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4. Locations

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Location No. 08

Approach outcrop via road from Västervik to Händelöp, turn left sideroad short after Grimsvik until the coast is reached, pass of outcrop from the northwest to southeast direction (ca. 2.5 - 3 km).

R: 1553360 - H: 6397040
RT 90: N 57° 49' 53.8'' - E 016° 26' 47.4''
WGS 84: N 57° 49' 52.6'' - E 016° 26' 36.7''

Keywords: granodiorite, metagabbro, basic dike, magma mingling, hydraulic brecciation, ductile deformation


Description:

This excellent outcrop along the coast gives you the opportunity to follow the agmatic brecciation of a metagabbro dike by granitic magma. The hydraulic brecciation and ductile overprinting of this metagabbro increases from northwest to southeast (cf. fig. 4.8a). Host rock of the metagabbro dike is the granodiorite from the Central Granodiorite Belt.

Starting point is a headland at the entry to the bay of Hornsgloet. Here the metagabbro starts as a dike of about 50 m thickness, and already shows a slight brecciation by leucocratic, granitic veins of only few cm into well-fitting polygonally shaped fragments (cf. fig. 4.8b). According to a description by v. Drachenfels (2004), the main components of the metagabbro are plagioclase and hornblende. The leucocratic veins originate from the granodiorite and consist mainly of quartz and feldspars. A few meters along a southeasterly direction the fragments are already slightly rounded. Brecciation continues in combination with rotation of the fragments (cf. fig. 4.8c). The proportion of leucocratic material from the granodiorite increases towards the southeast and the metagabbro dike gets more and more brecciated and rounded (cf. fig. 4.8d-e). Far to the south the relationship between granodiorite and metagabbro gets quite complicated. Fig. 4.8f shows the contact area between metagabbro and granodiorite with ductile overprinting of the metagabbro fragments, while fig. 4.8g shows xenoliths of metagabbro which in turn contain xenoliths of the granodiorite.



Further Reading:

Kresten, P., 1972. Der basische Magmatismus und seine Stellung in der geologischen Entwicklung des Västervik-Gebietes, Südostschweden, GFF, 94, 91-109.



Fig. 4.8a: Simplified location map pointing the outcrops of the agmatic metagabbro. Areas where fragments of the metagabbro are brecciated almost to the point of assimilation by the granodiorite are signed with diamond symbol. (modified after v. Drachenfels 2004)
Fig. 4.8b: Partial view shows fragments of metagabbro brecciated by small leucocratic veins producing a mosaic shape. (Photo: M.-V. v. Drachenfels, pers. Comm.)
Fig. 4.8c : Partial view of slightly rounded fragments of metagabbro with increasing content of leucocratic material. (Photo: M.-V. v. Drachenfels, pers. Comm.)
Fig. 4.8d: Partial view of the ongoing brecciation and rounding of the fragments. (Photo: M.-V. v. Drachenfels, pers. Comm.)
Fig. 4.8e: Close up view on brecciated metagabbro. (Photo: M.-V. v. Drachenfels, pers. Comm.)
Fig. 4.8f: Partial view of ductile overprinting of the metagabbro fragments within the contact area of metagabbro and granodiorite. (Photo: M.-V. v. Drachenfels, pers. Comm.)
Fig. 4.8g: Partial view of an area where xenoliths of metagabbro contain xenoliths of the granodiorite itself. (Photo: M.-V. v. Drachenfels, pers. Comm.)


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Fig. 4.8a
Fig. 4.8a

Fig. 4.8b
Fig. 4.8b

Fig. 4.8c
Fig. 4.8c

Fig. 4.8d
Fig. 4.8d

Fig. 4.8e
Fig. 4.8e

Fig. 4.8f
Fig. 4.8f

Fig. 4.8g
Fig. 4.8g
 

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