An Archean quartz arenite–andesite association in the eastern Baltic Shield, Russia: implications for assemblage types and shield history

摘要: Abstract Shallow water sedimentary units are generally considered scarce in Archean greenstone belts. We describe an unusual quartz arenite-subaerial andesite association within the Hisovaara belt, a fragment of Parandovo-Tikshozero belt Karelian craton Baltic Shield. The consists several lithotectonic assemblages: (1) komatiite-tholeiite assemblage>2803 Ma (based on ages cross-cutting dikes); (2) andesite-quartz arenite assemblage cut by similar dikes; (3) coarse volcaniclastic rocks, and (4) upper mafic tholeiitic basalts with minor pyroxene komatiite volcanic rocks. (100 to ca. 750 m thick) has basal amygdaloidal fragmental andesites overlain massive andesites, then plagioclase phyric andesites. Unconformably overlying is unit quartz-rich sandstones (6–40 dominated extending km along strike. At north end, succession exhibiting hummocky cross-stratification followed aluminous metasediments sulfidic argillite unconformably tholeiite/komatiite unit. south andesite, regolith, cross-bedded arenite, weathered second subaerial rhyolite. REE HFSE geochemistry been obtained rocks assemblage. arenites contain low abundances chondrite normalized patterns vary from relatively fractionated flat most variation related grain size, pebbly having higher abundance more patterns. Combined major trace element indicates that sodic felsic source some admixture material will explain arenites. display moderately spidergrams negative anomalies at Ti, Ta Nb typical arc volcanism. represents accumulation shallow rich sediments setting later stages volcanism which edifice southern end However, our evidence interpreted as indicating andesitic volcanism, subsidence marine basin deepens rifts. Therefore provides linkage greenstones between assemblages representing continental platform-to-rift setting. presence erosional interval in>2.8 Ga suggests possible pre-2.7 orogeny shield. quartzrich sedimentation age platformal North Caribou terrane Superior Province, Canada.