigenous rocks. Felsic rocks dominate over basites, and tuffogenic rocks dominate over effusives. There is some evidence that the formation emerged in a subaerial setting, with explosive eruptions, and the petrogeochemical features of the effusive rocks are typical for subduction environment. The felsic effusive rocks have high negative εNd from –11.5 to –12.8 and Early Precambrian model age TNd(DM)=2.4–2.5 Ga, which indicates the presence of an ancient crust at the depth and its involvement in magma. The evidence supports the formation of volcanic rocks within an active continental margin. The continental-margin formation stage ranges from ~860 Ma to ~780 Ma based on the LA-ICP-MS U-Pb dating of zircons.The Tsetsen-Uul (Yargait) formation is similar in structure and composition to the Zavkhan formation of the Zavkhan terrane and the Sarkhoi group of the Tuva-Mongolian massif, and partially overlaps them in formation time. It is concluded that all three volcanogenic formations emerged in the same geodynamic setting and in the same time interval, and are the fragments of a continental volcanic arc belonging to both Zavkhan and Tuva-Mongolian paleomicrocontinents

НЕОПРОТЕРОЗОЙСКАЯ АКТИВНАЯ КОНТИНЕНТАЛЬНАЯ ОКРАИНА ДЗАБХАНСКОГО ПАЛЕОМИКРОКОНТИНЕНТА (МОНГОЛИЯ): РЕЗУЛЬТАТЫ ИЗОТОПНО-ГЕОХРОНОЛОГИЧЕСКИХ ИССЛЕДОВАНИЙ

There have been presented the results of the study of a thick (no less than 2–3 km), extended (for more than 200 km) volcanogenic formation (Tsetsen-Uul or Yargait) in the south of the Zavkhan terrane of the Central Asian fold belt. The formation is an assemblage of frequently intercalating effusive rocks of the subalkaline basalt-andesite-dacite-rhyolite series, their tuffs, tuffites, ignimbrites, and terrigenous rocks. Felsic rocks dominate over basites, and tuffogenic rocks dominate over effusives. There is some evidence that the formation emerged in a subaerial setting, with explosive eruptions, and the petrogeochemical features of the effusive rocks are typical for subduction environment. The felsic effusive rocks have high negative εNd from –11.5 to –12.8 and Early Precambrian model age TNd(DM)=2.4–2.5 Ga, which indicates the presence of an ancient crust at the depth and its involvement in magma. The evidence supports the formation of volcanic rocks within an active continental margin. The continental-margin formation stage ranges from ~860 Ma to ~780 Ma based on the LA-ICP-MS U-Pb dating of zircons.The Tsetsen-Uul (Yargait) formation is similar in structure and composition to the Zavkhan formation of the Zavkhan terrane and the Sarkhoi group of the Tuva-Mongolian massif, and partially overlaps them in formation time. It is concluded that all three volcanogenic formations emerged in the same geodynamic setting and in the same time interval, and are the fragments of a continental volcanic arc belonging to both Zavkhan and Tuva-Mongolian paleomicrocontinents.Приведены результаты исследования разреза мощной (не менее 2–3 км), протяженной (более 200 км) вулканогенной цосулинской (яргайт) свиты на юге Дзабханского террейна Центрально-Азиатского складчатого пояса. Свита сложена эффузивами субщелочной базальт-андезит-дацит-риолитовой серии, их туфами, туффитами, игнимбритами и терригенными породами, находящимися в частом переслаивании. Преобладают кислые породы над основными и туффогенные над эффузивами. По ряду признаков накопление толщи происходило в субаэральной обстановке с эксплозивными наземными извержениями, а петрогеохимические особенности эффузивов типичны для условий субдукции. Эффузивы кислого и среднего состава характеризуются большими отрицательными значениями εNd – от −11.5 до −12.8 и раннедокембрийским модельным возрастом TNd(DM)=2.4–2.5 млрд лет, что указывает на присутствие на глубине древней коры и на ее вовлечение в магму. Полученные факты свидетельствуют в пользу образования вулканитов в условиях активной континентальной окраины. Крайние временные границы, в пределах которых формировалась окраинно-континентальная система по результатам U-Pb определений по цирконам методом LA-ICP-MS, оцениваются в ~860–780 млн лет.Цосулинская (яргайт) свита по строению и составу вулканитов близка дзабханской свите одноименного террейна и сархойской серии Тувино-Монгольского массива и частично перекрывается с ними по времени образования. Таким образом, все три вулканогенные толщи сформировались в однотипной геодинамической обстановке, в одном временном интервале и являются фрагментами континентальной вулканической дуги, общей для Дзабханского и Тувино-Монгольского палеомикроконтинентов

ГЕНЕЗИС ГРАНАТ-ПИРОКСЕНОВЫХ СИЕНИТОВ (СВЯТОНОСИТОВ) МАЛОБЫСТРИНСКОГО МАССИВА (СЛЮДЯНСКИЙ КОМПЛЕКС, ЮЖНОЕ ПРИБАЙКАЛЬЕ): РЕЗУЛЬТАТЫ ГЕОХИМИЧЕСКИХ И ИЗОТОПНЫХ ИССЛЕДОВАНИЙ

This paper deals with the study of syenites and sviatonossites (andradite-bearing syenites) of the Malobystrinsky massif of the Slyudyanka complex (South Baikal region, Siberia), and a large monzonite dike similar in age and composition to the rocks of the massif considered. The studied rocks belong to a series of highly ferriferous and metaluminous A-type granitoids (ASI index <1). They are characterized by SiO2 45–65 wt. %, K2O+Na2O up to 12 wt. %, MgO <4 wt. %, TiO2 up to 2.5 wt. %, and Al2O3 up to 17 wt. %. CaO varies in a wide range, from 2.2 to 14.7 wt. %. The rocks are similar to each other in trace element composition and show patterns with troughs for Th-U, Nb-Ta and Ti. Low-amplitude negative Eu anomaly is observed in the distribution spectra of rare earth elements for the entire rock complex. The obtained Sm-Nd age of sviatonossites in the Malobystrinsky massif is 487.1±6.1 Ma (MSWD=0.99). Our results indicate that syenites and monzonites have εNd(t) –1.9…–2.8, at εSr(t) 21–30, and sviatonossites have εNd(t) –3.8…–4.1 at εSr(t) – 26. Model ages TNd(DM) for all rock types are Mesoproterozoic (1.3–1.4 Ga). Based on the chemical and Sr-Nd isotopic composition of the magmatic rocks studied, it can be assumed that they have been generated by partial melting of lower crustal rocks (amphibolites). Crystallization of andradite garnet in syenite magma can occur due to melt contamination with metamorphic host rocks of the Slyudyanka complex.Исследованы сиениты и святоноситы (андрадитсодержащие сиениты) Малобыстринского массива слюдянского комплекса (Южное Прибайкалье, Сибирь), а также крупная дайка монцонитов, по возрасту и составу сходная с породами рассматриваемого массива. Исследованные породы относятся к ряду существенно железистых и метаглиноземистых с индексом ASI ниже 1. Породы характеризуются содержанием SiO2 49–65 мас. % и суммой щелочей K2O+Na2O до 12 мас. %, MgO ниже 4 мас. %, высокими содержаниями TiO2 – до 2.5 мас. %, Al2O3 – до 17 мас. %. СаО варьируется в широком интервале значений – от 2.2 до 14.7 мас. %. По микроэлементному спектру породы близки между собой и характеризуются общими трогами Th-U, Nb-Ta и Ti. На спектрах распределения редкоземельных элементов для всего комплекса пород наблюдается очень слабая отрицательная аномалия Eu. Полученный Sm-Nd возраст святоноситов Малобыстринского массива 487.1±6.1 млн лет (СКВО=0.99). Диапазон скорректированных на возраст значений εNd(t) в сиените и монцоните составляет –1.9…–2.8, при εSr(t) 21–30, а в святоноситах εNd(t) –3.8…–4.1 при близких εSr(t) – 26. Модельный возраст для всех рассматриваемых пород TNd(DM) имеет мезопротерозойские значения 1.3–1.4 млрд лет. Основываясь на химическом и Sr-Nd-изотопном составе исследованных магматических пород, можно предположить, что их образование связано с плавлением коровых амфиболитов. Кристаллизация андрадитового граната в сиенитовой магме вызвана контаминацией расплава вмещающими метаморфическими породами слюдянского комплекса

Segregation of In to dislocations in InGaN.

Dislocations are one-dimensional topological defects that occur frequently in functional thin film materials and that are known to degrade the performance of InxGa1-xN-based optoelectronic devices. Here, we show that large local deviations in alloy composition and atomic structure are expected to occur in and around dislocation cores in InxGa(1-x)N alloy thin films. We present energy-dispersive X-ray spectroscopy data supporting this result. The methods presented here are also widely applicable for predicting composition fluctuations associated with strain fields in other inorganic functional material thin films.This work was funded in part by the Cambridge Commonwealth trust, St. John’s College and the EPSRC. SKR is funded through the Cambridge-India Partnership Fund and Indian Institute of Technology Bombay via a scholarship. MAM acknowledges support from the Royal Society through a University Research Fellowship. Additional support was provided by the EPSRC through the UK National Facility for Aberration-Corrected STEM (SuperSTEM). The Titan 80- 200kV ChemiSTEMTM was funded through HM Government (UK) and is associated with the capabilities of the University of Manchester Nuclear Manufacturing (NUMAN) capabilities. SJH acknowledges funding from the Defence Treat Reduction Agency (DTRA) USA (grant number HDTRA1-12-1-0013).This is the accepted manuscript. The final version is available at http://pubs.acs.org/doi/abs/10.1021/nl5036513

NEW DATA ABOUT AGE AND GEODYNAMIC NATURE OF HAMSARA TERRANE

On the basis of isotopic-geochemical studies and analysis of geological evidences heterogeneity of Hamsara terrane has been determined. Formation of stationed metamorphosed layers underlying the Hamsara formation occurred not earlier than 630 Ma, probably in the oceanic island arc system. Acidic effusive rocks of Hamsara formation were formed in intraplate condition in the range of 462–464 Ma. Sediments of Hamsara formation couldn’t be the part of island arc system and belong to completely other period of geological region development. This is the time of completion of accretion-collision events in the northern part of Altai-Sayan fragment of CAFB adjacent to the Siberian platform

Kyzylkumite, Ti2V3+O5(OH): new structure type, modularity and revised formula

The crystal structure of kyzylkumite, ideally Ti2V3+O5(OH), from the Sludyanka complex in South Baikal, Russia was solved and refined (including the hydrogen atom position) to an agreement index, R1, of 2.34 using X-ray diffraction data collected on a twinned crystal. Kyzylkumite crystallizes in space group P21/c, with a = 8.4787(1), b = 4.5624(1), c = 10.0330(1) Å, β = 93.174(1)°, V = 387.51(1) Å3 and Z = 4. Tivanite, TiV3+O3OH, and kyzylkumite have modular structures based on hexagonal close packing of oxygen, which are made up of rutile TiO2 and montroseite V3+O(OH) slices. In tivanite the rutile:montroseite ratio is 1:1, in kyzylkumite the ratio is 2:1. The montroseite module may be replaced by the isotypic paramontroseite V4+O2 module, which produces a phase with the formula Ti2V4+O6. In the metamorphic rocks of the Sludyanka complex, vanadium can be present as V4+ and V3+ within the same mineral (e.g. in batisivite, schreyerite and berdesinskiite). Kyzylkumite has a flexible composition with respect to the M4+/M3+ ratio. The relationship between kyzylkumite and a closely related Be-bearing kyzylkumite-like mineral with an orthorhombic norbergite-type structure from Byrud mine, Norway is discussed. Both minerals have similar X-ray powder diffraction patterns