The Khorinka volcanoplutonic structure lies in the central part of the Mongolo-Transbaikalian alkali-granite belt (MTB) extending for more than 2500 km through Northern Mongolia and Transbaikalia. The MTB formed in two stages: 280-270 and 230-210 Ma. The Khorinka structure is ca. 3000 km2 in area. Syenites and granites prevail at the modern denudation level of its rocks. Only a minor part of volcanic comagmates (bimodal trachybasalt-rhyolite series) has been preserved in this structure. The volcanic stage was preceded by the formation of a bimodal dike belt. Granitoid massifs resulted from the subsequent intrusion of alkali-feldspathic, alkaline, and syenogranitic magmas. Rb-Sr isotope dating has shown that the Khorinka structure was produced at the early stage of the MTB formation (-280 .. 5 Ma). The Rb-Sr dates for alkali granitoids agree with the literature U-Pb zircon ages of these rocks. The ( 87Sr/86Sr)0 value is 0.7073 in alkali and feldspathic granitoids and 0.7033 in syenogranites, which points to different sources of their parental acid magmas.
|Number of pages||8|
|Journal||Geologiya i Geofizika|
|State||Published - 1 Dec 2005|
- Alkali granites
- Rb-Sr dates
ASJC Scopus subject areas
- Earth and Planetary Sciences (miscellaneous)