Abstract
Basaltic rocks and their content of ultramafic xenoliths are common in the Ghab Pliocene Volcanic Field in northwestern Syria in the form of lava flows, cinder cones and pyroclastic deposits. The rocks occur within the Ghab pull- apart graben that formed by sinister strike slip faults within the zone that defines the boundary between the African and the Arabian plates. Three petrographic types occur: basanite, olivine basalt and more commonly alkali olivine basalt. The peridotite xenoliths are spinel lherzolite and harzburgite. Geochemical analysis indicates that the basalts are mostly alkaline to subalkaline. A distinctive feature of these rocks is the narrow compositional variations in the content of most major oxides and minor elements, SiO2 (44.33 - 46.43 wt%) and MgO (4.01 - 8.28 wt%). Some of the refractory and high field strength elements and incompatible minor elements in the basalts are relatively high (Cr average = 303 ppm and Ni average = 185 ppm) compared with their content in average basalts. These geochemical characteristics reflect crystallization of the Ghab basalts from pristine and primary magmas that have experienced minimal fractional crystallization and crustal contamination. Similarly, chemical compositions of the ultramafic xenoliths vary within a restricted geochemical range. They are compatible with the generation of these rocks from partial melting of a primitive mantle pyrolite to yield the xenoliths. These magmatic processes operated during the Pliocene in a regional transtensional stress environment attending the development of the Dead Sea Rift.
Highlights
The northwestern part of the Arabian Plate, especially along the Dead Sea Fault Zone (DSFZ; Figure 1(a)), has experienced a repeated and voluminous volcanic activity during the last 20 Ma [1] and has continued from the Miocene to the present. [2] suggested a period of volcanic quiescence between 16 and 8 Ma.The Ghab Pliocene Volcanic Field (GPVF), which is the focus of this paper, comprises a small part of the eastern-most province of the encompassing CircumMediterranean Anorogenic Cenozoic Igneous Province (CMACI) described by [3].[4] represented a petrographic evidence, as well as major element, trace element, and isotopic data, from the Ghab and Homs region
The rocks occur within the Ghab pullapart graben that formed by sinister strike slip faults within the zone that defines the boundary between the African and the Arabian plates
The GPVF is localized within the DSFZ that marks the tectonic plate boundary between the African and the Arabian plates
Summary
The northwestern part of the Arabian Plate, especially along the Dead Sea Fault Zone (DSFZ; Figure 1(a)), has experienced a repeated and voluminous volcanic activity during the last 20 Ma [1] and has continued from the Miocene to the present. [4] represented a petrographic evidence, as well as major element, trace element, and isotopic data, from the Ghab and Homs region. They suggested a possible model for the derivation of basaltic magmas attendant with the propagation of the Dead Sea Rift. The paper serves to add geochemical data to the dataset on the GPVF and to enhance the geochemical archives on the Syrian volcanic rocks [7]
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