CHARACTERISTICS OF ROCK SAMPLES SELECTED FROM THE LAURENTIAN CONE (NORTHWESTERN PART OF THE ATLANTIC OCEAN)

Abstract

The Lawrence Cone is a depository of Pleistocene glacial sediments. It was formed by the Neogene fluvial system and later was “captured” by the glacial flow of the Lawrence Gulf, which moved in a southeast direction and was active during the last (Visconsyn) glaciation. The rocks of the Laurentian outcrop cone have rounded, smoothed surfaces, which indicates their migration from the original sediments over considerable distances. According to the results of our research, these are the following rocks: granite, metamorphosed granite, and quartz-carbonate rock. Mineral composition (according to microprobe analysis) of granite: feldspar, quartz, mica, epidote, chlorite, carbonate (calcite); ore minerals – magnetite; accessories – titanite, zircon. Mineral composition of metamorphosed granite: mica (siderophyllite), quartz, acidic plagioclase (oligoclase), chlorite, carbonate and ore mineral. The granite was metamorphosed in the thermodynamic conditions of the greenschist facies of regional metamorphism, which confirm the results of calculating the temperature of the mineralforming environment using a chlorite thermometer: from 239 to 294 °С. One grain of the rare mineral halgenbergite-(Ce) was discovered. It is an aqueous carbonate-(Ce) Ca(Ce,La,Nd)2(CO3)4·H2O, which forms acicular to rosette-like formations. Quartz-carbonate rock is composed of carbonates (calcite, dolomite), quartz, feldspars (albite, alkali feldspar), muscovite. The migration paths of the Lawrence Glacier, which moved in a southeast direction and was active during the last (Wisconsin) glaciation, were analyzed. Having compared the material composition of the rocks taken from the Laurentian Cone of Outcrop with the rocks that form the Appalachian Orogen, we came to the conclusion that the latter can be considered the original source of the rocks we studied.