PETROLOGICAL AND GEOCHEMICAL INVESTIGATION OF ROCKS FROM THE DAVIE-FRACTURE ZONE (MOZAMBIQUE CHANNEL) AND SOME TECTONIC IMPLICATIONS

被引:36
作者
BASSIAS, Y
机构
[1] Laboratoire de Géologie, Muséum National d'Histoire Naturelle, 75005 Paris Cédex, 43, Rue Buffon
来源
JOURNAL OF AFRICAN EARTH SCIENCES | 1992年 / 15卷 / 3-4期
关键词
D O I
10.1016/0899-5362(92)90018-8
中图分类号
P [天文学、地球科学];
学科分类号
07 ;
摘要
The Davie Ridge is an important structural feature of the Mozambique Channel. It represents the actual configuration of an old fracture zone (Davie Fracture Zone) between Africa and Madagascar along which Madagascar drifted southward during Late Jurassic and Early Cretaceous times. This fracture zone is built of crystalline continental basement (granites, gneisses and meta-arkoses) locally covered by a deformed <<flysch>> sequence, by alkaline lavas, tuffs and breccias and by a thin succession of carbonate oozes ranging in age from Cretaceous to Pleistocene. The sedimentary terrigeneous products derived from the fractured and eroded African basement and were deposited during an initial rifting/transtension in the incipient Somali Basin. During the southwards displacement of Madagascar, the lowermost arkosic sediments suffered low grade metamorphism in a collisional setting. The peak metamorphic conditions reached 4.5-5 kb and 350-400 degrees-C. These conditions imply at least 10-12 km deep burial of sediments (in transtensional?) and subsequent uplift (in transpressional setting?) to the present surface. Deep fracturing along the Davie Fracture Zone allowed the emplacement of alkaline within plate basalts in a marginal basin setting. However, these basalts were emplaced only at die northern and southern extremities of the fracture zone, while the central parts remained, at least superficially, undisturbed. Thermobarometric calculations on fragments of the old African continental basement found in the meta-arkoses confirm that the crustal pile below the present central parts of the fracture zone underwent slow uplift and erosion. These features imply that, during Paleozoic and Mesozoic and before the symmetric rifting in the Somali and the Mozambique Basins, the crustal pile between Africa and Madagascar underwent slow uplift and erosion. Unlike the evolution of the Limpopo belt in southeastern Africa and the western India basement (where uplift patterns are steeper or disturbed), the crustal thickness between Africa and Madagascar seems to have inhibited the emplacement of huge volumes of magma along the Davie Fracture Zone. Although the amplitude of lithospheric thinning was the guiding mechanism for the volcanic activity along the fracture zone, both the basement reactivation and the volcanic activity along die Davie Facture Zone were controlled by the amplitude of uplift and erosion.
引用
收藏
页码:321 / 339
页数:19
相关论文
共 73 条
  • [1] Ackermand, Windley, Razafiniparany, The Precambrian mobile belt of southern Madagascar, Evolution of Metamorphic belts, 43, pp. 293-296, (1989)
  • [2] Barton, Moyes, Cooling patterns in western Dronning Maud Land, Antarctica, and southeastern Africa and their implication to Gondwana, Workshop on Antarctic Geochronology, 1-3, pp. 20-33, (1990)
  • [3] Bassias, Triboulet, Progressive compositional changes in phengites and related water fugacity variations during successive metamorphic episodes in the Phyllites of Parnon (Peloponnesus, Greece), N. Jb. Geol. Paläont. Abh., 174, pp. 261-281, (1987)
  • [4] Bassias, Leclaire, Denis-Clocchiatti, Les basaltes et le magmatisme de la ride de Davie: une première approche. P. I. C. G. 277, Le magmatisme mésozoïque à actuel de la plaque Afrique et son contexte structural, 15, pp. 26-32, (1988)
  • [5] Bassias, Leclaire, Crystalline basement and intraplate mesozoic magmatism of the Davie Fracture Zone, N. Jb. Geol. Paläont. Mh., 2, pp. 67-90, (1990)
  • [6] Bence, Albee, Empirical correction factors for the electron microanalysis of silicates and oxides, The Journal of Geology, 76, pp. 382-403, (1968)
  • [7] Besairie, Précis de Géologie malgache, Annales géol. Madagascar, 36, pp. 109-141, (1973)
  • [8] Bird, Fawcett, Stability relations of Mg-chlorite-Muscovite and Quartz between 5 and 10 kb water pressure, J. Petrol., 14, pp. 415-428, (1973)
  • [9] Cahen, Snelling, Delhal, Vail, The Geochronology and Evolution of Africa, (1984)
  • [10] Chatterjee, Low temperature compatibility relations of the assemblage quartz-paragonite and the thermodynamic status of the phase rectorite, Contributions to Mineralogy and Petrology, 45, pp. 259-271, (1973)