Wykształcenie litologiczne i okruszcowame dolomitów dolnego wapienia muszlowego w kopalni Trzebionka

Abstract

Dolomites and ore horizons in the Lower Muschelkalk of Trzebionka mine (Cracow-Silesian region) The purpose of this paper is to present a detailed section of the Lower Muschelkalk dolomites in the Trzebionka mine, west of Cracow. These dolomites represent a marginal facies of the Muschelkalk and host zinc and lead ores. The nature of the dolomites has been discussed by several authors, but no representative cross-section of these rocks has ever been given. The dolomites here described include: 1) „primary” dolomites produced by sedimentary and/or early-diagenetic processes and, 2 ) the so called „ore-bearing” dolomite, i.e. an assemblage of secondary crystaline dolomites showing cross-cutting metasomatic contacts with enclosing carbonates (for details and discussion see K. Воgaсz et al. 1972). In the section discussed eight lithologie members have been differentiated and correlated with the well known subdivisions of the Lower Muschelkalk in the Silesian Basin. The members differentiated are shown in fig. 1 and their detailed description is given in the Polish text. Member 1 corresponds to the Gogolin beds. It is made up of the ore- -bearing dolomite that replaced the Gogolin limestones. Members 2 to 4 correspond to the Górażdże beds. They also consist of the ore-bearing dolomite, whereby the members 2 and 3 represent the dolomitized Górażdże limestones and the member 4 is a transformed primary dolomite. In this connection it should be noted that starting from member 4 upwards the ore-bearing dolomite has been formed at the expense of primary dolomites. Member 5 consist of laminated primary dolomites and corresponds to so called „Płaza dolomite” that occurs in the upper part of the Górażdże beds. Members 6 to 8 show similarities to the so called „Siewierz dolomites” and include both primary dolomites and the ore-bearing dolomite. The members 6 to 8 are here regarded as one mapable lithostratigraphic unit that corresponds to the Terebratula and Karchowice beds of the Silesian basin. The sulfide ores are scattered throughout the whole section of the dolomitic rocks but larger concentrations are limited to members 1, 3, and 7. The sulfide mineralization takes a form of stratabound and nest -like deposits. Such deposits tend to occur at certain levels or „ore horizons” within the above mentioned members. Three ore horizons have been differentiated by the present authors and are shown in fig. 1 and 3. These horizons are traced over considerable distances beyond the mining area, whereby the first horizon is the most extensive.