The mineralogy, elemental composition and modes of element occurrence in a vitrain lens from the western and peripheral part of the Vulche Pole coal deposit (Bulgaria) were studied. The total concentration of trace elements established in the lens is 12.7 % (ash basis) including 7.75 % Ge which is among the highest contents of the element reported until now. The low ash coal lens (7.8 % ash) contains a great variety of detrital and authigenic minerals. The group of detrital minerals and phases includes quartz, K-feldspars, plagioclases, biotite, amphibole, zircon, apatite (coarse crystalline), volcanic glass and native Au. The authigenic minerals are presented by pyrite, sphalerite, galena, gypsum, jarosite and anglesite. The identified minerals such as opal, cristobalite, kaolinite, illite, muscovite, Fe oxides-hydroxides, delafossite, apatite (fine crystalline), monazite, xenotime, gamagarite and stolzite could have a detrital and/orauthigenic origin. Despite extremely high (over Clarke) concentrations of such elements as Ge, U, Sb, Sm, V, Mo, Ce, Hf, Y, Yb, Zn, As, Tb and Zr, these elements demonstrate a strong association or dominant affinity with the organic matter. Some of the aforesaid elements occur as discrete minerals (Zn, Zr, Ce, Y, V, Hf) and as impurities in the minerals (Zn, As, V, Ge, Hf, U, Zr). However, the mineral matter is only a minor constituent in the lens and its contribution to the enrichment of these elements is not of great significance.

U-Pb-zircon and monazite ID-TIMS and in-situ LA-ICP-MS and EPMA analyses are combined to define the magmatic age of the Igralishte granite, which is exposed over 32 km2 in the high-metamorphic rocks of the Serbo-Macedonian Massif (Ograzhden Mountain, SW Bulgaria). The granite is dated at 243.28 ± 0.84 Ma by concordant zircons (ID-TIMS data) and this intrusion age is confirmed also by in-situ LA-ICP-MS and EPMA monazite analyses. The intrusion of the Igralishte granite at middle Triassic time defines the age of the high-grade metamorphism in Ograzhden Mountain as Pre-Triassic. A tectonic and hydrothermal overprint is dated at 36.36 ± 0.56 Ma by the Rb-Sr whole-rock-biotite reference line. This age is considered as the youngest thermal event in the region of the Igralishte pluton that reached the 300 ± 50 °C closing temperature of the Rb-Sr isotope system in the biotite, but could not fully reset the Rb-Sr isotope system of the muscovite. The initial strontium ratio of 87Sr/86Sri = 0.7078 and the inheritance of old lead components in the zircons suppose crustal-dominated source of the magma. Preferred tectonic scenario suggests dehydration melting and granite formation in the middle/upper crust at the Permian-Triassic boundary and the Lower-Middle Triassic caused by mafic intrusions at the base of the crust.

The Rietveld method using X-ray powder diffraction data was applied to selected skarn samples for quantitative determination of the present minerals. The specimens include garnet, clinopyroxene–garnet, plagioclase–clinopyroxene–wollastonite–garnet, plagioclase–clinopyroxene–wollastonite, plagioclase–clinopyroxene–wollastonite–epidote, and plagioclase–clinopyroxene skarns. The rocks are coarse- to fine-grained and characterized by an uneven distribution of the constituent minerals. The traditional methods for quantitative analysis (point-counting and norm calculations) are not applicable for such inhomogeneous samples containing minerals with highly variable chemical compositions. Up to eight individual mineral phases have been measured in each sample. To obtain the mineral quantities in the skarn rocks preliminary optical microscopy and chemical investigation by electron probe microanalysis (EPMA) were performed for the identification of some starting components for the Rietveld analysis and to make comparison with the Rietveld X-ray powder diffraction results. All of the refinements are acceptable, as can be judged by the standard indices of agreement and by the visual fits of the observed and calculated diffraction profiles. A good correlation between the refined mineral compositions and the data of the EPMA measurements was achieved.