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Ważne i użyteczne fakty dotyczące inkluzji fluidalnych w minerałach w kontekście rozpoznawania systemów naftowych

Jarmołowicz-Szulc Katarzyna

Przegląd Geologiczny

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2023

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Vol. 71, nr 4

184--187

EN

Samples of minerals, solid bitumen and rocks from different localities and different basins have been an object of mineralogical, petrographic and geochemical analyses. Their microfissures (microfractures) are often filled with fluids forming “fluid inclusions” (FI). Such inclusions are small portions of palaeofluids that existed in the basin during the mineral formation, which may be a significant record from the geological past. Analytical procedures comprised several stages: preparation of thin and thick sections, microscopic evaluation of the material (organic matter, minerals, inclusions), FI microthermometric determinations, geochemical analyses, and auxiliary studies. General microscopic observations were conducted using a polarization microscope, cold cathode, and the special heating-freezing stage. Fluid inclusions in minerals were studied aiming at the characterization of fluids that fill these micro-volumes in crystals. The undertaken analytical steps have led to determination of the fluids trapped in inclusions as brine and/or hydrocarbons (based on fluorescence abilities). Furthermore, they have resulted in the measurement of the homogenization temperatures of inclusions (values positive for, e.g., oil, negative for methane, pure or with admixtures), and determinations of the eutectic and ice-melting temperatures of the aqueous inclusions. Thermometric studies in the heating mode generally lead to determination of temperatures of mineral crystallization since it has been assumed that the homogenization temperature of the primary aqueous inclusions represents a minimum temperature of fluid trapping during mineral precipitation. Complementary analyses, as the Raman spectrum analysis and studies on the organic matter, lead to the interpretation of the results richer, clearer and meaningful for the hydrocarbon systems context, what has been proved on some examples.

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Native silver in the eastern part of the Karkonosze granitoid pluton, Lower Silesia, Poland

Kozłowski Andrzej, Matyszczak Witold

Acta Geologica Polonica

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2023

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Vol. 73, no. 2

223--245

EN

This article describes silver specimens of the size of tenths to a few millimetres, found in small pegmatites and quartz veinlets of the porphyritic granitoid area in 22 sites in the eastern part of the Variscan granitoid Karkonosze pluton, from 20 of which native silver occurrences were previously not known. The sites are scattered on the whole surface of the granitoid. The native silver occurred in wire, rod, platy, dendritic, anhedral granular and euhedral cubic and octahedral habits; in some specimens twins and fenster faces were also found. Associated with native silver small amounts of acanthite crystallized commonly, sometimes apparently formed by sulphur diffusion into silver. Inclusions of native gold, electrum, galena, chalcopyrite and pyrite occurred in the native silver. The parent fluids of the specimens were epithermal, because the homogenization temperature (Th) of inclusions in quartz, calcite and cleavelandite that were the host minerals of the native silver was generally 91–165ºC and for individual samples the Th range was 4–11ºC. The total salinity of the fluid was 2.4–7.2 wt. % with Na and Ca (hydro)carbonates as the main dissolved components and admixtures of K, Mg, Fe, Al, S, Cl and F. The parent granitoid contains Ag in trace amounts (0.034–0.056 ppm) and was probably the source of this element for the crystals of native silver. Migration of Ag was made easier by the presence of fluoride ions in fluids.

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Interaction between tectonics, plutonism and mineralization of the Duna Pb-Ba ore deposit regarding fluid inclusion study (Central Alborz, Iran)

Sadeghi Alireza, Asiabar Saeid Hakimi, Nezafati Nima, Ganji Alireza, Mukherjee Soumyajit

Acta Geologica Polonica

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2023

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Vol. 73, no. 2

201--222

EN

This article discusses the impacts of overprinting of tectonic and plutonic events on the mineralization of the Duna Pb-Ba ore deposit, according to geologic settings and fluid inclusion studies. The Duna carbonate-hosted deposit contains a significant amount of Ag (18.9–264.3 ppm ), Cu (77–41600 ppm), Sb (32.7–11000 ppm), Sr (63.5–15100 ppm), and Fluid inclusions with 7.34–23.65 wt.% NaCl equivalent. The homogenization temperature of about 110–285°C, as well as the paragenesis of the minerals shows a difference compared with other Pb-Zn deposits such as the Irish-type and MVT. The ore mineralization in the Duna mine occurred as stratabound, open space-filling, and along the brecciated fault zones. The concordant (stratabound) type of mineralization, with salinity and homogenization temperature of 18.54 to 23.65 wt.% NaCl equivalent, and 113°C to 165°C respectively, is usually typical of MVT-ore deposits, which in this area evolved during the Early Cimmerian orogeny and was later interrupted by mineralization along younger brecciated fault zones with salinity and homogenization temperature of 7.34 to 23.65 wt.% NaCl equivalent, and 113°C to 285°C respectively. This discordant mineralization, which occurred along the faults, formed by the end of the Late Cretaceous and during the Cenozoic as a result of the intrusion of a plutonic mass, and is comparable to the Irish-type ore deposits.

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Geological and geochemical implications of the genesis of the Qolqoleh orogenic gold mineralisation, Kurdistan Province (Iran)

Taghipour B., Ahmadnejad F.

Geologos

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2015

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Vol. 21, No. 1

31--57

EN

The Qolqoleh gold deposit is located in the northwestern part of the Sanandaj–Sirjan Zone (SSZ), within the NE–SW trending Qolqoleh shear zone. Oligocene granitoids, Cretaceous meta-limestones, schists and metavolcanics are the main lithological units. Chondrite-normalised REE patterns of the ore-hosting metavolcanics indicate REE enrichment relative to hanging wall (chlorite-sericite schist) and footwall (meta-limestone) rocks. The pattern also reflects an enrichment in LREE relative to HREE. It seems that the LREE enrichment is related to the circulation of SO42- and CO2-bearing fluids and regional metamorphism in the Qolqoleh shear zone. Both positive and negative Eu anomalies are observed in shear-zone metavolcanics. These anomalies are related to the degree of plagioclase alteration during gold mineralisation and hydrothermal alteration. In progressing from a metavolcanic protomylonite to an ultramylonite, significant changes occurred in the major/trace element and REE concentration. Utilising an Al-Fe-Ti isocon for the ore-hosting metavolcanics shows that Sc, Y, K, U, P, and M-HREE (except Eu) are relatively unchanged; S, As, Ag, Au, Ca, LOI, Rb and LREE are enriched, and Sr, Ba, Eu, Cr, Co and Ni decrease with an increasing degree of deformation. Based on geochemical features and comparison with other well-known shear zones in the world, the study area is best classified as an Isovolume-Gain (IVG) type shear zone and orogenic type gold mineralisation. Based on the number of phases observed at room temperature and their microthermometric behaviour, three fluid inclusion types have been recognised in quartz-sulphide and quartz-calcite veins: Type I monophase aqueous inclusions, Type II two-phase liquid-vapour (L-V) inclusions which are subdivided into two groups based on the homogenisation temperature (Th): a) L-V inclusions with Th from 205 to 255°C and melting temperature of last ice (Tm) from –3 to –9°C. b) L-V inclusions with higher Th from 335 to 385°C and Tm from –11 to –16°C. Type III three-phase carbonic-liquid inclusions (liquid water-liquid CO2-vapour CO2) with Th of 345–385°C. The mean values of the density of ore-forming fluids, pressure and depth of mineralisation have been calculated to be 0.79–0.96 gr/cm3, 2 kbar and 7 km, respectively. The δ18Owater and δD values of the gold-bearing quartz-sulphide veins vary from 7.2‰ to 8‰ and –40.24‰ to –35.28‰, respectively, which are indicative of an isotopically heavy crustal fluid and likely little involvement of meteoric fluid. The δ18Owater values of the quartz-calcite veins have a range of –5.31‰ to –3.35‰, and the δD values of –95.65‰ to –75.31‰, which are clearly lower than those of early-stage quartz-sulphide-gold veins, and are close to the meteoric water line. Based on comparisons of the D–O isotopic systematics, the Qolqoleh ore-mineralising fluids originated from metamorphic devolatilisation of Cretaceous volcano-sedimentary piles. Devolatilisation of these units occurred either synchronously with, or postdates, the development of penetrative (ductile) structures such as shear zones and during overprinting brittle deformation.

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Vozmoznosti ispol'zovania fluidnyh vklucenij pri izucenii processov migracii uglevodorov ("Marmarosskie diamanty")

Dubok I. V., Jarmołowicz-Szulc K.

Prace Instytutu Górnictwa Naftowego i Gazownictwa

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2000

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nr 110 wyd. konferencyjne

447--450

EN

A detailed analysis of fluid inclusions in the minerals in petroleum reservoirs points to the facts on the possibilities of their application to the studies on hydrocarbon migration. The migration processes by means of fluid inclusions may be totally reconstructed due to the analysis of the vein (epigenetic) minerals. The following complex studies should be performed: - macro- and microscopic morphological and genetical description of the vein structures; - determination of different generations of vein bitumens; mass-spcctrometric analyses of gas and isotope composition of main vein minerals (e.g. of quartz and calcite); petrography of fluid inclusions in vein minerals; ultraviolet studies of inclusions: microthermometry of inclusions (freezing, heating). Such analytical methods were applied by the present paper authors to the vein material from the Carpathians at the territory of SE Poland and W Ukraine. Numerous fault zones within the sedimentary rocks in the Carpathians being genetically connected with the formation of the mountain complex have been significant for fluid migration and creation of oil and gas fields. These zones have been filled with vein minerals, in that calcite, quartz in form of the so called "Marmarosh diamonds", different types of the organic matter as well as with oil itself. From the theoretical point of view the authors concern the vein structures as the healed channels which had once been paths for the migration of the aqueous and hydrocarbon fluids. The veins have at present a variated thickness and diversified content. Calcite of the rhomboheral crystal habit is the primary vein mineral. The co-occurring "Marmarosh diamonds" deserve a special attention due to the richness of the fluid inclusion types. They contain, namely, numerous hydrocarbon inclusions which display different size, shape and composition. Resulting from the hydrocarbon and aqueous inclusion studies in the quartz the sequence of these inclusions and the trapping conditions may be reconstructed. The following conclusions may be drawn from the analysis done by the authors: in the Carpathians, the hydrocarbon fluids different in composition co-migrated with the low-temperature aqueous solutions (chlorine-sulphate-carbonate solutions); evolution of the pT parameters in the quartz has been connected with the tectonic evolution of the Carpathian sedimentary structure; phase composition of the hydrocarbons points to the possibilities of the gas-condensate (methane) fields in the SE of the Carpathians whereas to the oil fields in NW part in the Dukla and Krosno (Silesia) units.

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Quartz cements in the Cambrian sandstones, Żarnowiec region, N Poland : a fluid inclusion study

Jarmołowicz-Szulc K.

Kwartalnik Geologiczny

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1998

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Vol. 42, nr 3

311-318

EN

Fluid inclusion studies were conducted in quartz cements of the Cambrian sandstones from two boreholes in the Żarnowiec regions (northern Poland). The research based on the microscope observations of inclusions aiming at their petrography and fluorescence characteristics as well as it comprised the routine microthermometric runs. The cathodoluminescencce studies resulted in determination of generation of quartz cementing the sandstones. Two types of fluid inclusions have been found --aqueous and hydrocarbon ones. They are connected with two genetrations of the quartz cements in the sandstones under discussion. The aqueous inclusions yield homogenisation temperatures of about 100 C and salinities of about 8% eq. NaCl. The hydrocarbon inclusions studied display three temperature groups ranging from 71 to 110 C. An attempt of interpretation of the entrapment conditions of coeval oil and aqueous inclusions was made resulting in p-T values. Due to the limited number of fluid inclusions in the cements the representativeness of the data is however, rather poor.

PL

W czasie tworzenia się cementów diagenetycznych w mikroprzestrzeniach minerałów powstają mikrowrostki - inkluzje fluidalne. Mogą one byś użyte do określania paleotemperatur przy wprowadzeniu szeregu założen. Inkluzje fluidalne badano w cementach kwarcowych skał kambru środkowego w rejonie Żarnowca. Badania przeprowadzono mikroskopowo w specjalnie obustronnie polerowanych preparatach z użyciem aparatury wymrażająco-grzewczej Fluid Inc. I zestawu fluorescencyjnego Nikon. Inkluzje fluidalne zaobserwowano w cemencie kwarcowym typu obwódek wokół ziaren detrytycznych oraz wtórnych zabliźnień kwarcem spękań i mikroszczelinek. Generalnie w piaskowcach z otworów Żarnowiec istnieją dwa typy inkluzji (wodne i węglowodorowe). Genetycznie wiążą się one z dwoma rodzajami spoiwa kwarcowego piaskowców. Wrostki te są bardzo małe i nieliczne. Charakterystyczny dla nich jest brak zabarwienia w świetle przechodzącym. Inkluzje o wyraźnie biało-niebieskiej fluorescencji (UV) występują przede wszystkim w asocjacji Q3 i przeważają w otworze wiertniczym Żarnowiec, zwłaszcza w górnej partii opróbowanej. Wykonano badania eksperymentalne homogenizacji inkluzji wodnych i węglowodorowych. Oba typy inkluzji dwufazowych homogenizowały w fazę ciekłą, a temperatury wyniosły odpowiednio 87-90 0 107 C. Pomiar zasolenia był utrudniony z racji małej wielkości inkluzji wodnych, ale uzyskane wyniki odpowiadają wartościom około 8% wag. NaCl. Temperatury homogenizacji dla inkluzji węglowodorów grupują się w trzech przedziałach wartości, ogólnie w obrębie 74-110 C. Przeprowadzona została próba wspólnej interpretacji izochorycznej obu typów inkluzji fluidalnych. Izochory uzyskane na podstawie przeprowadzonych prac badawczych i założeń metodycznych, przecinają się w punkcie o współrzędnych temperatury i ciśnienia, które interpretować można jako przybliżenie warunków uwięzienia tych fluidów w spoiwie kwarcowym. Jest to pierwsza próba przeprowadzenia tego typu interpretacji na obszarze Żarnowca i w obrębie basenu kambryjskiego, przy czym z racji niewielkiej liczebności współwystępujących inkluzji pożądane są dalsze badania w celu sprawdzenia wyników i polepszenia ich wiarygodności.