Mafic microgranular enclaves in Late Paleozoic granitoids in the Burgasy quartz syenite massif, western Transbaikalia: Composition and petrogenesis

Abstract:Our study investigates a possibility of using isotope ratios of U-Th-Pb system in zircon analysis by the LA-ICP-MS technique and monitoring of precision, convergence and accuracy. New U-Pb isotope-geochronological data has been obtained for the salic and mafic members of the bimodal Late Paleozoic series of subparallel dykes in the central part of the Western Transbaikalia. It is shown that a series of subparallel dykes (290-280 Ma) gives evidence of extension of the continental crust at the final stage of the Late Paleozoic granitoid magmatism. Similar ages of zircons in the salic and mafic subvolcanic rocks confirm the geological indicators of the coexistence and interactions between the magmas of contrasting compositions.

Section: Discussionunclassified

U‐pb La‐icp‐ms Dating of Zircons From Subvolcanics of the Bimodal Dyke Series of the Western Transbaikalia: Technique, and Evidence of the Late Paleozoic Extension of the Crust

Буянтуев¹,

Хубанов²,

Врублевская³

2017

“…2), where the fragments of accretionary and paleooceanic complexes still exist, mafic magmas could easily penetrate into the lower crust through the quite thin lithosphere. This may lead to intensive interactions of the mafic magmas with the crustal substrates and anatectic melts, forming the gabbro-monzonitegranite intrusions with a wide spectrum of rocks and mingling and mixing processes, and the appearance of syn-plutonic Mafic Microgranular Enclaves (MME) and combined mafic-felsic dikes [Wiebe, 1973;Furman, Spera, 1985;Litvinovsky et al, 1995;Barbarin, 2005;Renna et al, 2006;Burmakina, Tsygankov, 2013;Burmakina et al, 2018] In the northeastern part of the territory, clastic sediments (sandstones and siltstones) deposited in the Devonian-Early Carboniferous within the Kalba-Narym terrane were deformed and metamorphosed in the course of collisional processes, and then were molten anatectically at high temperature gradients across the mantle chambers. Mafic Fig.…”

Section: Correlation Of Magmatic Events and Mechanisms Of Plume-lithomentioning

confidence: 99%

A Review of Early Permian (300–270 Ma) Magmatism in Eastern Kazakhstan and Implications for Plate Tectonics and Plume Interplay

Хромых

Котлер

Изох

et al. 2019

The history of the Central Asian Orogenic Belt (CAOB) was marked by several major events of magmatism which produced large volumes of volcanic and intrusive (mafic-ultramafic and granitic) rocks within a relatively short time span (30–40 Ma) over a vast area. The magmatic activity postdated the orogenic stages of accretionary-collisional belts in Central Asia and likely resulted from the impact of mantle plumes that formed Large Igneous Provinces (LIPs). The formation of the Tarim–South Mongolia LIP at 300–270 Ma is the best known among the major Permian events of basaltic and granitic magmatism. Early Permian igneous rocks (volcanic, subvolcanic and intrusive suites that vary from ultramafic to felsic compositions) of the same age range (300 to 270 Ma) have been recently found also in Eastern Kazakhstan, within the late Paleozoic Altai collisional system. The compositions and ages of the rocks suggest that the Eastern Kazakhstan magmatism was the northward expansion of the Tarim LIP. The spread of the Tarim LIP was apparently facilitated by lithospheric extension after the Siberia-Kazakhstan collision. The extension led to rheological weakening of the lithosphere whereby deep mantle melts could penetrate to shallower depths. The early Permian history of Eastern Kazakhstan was controlled by the interplay of plate tectonic and plume processes: plate-tectonic accretion and collision formed the structural framework, and the Tarim mantle plume was a heat source maintaining voluminous magma generation.

“…Для «плутонической» группы магматического минглинга ранее было предложено несколько моделей, опирающихся преимущественно на плотностные, кристаллизационные и дилатационные эффекты [Litvinovsky et al, 1995a[Litvinovsky et al, , 1995bBindeman, 1995;Castro et al, 2008;Burmakina, Tsygankov, 2013;Polyansky et al, 2017;Khromykh et al, 2017;и др.]. Они позволяют непротиворечиво объяснить возникновение условий для инъецирования базитовых расплавов в магматические камеры гранитоидного состава, а также механизмы внутрикамерного смешения и течения контрастных по составу расплавов.…”

Section: две группы магматического минглингаunclassified

“…Интерес к данной проблеме отражен в обзорах [Wilcox, 1999;Sklyarov, Fedorovskii, 2006;Karmysheva et al, 2015;и др. ] и многочисленных публикациях [Windley, 1965;Wiebe, 1973;Gamble, 1979;Marshall, Sparks, 1984;Furman, Spera, 1985;Frost, Mahood, 1987;Cook, 1988;Huppert, Sparks, 1988;Didier, Barbarin, 1991;Zanvilevich et al, 1991;Litvinovsky et al, 1995aLitvinovsky et al, , 1995bLitvinovsky et al, , 2017Nardi, de Lima, 2000;Perugini, Poli, 2005;Dokukina, Vladimirov, 2005;Burmakina, Tsygankov, 2013;Vladimirov et al, 2016Vladimirov et al, , 2017Khromykh et al, 2017;и др.]. Актуальность подобных исследований обусловлена уникальной природой магматического минглинга, являющегося индикатором условий сосуществования контрастных по составу (салических и базитовых) расплавов.…”

Section: Introductionunclassified

Mechanisms of Magmatic Mingling in Composite Dykes: Models of Dispersion and Shear Dilatation

Владимиров¹,

Яковлев²,

Кармышева³

2019

This article is focused on the intrusion and formation of combined dykes. Two main groups of conventionally magmatic mingling are distinguished: (1) plutonic bodies, and (2) combined dykes. The first group is represented by small basite inclusions that are uniformly scattered in granitoid bodies, and includes elongated swarms and tails of small bodies. The second group includes composite dykes with the indicators of mechanical mingling of basic and acid melts. Despite the similarities in the structural and textural features and the indicators of mechanical mingling of melts, these two groups are characterized by clearly different proportions of the volumes of contrasting melts and differ in the duration of formation, place of melt mingling, and tectonic setting. None of the available models was able to explain the occurrence of magmatic mingling structures in individual dykes. In our study, the mingling mechanisms of contrasting melts are discussed using the data on the geological objects located in West Sangilen, an area of the Central Asian Orogenic Belt (CAOB). The general and specific parameters of combined dikes of the Saizyral and Tavyt‐ Dag sites are considered. The models of shear dilatation and dispersion are proposed for explaining the mechanisms of magmatic mingling in combined dykes.