Argutnents for the existence of a volcanic structure in the Lake Dracului — Comsa Hill area (Northern Harghita Mts) – The Köves (Stanca) structure

Abstract

During 2002 , geological investigations were carried out in the Northern Harghita Mountains. Due to
certain morphostructural and geological characteristics, it was concluded that the Köves (Stanca)
volcanic structure, contoured in the riverhead of the §ugó and Sicasáu streams (based on
aeromagnetometric and gravimetric prospection dates by SUCEAVÁ & PROCA 1970 ; CRISTESCU et al. 1971) ,
actually exists. It is not simply a conjecture.
The main arguments for the existence of this volcanic structure" s are indicated by the drillings F I and
F 2 Com§a - 10 0 m (2002 , 2003) . These intercepted an intrusive body (microdiorite with hornblende and
pyroxene) with breccified zones- Light mining operations produced further evidence. The light mining
operations demonstrated a large zone with hydrothermal-metasomatic alterations and sometimes
mineralized rocks (argilization, silicification, carbonatization, pyritization and tourmalinization).
The metallogenetic activity from this area took place alongside poor mineralization. The latter was the
result of hydrothermal activities with a sulphur deficit. The metallic minerals förmed in this ore deposit
are represented mainly by pyrite and marcasite and subordinately by sphalerite, ilmenite, rutile,
magnetite and haematite.
Geophysical and geological data are supported by the existence of a depression zone where currently
there is a bog, called Lacul Dracului (Devil's Laké); thi is what remains of an intracraterial lake. There is
a sand deposit on the most southern verge of this bog and a peat bank on highest levél (which marks the
actual verge of the bog).