The Dinaride Ophiolite Belt formed from the Jurassic part of the Neotethys. The investigated Ozren ophiolite complex in Bosnia and Herzegovina consists of peridotites, plagioclase peridotites, plagiogranites, troctolites and other gabbroic rocks, and fewer basalts. Lherzolites and harzburgites contain corroded ortho- and clinopyroxene1 porphyroclasts enclosed in the olivine matrix. The boundaries between olivine aggregates and pyroxene1 and spinel1 are infilled by medium-grained undeformed aggregates of clinopyroxene2, less orthopyroxene2, spinel2, and often clinopyroxene3-spinel3 symplectites. These textures indicate the final crystallization of peridotite in subsolidus conditions. Partial dissolution of deformed pyroxene1 porphyroclasts and coarse-grained spinel1 most likely occurred due to their reaction with the rest melt present in the grain boundaries. The Al decrease from pyroxene1 to pyroxene2 and 3, or the Cr decrease and Al increase from spinel1 to spinel2 and 3 is characteristic. Peridotites are associated with inferred remnants of a gabbro-dolerite layer, whereas basalts and radiolarites occur as rare dm-size fragments in an ophiolitic breccia. Troctolites display interstitial crystallization of plagioclase, clinopyroxene, less Na-Ti-rich amphiboles, and phlogopite in the olivine-spinel matrix, indicating the replacive character of impregnating melt within the dunite layers. Clinopyroxene-plagioclase-ilmenite-±amphibole gabbroic and fewer basaltic dykes in peridotites formed due to subridge extension, mantle thinning, and the deeper mantle melting. Iron-enriched olivines occur in the peridotite-dyke interfaces and troctolites. Hydrated ultramafics and mafics contain amphiboles, biotite, phlogopite, clinozoisite, epidote, and chlorite aggregates. Estimated magmatic to subsolidus T from peridotite two-pyroxene thermometry are 1000–850 °C, for the spinel facies. Ca-in-orthopyroxene1 thermometry provided T of 1028–1068 °C, and Ca-in-orthopyroxene2 thermometry gave 909–961 °C at estimated P of 1.1–0.9 GPa. However, the gabbroic dyke magmatic crystallization T was constrained to 1200–1100 °C at P of 0.45–0.15 GPa by single clinopyroxene thermobarometry. The obtained P–T conditions constrained the deeper mantle environment for the formation of peridotites than troctolites and crosscutting dykes. The ophiolitic thrust-sheet hanging wall conditions in an obduction-related accretionary wedge were estimated from amphibolites at 620 °C and 0.85 GPa by Ti-in-amphibole thermometry and amphibole-plagioclase thermobarometry. 300 °C and 0.5 GPa were determined from an exhumation shear zone using a combination of chlorite thermometry and Si-in-phengite barometry.

The Ozren ophiolite complex (OOC) of the Dinaridic Ophiolite Belt is one of the six ophiolite complexes in Bosnia and Herzegovina. This paper deals with the mineral chemistry of amphiboles determined by electron probe micro-analysis and micro-Raman spectroscopy. The detected amphibole generations and types in mafic, ultramafic, and metamorphic rocks suggest a polystage evolution and are therefore useful petrogenetic indicators of the investigated OOC. Most gabbroic rocks and dolerites contain primary magmatic amphibole1 (magnesio-hornblende to pargasite, occasionally hastingsite) and prismatic to needle-like aggregates of late magmatic amphibole2 (magnesio-hornblende), while plagiogranite contains ferri-winchite and ferro-ferri-winchite as primary magmatic amphibole. Post-magmatic amphiboles were detected in dolerites, troctolites, and lesser in peridotites. The Na-(Ti)-rich amphibole3 (ferri-winchite and ferro-ferri-winchite to katophorite and ferri-katophorite) with amphibole4 (grunerite) rim formed along the grain boundaries of clinopyroxene, amphibole1, and plagioclase in dolerites. A part of these amphiboles grows into amphibole1, 2. Kaersutite to ferri-kaersutite, associated with phlogopite, occur in troctolites and dunites, while Mhbl was detected in harzburgite. The ultramafic rocks (lherzolites, harzburgites, and dunites) and the gabbroic layer are crosscut by clinopyroxene–plagioclase gabbroic and clinopyroxene–plagioclase–amphibole gabbro–dolerite dykes, suggesting ‘dry’ and ‘hydrated’ percolating melts generated in inferred subridge and supra-subduction settings, respectively. The amphibole3 and 4 in gabbros and dolerites and similar amphibole types in ultramafic rocks could be related to inferred arc-type basaltic and plagiogranitic percolating melts and fluids. Low-Al amphibole5 (tremolite and actinolite) and associated chlorite, albite, and clinozoisite represent the ocean-floor alterations in mafic rocks. Amphibole6 (magnesio-hornblende to pargasite) was identified in metamorphic sole amphibolites. Micro-Raman spectroscopy provided typical Raman spectra for the studied amphiboles, highlighting distinct features such as bands related to ^CMg content, ^CFe³⁺ presence, TO₄ ring-breathing mode, TiO₆ stretching mode, presence > 0.3 apfu of ^CTi, and TO₄ stretching indicating ^CFe²⁺ in the structure. Applied amphibole geothermobarometry revealed the formation P–T conditions of amphibole (Amp)1 (avg. 863 °C at 0.23 GPa), Amp2 (avg. 747 °C at 0.17 GPa), Amp in the mantle rocks (avg. 853 °C at 0.64 GPa), Amp5 (avg. 349 °C at 0.03 GPa), and Amp6 (avg. 694 °C at 0.46 GPa).

Research on potentially toxic elements chromium and nickel and laboratory testing of their concentrations was carried out in the wider area of Maglaj, with the aim to detect and determine their quantities, which gave basis for discussion about origins of these pollutants in soil. Field and laboratory observations included 45 soil samples, taken by the network, which is dictated by geomorphological conditions. The most frequently sampled type of soil are fluvisol and humofluvisol. Concentration of chromium (Cr) and nickel (Ni) are obtained by the most sophisticated laboratory method (ICP-MS), with a highly sensitive detection threshold (0.1 to 10,000 ppm). Evaluation of test results showed that concentrations of Cr (max. 954 ppm, min 154 ppm, average 457.5 pmm) and Ni (max 504.5 ppm, min 103.5 ppm; average 275.57 pmm) are significantly increased compared to the concentrations prescribed in the Regulations on determination of allowed amounts of harmful and hazardous substances in soil (Cr max = 100 ppm and Ni max = 50 ppm). Considering geological settings of surrounding area (the dominant presence of igneous ultramafic and mafic rocks) it can be concluded that high concentrations of Cr and Ni have geogenic origins, what is mean that they originate from source rocks from which they are separated through the long-term decomposition and disintegration processes.

The Ozren ophiolite complex (OOC) is the second largest ophiolite complex in Bosnia and Herzegovina, and it is a part of the huge Dinaride ophiolite belt [1 and reference therein]. This contribution comprises mineralogical-petrographical descriptions of representative rocks of the OOC which were determined from polished sections by polarized light microscopy and introductory EPMA. The investigated harzburgites are composed of Ol (55%), Opx porphyroclasts with Cpx exsolution lamellae (35%), Cpx with Opx exsolution lamellae (5%) the latter following Ol-Opx boundaries or ingrowing Opx and Ol matrix. Spinel occurs in the form of anhedral grains. Lherzolites contain Ol (55%), Opx (25%) and Cpx (15%). Anhedral Opx porphyroclasts have Cpx exsolution lamellae. Similarly, porphyroclastic Cpx contains Opx exsolution lamellae. Late magmatic Cpx and Opx aggregates are ingrowing the Ol matrix and these are also surrounding deformed Opx porphyroclasts. Spinel is immersed in the Ol matrix. Dunites are rare. A remnant of the gabbroic layer is inferred only from a borehole core. This gabbro has ophitic texture and contains primary magmatic porphyric Pl, Cpx and green Amp1. Pyroxene and Amp1 are partially replaced by Amp2 and Chl. Plagioclase is weakly altered. Moreover, we found cross-cutting dykes of gabbros (micro-gabbros, called dolerites, to gabbro-pegmatites, and dunite-associated troctolite) in peridotite. These dykes have randomly oriented minerals, only locally showing mylonitization signatures. Most dykes have a discordant relationship to the peridotite structures. Dolerites and basalts also occur in the form of relatively thicker lens-like bodies in serpentinites. A basaltic dyke cross-cuts layered gabbro (in borehole). Most dolerites are composed of Cpx, Amp and Pl but we also found an exceptional Ol-dolerite dyke cross-cutting peridotite. It has well preserved magmatic ophitic texture composed of Ol, Opx, Cpx, Amp, Pl, Ilm and Ap. Pyroxenes and amphiboles are weakly chloritized and Ol is serpentinized. Dolerites and basalts have an ophitic texture, defined by fine-grained prismatic Pl, Px and Amp. Secondary Amp2 and Chl follow the grain boundaries of magmatic minerals. Ophiolitic breccias cover some peridotite parts. These breccias contain 1cm – 10m fragments of all lithological sequences of the OOC including reddish radiolarite sediments. Gabbros from ophiolitic breccia have coarse grained Pl and Px. Exsolution lamellae in Px and kink-banding are characteristic features from subsolidus magmatic conditions. A rare plagiogranite intrusion in peridotite is composed of Qz, Pl and needle-like Amp aggregates after Bt. Such an association of ultrabasic and basic rocks may indicate percolating gabbroic magmas through the peridotites. Amphibolites were found only at one locality so far and these are composed of oriented Amp and Pl aggregates in the metamorphic texture, most likely indicating metamorphic sole of an ophiolitic thrust sheet. These preliminary results shed light on the lithology and petrography of the OOC and have arisen problems for further research. References: [1] Babajić E. (2019) Krivaja-Konjuh ophiolite complex – petrology, geochemistry and geotectonics of mafic sequences. (Monograph), MIT-ALEX, Tuzla (Bosnia and Herzegovina) Acknowledgement: APVV Agency Project No. APVV-19-0065 (M.P.) is acknowledged.

The Ozren and Borja-Mahnjača ophiolite complexes in Bosnia and Herzegovina are part of the Dinaridic Triassic-Jurassic ophiolite belt (Putiš et al., 2022; Minerals). Triassic oceanic crust was dated at 242±1 Ma from a relic zircon population in a plagiogranitic layer of partially melted eclogitic sole by LA-ICP-MS U-Pb method, while the main zircon population of 176±1 Ma dates the crystallization of this layer from a metamorphic-anatectic melt. The host sole (Cpx-Grt-Rt) eclogite yielded metamorphic, most likely exhumation zircon age of 168±5 Ma, while rutile gave an age of 165±3 Ma. Jurassic lower oceanic crust was dated from an isotropic gabbro (178±1 Ma, zircon) and plagiogranite (177±1 Ma, zircon). The mantle spinel lherzolites, harzburgites, and dunites are crosscut by Cpx-Pl and Amp-Pl gabbroic, gabbro-pegmatitic, leuco-gabbroic (174±1 Ma, zircon), and doleritic (174±5 Ma, apatite) dykes, all suggesting an advanced evolutional stage and a shallower level of ophiolites due to extension and the deeper mantle melting. The upper oceanic crust pillow basalts are alternating with Bajocian to Callovian radiolarites (~171-162 Ma; Ustalić, Soták et al., 2023; Newsletter of the Slovak Geological Society). The dated N-MORB type sole eclogites-amphibolites indicate the intra-oceanic subduction of the Triassic gabbroic oceanic crust to about 55-60 km that was estimated from Perple_X modelling of 1.9-2.1 GPa and 780°C. Partial melting of subducted slab and a mantle wedge initiated the formation of Jurassic supra-subduction ophiolitic complex detected at ~178-162 Ma. Inferred slab roll-back enhanced the sole extension exhumation between ~170-160 Ma that was coeval with the formation of the upper oceanic crust basalt-radiolarite section. The mineral chemistry-based discrimination diagrams of ultramafic rocks constrain an evolutional trend from MORB to supra-subduction types of ophiolites. An increased depletion of ultramafic rocks is indicated by an increase of Cr# in spinel from ~30 to 60, exceptionally to 75, suggesting transitional abyssal to supra-subduction peridotites and dunites. Relatively thin, often hydrated (Amp-rich) gabbro-dolerite layer of this ophiolite complex may have formed in a fore-arc/back-arc slow-spreading ridge. Ophiolitic breccia, with fragments of the Jurassic oceanic crust and rare Triassic radiolarites, indicates the closure of the Jurassic Neotethys from approximately 160 Ma.Funding from The Slovak research and development agency projects (APVV-19-0065, APVV-20-0079, APVV-22-0092), VEGA agency (1/0028/24, 2/0012/24), and the RVO67985831 program is acknowledged.