Structure across a possible intra-oceanic suture zone in the low-grade Pan-African rocks of northern Ethiopia

Gold-bearing quartz veins of the Umm Rus area occur at the south-eastern contact of a Precambrian granodiorite cupola within younger gabbros of 573-615 Ma belonging to the Pan African orogenic belt. The rocks are intruded within low-grade metasediments. At such contact, a hybrid zone is developed characterized by the occurrence of quartz diorite which grades into diorite and meta-ferrogabro. A limited number of mineralized quartz veins cut the granodiorite-gabbro complex. Different alteration zones are developed in the vicinity of the quartz veins. The quartz veins have two main trends; NS and N30 E, the latter one is usaually gold-bearing. The mineralized parts of the veins commonly consist of highly sheared and banded smoky quartz, and the gold content depends on the relation with the dykes. The element is strongly correlated with As and Ag, but moderately with Cu. Near to intermediate and basic dykes, the contents of Au, Ag and As are noticably increased

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Petrological and Geochemical Characteristics of Mafic Granulites Associated with Alkaline Rocks in the Pan-African Dahomeyide Suture Zone, Southeastern Ghana

Petrology - New Perspectives and Applications ◽

10.5772/24563 ◽

2012 ◽

Author(s):

Prosper M. ◽

Kodjopa Attoh ◽

John W. ◽

Gordon Foli

Keyword(s):

Suture Zone ◽

Geochemical Characteristics ◽

Alkaline Rocks ◽

Pan African

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Accretion tectonics in northern Eritrea revealed by remotely sensed imagery

Geological Magazine ◽

10.1017/s0016756800009845 ◽

1993 ◽

Vol 130 (2) ◽

pp. 177-190 ◽

Cited By ~ 33

Author(s):

S. A. Drury ◽

S. M. Berhe

Keyword(s):

Remotely Sensed ◽

Ductile Deformation ◽

Low Grade ◽

Arc Volcanism ◽

Remotely Sensed Imagery ◽

Pan African ◽

Major Fault ◽

High Level ◽

Back Arc ◽

Layered Sequence

AbstractNew details from remotely sensed images of the structure and disposition of broad lithological variations in the Pan-African of northern Eritrea are discussed in the context of accretionary tectonics. The recognition of major north-south structural discontinuities allows the area to be divided into three discrete terranes with apparently different histories of deformation and metamorphism, magmagenesis and sedimentation. The central Hagar Terrane is dominated by large ultramafic masses with a volcano-sedimentary layered sequence, and shows the effects of major sinistral transpression and lateral expulsion. It is bounded to the west by a major fault, the Barka suture, and abuts the older Barka Terrane that comprises metasediments with evidence for polyphase ductile deformation and pre-kinematic dyke emplacement. The Hagar Terrane is thrust against the eastern Nacfa Terrane, which is dominated by low-grade calc-alkaline metavolcanics and immature volcanoclastic sediments intruded by syn-kinematic plutons. These units are pre-dated by an earlier high-grade basement and post-dated by high-level unmetamorphosed silicic volcanics and redbed sediments. The complex is suggested to have been assembled by oblique accretion from the southeast after arc volcanism in the Nacfa Terrane and back-arc extension in the Hagar Terrane ended with the cease of subduction.

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