The First Precise Data on the Age of Charoite Mineralization (Eastern Siberia, Russia)

40Ar/39Ar Geochronology of the Malyy (Little) Murun Massif, Aldan Shield of the Siberian Craton: A Simple Story for an Intricate Igneous Complex

“…A few attempts were also made recently to limit the timing of the charoite mineralization by 40 Ar/ 39 Ar dating [39,40]. In this study, we provide new 40 Ar/ 39 Ar results on all major igneous and hydrothermal stages recognized in the Malyy Murun massif. We use this geochronological information to constrain the duration of magmatic and later hydrothermal activity within the massif and to compare it with the information on alkaline magmatism of the Aldan Shield of the Siberian Craton and the Transbaikalian rifted region [41][42][43][44][45][46][47][48][49][50][51][52][53] (Figure 1).…”

“…Minerals 2018, 8, x FOR PEER REVIEW 3 of 21 40 Ar/ 39 Ar dating, we separated mica from abundant biotite-pyroxene-K-feldspar syenite (referred to as alkaline syenite by Russian geologists). The volcanic stage was recognized by the lava of leucitic lamproites and melaphonolites and volcanic breccia.…”

“…Dykes of tinguaites, richterite-sanidine lamproites, trachyte-porphyries, syenite-porphyries, and (eudialyte-bearing) lujavrites were included into the volcanic stage. For 40 Ar/ 39 Ar dating, we separated mica from leucitic lamproite lava and lujavrite dyke.…”

“…In addition, we included, into the late intrusive stage, alkaline granites of spatially-separated Kedroviy stock ( Figure 2), which were considered within the main intrusive stage [15] or a late stage [22]. For 40 Ar/ 39 Ar dating of the late intrusive stage, we separated tinaksite and K-feldspar from benstonite carbonatite and K-feldspar from calcite carbonatite. In Rocks of the main intrusive stage composed the central part of the massif (Figure 2), which consists of different types of syenites (leucitic, feldspar-calcilitic, biotite-pyroxene-K-feldspar).…”

“…Despite the enormous efforts for understanding the geology of the Malyy Murun massif, its geochronology was constrained to Early Cretaceous by an outdated K-Ar dating of voluminously predominant syenites [38]. A few attempts were also made recently to limit the timing of the charoite mineralization by 40 Ar/ 39 Ar dating [39,40]. In this study, we provide new 40 Ar/ 39 Ar results on all major igneous and hydrothermal stages recognized in the Malyy Murun massif.…”