20.500.12556/DiRROS-24905 Petrography and geothermobarometry of quartz diorite from Pohorje Mountains, Slovenia Petrografija in geotermobarometrija kremenovega diorita s Pohorja The mineral composition and pressure–temperature conditions of Pohorje quartz diorite were investigated to reconstruct crystallization sequence and integrate the results with previous data on the Pohorje igneous complex, providing insights into its petrogenesis. Pohorje quartz diorite has phaneritic texture and is medium- to coarse-grained. The major minerals include light green clinopyroxene, dark green amphiboles, and white feldspars; the first two give the rock its characteristic colour. The proportion of dark- to light-colored minerals is approximately 4:1. Clinopyroxene predominates and correspond to diopside (XCa = 0.47–0.51, XMg = 0.41–0.49, XFe = 0.05–0.09). Amphiboles are Ca-amphiboles and are divided into two types: Type I amphiboles occur as single grains with distinctive core and rim zones, whereas Type II amphiboles replace clinopyroxene grains. Type I amphibole cores are classified as magnesiohornblende, tschermakite, edenite, pargasite, or magnesiohastingsite; Type I amphibole rims are classified as magnesiohornblende and actinolite; and Type II amphiboles are classified as magnesiohornblende. The dominant feldspars are oligoclase to andesine (XAb= 0.61–0.73), often replaced by potassium feldspar orthoclase. Minor minerals include quartz, biotite group minerals, apatite group minerals, titanite, epidote group minerals (allanite), and magnetite, while secondary minerals comprise chlorite group minerals and calcite. Various thermometers and barometers were applied to reconstruct the crystallization history of the quartz diorite and link it to the evolution of the host granodiorite intrusion. Thermobarometric data indicate that clinopyroxene in the quartz diorite, which is considered the earliest cumulate product from basaltic melts, crystallized under the highest P–T conditions (840–905 °C; 6.70–7.70 kbar), consistent with petrographic evidence. Subsequent crystallization of Type I amphibole cores occurred at 675–730 °C and 6.45–6.50 kbar, conditions comparable to those of the less evolved granodiorite, suggesting coeval formation. Later stages involved the formation of Type I amphibole rims at 585–640 °C and ~2.00 kbar, Type II amphiboles at 615–680 °C and 2.59–2.79 kbar, and biotites at 670–690 °C, associated with the emplacement of more evolved granodiorite at shallower crustal levels. Proučili smo mineralno sestavo in tlačno-temperaturnepogoje nastankapohorskega kremenovega diorita, z namenom določitve zaporedja kristalizacije posameznih mineralov. Dobljene rezultate smo povezali z objavljenimi podatki o pohorski granodioritni intruziji, kar omogoča dodaten vpogled v petrogenzo kremenovega diorita. Pohorski kremenov diorit ima faneritsko strukturo in je srednje do debelozrnat. Glavne minerale predstavljajo svetlozeleni klinopirokseni in temnozeleni amfiboli, ki dajo kamnini značilno barvo, ter beli glinenci. Razmerje med temnimi in svetlimi minerali je približno 4:1. V kamnini prevladuje klinopiroksen, ki ustreza diopsidu (XCa = 0,47–0,51, XMg = 0,41–0,49, XFe = 0,05–0,09). Amfiboli so Ca-amfiboli in jih lahko razdelimo na dve vrsti: amfiboli tipa I se pojavljajo kot posamezna zrna z značilno različno sestavo jedra in robnih delov, medtem ko amfiboli tipa II nadomeščajo zrna klinopiroksenov. Jedra amfibolov tipa I pripadajo magnezijski-rogovači, tschermakitu, edenitu, pargasitu ali magneziohastingsitu; robni deli amfibolov tipa I pripadajo magnezijski-rogovači in aktinolitu; amfiboli tipa II so po klasifikaciji vsi magnezijska-rogovača. Med glinenci prevladujejo plagioklazi sestave oligoklaz do andezin (XAb = 0,61–0,73), ki so pogosto nadomeščeni z ortoklazom. Med manj zastopanimi minerali se pojavljajo kremen, biotiti, apatiti, titanit, minerali epidotove skupine (allanit) in magnetit, od sekundarnih mineralov so prisotni kloriti in kalcit. Da bi rekonstruirali zgodovino kristalizacije kremenovega diorita in ga povezali z razvojem glavnega granodioritnega intruziva smo uporabili različne geotermometre in geobarometre. Rezultati geotermobarometrije kažejo, da so klinopirokseni v kremenovem dioritu, ki velja za najzgodnejši kumulat bazaltnih talin, kristalili pri najvišjih P–T pogojih (840–905 °C; 6,70–7,70 kbar), kar je skladno s petrografskimi dokazi. Sledila je kristalizacija jeder amfibolov tipa I, ki je potekala pri 675–730 °C in 6,45–6,50 kbar, kar ustreza pogojem kristalizacije manj razvitega granodiorita in nakazuje njihov sočasni nastanek. Kasnejše faze so vključevale nastanek robnih delov amfibolov tipa I pri 585–640 °C in ~2,00 kbar, amfibolov tipa II pri 615–680 °C in 2,59–2,79 kbar, ter biotitov pri 670–690 °C in so povezane z intruzijo bolj razvitega granodiorita v višje nivoje skorje. quartz diorite “cizlakite” petrography clinopyroxene geothermobarometry amphibole geothermobarometry amphibole–plagioclase thermometry Pohorje Mountains kremenov diorit “čizlakit” petrografija klinopiroksenova geotermobarometrija amfibolova geobarometrija amfibol–plagioklaz barometrija Pohorje true false true Geološki zavod Slovenije Angleški jezik Slovenski jezik Neznano 2025-12-24 08:33:15 2025-12-24 08:34:49 2025-12-25 03:44:40 0000-00-00 00:00:00 2025 0 0 str. 269-286 no. 2 vol. 68 2025 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 2025-12-10 55 0016-7789 10.5474/geologija.2025.012 259322883 1941-Article_Text-12342691-3-10-20251222.pdf 1941-Article_Text-12342691-3-10-20251222.pdf 1 D7BF766696FBFC37DAA21203881D98E8 3b42267d16455705e2ce953395248b1010741d8002696825937996e07f262474 2b1a6a98-e09b-11f0-94a7-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=37280 Geološki zavod Slovenije Geologija 0 0 0