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Location No. 09

Outcrop at the shoreline of Huvudet, southeastern part of Händelöp. Park at the harbor. Time should be taken to observe the many details.

R: 1556262 - H: 6394748
RT 90: N 57° 40' 28.0'' - E 016° 45' 04.8''
WGS 84: N 57° 40' 26.9'' - E 016° 45' 18.8''

Keywords: synmagmatic mafic veins, amphibolite, granodiorite


Description:

This outcrop gives an excellent example on the effect of mafic magma spreading and intruding anatectic granitoids along their foliation. It shows disrupted amphibolitic dikes in a granodiorite (cf. fig. 4.9a).

The granodiorite is massive and irregularly grained. According to a description by v. Drachenfels (2004), the granodiorite consists of coarse-grained hornblende and feldspar within a fine-grained matrix of recrystallized quartz and feldspars, green hornblende and biotite. The hornblende grains are hypideomorphic to idiomorphic in shape and contain inclusions of muscovite and zircon.

The main components are hornblende, plagioclase (mostly saussuritized and sericitized) and chlorite. Muscovite, apatite and ore minerals occur in minor amounts (v. Drachenfels 2004).

Some of the amphibolite fragments are of angular shape, and mostly in sharp contact with the surrounding rock (cf. fig 4.9a-c). The grain size increases from the contact zones to the center of the fragments. Partly extremely fine-grained “chilled margins” are developed. Some dikes show a ductile boudinage fabric, i.e., they probably have been deformed by granitic magma shortly after emplacement. Small scaled late magmatic coarse-grained veins intruded the mafic dikes, forming an irregular network of agmatic brecciation (cf. fig. 4.9b). Sometimes the borders of these mafic dikes and also restites of schlieren shape, which are mostly aligned parallel to the foliation of the granites (cf. fig. 4.9d), are diffuse. Fig 4.9c shows a partial view of an amphibolitic dike which has been affected by dextral shearing. These fault zones are partly filled with greenschist facies minerals, possibly epidote and/or pumpellyte. The NW-SE striking direction and the dextral sense of shear point to a coherence with the LLDZ.



Further Reading:

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



Fig. 4.9a: Partial view of the outcrop at the shoreline shows disrupted amphibolitic dikes within a granodiorite.(Photo: M.-V. v. Drachenfels, pers. comm.)
Fig. 4.9b: Close up view shows agmatic brecciation of an amphibolitic dike. (Photo: K. Wemmer, pers. comm.)
Fig. 4.9c: Close up view shows an amphibolitic dike that has been affected by dextral shearing (Foto: K. Wemmer, pers. comm.)
Fig. 4.9d: Close up view on mafic restites aligned parallel to the granitic foliation.


(top)

Fig. 4.9a
Fig. 4.9a

Fig. 4.9b
Fig. 4.9b

Fig. 4.9c
Fig. 4.9c

Fig. 4.9d
Fig. 4.9d
 

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