Mineralogical notes and fluid inclusion studies on quartz-feldspar granite pegmatites and quartz veins from Mórágy and Erdősmecske granitoid, S-Hungary
Reference
Acta Mineralogica-Petrographica, Szeged 2004, Vol. 45/1, pp. 39–48
Szerző:
Gatter István
Török Kálmán
Abstract:
This paper is devoted to investigation of quartz–feldspar granite pegmatites and quartz–calcite veins from Mórágy and Erdősmecske Granitoid, South Hungary, by microprobe and fluid inclusion studies. The result is the first verification of the presence of native gold, arsenopyrite, stibnite, cassiterite and scheelite. Three types of constituents can be divided into the following groups:
“granitophile”, early-formed accessory minerals: ilmenite, rutile, thorite, garnet, allanite, titanite, zircon, apatite, monazite, Y-, Ce-La-Ca phosphates, etc.
“granitophile”, high temperature – hydrothermal – minerals: arsenopyrite, molybdenite, cassiterite and scheelite, which sometimes associated with other sulphides (pyrite, chalcopyrite, fahlore, sphalerite, and galena).
“epithermal” type, low temperature hydrothermal assemblage: – gold, stibnite, barite, carbonate phases including bastnäsite, Ce-La-Nd carbonates and Ca-Fe-Mn-Mg double carbonates. The gold–stibnite pair can be interpreted as a decomposition of the Sb-bearing ligand during the transportation of gold. In granite environments, the Au-Sb association is not infrequent.
The microthermometric study with limited number of fluid inclusion samples does not allow detailed interpretations. However a few remarks can be made. The Th distribution shows three maxima – 140–150 oC, 200–210 oC and 260–270 oC, suggesting a wide range of fluid temperature history both in the pegmatite and the grown-up (vein) quartz-calcite materials. The uncertainty of the genetic type of inclusions does not allow speculations regarding to the fluid evolution from high PT conditions. The registered Th data set reflects some “late” history of fluids, without any time-related considerations.
The fluid character is mainly Na-Ca-Cl type. The influence of Ca-bearing fluids can be traced also by the following facts: a) Garnet overgrowth by Ca-rich rim, b) Allanite overgrowth by Ca-rich rim, c) Decomposition–redistribution process of REE-bearing minerals like monazite, allanite, etc. to REE-bearing carbonate species like bastnäsite, or other REE-bearing carbonate during a “hydrothermal” process, d) Formation of “sterile”, late carbonate-bearing veinlets.
The calculated salinity (expressed in NaCl eq.wt. %) is low: 6–0 NaCl eq.wt.%
The Th/c plot shows the trapping of fluids in a wide density range. Comparing to the similar data of Velence Mts., it exhibits the presence of significantly lower salinity fluids in Erdősmecske–Mórágy Granitoid. These data suggest an overlapping as a result of subsequent tectonic and fluid rejuvenation events.
accessory minerals, acta2004, Erdősmecske–Mórágy Granitoid, fluid inclusions, granite pegmatite
