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Suomen geologinen kartta 1 : 100 000, Kallioperäkarttojen selitykset, lehdet 1041 ja 1043Ritva KarhunenPLUTONIC ROCKSSynorogenic granitoids and dioritesThe synorogenic plutonic rocks in the Iniö and Turku map-sheet areas consistmainly of granodiorite, tonalite and trondhjemite. Diorite and gabbro occur as small,separate intrusions and as fragments in other plutonic rocks. The gabbros are usuallyeven-grained and medium- to coarse-grained. Granodiorite and tonalite cover largecontinuous areas in the middle of both the Iniö and Turku map-sheet areas. Theserocks are pale, medium- to coarse-grained and often foliated or gneissose. K-feldspar-porfyritic,veined gneiss-type granodiorite has been found in the Iniö commune.Some granodiorite varieties contain pyroxene. Garnet is present at several granodioriteoutcrops in the Iniö map-sheet area, i.e. in Iniö and Keistiö (1041 05 and 08)and in the small islands of Korppoo. Also tonalite and trondhjemite may containpyroxene in places.Lateorogenic microcline granitesRed and greyish red microcline granites occupy large areas especially in the easternmostand southern areas of the Iniö map-sheet. In the Turku map-sheet area thegranite occupies almost entirely the lower eastern quarter of the map-sheet.The granite is heterogeneous, medium- to coarse-grained and often grades intopegmatite. Migmatized veins and irregular dykes intrude the supracrustal rocks aswell as the granodiorites and tonalites. The medium-grained granites often show adistinct foliation parallel to foliation in the adjacent supracrustal rocks, while thecoarse-grained and pegmatitic types are more massive. A large porphyritic microclinegranite body occurs in the southeastern corner of the Turku map-sheet area.The microcline granite contains abundant cordierite and garnet. Granite with ahigh cordierite content has been found e.g. in Velkua (1041 12C) and in Turku (104309D, the Kakola granite). Generally, the granites in the Turku map-sheet area arericher in garnet than the granites further west.Postorogenic granites and monzonitesTwo conspicuous circular structures are visible in the archipelago of the Iniö mapsheetarea. These morphological outlines are formed by two postorogenic intrusions;the Åva ring complex and the Fjälskär intrusion. The granitic-monzonitic Åva intrusionhas long been interested by geologists, and was first described already in 1889(Moberg). More recently, the Åva intrusion was described by Kaitaro (1953), Ehlers& Bergman (1984) and Bergman (1986). The Åva intrusion, dated at 1803±10 Ma(Suominen 1991), consists of a series of inward-dipping ring intrusions, usually parallelto the steep schistosity of the surrounding supracrustal rocks.The earliest rocks of the Åva intrusion consist of medium-grained quartz monzoniteand monzonite often with xenoliths of gneiss and microcline granite.The monzonite was followed by medium- to coarse-grained, porphyritic granite.The contact between these two rocks is usually sharp, although some hybridizationmay be present. The porphyritic biotite-granite is red or reddish brown with an occa-68