Wyniki wyszukiwania - BazTech

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Wstępne wyniki badań petrograficznych archaicznych gnejsów Uivak (Prowincja Nain, Labrador)

Sałacińska A., Kusiak M. A.

Przegląd Geologiczny

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2017

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Vol. 65, nr 6

383--391

EN

The Saglek Block of the Nain Complex in Northern Labrador forms the westernmost part of the North Atlantic Craton. It is one of the few regions on Earth where early Archaean crust is preserved. It consists of regionally metamorphosed gneisses to either granulite-facies from 2.74 to 2.71 Ga or amphibolite-facies at ca. 2.70 Ga. The Saglek Block is dominated by two suites of metaigneous gneisses: the Uivak I TTG suite (>3.6 Ga) and the Uivak II augen gneisses (ca. 3.4 Ga). Four samples offelsic Uivak I orthogneiss were selected to petrographi- cal and mineralogical studies: Johannes Point Cove (L1419), TigigakyukInlet (L1434; L1440) and Big Island (L1443). Sample composition (granodiorite-tonalite) and mineralogy (mostly plagioclase and quartz, with minor K-feldspar and biotite, and accessory zircon and apatite) for three of the four samples are consistent with published data of the Uivak I gneiss. Sample L1434 contains ferroean diopside and hornblende, which are absent in the other samples. Based on detailed mineralogical analyses, authors concluded that more mafic sample, can not belong to the suite of the Uivak I gneisses. Most probably it represents the younger Uivak II. Further, geochronological study is going to be conducted to characterise both, Uivak I and Uivak II gneisses isotopically.

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W poszukiwaniu fragmentów najstarszej skorupy kontynentalnej na Labradorze

Kusiak M. A., Sałacińska A.

Przegląd Geologiczny

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2016

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Vol. 64, nr 11

896--901

EN

There are few unresolved questions in the Earth Sciences which generate as much debate as the nature of the Hadean Earth: i.e. the rock record between the Earth’s formation and about 3.8 billion years ago. Current knowledge of the nature and origin of the earliest crust comes largely from studies of the mineral zircon (ZrSiO4). The oldest zircon grains on Earth (4.46 Ga) are found in Jack Hills, Australia. They represent a time capsule of what the Earth was like from ca. 4.4-4.0 Ga during the Hadean. The other ancien rocks (>3.8 Ga) are preserved in Antarctica, Canada, China, Greenland, Labrador, Western Australia and Swaziland, with the oldest known rochi on Earth from the Acasta gneiss in Northern Canada, dated at 4.03 Ga. Most likely, the second oldest rock record in the world (>3.9 Ga) may be derivedfrom the Nanok gneiss in the Nain Complex of the Saglek-Hebron area in the northern part of the Labrador Peninsula. Extensive investigation of these rocks will allowfurther characterizing the nature of the earliest preserved crust.

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SHRIMP U-Pb zircon chronology of the Polish Western Outer Carpathians source areas

Budzyń B., Dunkley D. J., Kusiak M. A., Poprawa P., Malata T., Skiba M., Paszkowski M.

Annales Societatis Geologorum Poloniae

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2011

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Vol. 81, No 2

161-171

EN

The Western Outer Carpathians flysch of Poland comprises clasts of crystalline rocks representing source areas that supplied sedimentary basins with clastic material. Zircon from quartz syenite and granite cobbles representing the Silesian Ridge, the currently unexposed source area located at the southern margin of the Silesian Basin, yielded uniform U-Pb dates of 604š6 Ma and 599š6 Ma. These are interpreted as the age of igneous crystallization. Similarly, zircon from a gneiss cobble derived from the northern source terrain gave 610š6 Ma date, which is interpreted as the age of crystallization of the granitic protolith to the gneiss. The Neoproterozoic magmatism is interpreted to have occurred at the Gondwana active margin.

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Chemistry of monazites as provenance indicator - case study from the Upper Silesia Coal Basin (Poland)

Kusiak M.A., Bakun-Czubarow N.

Studia Geologica Polonica

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2008

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Vol. 129

107-130

EN

Mineral chemistry and homogeneity, as well as crystal structure and unit cell parameters of detrital monazites isolated from sandstones of the Upper Silesia Coal Basin were studied using electron microprobe analysis (EPMA) and X-ray diffractometry (XRD). Analyzed monazite grains are chemically almost homogenous, only in a very few cases, parts of the grain are enriched in thorium and depleted in yttrium content. Typical feature of monazite from the Poruba Beds is relatively high content of Y (up to 4 wt. % Y2O3), what could point to higher temperature of crystallization. Monazite from the Kwaczała Arkose are, on average, richer in huttonite and slightly poorer in cheralite end-members than monazite from the Poruba Beds. Monazite from Kwaczała Arkose reveals the following unit cell parameters: a = 6.794(1) A*, b = 7.008(2) A*, c = 6.479(2) A*, b = 103.82(2)°, whereas for the Poruba Beds monazite these parameters, excluding b-value, are slightly higher: a = 6.804(3) A*, b = 7.002(5) A*, c = 6.488(4) A*, b = 103.85(3)°.