RESUMEN
Light-blue barite from Jebel Ouichane in Morocco forms blade-like tabular crystals (up to ca. 10 cm) with superb transparency and lustre and represents one of the most spectacular gem-quality worldwide. The barite is hosted by iron-ore-bearing skarns, developed within Jurassic-Cretaceous limestones, and occurs in close spatial association with calcite. The crystals have their cores enriched in Sr and contain abundant monophase (liquid) fluid inclusions of primary and pseudosecondary origin. The barite probably precipitated slowly at a relatively low supersaturation and under the control of a surface reaction precipitation mechanism. However, there were some episodes during its formation with a fast growth rate and the coupled dissolution and recrystallization processes. A combination of fluid inclusion data and stable δ18O value for barite (+ 6.71 VSMOW) suggests that low-salinity barite-forming solutions resulted from the mixing of strongly-diluted meteoric waters (enriched in light oxygen isotope) with magmatic-hydrothermal fluids under low-temperature conditions (< 100 °C). Meanwhile, the mineralizing fluids must have been enriched in Ba, Sr, Ca, Mg, and other elements derived from the alteration of carbonate and silicate minerals in sedimentary and igneous rocks. The coupling between sulphur and oxygen isotope data (+ 16.39 VCDT and + 6.71 VSMOW, respectively) further suggests that barite crystallized in steam-heated environment, where SO42- derived from magmatic-hydrothermal SO2 reacted with sulphates that originate from the oxidation of H2S under near-surface conditions.
RESUMEN
The occurrence of organic matter (OM) in a salt dome cap-rocks is very rare in Zechstein formation in the Europe. Within the Klodawa Salt Dome (KSD) cap-rock and Triassic cover OM occur relatively often and it is accompanied by some rare minerals. The OM in cap-rocks occurs in two forms i.e. as a finely dispersed matter not recognizable in a microscopic image and as organic particles or small veins. Based on the Raman spectroscopy and measured reflectance both forms show similar thermal maturation but finely dispersed matter display higher variability. The temperature of the maturation reaches up to 220⯰C and mostly is about 150⯰C. Within the solid bitumen (SB) was also found OM particles which show thermal transformations above 300⯰C. Within the Triassic cover SB veins and particles prevail. The finely dispersed matter is occasionally found. In terms of thermal maturation, the SB is similarly developed as in the cap-rocks. It also contains OM particles which show higher thermal transformations, as well as graphite-like particles. Therefore, it indicates the continuation of bitumen migration from cap-rock. Additionally, clasts of brown coal which show low thermal maturation occur in Triassic sediments. The SB is sometimes accompanied by two types of hydrocarbons (HC) i.e. with prevailing aliphatic or aromatic compounds as well as titanium minerals (anatase, rutile). Two source rocks for SB and HC generation seem to be: 1) the Stinking Shale (T1) and Main Dolomite (Ca2) members that occur in KSD, 2) the deep basement of Zechstein salt formation. The thermal maturity of OM confirms that the migration of hydrothermal solutions took place during KSD development. The origin of such a hot solution is connected with tectonic activity in the basement of salt formation during Mesozoic.
RESUMEN
Raman spectroscopy was applied to determine the degree of recrystallization and the influence of the secondary solution migration on the Oldest Halite (Na1) in Lubin-Glogów Copper District (LGOM). Numerous organic matter (OM) inclusions which generally show weak structural ordering was found in halite crystals. In this context they are similar to solid bitumens or carbonaceous matter of low thermal alteration. The difference in the Raman line-shape of OM indicated various thermal alteration of salt from the Oldest Halite formation due to hot fluid flow. Solutions included in the secondary fluid inclusions often contain dissolved gases such as CH4, N2, H2S. The presence of these gases is connected with migration process from basement to the salt formation. Moissanite in fluid inclusions was accidentally trapped during inclusion formation, i.e. is not a daughter mineral. It was also found in the halite as an individual solid inclusions as well as in the anhydrite concentrations. Raman spectroscopy allowed to determine also such solid inclusions in halite as celestine, magnesite, pyrite, lepidocrocite and goethite as well as hydrocarbons.
RESUMEN
Differently colored authigenic quartz crystals were found as the druses compound within mudstone heteroliths from the Pepper Mts. Shale Formation (Cambrian unit of the Holy Cross Mts., Central Poland). The genesis of this mineral was established on the basis of fluid inclusion study. Raman microspectroscopy was the key instrumental technique to identify the nature of the compounds trapped in the fluid inclusions. Methane (2917cm-1) or water vapor (broad band ~2500-3000cm-1) occur within two-phased primary inclusion assemblages, while nitrogen (2329cm-1) associated with methane and trace amount of carbon dioxide (1285, 1388cm-1) occur within secondary fluid inclusion assemblage. Temperatures of homogenization of primary fluid inclusions was obtained on the basis of heating experiments and ranged from 171° to 266°C. These values are much higher than expected for the diagenetic system without metamorphic changes what may imply hydrothermal origin of quartz crystals. The source of fluids is uncertain as in the Holy Cross Mts. there was no volcanic activity to the end of Late Devonian. However, fluids originated in metamorphic basin could use deep faults as the migration paths.