OPTIMALNI POSTUPAK PRIPREME UZORAKA SILIKATNE STIJENE ZA ANALITIČKE SVRHE

The purpose of this study was to determine an optimal dissolution method for silicate rock samples for further analytical purposes. Analytical FAAS method of determining cobalt, chromium, copper, nickel, lead and zinc content in gabbro sample and geochemical standard AGV-1 has been applied for verification. Dissolution in mixtures of various inorganic acids has been tested, as well as Na2CO3 fusion technique. The results obtained by different methods have been compared and dissolution in the mixture of HNO3 + HF has been recommended as optimal.Svrha rada bila je utvrđivanje optimalnog postupka otapanja uzoraka silikatne stijene za dalje analitičke svrhe. Za verifikaciju je primijenjena analitička metoda FAAS određivanja udjela kobalta, kroma, bakra, nikla, olova i cinka u uzorku gabra i u geokemijskom standardu AGV-1. Istraženo je otapanje u smjesama različitih anorganskih kiselina kao i taljenje s Na2CO3. Uspoređeni su rezultati dobiveni različitim postupcima te se kao optimalni postupak preporuča otapanje u smjesi HNO3 + HF

"GUTTER CAST" TEXTURE AS POSSIBLE CORRELATIVE MARKER - EXAMPLE OF LOWER TRIASSIC SEDIMENTARY SEQUENCE PLAVNO AND STRMICA (CROATIA AND BOSNIA AND HERZEGOVINA)

Na profilima Plavno i Strmica u okolici Knina istraženi su sedimenti donjeg trijasa - skita koji u oba slijeda pokazuju iste litofacijesne značjke. Karakteristike Siliciklastičnog litofacijesa, koji odgovara sedimentima donjeg skita,te Muljnog i Siltozno-muljnog litofacijesa gornjeg skita odražavaju utjecaj oluja u plićim i dubljim dijelovima šelfa, kao i oscilacije razine mora koja se manifestira nizanjem ciklusa pretpostavljenog 5, 4. i 3. reda. Na otvorenim donjim slojnim plohama sedimenata Muljnog i Siltozno - muljnog litofacijesa uočena je "gutter crust" tekstura nastala uslijed helikoidalnog (vrtložnog) strujanja čija je os paralelna površini sedimenta. Takvo strujanje moguće je interpretirati kao posljedicu djelovanja jednosmjernih struja tijekom oluje. uslijed erozije vrtloženjem nastaju plitki dugački ravni ili prepleteni žljebovi. Tekstura je vezana uz sedimente vanjskog šelfa i predstavlja karakteristični, istovremeni olujni zapis na širem prostoru. Zahvaljujući ovoj teksturi i njenoj jednoobraznoj genezi sedimenti vertikalnog slijeda oba istaložena lokaliteta mogu se, u nedostatku drugog biostratigrafskog ili litostratigrafskog markera, međusobno korelirati. Kao osnova za korelaciju može poslužiti prva pojava "gutter cast" teksture vertikalno u slijedu sedimenata. Tako načinjena korelacija grupira "gutter cast-e" oba istražena slijeda u određeni vremenski (vertikalni) interval. "Gutter cast" tekstura predstavlja, u tom slučaju, kronostratigrafski marker. U slučaju takvog pristupa korelaciji razlika debljine litofacijesa pojedinih lokaliteta može se objasniti položajem u sedimentacijskom bazenu bliže ili dalje od obale. Korelacijski princip spajanja granice donjeg i gornjeg skita, što je uvriježeni princip korelacije, može se u tom slučaju isključiti kao neodgovarajući.Lower Triassic (Scythian) sedimentary sequence developed in similar lithofacies were studied at two sections in vicinity of Knin - Plavno (in Croatia) and Strmica (in Bosnia and Herzegovina). Characteristics of the Siliciclastic lithofacies, which corresponds to the Lower Scythian, Seis beds, and of the Mudstone and Siltstone - mudstone lithofacies of Upper Scythian, Campil beds, reflect the storm influence at the shallower and deeper parts of shelf, as well as the sea-level oscilations resulting in a presumed 5th, 4th and 3rd order cycles. Appearance of gutter casts exposed on lower bedding planes of sedimentary rocks in Mudstone and Siltstone-mudstone lithofacies has been considered as a consequence of bottom current flow component in the outer shelf area. This unidirectional current flow has a helicoidal component with horizontal axis parallel to the sediment surface. The flow generates characteristic storm imprint on the broad shelf area. Lacking any other types of either the biostratigraphic or litostratigraphic marker horizons, this structure, having only one way of formation, allows the improvement of chronostratigraphic correlation of the vertical sequence on both explored locations. The firs appearance of this structure in sediment successions of Plavno and Strmica, may serve as possible correlative marker. Using such a correlative principle gutter casts are in vertical succession grouped in interval, which signifies approximately penecontemporaneous events. Should the correlation be based on the gutter cast structure, the differences in thickness at both location can be explained by their more proximal or more distal position within the sedimentary basin. If this is true, the inveterate principle of correlating the contact between of Lower Scythian and Upper Scythian sediments as a contact between the red, dominantly clastic Seis beds and grey, dominantly calcareous Campil beds, is therefore found to be chronostratigraphically inadequate and can be excluded

SASTAV I PROVENIJENCIJA GREDENSKIH PJEŠČENJAKA VELEBITA

Six samples of Gröden sandstones (Middle Permian) were analysed: Five of them were from Pikovac Creek valley (in the vicinity of Brušane village at Velebit Mts., Croatia) and one was from the locus typicus Gröden/Val Gardena (Italy). Based on the micropetrographical characteristics of sandstones, as well as on the modal composition and heavy mineral association, origin of material, weathering index of source rocks, climate and relief in the period of deposition have been supposed. Four samples from Pikovac Creek were petrographicaly determined as lithic greywackes, one as densely packed lithic arenite, while a specimen from Gröden locus typicus represents feldspar greywacke. Lithic greywackes/arenites imply very low maturity and suggest a close proximity of source rocks as well as the active tectonics in the hinterland of the depositional basin. Heavy mineral association in the samples from Pikovac Creek valley, with a large amount of fairly rounded stable grains (zircon, tourmaline and rutile), indicate that clastic material was derived from recycled orogen, and probably from reworked sedimentary rocks. The presence of kyanite and chlorite in the heavy mineral assemblage suggest their origin is from metamorphic rocks. This data assumes that Gröden sandstones from Pikovac Creek were possibly deposited in the fan delta or braided delta depositional environment as a part of a rift system (recycled orogen). The composition of the sample Gröden s. locus typicus (light and heavy mineral fractions) suggests the vicinity of magmatic rocks in the source area. All analysed samples are red coloured and have a large amount of limonitized grains in the heavy mineral assemblage, that point to the arid climate at the time of deposition. A weathering index diagram for Pikovac sandstones implies an arid/semiarid climate and high relief of the source area where metamorphic or sedimentary rocks dominate, while an arid/semiarid climate and high relief with plutonic source rocks were supposed for the provenance of Gröden s. locus typicus.Analizirano je šest uzoraka srednjopermskih gredenskih pješčenjaka: pet uzoraka iz doline Pikovačkoga potoka u okolici Brušana na Velebitu i jedan uzorak s locus typicus lokaliteta Gröden/Val Gardena u Italiji. Na temelju mikropetrografskih karakteristika pješčenjaka, njihova mineralnog sastava te sastava teške i lake mineralne frakcije, interpretirano je podrijetlo materijala, indeks trošenja matičnih stijena te klima i reljef u vrijeme taloženja. Četiri uzorka pješčenjaka iz Pikovačkoga potoka petrografski su određena kao litične grauvake, a jedan uzorak kao gusto pakirani litični arenit, dok je uzorak pješčenjaka s locus typicus lokaliteta Gröden određen kao feldspatska grauvaka. Litične grauvake/areniti podrazumijevaju vrlo nisku zrelost i sugeriraju blizinu matičnih stijena, kao i aktivnu tektoniku u zaleđu sedimentacijskoga bazena. Asocijacija teških minerala u uzorcima iz Pikovačkoga potoka, s velikom količinom dobro zaobljenih stabilnih zrna (cirkon, turmalin i rutil), upućuje na to da klastični materijal potječe iz recikliranoga orogena, i to vjerojatno od pretaloženih sedimentnih stijena. Prisutnost distena i klorita u teškoj mineralnoj frakciji sugerira podrijetlo iz metamorfnih stijena. Rezultati upućuju na to da su gredenski pješčenjaci iz doline Pikovačkoga potoka možda taloženi u okolišu lepezne delte koja je dio riftnoga sustava (reciklirani orogen). Sastav lake i teške mineralne frakcije uzorka Gröden s. locus typicus sugerira podrijetlo iz magmatskih stijena. Svi analizirani uzorci crvene su boje i imaju veliku količinu limonitiziranih zrna u teškoj mineralnoj frakciji, što upućuje na aridnu klimu u vrijeme taloženja. Dijagram indeksa trošenja pješčenjaka iz Pikovačkoga potoka upućuje na aridnu/semiaridnu klimu i visoki reljef izvorišnoga područja koji je izgrađen od sedimentnih i metamorfnih stijena, dok uzorak Gröden s. locus typicus pješčenjaka ukazuje na aridnu/semiaridnu klimu i visoki reljef, s magmatskim matičnim stijenama i izvorišno područje magmatskoga luka

CONTACT PHENOMENA IN THE ROCKS OF MT. KALNIK (NW CROATIA)

Na području Kalničkog gorja istraženi su malobrojni kontakti magmatskih i sedimentnih stijena. Neki kontakti imaju elemente tektonizacije. Primarni kontakti su ili bez kontaktnometamorfnih promjena, ili s izraženim promjenama. Na neke kontakte, uz prostorni odnos magmatske i sedimentne stijene, ukazuju i kontaktne pojave u sedimentnim stijenama. Magmatske stijene su u kontaktu sa šejlovima, vapnencima dolomitima i litičnim grauvakama. Među kontaktnim strukturno-teksturnim i kemijskim pojavama zapažene su izrazito jaka listatost sedimenata s prijelazom u škriljavost, kontaktne eruptivne breče, anklave vapnenaca, klinasto utiskivanje, raspucanost sedimenata, transformacija matriksa, sekundarni sastojci u žilicama i gnijezdima u sedimentnim stijenama, rekristalizacija, dolomitizacija, skarnska parageneza, silicifikacija, hematitizacija i pojava ferokalcita. Navedene pojave ukazuju na sinsedimentacijske i/ili postsedimentacijske višekratne efuzije i plitke intruzije bazične lave. Različitost kontaktnih pojava upućuje na različite brzine izlijevanja, količine i temperature lave i različiti stupanj konsolidiranosti sedimentnih stijena.Scarce contacts between magnetic and sedimentary rocks have been investigated on the Mt. Kalnik. Magmatic rocks are in contact with shales, limestones, dolomites, and lithic greywackes. Some contacts are characterized by the tectonic nature. The primary contacts are either without contact metamprphic changes, or with them, whereas some contacts are characterized by close space relationship between magmatic and sedimentary rocks and also with contact phenomena in sedimentary rocks. The observed textural and chemical contact phenomena are the pronounced schistosity of sediments grading to the cleavage, contact extrusive breccias, limestone enclaves,wedge shaped denting, cracked sediments, the transformation of matrix, secondary minerals in veinlets and nests in sedimentary rocks, recrystallization, dolomitization, skarn paragenesis, silification, hematitization and the occurrence of ferrocalcite. Mentioned phenomena point to the synsedimentary and/or postsedimentary repeated extrusions and shallow intrusions of basic lavas. The diversity of contact phenomena indicates variable rates of extrusion, quantity and temperatures of lavas as also different grade of consolidation of sedimentary rocks

Composition and provenance of Gröden sandstone from the Velebit Mts.

Six samples of Gröden sandstones (Middle Permian) were analysed: Five of them were from Pikovac Creek valley (in the vicinity of Brušane village at Velebit Mts., Croatia) and one was from the locus typicus Gröden/Val Gardena (Italy). Based on the micropetrographical characteristics of sandstones, as well as on the modal composition and heavy mineral association, origin of material, weathering index of source rocks, climate and relief in the period of deposition have been supposed. Four samples from Pikovac Creek were petrographicaly determined as lithic greywackes, one as densely packed lithic arenite, while a specimen from Gröden locus typicus represents feldspar greywacke. Lithic greywackes/arenites imply very low maturity and suggest a close proximity of source rocks as well as the active tectonics in the hinterland of the depositional basin. Heavy mineral association in the samples from Pikovac Creek valley, with a large amount of fairly rounded stable grains (zircon, tourmaline and rutile), indicate that clastic material was derived from recycled orogen, and probably from reworked sedimentary rocks. The presence of kyanite and chlorite in the heavy mineral assemblage suggest their origin is from metamorphic rocks. This data assumes that Gröden sandstones from Pikovac Creek were possibly deposited in the fan delta or braided delta depositional environment as a part of a rift system (recycled orogen). The composition of the sample Gröden s. locus typicus (light and heavy mineral fractions) suggests the vicinity of magmatic rocks in the source area. All analysed samples are red coloured and have a large amount of limonitized grains in the heavy mineral assemblage, that point to the arid climate at the time of deposition. A weathering index diagram for Pikovac sandstones implies an arid/semiarid climate and high relief of the source area where metamorphic or sedimentary rocks dominate, while an arid/semiarid climate and high relief with plutonic source rocks were supposed for the provenance of Gröden s. locus typicus

SREDNJOTRIJASKE AUTOKLASTIČNE NASLAGE U OKOLICI BOSANSKOG GRAHOVA (JUGOZAPADNA BOSNA I HERCEGOVINA)

Middle Triassic volcanic and volcaniclastic rocks have been recognized at several localities near Bosansko Grahovo, in southwestern part of Bosnia and Herzegovina in the External Dinarides. Peculiar types of autoclastic rocks were investigated. These are peperites and hyaloclastites. Regarding specific structures, mineral composition and micropetrographic characteristics it was possible to further differentiate hyaloclastites into in situ hyaloclastites and slightly resedimented hyaloclastites that represent genetic succession. All rock types occurred in a deep sea troughs that formed as a consequence of Middle Triassic extensional tectonic and rift related wrench faulting. In situ hyaloclastites and slightly resedimented hyaloclastites were formed due to quenching at the contact of lava effusions with sea water. Genesis of peperites is related to lava emplacement in unconsolidated water saturated lime mudstones that were deposited in deep sea basin. All investigated rock types represent first findings of autoclastic deposits in the External Dinarides. Biostratigraphic constraints achieved by means of conodont species Neogondolella excentrica, Paragondolella excelsa, Paragondolella trammeri and Gladigondolella tethydis indicate Late Anisian to Early Ladinian interval of the autoclastic deposits from Bosansko Grahovo.U okolici Bosanskoga Grahova u jugozapadnome dijelu Bosne i Hercegovine (vanjski Dinaridi) istražen je specifičan tip vulkanoklastičnih stijena – autoklastične stijene srednjotrijaske starosti. Izdvojena su dva osnovna tipa autoklastičnih naslaga: peperiti i hijaloklastiti. Geneza peperita povezana je s procesima smještanja lave u nekonsolidirane, vodom zasićene vapnenačke madstone koji imaju karakteristike taloženja u pelagičkome okolišu. S obzirom na specifičnu teksturu, mineralni sastav i mikropetrografske karakteristike hijaloklastiti predstavljaju genetski slijed na opisanome lokalitetu Bosansko Grahovo I, te su podijeljeni na a) in situ hijaloklastite, b) neznatno pretaložene hijaloklastite i c) pretaložene hijaloklastite. In situ hijaloklastiti i neznatno pretaloženi hijaloklastiti nastali su fragmentacijom užarene lave bazaltnoga sastava u doticaju s hladnom morskom vodom, dok pretaloženi hijaloklastiti predstavljaju dominantno vulkanski detritus s kojim je pomiješana mala količina klasta vapnenaca i/ili rožnjaka, te se smatra da je detritus pretaložen nakon fragmentacije, vjerojatno, u blizini primarnih magmatskih izljeva bazaltne lave. Svi tipovi stijena označavaju magmatsku aktivnost u dubokomorskim jarcima formiranim kao posljedica srednjotrijaske ekstenzije i normalnoga rasjedanja asociranoga s procesima nastajanja rifta. Opisane autoklastične stijene prvi su pronalazak autoklastičnih naslaga u vanjskim Dinaridima. Biostratigrafska odredba temeljena na nalazima konodontnih vrsta iz vapnenaca peperita (Neogondolella excentrica, Paragondolella excelsa, Paragondolella trammeri i Gladigondolella tethydis) upućuje na kasnoanizičku do ranoladiničku starost autoklastičnih naslaga Bosanskoga Grahova, a time i na početak vulkanske aktivnosti već u aniziku

The origin and composition of flysch deposits as an attribute to the excessive erosion of the Slani Potok valley („Salty Creek“), Croatia

Flysch deposits that crop out in the elongated coastal area of the Vinodol Valley (External Dinarides), and particularly in the Slani Potok (&lsquo;Salty Creek&rsquo;) catchment, are characterized by excessive erosion. Formation of badlands, creeping and sliding processes have been related to crystallization of thenardite. Unusually intense erosion is caused by the dispersive effect of sodium on clay particles (derived from pelitic flysch intervals) in solution, as well as by expansion of thenardite during transformation into a deckahydrate (with a four fold increase in volume). The search for a sodium source required for thenardite crystallization has focused on a particular composition of Slani Potok Eocene fl ysch rock types. Slani Potok flysch is predominantly composed of pelitic intervals, with subordinate sandstones and biocalcirudites. Sandstones and biocalcirudites contain appreciable amounts of siliciclastic detritus. Lithic fragments are represented by volcanic rocks revealing porphyry structures - possibly andesite or altered volcanic glass fragments, quartzite, schists, shales, and carbonate grains. High amounts of sodium and barium (0.93&ndash;1.09 % and 267&ndash;276 mg/kg respectively), in marls and sandstones, is essentially ascribed to a particular composition of flysch, refl ecting its area of provenance. A Palaeozoic clastic complex with barite mineralization, (black shales, sandstones and conglomerates), as well as a Mesozoic hornblende andesite located near Fužinski Benkovac in the Gorski Kotar region, are interpreted as flysch source rocks. Sodium at least could be partly leached from the lithic and feldspar grains in clastic rocks, due to circulation of pore fluids. An increased amount of sulphur, barium and strontium in flysch can be related to that of a barite ore complex in the source area of the Gorski Kotar region. Transportation and deposition of material eroded from the hinterland (North of Slani Potok), suggests turbidity current flow was transverse to the main axis of the Eocene foreland basin striking NW-SE.Abstract. Flysch deposits that crop out in the elongated coastal area of Vinodol Valley (External Dinarides) and particularly in the Slani Potok (&lsquo;Salty creek&rsquo;) catchment area have particular composition. Sandstones and biocalcrudites from the flysch in Slani Potok contain appreciable amount of siliciclastic material opposite to the other flysch domains in the External Dinarides where carbonate detritic material prevails. Siliciclastic component of sandstones and biocalcrudites contains ca 50% quartz, 30% lithic and 20% feldspar grains. Lithic fragments are represented by volcanic rocks revealing porphyric structures (possibly andesite) or altered volcanic glass fragments. The differences in flysch composition, also documented by high amount of sodium and barium measuring 0.93-1.09 % and 267- 276 mg/kg, respectively, is essentially ascribed to the different rocks in the provenance area of the Gorski Kotar region located in the hinterland of the Vinodol Valley. Occurrence of andesite near Fužinski Benkovac and Palaeozoic complex with barite mineralization in the Gorski Kotar, are considered as source. Proximity of the source area and its position straight north of Slani Potok imply that the direction of turbidity currents that deposited the flysch sediments in Slani Potok were transverse to the main axis of the Eocene foreland basin striking NW-SE.A particular composition of sandstones and biocalcrudites in the Slani Potok area attributed the formation of thenardite mineral. Source of sodium and sulphur for formation of thenardit is volcanic particles found in the flysch. Unusually intense erosion, having a varied character to the landscape, is caused by dispersive effect of sodium in solutions to clay particles derived from pelitic flysch rocks, as well as by expanding of thenardite while transforming into a deckahydrate (enlarging its volume at least 4 times). </p

PRVI NALAZ REITZIITES REITZI MARKERA GORNJOILIRIČKE AMONITNE PODZONE U KRŠKIM DINARIDIMA

Middle Triassic deposits in the Karst Dinarides (south Lika area, near Gračac) were investigated for petrological, sedimentological and biostratigraphic determinations. Within two continuously recorded sections of sedimentary carbonates and interlayered pyroclastic rocks (Mali Kunovac and Kunovac sections) reflecting variable sedimentary-magmatic environments, valuable cephalopod fauna ranging from the middle Illyrian to the upper Illyrian age was found. The most significant was the recovery of the ammonoids Asseretoceras sp., indicating the upper part of the Illyrian Paraceratites trinodosus Zone, and Reitziites reitzi species which marks the upper part of the Illyrian Reitziites reitzi Zone. The discovery of the Reitziites reitzi species was not known from the Karst Dinarides until this finding.Srednjotrijaske naslage u krškim Dinaridima (okolica Gračaca u južnoj Lici) istraživane su s ciljem njihove petrološke i sedimentološke odredbe te odredbe njihove biostratigrafske pripadnosti. Unutar dvaju snimljenih kontinuiranih sljedova koji se sastoje od izmjene karbonatnih sedimentnih stijena i piroklastita (Mali Kunovac i Kunovac), a koji odražavaju varijabilne sedimentacijsko-magmatske okoliše njihova postanka, prikupljena je relativno malobrojna, ali vrijedna kolekcija cefalopoda srednjoiliričke i gornjoiliričke starosti. Najvažniji su nalazi amonitne vrste Asseretoceras sp. koja upućuje na gornji dio iliričke Paraceratites trinodosus zone te vrste Reitziites reitzi koja označava gornjoiliričku Reitziites zonu. Pronalazak vrste Reitziites reitzi do sada nije bio zabilježen na području krških Dinarida

OPTIMALNI POSTUPAK PRIPREME UZORAKA SILIKATNE STIJENE ZA ANALITIČKE SVRHE

The purpose of this study was to determine an optimal dissolution method for silicate rock samples for further analytical purposes. Analytical FAAS method of determining cobalt, chromium, copper, nickel, lead and zinc content in gabbro sample and geochemical standard AGV-1 has been applied for verification. Dissolution in mixtures of various inorganic acids has been tested, as well as Na2CO3 fusion technique. The results obtained by different methods have been compared and dissolution in the mixture of HNO3 + HF has been recommended as optimal.Svrha rada bila je utvrđivanje optimalnog postupka otapanja uzoraka silikatne stijene za dalje analitičke svrhe. Za verifikaciju je primijenjena analitička metoda FAAS određivanja udjela kobalta, kroma, bakra, nikla, olova i cinka u uzorku gabra i u geokemijskom standardu AGV-1. Istraženo je otapanje u smjesama različitih anorganskih kiselina kao i taljenje s Na2CO3. Uspoređeni su rezultati dobiveni različitim postupcima te se kao optimalni postupak preporuča otapanje u smjesi HNO3 + HF