Morfološke značilnosti kalcita iz kamnoloma Brezovica v Pečeh pri Kropi na Gorenjskem

Peklič, Janja (author), Vrabec, Mirijam (mentor), Jeršek, Miha (co-mentor)

V svoji raziskovalni nalogi sem preučevanju kalcitne kristale iz Peči na Gorenjskem, vzhodno od Krope. Kalcit je v Sloveniji eden izmed najpomembnejših mineralov. V Lipniški dolini so bili zaradi apnenca nekdaj aktivni štirje kamnolomi, danes sta delujoča le še dva. Kalcit, ki je predmet moje naloge, se nahaja v manjših razpokah ali geodah v približno 60 m širokem pasu okoli osrednje razpoke, ki se razteza preko vseh etaž kamnoloma. Z zbirateljem mineralov Davorinom Preisingerjem sem iz njegove zbirke in z nadaljnim nabiranjem v kamnolomu pridobila vzorce za nadaljnje raziskave. Vzorce sem makroskopsko pregledala in jih kristalografsko določila. Kristali so nastajali v treh ali celo štirih generacijah. Najprej so nastajali skalenoederski kristali, za drugo generacijo je značilen pozitiven romboederski habitus. Za tretjo generacijo kristalov je značilen negativni položni romboeder. Med zadnjimi so nastajali kristali strmega romboedra. Iz izbranih vzorcev smo izdelali polirane zbruske in pripravili vzorce za analize stabilnih izotopov. Z mikroskopom sem iskala prehode med generacijami in analizirala drobne vključke. S stabilnimi izotopi kisika smo ugotovili, da so kalcitni kristali strmega romboedra kristalili pri najvišji povprečni temperaturi 554 °C, sledijo kristali osnovnega romboedra pri 536 °C, nato skalenoedrski kristali pri 519 °C in na koncu kristali položnega romboedra pri 451 °C.

• Language: Slovenian
• Keywords: kalcit, Peči pri Kropi, preraščanje, vključki, paleotemperatura
• Work type: Final paper
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Year: 2020
• PID: 20.500.12556/RUL-114108
• COBISS.SI-ID: 1553246
• Publication date in RUL: 16.02.2020

Secondary language

• Language: English
• Title: Morphological characteristic of calcite from Brezovica quarry in Peči near Kropa in the Gorenjska region

Abstract

The topic of my research paper are calcite crystals from Peči in the Gorenjska region, east of Kropa. Calcite is one of the most important minerals in Slovenia. In the Lipnica Valley, four limestone quarries were active in the past, and only two are still active today. Calcite, which is the subject of my research, is located in small cracks or geodes in an approximately 60 m wide belt around a central crack that extends across all quarry floors. With mineral collector Davorin Preisinger, I obtained specimens from his collection and at the quarry for further research. The samples were examined macroscopically and crystallographically determined. Crystals have been formed over three or even four generations. Scalenohedral crystals were formed first and the second generation was characterized by a positive rhombohedral habitus. The third generation of crystals is characterized by a negative rhombohedron. The last were crystals of steep rhombohedron. Polished thin sections were made from the selected crystals and samples were prepared for stable isotope analyzes. Using the microscope, transitions between generations and tiny inclusions were analyzed. With stable oxygen isotopes, we found that the calcite crystals of the steep rhombohedral crystallized at a maximum average temperature of 554 ° C, followed by the crystals of the basic rhombohedron at 536 ° C, followed by the scalenohedral crystals at 519 ° C, and finally the crystals of the rhombohedron at 451 ° C.

• Keywords: Calcite, Peči at Kropa, the outgrowht of crystals, inclusions, paleotemperature