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Journal of Asian Earth Sciences 21 (2003) 467–472
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Phases of activity and geochemistry of basaltic dike systems in northeast
Jordan parallel to the Red Sea
Khalil M. Ibrahima,*, Khalid Tarawnehb, Ibrahim Rabba’b
a
Department of Earth and Environmental Sciences, Institute of Land, Water and Environment, The Hashemite University, P.O. Box 150459, Zarqa 13115,
Jordan
b
Geological Mapping Division, Natural Resources Authority, P.O. Box 7, Amman 11118, Jordan
Received 15 January 2002; revised 24 May 2002; accepted 25 June 2002
Abstract
K – Ar dates, petrographic and chemical data were obtained from representative samples from three NW –SE trending basaltic dikes in the
Harrat Ash Shaam Volcanic Field, northeast Jordan. Compared with other NE – SW trending dikes in Jordan, three phases of activity were
determined for the studied dikes starting from the oldest (around 23 Ma) to the youngest at around 1.7 Ma. Three dominant petrotypes of
basalt were distinguished and related to the three phases. During the Early Miocene, there was emplacement of a pyroxene– iddingsite basalt
(23%), which is characterized by a tholeiitic composition. Later, in the Middle to Late Miocene, the composition was that of pyroxene olivine
basalt (34%) with an increase in the alkaline character of the magma chamber. In the final stage, the dikes comprised olivine basalt (22%)
with a basanite composition. It is reasonable to assume that the emplacement of the dikes was part of the same volcanic phase and regional
tectonic regime associated with the phases of volcanic activity of the Red Sea System.
q 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Red Sea; Basaltic dike; Tectonic regime
1. Introduction
Neogene –Quaternary basaltic rocks are known from
outcrops and from the subsurface in several areas of the
Harrat Ash Shaam Volcanic Field (HASVF) in NE Jordan
and adjacent countries (Fig. 1). In Jordan, a series of
geological and geochemical studies have been performed
during the past years. Ibrahim (1993) established the present
volcano-stratigraphic hierarchy of the HASVF rock units,
which were analyzed later by Tarawneh et al. (2000) using
K – Ar dating to identify the age relationships. The
lithological characteristics and distribution in space and
time of the rock units of the HASVF is presented in Ibrahim
et al. (2001). Illani et al. (2001) explained the implication of
HASVF ages to the volcano-tectonic evolution of the
Arabian plate.
Previous studies regarding the volcanic activity related to
diking events in the HASVF are scarce. It was indicated in
previous studies that the NW –SE dike trend is related to one
event which represents the initial phase of volcanic activity
* Corresponding author. Fax: þ 962-5-3-82-68-23.
E-mail address: [email protected] (K.M. Ibrahim).
in the HASVF that started at about 20 Ma (Barberi et al.,
1979; Moffat, 1988). The present study aims to shed light on
the geochemical affinities of the NW – SE trending dikes in
the HASVF, based on new geochemical data. These new
data allow a better understanding of the volcano-tectonic
history of the HASVF in relation to the tectonic history of
the Red Sea.
2. Geological setting
Sets of regional dike systems have been identified in the
HASVF in northeast Jordan, having a prominent NW –SE
trend (Fig. 1), parallel to the Red Sea. However, there are
also minor dikes trending E– W, NNW –SSE and N – S.
Most of the dikes are continuously traceable and can be
clearly detected from Landsat imagery. The dikes have a
strong influence on the drainage pattern and mudflats in the
study area, where linear wadi segments that are straight to
slightly curved are normal.
The major NW – SE trending dikes recognized in the
HASVF (Fig. 1) include the Qitar El Abed dike (QAD), Esh
Shurafa dike and Kaff el Kalb dike which have thick basaltic
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