Šebkovice ultrapotassic lamproite dyke, Šebkovice, Třebíč District, Vysočina Region, Czech Republici

Regional Level Types
Šebkovice ultrapotassic lamproite dyke	Dike
Šebkovice	Municipality
Třebíč District	District
Vysočina Region	Region
Czech Republic	Country

Lukáš Krmíček wrote me (Christian Brand) an email with the distinct location of the ultrapotassic lamproite dyke in the southern Czech Republic (Třebíč district, western Moravia): Its local outcrops extend to 140 m, striking WSW-ENE, about in the middle of the distance between the villages Šebkovice and Loukovice; the exact coordinate range is:
from 49° 7'47.82"N / 15°48'13.10"E
to 49° 7'49.93"N / 15°48'19.30"E.

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Abstract of Krmíček et al. (2011) paper:
"A peralkaline, ultrapotassic dyke found at Šebkovice (Třebíč district, western Moravia) is a mineralogically extreme member of a dyke swarm occurring along the south-eastern border of the Moldanubian Region of the Bohemian Massif. The dyke shows a simple zoning, with a very fine-grained marginal zone grading into a medium-grained central zone. It has a primary mineral assemblage of microcline and potassic amphiboles, with accessory apatite and altered phlogopite [...]. Amphiboles have very high K [...] and Si contents; their compositions follow an alkaline fractionation trend [...]. The core of the dyke and late veinlets contain unique late- to post-magmatic Ba–Ti–Zr-bearing mineral assemblages of baotite, henrymeyerite, titanite, rutile, benitoite and bazirite. Anhedral baotite fills interstices distributed inhomogeneously in the dyke centre; it is locally replaced by a Ba-bearing titanite+ henrymeyerite+rutile+quartz assemblage [...]. Euhedral crystals of benitoite and bazirite are enclosed in the late-stage quartz–titanite–apatite veinlets in the finegrained margin of the intrusion. In terms of a mineralogical–genetic classification, the Šebkovice dyke can be considered as a new high-silica (~57 wt.% SiO2) variety of lamproite (variety Šebkovice), and represents a unique expression of post-collisional potassic magmatism on the south-eastern border of the Bohemian Massif. The peralkaline dykes from this area show mineralogical and geochemical features similar to those of silicarich orogenic lamproites emplaced at destructive plate margins. In terms of the modern classification of lamproites, the Šebkovice dyke [Not yet published]is the first lamproite recognised in the Variscan orogenic belt."

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References