PLAGIOGRANITI IZ OFIOLITNIH KOMPLEKSA ZONE DINARIDA I VARDARA

Geochemical dana of plagiogranites associated with ophiolite conplexes of Central Dinaride Ophiolite Belt (CDOB) and Vardar Zone Ophiolite Belt (VZOB) are presented. Plagiogranites occur as dikes or small intrusive bodies in the upper part of the gabbrodolerite or diabase section in the ophiolite sequence. On the basis of normative An-Ab-Or diagram most of studied plagiogranites are classified as trondhjemites. They are typically low in K2O, Rb and MgO and contain low to moderate Al2O3, but light SiO2 and Na2O. Their ocean ridge granite normalized patterns of trace elements displaying low contents of HFS and high contents of LIL elements are very similar to those of the volcanic arc granites. But assuming that in trace element pattern elevated K2O and Rb contents are result of alteration, the studied plagiogranites have also strong similarity with typical Troodos supra-subduction ocean ridge granite. The using of Peacock indeks reveals that they are characterized by calcic character what is typical for supra-subduction ocean ridge granite. The studied plagiogranites are probably formed in extensional conditions above a subduction zone and in terms of their origin the most probably related to crystal-liquid differentiation process.Prikazani su geokemijski podaci plagiogranita koji se nalaze u ofiolitnim kompleksima Centralne ofiolitne zone Dinarida (CDOB) i Vardarske ofiolitne zone (VZOB). Plagiograniti se pojavljuju kao dajkovi ili mala intruzivna tijela u gornjem dijelu gabro-doleritne ili dijabazne jedinice ofiolitne sekvence. Na temelju normativnog An-Ab-Or dijagrama većina proučavanih plagiogranita je klasificirana kao trondhjemiti. Oni tipično imaju niske sadržaje K2O, FeO i MgO, niski do srednji sadržaj Al2O3, ali visoke sadržaje SiO2 i Na2O. Usporedba elemenata u tragovima u plagiogranitima s onima tipičnim za granite oceanskog grebena pokazuje da plagiograniti imaju viši sadržaj elemenata velikog radijusa (LIL elementi), a niži sadržaj elemenata malog radijusa i visokog naboja (HFS elementi). Slično ponašanje elemenata u tragovima pokazuju i graniti vulkanskog luka uspoređeni s onima u granitima oceanskog grebena. Međutim, ako se pretpostavi da je povišeni sadržaj K2O i Rb u proučavanim plagiogranitima rezultat alteracije, tada oni imaju također veliku sličnost s Trodos granitom koji je tipični predstavnik granita suptra-subdukcijskih oceanskih grebena. Upotreba Peacock indeksa polazuje da su plagiograniti karakterizirani kalcijskim karakterom što je tipično za granite supra-subdukcijskih oceanskih grebena. Proučavani plagiograniti su vjerovatno formirani u ekstenzijskim uvjetima iznad subdukcijske zone, a njihov postanak je najvjerovatnije vezan za procese kristalno-likvidne diferencijacije

PETROLOŠKE KARAKTERISTIKE KLASTIČNIH TALOŽNIH STIJENA IZ RUDNIKA SVETA BARBARA U RUDAMA KRAJ SAMOBORA

In the scope of this research, the petrographic and geochemical analyses of clastic sedimentary rocks from the St. Barbara, copper and iron ore mine in Rude near Samobor, have been made, aiming to classify and determine the provenance and environment of formation of clastic sedimentary rocks, as well as the influence of hydrothermal fluids on their properties. Eight samples were collected in total from different locations in the mine. Six of those samples have been studied in detail. The results showed structural and geochemical variability and uneven hydrothermal alteration intensity in the samples. Based on petrographic analyses, three rocks are classified as sublithoarenite, quartz arenite and quartz greywacke. Three of the samples are classified as ore breccia, ore sandstone, and ore silt-sandstone due to the pronounced hydrothermal alterations and ore mineralisation. Comprehensively, petrographic and geochemical analyses indicate that the source rocks of the investigated clastic sedimentary rocks were felsic (La/Sc = 0.9-6.2; Th/Sc = 1.3-2.4), most probably sedimentary, possibly resedimented rocks. The extent of source rock weathering was very high (Chemical Index of Alteration CIA = 52.1 - 81.3 %) and the geotectonic position of the sedimentary basin was very likely to be at the passive continental margin.U okviru ovoga istraživanja napravljene su petrografske i geokemijske analize klastičnih taložnih stijena iz rudnika bakra i željeza Sveta Barbara u Rudama kraj Samobora s ciljem da se klasificira i odredi podrijetlo sedimenata, kao i okolina formiranja klastičnih taložnih stijena te utjecaj hidrotermalnih fluida na njihova svojstva. Ukupno je prikupljeno osam uzoraka s različitih lokaliteta unutar rudnika, od čega je šest uzoraka detaljno analizirano. Rezultati su pokazali strukturnu i geokemijsku varijabilnost i nejednak intenzitet hidrotermalne alteracije u uzorcima. Na temelju petrografske analize tri stijene klasificirane su kao sublitoarenit, kvarcni arenit i kvarcna grauvaka. Tri uzorka klasificirana su kao orudnjena breča, orudnjeni pješčenjak i orudnjeni siltozni pješčenjak zbog izrazite hidrotermalne alteracije i rudne mineralizacije. Petrografske i geokemijske analize pokazuju da su ishodišne stijene istraživanih klastičnih sedimenata bile felzične (La/Sc = 0,9 – 6,2; Th/Sc = 1,3 – 2,4), najvjerojatnije taložne, i moguće pretaložene. Stupanj trošenja ishodišnih stijena bio je vrlo visok (kemijski indeks alteracije – CIA = 52,1 – 81,3 %), a geotektonska pozicija sedimentnoga bazena vrlo je vjerojatno bila na pasivnome kontinentalnom rubu

Geochemical characteristics of different iron ore types from the Southern Tomašica deposit, Ljubija, NW Bosnia

Pulverized limonite ore from a Pleistocene–Quaternary lake deposit and compact limonite ore from the Olistostrome member of the Javorik flysch formation, in the Southern Tomašica iron ore deposit, were investigated and compared with different types of siderite and ankerite, limestone and carbonate shale from the same location in order to determine their possible protolith. Two limonite types display a notably distinct REE pattern, REE fractionations, Eu anomalies and other trace element and main oxide content. The REE pattern of compact limonite is characterized by relatively low light ((La/Sm) N = 2.87), heavy ((Gd/Yb) N = 0.98) and total ((La/Yb) = 3.19) REE fractionations, a strong positive Eu anomaly (Eu/Eu* = 2.11) and weakly expressed negative Ce anomaly (Ce/Ce* = 0.82). The compact limonite and siderite REE patterns almost overlap suggesting a common REE source. The same is valid for their Zr/TiO2 N  ratios (0.040 in the compact limonite, 0.033–0.053 in the siderites). Pulverized limonite shows remarkably different REE patterns and the highest REE concentrations, (up to 6 to 13 times higher relatively to the other samples). Its REE fractionation pattern ((La/Sm) N  = 3.68, (Gd/Yb) N = 1.58, (La/Yb) N = 9.41, Eu/Eu* = 1.10 and Ce/Ce*= 0.81) is very similar to those in the carbonate shale, identifying it as the possible protolith of pulverized limonite. The same is valid for the Zr/TiO  ratios (0.025 in pulverized limonite and 0.017 in carbonate shale). The REE pattern of fine grained ankerite ((La/Yb) 2 N = 2.15, Eu/Eu* = 1.95, Ce/Ce* = 0.78) and its Zr/TiO  ratio (0.030) are similar to those in siderite, and could, assuming extensive contamination of pulverized limonite, also represent its protolith. However, the REE patterns of coarse grained ankerite exhibit remarkable depletion of LREE over HREE and a strong reverse LREE pattern ((La/Yb) N  =0.05–0.20, (La/Sm) N = 0.04–0.10, (Gd/Yb) N 2 = 1.77–1.91). They have (similar to the other studied samples), a positive Eu anomaly (Eu/Eu* = 2.16–2.75) and negative Ce anomaly (Ce/Ce* = 0.32–0.83). Their Zr/TiO  ratio (0.004–0.010) excludes coarse grained ankerite as the possible protolith of pulverized limonite. </p

Geochemical characteristics of mercurian tetrahedrite, barite and fluorite from the Duboki Vagan, Glumac and Dubrave-Dugi Dol barite deposits, south of Kreševo, Mid-Bosnian Schist Mts.

The geochemical characteristics of tetrahedrite and barite of the Duboki Vagan barite deposit near the town of Kreševo in the MBSM (Mid-Bosnian Schist Mountains) have been determinated and correlated with the results of previously studied barite, from the adjacent Glumac deposit, and fl uorite, from the Dubrave-Dugi Dol barite deposits. The studied tetrahedrite is characterized by a high content of Au (39 ppm) and Ag (>300 ppm), the presence of Co (63.5 ppm), Ni (266.2 ppm) and Cd (313,6 ppm) in the crystal lattice and negative δ34SCDT values (–11.80‰). On the plot of its C1 chondrite-normalized REE abundances, a slightly expressed positive Eu anomaly and high HREE concentrations are observed. The high content of SrSO4 (2.33 to 3.42 wt.%) in the barite crystal lattice indicates hydrothermal parent solutions. The δ34SCDT values of the studied barite are +10.40‰, which is typical for Permian seawater and its δ18OSMOW values range between 15.6 and 17.7‰. A distinct positive Eu anomaly is shown on the plot of the C1 chondrite-normalized REE abundances in barite. Geochemical characteristics of the studied tetrahedrite and barite of Duboki Vagan are very similar to those of previously investigated Glumac and Dubrave-Dugi Dol barite deposits. The fluorite from the Dubrave-Dugi Dol deposits displays a negative Eu anomaly and its Tb/La and Tb/Ca ratios indicate a quite different origin in relation to barite formation. This is all in the accordance with the possible existence of two different paragenetic types of barite deposits in the MBSM and SEB (Southeastern Bosnia), which significantly differ in the δ18OSMOW ranges of their barites and δ34SCDT values of their sulphides. The first type of barite deposits originated in the Late Variscan phase (Lower Permian). It is characterized by numerous Cu, Fe, Zn, Sb, As, Pb sulphides and Cu-Sb-tetrahedrite without mercury, all having positive δ34SCDT values (0 to +5 ‰). Early intercontinental rifting took place between the uppermost Permian and Lower Triassic and enabled, in a great number of barite deposits, (especially in the MBSM), remobilization and partial fluidization of their Fe, Cu, Zn, Sb and Pb sulphides which reacted with ascended mercury, sulphur and fluorine rich mantle fluids and resulted in the formation of Hgtetrahedrite and octahedral fluorite. These processes caused the occurrence of the second paragenetic type of barite deposit with Hg-tetrahedrite as the main ore mineral, but characterized by strongly negative δ34SCDT values.</p

RAZLIČITE GEOKEMIJSKE ZNAČAJKE RAZVIJENE U BAZIČNIM MAGMATSKIM STIJENAMA KALNIKA (SJEVERNA HRVATSKA)

Basic magmatic rocks of Mt. Kalnik experienced hydrothermal alteration and low grade metamorphism. In such circumstances the most useful tracers of their magma sources and tectonic settings are REE patterns and other normalized trace element abundance plots. Gabbro, basalt, diabase and two samples of metabasalts were investigated in this preliminary study. Geochemical signature of gabbro points to the mantle source of magma and those of metabasalts indicates continental crust source. According to its features basalt could have been derived from the same magma as gabbro by process of magmatic differentiation. The magma giving diabase arised most probably from mantle wedge enriched by hydrothermal fluids ascending from the subducting slab.Bazične magmatske stijene Kalnika su hidrotermalno alterirane i metamorfozirane do niskog stupnja. Za takve stijene najbolji pokazatelji izvora njihove magme i tektonskog položaja jesu obrasci elemenata rijetkih zemalja i drugi dijagrami normaliziranih elemenata u tragovima. U ovoj preliminarnoj studiji istraženi su gabro, bazalt, dijabaz i dva uzorka metabazalta. Geokemijske značajke gabra ukazuju na plaštni izvor magme, a one metabazalta ukazuju na kontinentalnu koru kao izvor. Prema svojim obilježjima bazalt je mogao nastati iz iste magme kao i gabro procesom magmatske diferencijacije. Magma iz koje je nastao dijabaz potječe najvjerojatnije iz omotačkog klina obogaćenoga hidrotermalnim fludima koji se dižu sa subducirajuće ploče

METARHYOLITES OF VRANICA MOUNTAIN IN PALEOZOIC OF CENTRAL BOSNIA

Metarioliti Vranice planine su stijene naglašene porfirne strukture u kojima se kao fenokristali nalaze kvarc, K-feldspat i vrlo rijetki albit. Osnova je mikrokristalna, karakterizirana sitnolistićastim fengitom, biotitom i područjima u kojima granofirski prorastaju kvarc i feldspati. Akcesorni minerali su ilmenit, rutil, apatit, cirkon i klorit. Metarioliti su peraluminijske stijene (PI=1,5-4,1), naglašenog kalcijskog karaktera (K2O/Na2O=1,3-13,8). Inkompatibilni elementi su vrlo obogaćeni u odnosu na prosjećni sustav hondrita, što ukazuje na krustalno porijeklo magmi metariolita. Iako se fengiti najčešće nalaze u stijenama visokog tlaka, fengiti metariolita Vranice planine najvjerojatnije pripadaju rjeđoj grupi fengita koji se nalaze u stijenama niskih do srednjih tlakova.Metharyolites of Vranica mountain are roks of emphasized porphyritic texture containing phenocrysts of quartz, K.feldspar and very rarely albite. The groundmass is microcrystallinic, characterized by finegrained phengite, biotite and area consisting of granophyric intergrowths of quartz and feldspar. Accessory minerals are ilmenite, rutila, apatite, zircon and chlorite. Metarhyolites are peraulminous rocks (PI=1.-4.1) having dominantly potassium character (K2O/Na2O=1,3-13,8). Incompatible elements are enriched relative to the normalizing chondrite composition, pointing to the crustal origin of metarhyolite magma. Although phengites typically occur in high pressure rocks, it seems that phengites of metarhyolites of Vranica mountain belong to the seldom group of phengites occurring in the low to medium pressure rocks

Geochemical characteristics of the barite occurrences in the Paleozoic complex of the Southeastern Bosnia and their relationship to the barite deposits of the Mid-Bosnian Schist Mountains

In Paleozoic rocks of Southeastern Bosnia (SEB) there are numerous, but very small vein and replacement barite ore deposits containing up to 10% Pb-Zn-Fe-Cu sulphides. Their geochemical characteristics are compared with large barite monosulphide (Hg-tetrahedrite) ore deposits in Mid-Bosnian Schist Mountains (MBSM). The 87Sr/86Sr isotope ratios in the barites of both area are very similar (0.710972 and 0.714170 in SEB, 0.711764 and 0.712548 in MBSM) and indicate epigenetic hydrothermal origin of barite ore deposits. To the same conclusion point elevated Sr content in barites of both area (0.48 to 2.83% in SEB, 1.44% in MBSM) and the δ13C and δ18O values in neominerals of barite ore deposits which are shifted toward lower values relative to typical values occurring in Devonian host rock. The δ18O values in barites from SEB (+14.2‰ to +15.6‰) are remarkably lower than those from MBSM (+15.8‰ to +22.4‰) what can be explained by lower temperature and lower salinity of mineralisation fluids in barite ore deposits of SEB. The δ34S values in barites of SEB are positive (+11.6‰ to 17.7‰) and enriched in heavy sulphur isotope in comparison with sulphides of SEB (-0.41 to +4.26‰), whereas those in tetrahedrites are negative (-4.95 in SEB, -5.50 to -15.40‰ in MBSM) indicating two remarkably different sulphur sources and time of formation.Barite ore deposits of both area, SEB and MBSM, have been genetically linked to fluids originated in the processes of Late Variscan S-type of magmatism and metamorphism of Upper Proterozoic and Lower Paleozoic rock complexes. However later, heating processes in Post Variscan/Eoalpine time affected significant parts of barite ore deposits in MBSM. They caused fluidization of sulphides in barite deposits, ascending of subcrustal deep-seated fluids enriched in H2S and mercury (± fluorine), which by passing through Upper Proterozoic and Caledonian ore deposits amalgamated their Au and Ag content and led to the formation of a new mineral, Hg-tetrahedrite rich in Au (10-50 g/t) and Ag (1000 do 3000g/t).</p

Geochemical characteristics of the barite occurrences in the Paleozoic complex of the Southeastern Bosnia and their relationship to the barite deposits of the Mid-Bosnian Schist Mountains

In Paleozoic rocks of Southeastern Bosnia (SEB) there are numerous, but very small vein and replacement barite ore deposits containing up to 10% Pb-Zn-Fe-Cu sulphides. Their geochemical characteristics are compared with large barite monosulphide (Hg-tetrahedrite) ore deposits in Mid-Bosnian Schist Mountains (MBSM). The 87Sr/86Sr isotope ratios in the barites of both area are very similar (0.710972 and 0.714170 in SEB, 0.711764 and 0.712548 in MBSM) and indicate epigenetic hydrothermal origin of barite ore deposits. To the same conclusion point elevated Sr content in barites of both area (0.48 to 2.83% in SEB, 1.44% in MBSM) and the δ13C and δ18O values in neominerals of barite ore deposits which are shifted toward lower values relative to typical values occurring in Devonian host rock. The δ18O values in barites from SEB (+14.2‰ to +15.6‰) are remarkably lower than those from MBSM (+15.8‰ to +22.4‰) what can be explained by lower temperature and lower salinity of mineralisation fluids in barite ore deposits of SEB. The δ34S values in barites of SEB are positive (+11.6‰ to 17.7‰) and enriched in heavy sulphur isotope in comparison with sulphides of SEB (-0.41 to +4.26‰), whereas those in tetrahedrites are negative (-4.95 in SEB, -5.50 to -15.40‰ in MBSM) indicating two remarkably different sulphur sources and time of formation.Barite ore deposits of both area, SEB and MBSM, have been genetically linked to fluids originated in the processes of Late Variscan S-type of magmatism and metamorphism of Upper Proterozoic and Lower Paleozoic rock complexes. However later, heating processes in Post Variscan/Eoalpine time affected significant parts of barite ore deposits in MBSM. They caused fluidization of sulphides in barite deposits, ascending of subcrustal deep-seated fluids enriched in H2S and mercury (± fluorine), which by passing through Upper Proterozoic and Caledonian ore deposits amalgamated their Au and Ag content and led to the formation of a new mineral, Hg-tetrahedrite rich in Au (10-50 g/t) and Ag (1000 do 3000g/t).</p