Paleotectonic setting of the circum-Karkonosze Lower Palaeozoic spilite-keratophyre suites based on geochemistry of iron group elements
Abstract
Pozycja paleotektoniczna wokólkarkonoskich dolnopaleoziocznych serii spilitowo-keratofirowych w świetle geochemii i pierwiastków grupy żelaza
Distinct differences in statistical parameters of distributions of Ti, Cr and Ni, as well as in total FeO and TiO(2) versus FeO/MgO trends in metabasic rocks of Lower Palaeozoic spilite-keratophyre suites of the Góry Kaczawskie Mts. and of the Rudawy Janowickie-Lasocki Grzbiet range are interpreted on the basis of recent data on geochemical diversity o f basalts originated under different tectonic setting. It is concluded that spilitic and associated volcamics of the Góry Kaczawskie Mts. are geochemically corresponding to the present Hawaiitic within-plate ocean- -island basalts, whilst those of the Rudanvy Janowickie-Lasocki Grzbiet range (representing E part of the SE metamorphic mantle of. the Karkonosze granite) — to island-arc tholeiites, genetically connected with Benioff zones. This conclusion is supported by various geological data and by the occurrence of traces of glaucophane schist belt at the outer boundary of the SE part of metamorphic mantle of the Karkonosze granite. Lack of typical ocean ridge basaltic series in this part of the Variscan geosyncline suggests the possibility of only local and small-scale oceanization preceding the formation of active arc-trench system in question.
Distinct differences in statistical parameters of distributions of Ti, Cr and Ni, as well as in total FeO and TiO(2) versus FeO/MgO trends in metabasic rocks of Lower Palaeozoic spilite-keratophyre suites of the Góry Kaczawskie Mts. and of the Rudawy Janowickie-Lasocki Grzbiet range are interpreted on the basis of recent data on geochemical diversity o f basalts originated under different tectonic setting. It is concluded that spilitic and associated volcamics of the Góry Kaczawskie Mts. are geochemically corresponding to the present Hawaiitic within-plate ocean- -island basalts, whilst those of the Rudanvy Janowickie-Lasocki Grzbiet range (representing E part of the SE metamorphic mantle of. the Karkonosze granite) — to island-arc tholeiites, genetically connected with Benioff zones. This conclusion is supported by various geological data and by the occurrence of traces of glaucophane schist belt at the outer boundary of the SE part of metamorphic mantle of the Karkonosze granite. Lack of typical ocean ridge basaltic series in this part of the Variscan geosyncline suggests the possibility of only local and small-scale oceanization preceding the formation of active arc-trench system in question.