Journal of African Earth Sciences 45 (2006) 173–186
www.elsevier.com/locate/jafrearsci
Geochemical constraints from the Hafafit Metamorphic
Complex (HMC): Evidence of Neoproterozoic back-arc
basin development in the central Eastern Desert of Egypt
H. Abd El-Naby
b
a,b,*
,
W. Frisch
b
a
Nuclear Materials Authority, P.O. 530 El-Maadi, Cairo, Egypt
Institut für Geologie und Paläntologie, Universität Tübingen, Sigwartstr. 10, D-72076 Tübingen, Germany
Received 8 June 2005; received in revised form 23 October 2005; accepted 2 February 2006
Available online 31 March 2006
Abstract
The Hafafit Metamorphic Complex (HMC) is a part of the Precambrian belt in the central Eastern Desert of Egypt. Two distinct
metamorphic units were identified: gneisses and amphibolites. The gneisses are subdivided on mineralogical grounds into granitic gneiss,
biotite-gneiss, hornblende-gneiss and psammitic gneiss. Using major elements discrimination criteria to discriminate between orthogneiss
and paragneiss, the granitic gneiss shows igneous origin, whereas biotite-gneiss, hornblende-gneiss and psammitic gneiss show sedimentary origin. The mineralogical and chemical compositions of the granitic gneisses indicate that they are tonalitic to trondhjemitic and
have compositions consistent with hydrous partial melting of a mafic source, suggesting subduction-related magmatism. Based on Si,
Al and alkali contents of paragneisses, the psammitic gneiss could be classified as metamorphosed lithic arenite, whereas biotite- and
hornblende-gneisses are classified as metamorphosed greywacke. Sedimentation may have occurred in a back-arc basin setting with transitional deposition from shallow-marine to terrestrial environment. This sedimentation was probably occurred on a tholeiitic basaltic
oceanic crust. The amphibolites are subdivided according to mineralogical basis into clinopyroxene-amphibolite, garnet-amphibolite
and garnet-free massive amphibolite. Chemical data of amphibolites shows tholeiitic affinity, which suggests a back-arc geotectonic setting. A generation of the leucogranite along thrust zones is related to the late phase of metamorphism of Hafafit rocks. This interpretation is supported by the similarity between metamorphic age and granite emplacement age.
Ó 2006 Elsevier Ltd. All rights reserved.
Keywords: Hafafit; Nugrus; Geochemistry; Back-arc; Gneisses; Amphibolites
1. Introduction
The Neoproterozoic evolution of the Arabian–Nubian
shield involves: (1) Formation of ophiolites by rifting of
Rodinia (Abdelsalam and Stern, 1996). The ages of the
ophiolites range between 900 and 740 Ma (Ries et al.,
1983; Kröner et al., 1992, 1994; Loizenbauer et al., 2001).
(2) Development of sutures associated with arc accretion
between 750 and 650 Ma (Abdelsalam and Stern, 1996;
Blasband et al., 2000). (3) Orogenic extension and exhuma*
Corresponding author. Present address: King Abdulaziz University,
Faculty of Earth Sciences, P.O. Box 80206, Jeddah 21589, Saudi Arabia.
E-mail address: hhabdel@yahoo.com (H. Abd El-Naby).
1464-343X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jafrearsci.2006.02.006
tion of core complexes as constrained by dating of core
complex exhumation (Fritz et al., 1996), late- to post-tectonic magmatic activity (Stern and Hedge, 1985; Hassan
and Hashad, 1990) and molasse basin formation (Grothaus
et al., 1979; Rice et al., 1993; Willis et al., 1988). The previous data suggest close association between tectonic and
magmatic activity between 620 and 580 Ma (Fritz et al.,
2002).
Hafafit area represents one of three major domal structures on the Eastern Desert of Egypt (Fig. 1, inset): Abu
Swayel (Finger and Helmy, 1998; Abd El-Naby and Frisch,
2002), Gabal Meatiq (Sturchio et al., 1983; Blasband et al.,
2000; Fowler and Osman, 2001; Loizenbauer et al., 2001)
and Hafafit area (El Ramly et al., 1984; Greiling et al.,
174
H. Abd El-Naby, W. Frisch / Journal of African Earth Sciences 45 (2006) 173–186
Fig. 1. (a) General geological map of the study area (modified from El Ramly et al., 1993). (b) Detailed geological map of dome A (after El Ramly et al.,
1993).
1988; Rashwan, 1991; Fowler and El Kalioubi, 2002). The
geology of Hafafit has long been recognized as highly complex (called Hafafit Core Complex), and many theories
have been proposed for its tectonic evolution. El Ramly
et al. (1984) interpreted the Hafafit gneisses, the associated
granitoid cores and the Wadi Ghadir melange (Fig. 1a) as a
result of Pan-African convergent and marginal ocean basin
processes. Hassan and Hashad (1990) interpreted the granitic gneisses at the core of the domes (Fig. 1) as gneissic
granitic intrusions. They named the rock assemblage above
the core granite and below the psammitic gneiss as a metamorphosed and deformed ophiolitic melange assemblage,
whereas the psammitic gneiss as a metamorphosed sedimentary unit of a quartozo-feldspathic composition.
Several models have been postulated to explain the
exhumation of Hafafit Metamorphic Complex (HMC).
Fritz et al. (2002) interpreted the exhumation of HMC as
a result of orogen-parallel extension during convergence.
Fowler and El Kalioubi (2002) interpreted the Hafafit
Complex as a result of fold interference patterns involving
multiply deformed sheath folds.
Understanding the geochemical characteristic of the
Hafafit unit helps in recognizing its tectonic setting and
reconstructing the evolution of a former plate margin. In
H. Abd El-Naby, W. Frisch / Journal of African Earth Sciences 45 (2006) 173–186
this paper we report the geochemical data of granitic gneisses, paragneisses, amphibolites and garnetiferous leucogranites, which is a useful guide to constrain the former
tectonic setting of the Hafafit Metamorphic Complex.
2. Geological setting and petrography
Hafafit area consists of five granite-cored domes (dome
A to dome E, Fig. 1a). These domes are composed of medium grade gneisses and are separated from the overlying
low grade metamorphic rocks by low angle thrust zones.
The rock assemblages in Hafafit area could be grouped into
two main units which are separated by Nugrus Thrust. The
eastern unit (Nugrus unit) is composed mainly of low grade
mica-schists and metavolcanics. This unit is associated with
remnants of ophiolitic altered ultramafic and metagabbros.
The western unit (Hafafit unit) forms Hafafit domes and
includes from core to rim (Fig. 2a): granite gneiss of tonalitic and trondhjemitic composition, banded amphibolite
which is overthrusted by ultramafic rocks, alternating
bands of biotite- and hornblende-gneiss and the psammitic
gneiss at the rim of the domal structure. In some parts, the
amphibolite is associated with metagabbro. Both units
have been intruded by undeformed leucogranites, especially along thrust zones.
Mica-schists are composed mainly of quartz + garnet + muscovite + biotite + plagioclase ± chlorite ± opaque
(Fig. 2b). These rocks are strongly microfolded as shown in
Fig. 2c. Most of these rocks are substantially altered, with
secondary chlorite replacing biotite and sericite replacing
plagioclase. The metavolcanics are encountered mainly at
the northern border of HMC. They are composed mainly
of greyish green,1 fine to medium grained meta-andesites
which are porphyritic in some places. They are composed
of hornblende and/or actinolite-tremolite and plagioclase
with variable proportions of epidote, chlorite and carbonate
depending upon the degree of alteration (El Ramly et al.,
1993).
The cored-granite gneisses are moderately foliated, with
a well-developed granoblastic-polygonal texture. Locally,
mylonitic texture is observed in strongly deformed varieties. Two main types of granite gneiss occur. The predominant is tonalitic gneiss, consisting of plagioclase, quartz,
biotite and, locally, garnet. The other type is trondhjemitic
in composition. These rocks show a well-developed millimetre-spaced gneissic banding. In some places, the tonalites are invaded by numerous thin pegmatitic veinlets.
The amphibolites form irregular lens-shaped bodies
overlain by altered ultramafic. At the southern part of
the dome A, the amphibolites are overlained by psammitic
gneiss of Gabal Hafafit. Based on their mineral constituents, amphibolites could be classified into clinopyroxeneamphibolite, garnet-amphibolite and massive amphibolite.
1
For interpretation of color in Figs. 2–4 and 9, the reader is referred to
the web version of this article.
175
The clinopyroxene-amphibolite is fine-grained and composed of amphibole + clinopyroxene + plagioclase with little quartz and iron oxides. It shows thin alternating bands
(few millimeters to one centimeter) of dark grey (amphibole-rich) and dark green (clinopyroxene-rich). The
strongly foliation of clinopyroxene-amphibolites (Fig. 2d)
could be related to the first deformational event, which
led to a metamorphic banding and may be synchronous
with the alternating bands of biotite- and hornblendegneisses under amphibolite facies condition. At the late
stage of this deformational event, the banding and foliation
were deformed by folding as shown in Fig. 2d. This event is
previously described by El Ramly et al. (1993). They concluded that the structural framework of the Hafafit area
could be a result of four main deformational events: early
foliation and folding (D1), thrusting and folding (D2),
regional thrusting and folding (D3) and a late phase of
gravitational deformation (D4). Details of these events
have been discussed by El Bayoumi and Greiling (1984),
Kröner et al. (1987), Greiling et al. (1988) and Rashwan
(1991).
The garnet-amphibolite is abundant in Gabal Hafafit and
in the area to the east of dome C. It consists of amphibole +
plagioclase + garnet + quartz ± clinopyroxene + iron oxides
(Fig. 2e). The garnet is coarse grained (up to 5 mm in diameter). The massive amphibolite is free from garnet and
clinopyroxene and found as lenses within the gneisses. It
is composed mainly of amphibole + plagioclase + quartz +
iron oxides. At the eastern side of Nugrus thrust, the
amphibolites are associated with metagabbros. These
metagabbros probably pertain to the calc-alkaline metagabbros associating Hafafit gneisses (El Ramly et al.,
1993). They are dark green in color, medium-grained and
composed of highly saussuritized plagioclase crystals and
hornblende which is altered partly to pale green actinolite
or chlorite.
The ultramafic rocks are found as small masses in the
core of the northern Hafafit dome (dome A, Fig. 1b) overlying amphibolites. The contact between them seems to be
tectonic where there is no sign for intrusive contact. They
are massive dark grey, brown or green in color and represented mainly by serpentinized dunite and pyroxenite. Less
altered samples are composed mainly of olivine in a mesh
texture of serpentine, whereas highly altered samples are
composed of serpentine, talc, chlorite, tremolite and calcite. The clastic sediments in this domain which gave rise
to the biotite schists and psammitic gneisses were deposited
in a basin associated with an active continental margin.
This basin is floored by an old oceanic crust now represented by the fore-mentioned ultramafic-mafic rocks
(Rashwan, 1991).
The alternating bands of biotite-rich gneiss and hornblende-rich gneiss are encountered between the amphibolites at the core of the domal structure and the psammitic
gneiss at the rim. The biotite-gneiss is composed essentially
of quartz, biotite, plagioclase, and zircon. Garnet is
observed in some samples. Chlorite and epidote are
176
H. Abd El-Naby, W. Frisch / Journal of African Earth Sciences 45 (2006) 173–186
Fig. 2. (a) Rock assemblages in Hafafit dome A. (b) Secondary electron image of large garnet porphyroblast in mica-schist. (c) Photomicrograph showing
micro-folded mica-schist (PPL). (d) Strongly foliated and folded clinopyroxene-amphibolites. (e) Photomicrograph showing garnet porphyroblast in
garnet-amphibolite (PPL).
occasionally present as alteration phases. The hornblendegneiss consists mainly of hornblende, plagioclase and
quartz with some opaques. The psammitic gneiss forms
the summits of the main mountain masses in the area
(e.g. Gabal Hafafit and Gabal Migif). It is composed essentially of quartz, potash feldspar, plagioclase with minor
amphibole, biotite, epidote and zircon. In Wadi Abu Rusheid, the psammitic gneiss is mylonitized and dissected by
several shear zones. It is highly metasomatized and reflects
high radioactive anomalies. Secondary uranium mineralization is found in the altered zone of the mylonitic psammitic gneiss. It occurs as stains along crevices and
fracture surfaces and as acicular crystals filling cavities.
Uranophane is the most abundant uranium mineral as
deduced from the EDX pattern (Fig. 3).
The latest Pan-African activity in the mapped area is
represented by a suite of leucogranites and minor
intrusions of felsite and aplite which intruded the Hafafit
H. Abd El-Naby, W. Frisch / Journal of African Earth Sciences 45 (2006) 173–186
177
Fig. 3. Secondary electron image showing uranophane crystal separated from Abu Rushied paragneisses and their EDX spectrum.
gneisses and the ophiolitic assemblage (El Ramly et al.,
1993). Elongated narrow intrusive leucogranite is found
in the eastern part of the mapped area and parallel to the
Nugrus Thrust (Fig. 1a). To the other side of Nugrus
Thrust, there is other elongated granitic belt forming Gabal
Nugrus. Generally, these leucogranites are garnet-bearing
and developed along thrust faults, e.g. garnetiferous granites to the south of Nugrus Thrust, Gabal Nugrus, Gabal
El-Faliq and Gabal Mudargag (to the northwest extension
of the mapped area). The leucogranites are composed
mainly of quartz, orthoclase, oligoclase, garnet and biotite.
Several small lens-like plutonic masses of leucogranites are
found also in Wadi Abu Rushied. They are medium- to
coarse-grained, garnet-bearing and contain abundant of
metasedimentary xenoliths. Large K-feldspar phenocrysts
are also observed in some localities. Geochronological constraints show that the emplacement ages of the leucogranites are between 594 ± 12 and 610 ± 20 Ma (Moghazi
et al., 2004).
3. Analytical methods
A total of thirty one representative samples were collected for whole-rock chemical analysis. The samples collected from the banded clinopyroxene amphibolites
include both dark grey (amphibole-rich) and dark green
bands (clinopyroxene-rich). All samples were crushed in a
steel jaw crusher to 3-cm-sized pieces. Fresh pieces were
selected, cleaned and crushed again to 3-mm pieces. The
products of the last crushing were then pulverised in an
agate mill. Loss on ignition (LOI) was determined by heating powdered samples at 850 °C for 3 h. Whole rock major
and some selected trace and rare earth elements were analysed using the X-ray fluorescence (XRF) technique at the
laboratories of the Mineralogical Institute, Tübingen
University, Germany. Absolute accuracy has been assessed
by comparison with international reference materials analyzed along with the samples and is generally better than
2%. The results of these chemical analyses are given in
Table 1. JEOL JXA-8900RL instrument at the University
of Tübingen, Germany, was used to identify some radioactive mineral grains. Analytical conditions were 15-kV accelerating voltage, 10–20-nA beam current, 1–2-lm beam
diameter and 10–20 s counting time.
4. Geochemistry
4.1. Geochemistry of paragneisses
Fig. 4a is a discrimination diagram (after Demant, 1992)
to distinguish between sedimentary and magmatic origins
of the gneisses. It shows that the cored granitic gneiss fall
in the orthogneiss field, whereas psammitic gneiss, biotiteand hornblende gneisses fall in the paragneiss field.
Paragneiss samples are plotted in (Na + Ca)/
(Na + Ca + K) versus Si/(Si + Al) (atomic proportions)
in Fig. 4b which defines compositional fields for various
sedimentary rocks (Wintsch and Kvale, 1994). Most of
the psammitic gneiss fall within the lithic arenite with some
samples plot in the arkose to subarkose fields. On the other
hand, biotite- and hornblende-gneisses fall within the field
of greywacke. Sedimentation may have occurred in a backarc basin setting with deposition of the greywacke in marine environment. This sedimentation was probably
occurred on a tholeiitic basaltic oceanic crust. This is indicated from the association of amphibolite representing oceanic crust with biotite- and hornblende gneisses. Plotting of
most of the psammitic gneisses in the lithic arenite field
may reflect deposition of materials of different sources in
a fluvial to shallow-marine environment. Whereas plotting
of some other psammitic gneiss samples in the arkose to
subarkose fields may indicate a marked transition from
sedimentation in shallow-marine environment to sedimentation in a terrestrial environment.
The depositional environment of paragneiss is constrained from Fig. 4c (Roser and Korsch, 1986). It suggests
sedimentation in an active continental margin setting, with
the exception of two samples which plot in the passive
Sample
Psammitic gneiss
H1
72.39
0.615
11.49
4.834
0.096
0.904
1.838
4.006
3.662
0.131
0.46
100.4
Trace elements (ppm)
Ba
898
Co
8
Cr
18
Rb
49
Sr
102
V
36
Y
159
Zn
186
Zr
946
Nb
37
Pb
32
Th
15
U
2.8
REE (ppm)
La
77
Ce
168
Nd
104
Sm
15
Eu
1.4
Yb
14
H2
76.99
0.293
11.01
3.239
0.063
0.65
0.181
4.209
4.111
0.023
0.23
100.9
Biotitet-gneiss
H3
91.55
0.035
4.065
1.224
0.019
0.124
0.02
1.738
1.082
0.011
0.16
100
SiO2
TiO2
Al2O3
Fe2O3
MnO
MgO
CaO
Na2O
K2O
P2O5
H5
77.29
0.027
11.09
1.261
0.054
0.205
0.036
5.071
3.517
0.041
0.86
99.45
764
1.7
8.4
45
18
8.9
215
188
1197
49
32
14
1.9
3.4
1.4
11
184
1.8
1.9
15
110
293
150
2.6
28
1.1
68
9.9
44
661
12
8
133
1075
5863
0
421
225
55
187
230
207
22
1.7
19
31
0
13
0
0
0.9
34
97
59
0
0
10
Granitic gneiss
H17
59.71
0.637
18.93
4.869
0.087
2.697
7.472
4.49
0.424
0.127
H4
H18
73.37
0.385
14.66
2.572
0.038
0.758
2.609
5.189
1.089
0.125
H6
77.18
0.029
11.06
1.229
0.066
0.716
0.007
5.203
3.652
0.025
0.49
99.65
H7
86.89
0.07
5.068
2.149
0.029
0.876
0.004
2.289
1.783
0.01
0.27
99.43
H8
76.16
0.034
11.08
1.606
0.06
0.993
0.065
5.442
3.442
0.034
0.44
99.35
77.133
0.199
10.51
2.348
0.046
1.064
3.13
3.412
0.933
0.04
0.37
99.18
H20
77.08
0.244
10.83
3.432
0.033
0.109
0.395
2.683
4.998
0.022
Granitic gneiss
H9
H10
H11
H12
H13
H14
65.99
1.037
12.05
8.28
0.144
2.39
3.139
2.994
2.697
0.391
0.92
100
78.76
0.227
10.93
2.541
0.086
1.185
2.042
3.045
1.42
0.02
0.75
101
61.14
0.398
14.54
8.416
0.152
3.976
9.087
1.636
0.592
0.076
0.62
100.6
52.64
1.351
18.02
8.854
0.14
4.515
10.06
3.673
0.348
0.168
0.63
100.4
66.71
0.455
17.17
2.734
0.042
1.699
5.488
4.501
0.862
0.13
0.91
100.7
68.35
0.22
17.81
1.653
0.033
0.707
4.358
5.337
1.061
0.075
0.61
100.2
H15
69.69
0.399
15.86
2.191
0.038
1.056
3.031
5.335
1.302
0.116
0.36
99.37
H16
77.39
0.287
11.99
3.429
0.066
0.898
4.08
2.746
0.108
0.034
0.13
101.1
28
11
35
979
0
10
90
89
3294
173
228
130
27
22
2.4
11
314
1.6
0.4
4.1
204
112
118
4.7
3.9
2.9
18
15
37
946
2.7
14
234
514
4563
217
42
136
31
267
1.2
10
18
144
9.9
23
17
160
0
3.9
2.3
0
682
15
86
57
226
47
92
139
513
21
16
8.7
1.3
525
3.1
13
29
118
4
39
46
175
0
9.3
1.8
0
75
23
68
8.3
139
245
17
71
36
0
6.1
1.1
0
123
33
99
5.1
398
196
25
74
69
0
2.2
0.8
0
229
6.9
28
22
519
47
14
37
164
0
8.3
3.4
1.9
254
1.4
11
24
340
17
12
22
159
0
4.9
9.4
2.8
242
4.4
14
43
333
26
13
32
170
0
8
3.7
2.2
35.5
7.6
18
2.6
159
45
0
12
219
0
3
0
3.6
41
0
36
0
0
7
30
0
3.8
3.5
0
0.5
42
91
60
6.1
0
21
38
0
8.7
0
0.3
1.7
50
73
68
9.4
1.4
8.2
27
0
13
0
0.3
3.5
53
0
5.1
0
0.6
1.7
44
0
21
2.2
1.2
2.4
52
0
9.2
3
1.3
0.9
66
54
30
4.2
1.1
0.7
55
30
19
2.6
0.9
0.8
39
0
5.9
0
0.5
0.7
Leucogranites
H19
67.06
0.318
14.2
5.809
0.124
1.985
6.143
3.495
0.681
0.065
Hornblende-gneiss
H21
76.51
0.06
12.93
1.051
0.013
0.112
0.257
4.979
3.774
0.014
H22
75.27
0.127
13.84
1.075
0.043
0.345
1.649
4.058
3.394
0.04
H23
75.91
0.16
13.36
1.32
0.022
0.177
1.42
2.88
4.35
0.05
H24
74.91
0.17
14.21
1.11
0.05
0.41
1.2
3.65
4.12
0.06
H25
75.56
0.09
13.01
1.6
0.13
0.22
0.76
3.93
3.86
0.03
Clinopyroxene amphibolites
Garnet amphibolites
H26
50.67
0.42
16.67
8.586
0.137
8.604
11.12
2.693
0.357
0.029
H29
57.25
0.534
14.12
11.04
0.144
5.774
8.93
1.186
0.325
0.06
H27
48.86
0.449
18.67
4.869
0.097
8.265
15.12
2.427
0.162
0.018
H28
52.18
0.329
16.04
9.32
0.13
4.662
11.8
3.894
0.515
0.158
H30
44.68
0.401
15.03
12.42
0.181
10.42
13.42
1.822
0.191
0.017
H31
47.77
0.336
12.24
7.516
0.147
15.51
12.79
1.332
0.549
0.015
H. Abd El-Naby, W. Frisch / Journal of African Earth Sciences 45 (2006) 173–186
SiO2
TiO2
Al2O3
Fe2O3
MnO
MgO
CaO
Na2O
K2O
P2O5
CO2
Total
178
Table 1
Major, trace and some rare earth elements of the Hfafit rocks
CO2
Total
0.59
100
0.47
100.3
Trace elements (ppm)
Ba
113
Co
14
Cr
24
Rb
4.4
Sr
527
V
95
Y
0
Zn
54
Zr
133
Nb
0
Pb
1.6
Th
0
U
1.8
840
3.2
7.5
17
690
25
0
52
267
0
20
14
3.8
83
14
30
4.7
155
160
17
50
64
0
6.3
2.7
0
REE (ppm)
La
53.9
Ce
0
Nd
16.7
Sm
0
Eu
1.2
Yb
0.9
110
150
47
8.3
2.1
0.8
50
0
9.5
0
0.5
1.6
0.57
100.4
0.57
100.3
0.44
100.3
0.32
99.96
0.55
100.4
341
2.8
16
79
37
5.7
165
179
1315
46
33
16
0
62
0
5.7
85
19
3.3
90
116
189
81
11
7.6
0
765
0.6
2.7
150.2
210
7.5
19.3
31
150
8.4
15
12
0
441
0.8
9
160
66
11
117
47
140
6
22
14
3.8
632
1.1
7
155
90
10
80
33
156
8.7
32
9
1.6
103
228
120
17
1.4
14.1
72
32
54
8.4
0.6
8.6
63
46
20
4.4
0.7
1.5
77
47
44
12
0.9
4.9
90
112
48
8
1.2
1.6
0.41
99.6
1.02
100.3
1.09
100
1.13
100.1
0.69
100.1
1.19
99.8
2.04
100.2
73
1.8
6
149
70
8
32
83
170
19
21
20
4
216
34.5
233
5.2
354
251
0
61
33
0
0
0
1
13
29
888
3.9
178
123
0
31
21
0
1.3
0
0.7
209
29
86
9.6
226
197
29
84
76
0
1.5
0
0
22
34
200
12
126
302
9.2
84
19
0
6
0
0
113
47
229
4.2
108
459
12
90
15
0
0.5
0
0
83.5
52.4
866
10
123
120
0
45
17
0
1.6
0
1
56
29
22
15
0.5
6
60
0
3.6
2.8
1.2
0.8
56
0
5.4
0
0.5
0.5
31
0
15
3.6
1
2.7
56
0
3.4
2.9
0.8
1
52
0
1.6
1.6
0.8
1.2
41
0
3.1
0.9
0.6
0.3
179
Fig. 4. (a) Al2O3 versus MgO discrimination diagram (after Demant,
1992). (b) Si/(Si + Al) versus (Na + Ca)/(Na + Ca + K) (mole percent)
plot for Hafafit paragneisses (after Wintsch and Kvale, 1994). (c) Diagram
of log K2O/Na2O versus SiO2 (Roser and Korsch, 1986) for Hafafit
paragneisses.
margin tectonic setting and hornblende-gneiss sample
which plot in the oceanic island arc margin setting.
H. Abd El-Naby, W. Frisch / Journal of African Earth Sciences 45 (2006) 173–186
0.37
100.2
180
H. Abd El-Naby, W. Frisch / Journal of African Earth Sciences 45 (2006) 173–186
Fig. 5. (a) AFM plot of granitic gneisses, leucogranites and amphibolites of Hafafit area. Line shows boundary between tholeiitic and calc-alkaline rocks
from Irvine and Baragar (1971). (b) Nomenclature of the granitoids of the Hafafit area judging from their normative mineral composition (after
O’Connor, 1965). (c) SiO2 versus A/CNK (A/CNK = molar Al2O3/CaO + Na2O + K2O) (Clark, 1992). (d) K2O–SiO2 for Hafafit granitic gneisses and
leucogranites. Fields of partial melts of different rock sources are after Gerdes et al. (2000) and references therein.
4.2. Geochemistry of granitic gneisses and leucogranites
The calc-alkaline character of Hafafit granitic gneisses
and leucogranites is indicated from the AFM diagram
(Fig. 5a). This diagram is commonly used to distinguish
between tholeiitic and calc-alkaline differentiation trends
in a magma series (Irvine and Baragar, 1971). Normative
mineral composition of Hafafit granitic samples is plotted
in Orthoclase-Albite-Anorthite diagram (Fig. 5b). It classifies the granitic gneiss into tonalite and trondhjemite,
whereas leucogranite plots in the field of granite.
On the SiO2–A/CNK diagram (Fig. 5c), most of granitic
gneiss samples plot in the I-type metaluminous field indicting an igneous source for these rocks, whereas the leucogranite plots in the S-type peraluminous field suggesting
partial melting of metasedimentary source. The possible
magma source of the studied granitic samples could be
inferred from Fig. 5d. It shows that the granitic gneiss
could be derived from partial melting of amphibolite
source, whereas leucogranite was formed by partial melting
of metagreywackes and metapellites.
Trace element concentrations of the studied granitic
gneiss are normalized to the Oceanic Ridge Granite values
as proposed by Pearce et al. (1984). In the diagram shown
in Fig. 6, two groups of elements can be distinguished. The
first group includes the large ion lithophile elements
(LILEs) Rb, Ba, K, Th, U, Sr and La that are highly
enriched relative to Oceanic Ridge Granite. The second
group consists of the high field strength elements (HFSEs)
Ce, Nb, Nd, Sm, Zr, Eu, Y and Yb that show values close
to or less than one in most samples. The strong difference
between LILEs and HFSEs excludes an oceanic ridge origin of the Hafafit granitic gneiss. The LILEs enrichment
characterizes volcanic arcs, within-plate and collision granites. The second group of elements correlates with granites
of volcanic arc and collision settings. Based on the tectonic
discrimination diagrams proposed by Batchelor and Bowden (1985), the granitic gneisses represent pre-plate collision pluton (subduction regime), whereas the
leucogranite is classified as intrusive in a syn-collision setting reflecting restricted range of S-type and anatectic
granites (Fig. 7).
H. Abd El-Naby, W. Frisch / Journal of African Earth Sciences 45 (2006) 173–186
181
Fig. 6. Ocean Ridge Granite-normalized multi-element diagrams for the Hafafit granitic gneisses. Normalization values from Sun and Mcdonough (1989).
Fig. 7. R1–R2 diagram for the Hafafit granitic gneisses and leucogranites
(after Batchelor and Bowden, 1985).
4.3. Geochemistry of amphibolites
On the diagram of K2O versus SiO2 for arc magmatic
series (Peccerillo and Taylor, 1976), the amphibolite sam-
ples plot in the low-K tholeiite series (Fig. 8a). The tholeiitic character of Hafafit amphibolite is also indicated on the
AFM diagram of Fig. 5a (Irvine and Baragar, 1971). Using
a discrimination diagram based on the relation of the ratio
Zr/TiO2 versus SiO2 (Winchester and Floyd, 1977), the
studied amphibolites are classified as subalkaline basalts
(Fig. 8b).
The mineral assemblage of the amphibolites (i.e., amphibole + plagioclase + clinopyroxene + garnet ± quartz +
opaques) is characteristic of the upper amphibolite facies
with temperatures around 600–700 °C and pressures
around 6–8 kb (Bucher and Frey, 1994). In Such conditions, the major elements may have been mobilized. So,
selected trace elements are often used to give information
about the tectonic setting of such highly metamorphosed
rocks. Among the trace elements, the high field strength
elements (HFSEs) including REE, are the most immobile.
Fig. 9 shows the normalized multi-element diagram. It
compares the rock chemistry of the studied amphibolites
with mid-ocean ridge basalts (the MORB-normalized form
proposed by Pearce (1982)). In typical magmatic arcs, the
Fig. 8. (a) Weight percent K2O versus SiO2 plot for Hafafit amphibolites. Series boundaries are after Peccerillo and Taylor (1976). (b) Log Zr/TiO2–SiO2
(Winchester and Floyd, 1977).
182
H. Abd El-Naby, W. Frisch / Journal of African Earth Sciences 45 (2006) 173–186
Fig. 9. MORB-normalized multi-element diagrams for the Hafafit amphibolites. Normalization values from Sun and Mcdonough (1989).
abundance of the LILEs (Rb, Ba, K, Th, U, Sr and La) is
controlled by the fluid phase and consequently shows variable enrichment. The HFSEs (Ce, Nb, Nd, Sm, Zr, Eu, Y
and Yb) are a function of the chemistry of the source and
crystal/melt processes and are normally depleted relative to
the LILEs (Rollinson, 1993). The amphibolites are variably
enriched in LILEs and depleted in HFSEs (Fig. 9). This
suggests a mantle source similar to those for E-MORBS
and BABBs (Back-Arc Basin Basalts). Field evidence for
the association of these amphibolites with paragneisses
and for intruding with tonalitic to trondhjemitic magmas
(granitic gneiss) precludes an origin in a mid-ocean ridge
Fig. 10. (a) Ti–V (Shervais, 1982), ARC = Island Arc Basalts, OFB = Ocean Floor Basalts. (b) Nb–SiO2 diagram (after Pearce and Gale, 1977). (c) Zr–Ti
(Pearce and Cann, 1973). LKT: low potassium tholeiites, CAB: Calc-Alkaline Basalts, OFB: Ocean Floor Basalts. (d) Zr–Sr/2-Ti/100 (Pearce and Cann,
1973).
H. Abd El-Naby, W. Frisch / Journal of African Earth Sciences 45 (2006) 173–186
183
Fig. 11. (a) Plot of Na8 versus Fe8; (b) Plot of Ba/La versus Ti8 for Hafafit amphibolites (after Taylor and Martinez, 2003). Na8 = [Na2O + 0.115 (8MgO)]/[1 + 0.133 (6-MgO)]; Fe8 = [FeO + 8-MgO]/[1 + 0.25 (8-MgO)] Ti8 = (TiO2) (MgO)1.7/34.3.
environment; therefore, we conclude that amphibolitic
magmas are BABBs associated with back-arc basin development during convergent process.
Because Ti and V are HFSEs and thought to be relatively immobile under conditions of high-grade metamorphism (Rollinson, 1993), we plot Ti versus V for the
Hafafit amphibolites (Fig. 10a). They plot in the arc field
which is well-correlated with the tectonic setting as suggested by TiO2–Zr diagram (Fig. 10b), where all amphibolite samples fall into the volcanic-arc field. The island-arc
character of the studied amphibolites could also be inferred
from Fig. 10c and d, where they plot in the filed of low-k
tholeiites and island arc basalts. This geochemical signature
is consistent with an ensialic back-arc basin origin according to Saunders and Tarney (1991) who stated that ‘‘basalts
from ensialic basins often show strong arc-like
characteristics’’.
Plot of Na8 versus Fe8 (after Taylor and Martinez,
2003) supports the conclusion of volcanic arc setting for
Hafafit amphibolites (Fig. 11a). Similarities between the
chemistry of the Hafafit amphibolites and composition of
lavas from active BAB spreading centers include arc-like
components is evidenced by low Na8, Ti8 and Fe8 and
the reversal relationship between Ti8 and Ba/La (Fig. 11b).
5. Discussion and conclusion
The Hafafit area represents one of the important suture
zones in the Eastern Desert of Egypt. It comprises two
main units, the western Hafafit unit and the eastern Nugrus
unit. The study area is characterized by a distinctive relationship between sedimentation (greywackes and lithic arenite to arkose rocks in back-arc basin which
metamorphosed later to paragneisses), tectonic deformation (thrusting and folding), metamorphism (amphibolite
facies in Hafafit unit, and greenschist facies in Nugrus
unit), and magmatism (arc-related and collision-related
granitoids). These processes lead to development of basins
(Fig. 12), mountain building and eventual exhumation of
HMC. Such features are characteristics of orogenic belts
which are located at convergent plate boundaries and along
lines of arc collision.
The geochemical data of the paragneisses suggested different sedimentary protolithes ranging from lithic arenite
to arkose for psammitic gneiss and greywacke for biotiteand hornblende-gneisses. Such variation in sedimentary
protolithes of paragneisses may attribute to the changing
of the depositional environment from shallow marine to
a terrestrial environment.
The magmatism in Hafafit area is represented by two
main magma generations. The early mafic magma produced tonalite and trondhjemite (precursor of the granitic
gneiss) in the early stage of underplating. During the collision stage, the metasediments underwent anatexis which
led to final magma producing leucogranite which could
be occurred at the waning stages of medium-grade regional
metamorphism of HMC. This conclusion is supported by
the isotopic compositions of leucogranites of Hafafit area
that suggest a metasedimentary source for these rocks
(Moghazi et al., 2004). The development of leucogranites
in Hafafit and Nugrus area along thrust faults reflects the
role of these faults as pathways for these leucogranites.
In other word, the shear heating of metasedimentary rocks
during synorogenic thrusting contributed to the leucogranite generation.
Abd El-Naby and Frisch (in review) interpreted the Sm/
Nd and Rb/Sr ages around 590 Ma as cooling ages from
the metamorphic thermal peak which was attained around
600 Ma or slightly earlier. This geochronological data is in
accordance with the emplacement ages of the leucogranites
in Nugrus area (594 ± 12 and 610 ± 20 Ma, Moghazi et al.,
2004). Because of the similarity between the dates of metamorphism and granite emplacement in Hafafit-Nugrus
area, we propose that both of metamorphic rocks and leucogranites are the products of the same event that occurred
during collision and thrusting of Nugrus unit over Hafafit
unit. There are many published data that advocated the
generation of leucogranite along shear zones and then, at
184
H. Abd El-Naby, W. Frisch / Journal of African Earth Sciences 45 (2006) 173–186
Fig. 12. Sketch diagrams illustrating the development of Hafafit Metamorphic Complex and its tectonic relation with Nugrus unit. (a) > 680 Ma:
subduction of the oceanic crust, ophiolite detachment and thrusting in the Wadi Ghadir, with arc volcanism, arc-related plutonism and back-arc basin
development in the Hafafit region. (b) 600 Ma: collision and thrusting of Nugrus unit over Hafafit unit, leucogranite intrusion along thrust zones and
regional metamorphism.
least partly, migrate along listric faults to higher levels in
the crust due to pressure gradients generated by buoyancy
and tectonic stresses (Moghazi et al., 2004; Nabelek et al.,
2001; Brown and Solar, 1998a,b; Solar et al., 1998).
Most of amphibolites are tholeiitic in composition
which supports their derivation from a mantle peridotite
source by fractional crystallization. This could be expected
in continental rift or back-arc basin tectonic settings (Reid
et al., 1987; Moore, 1989; Raith and Meisel, 2001).
The obtained geochemical data are used to construct a
model as shown in Fig. 12. This model is based on PanAfrican convergent and back-arc basin processes. The
Pan-African tectonic evolution in the Hafafit-Ghadir
region began before 680 Ma ago with the formation of
Wadi Ghadir ophiolites (El Ramly et al., 1984). This event
occurred synchronously with arc volcanism, arc-related
plutonism and back-arc basin development in the Hafafit
zone (Fig. 12a). This suggestion is based mainly on: (i)
the geochemical data of the cored granitic gneisses which
indicate that their protoliths are calc-alkaline, metaluminous, I-type, and generated in subduction-related environment; (ii) the sedimentary origin in active continental
margin setting of the psammitic, biotite- and hornblendegneisses as indicated from their geochemical characteristics
and (iii) trace element concentrations suggest that amphibolites were formed in an ensialic back-arc setting.
The arc-continent or arc-arc collision took place around
600 Ma (Abd El-Naby and Frisch, in review) and was
responsible for significant overthrust of the Nugrus unit
in a northwest-ward direction onto the back-arc basin
(Hafafit unit) and for the second regional metamorphism
with medium grade amphibolitic facies in Hafafit unit.
Crustal thickening during collision led to a widespread partial-melting and leucogranitic plutonism along thrust zones
(Fig. 12b).
The suggested model is generally agreeable with the general tectonic model for the entire Arabian–Nubian shield
which involves progressive cratonization by formation of
H. Abd El-Naby, W. Frisch / Journal of African Earth Sciences 45 (2006) 173–186
oceanic crust, subduction, magmatic arc development and
collision between arc complexes to assemble a continental
shield during the period between 900 and 550 Ma (e.g.
Frisch and Al Shanti, 1977; Vail, 1985; Kröner et al.,
1988; Stern, 1994; Abdel Rahman, 1995; Abd El-Naby
et al., 2000).
Acknowledgements
Our thanks are due to Deutscher Akademischer Austauschdienst (DAAD) for supporting the post-doctoral visit
of the first author at Tübingen University, Germany. We
are grateful to M. El Ahmadi, Egyptian Nuclear materials
Authority, for supporting us with field facilities.
References
Abd El-Naby, H., Frisch, W., 2002. Origin of the Wadi Haimur–Abu
Swayel Gneiss belt, South Eastern Desert, Egypt: petrological and
geochronological constraints. Precambrian Res. 113, 307–322.
Abd El-Naby, H., Frisch, W., in review. Tectono-metamorphic evolution
of the Hafafit Metamorphic Complex (HMC): an example of channel
flow and ductile extrusion during collision. Precambrian Res.
Abd El-Naby, H., Frisch, W., Hegner, E., 2000. Evolution of the PanAfrican Wadi Haimur metamorphic sole, Eastern Desert, Egypt. J.
Metamorph. Geol. 18, 639–651.
Abdel Rahman, A.M., 1995. Tectonic-magmatic stages of shield evolution: the Pan-African belt of northeastern Egypt. Tectonophysics 242,
223–240.
Abdelsalam, M.G., Stern, R.J., 1996. Sutures and shear zones in the
Arabian Nubian shield. J. Afr. Earth Sci. 31, 289–310.
Batchelor, R.A., Bowden, P., 1985. Petrogenetic interpretation of granitoid rock series using multi-cationic parameters. Chem. Geol. 48, 43–
55.
Blasband, B., White, S., Brooijmans, P., De Boorder, H., Visser, W., 2000.
Late Proterozoic extensional collapse in the Arabian–Nubian shield. J.
Geol. Soc. London 157, 615–628.
Brown, M., Solar, G.S., 1998a. Granite ascent and emplacement during
contractional deformation in convergent orogens. J. Struct. Geol. 20,
1365–1393.
Brown, M., Solar, G.S., 1998b. Shear-zone systems and melts: feedback
relations and self-organization in orogenic belts. J. Struct. Geol. 20,
211–227.
Bucher, K., Frey, M., 1994. Petrogenesis of Metamorphic Rocks, sixth ed.
Springer Verlag, Berlin, 318 p.
Clark, D.B., 1992. Granitoid Rocks. Chapman & Hall, New York, 283 p.
Demant, M., 1992. Granites and rhyolites from the northwestern USA:
temporal variation in magmatic processes and relations to tectonic
setting. Trans. R. Soc. Edin., Earth Sci. 83, 51–64.
El Bayoumi, R.M.A., Greiling, R., 1984. Tectonic evolution of a PanAfrican plate margin in southeastern Egypt—a suture zone overprinted by low angle thrusting? In: Klerkx, J., Michot, J. (Eds.),
African Geology, Tervuren, pp. 47–56.
El Ramly, M.F., Greiling, R., Kröner, A., Rashwan, A.A., 1984. On the
tectonic evolution of the Wadi Hafafit area and environs, Eastern
Desert of Egypt. Faculty of Earth Science, University of Jeddah,
Bulletin 6, 113–126.
El Ramly, M.F., Greilling, R.O., Rashwan, A.A., Rasmy, A.H., 1993.
Explanatory note to accompany the geological and structural maps of
Wadi Hafafit area, Eastern Desert of Egypt. Geological Survey of
Egypt. Paper No. 68.
Finger, F., Helmy, H.M., 1998. Composition and total-Pb model ages of
monazite from high-grade paragneisses in the Abu Swayel area,
southern Eastern Desert, Egypt. Mineral. Petrol. 62, 269–289.
185
Fowler, A., El Kalioubi, B., 2002. The Migif-Hafafit gneissic complex of
the Egyptian Eastern Desert: fold interference patterns involving
multiply deformed sheath folds. Tectonophysics 346, 247–275.
Fowler, T.J., Osman, A.F., 2001. Gneiss-cored interference dome associated with two phases of late Pan-African thrusting in the central
Eastern Desert, Egypt. Precambrian Res. 108, 7–43.
Frisch, W., Al Shanti, A., 1977. Ophiolite belts and the collision of island
arcs in the Arabian shield. Tectonophysics 43, 293–306.
Fritz, H., Wallbrecher, E., Khudeir, A.A., Abu El Ela, F., Dallmeyer,
R.D., 1996. Formation of Neoproterozoic metamorphic core complexes during oblique convergence (Eastern Desert, Egypt). J. Afr.
Earth Sci. 23, 311–329.
Fritz, H., Dallmeyer, R.D., Wallbrecher, E., Loizenbauer, J., Hoinkes, G.,
Neumayr, P., Khudeir, A.A., 2002. Neoproterozoic tectonothermal
evolution of the central Eastern Desert of Egypt: a slow velocity
tectonic process of core complex exhumation. J. Afr. Earth Sci. 34,
137–155.
Gerdes, A., Wörner, G., Henk, A., 2000. Post-collisional granite generation and HT-LP metamorphism by radiogenic heating: the Variscan
South Bohemian Batholith. J. Geol. Soc. London 157, 577–587.
Greiling, R.O., Kröner, A., El-Ramly, M.F., Rashwan, A.A., 1988.
Structural relationships between the southern and central parts of the
Eastern Desert of Egypt: details of a fold and thrust belt. In: El-Gaby,
S., Greilling, R.O. (Eds.), The Pan-African belt of Northeast Africa
and Adjacent Areas. Vieweg, Wiesbaden, pp. 121–146.
Grothaus, B.D., Eppler, D., Ehrlich, R., 1979. Depositional environment
and structural implications of the Hammamat Formation, Egypt. Ann.
Geol. Surv. Egypt 9, 564–590.
Hassan, M.A., Hashad, A.H., 1990. Precambrian of Egypt. In: Said, R.
(Ed.), The Geology of Egypt. A.A. Balkema, Rotterdam, Netherlands,
pp. 201–245.
Irvine, T.N., Baragar, W.R., 1971. A guide to the chemical classification of
the common volcanic rocks. Can. J. Earth Sci. 8, 523–548.
Kröner, A., Greiling, R.O., Reischmann, T., Hussin, I.M., Stern, R.J.,
Durr, S., Kruger, J., Zimmer, M., 1987. Pan-African crustal evolution
in the Nubian segment of northeast Africa. In: Kröner, A. (Ed.),
Proterozoic Lithospheric Evolution, Geodynamics Series, vol. 17.
American Geophysical Union, pp. 237–257.
Kröner, A., Reischmann, T., Wust, H., Rashwan, A.A., 1988. Is there any
pre-Pan-African (>950 Ma) basement in the Eastern Desert of Egypt?
In: El-Gaby, S., Greiling, R.O. (Eds.), The Pan-African Belt of
Northeast Africa and Adjacent Areas. Freidr. Viewing and Sohn,
Baunschweig, Wiesbaden, pp. 95–119.
Kröner, A., Todt, W., Hussein, I.M., Mansour, M., Rashwan, A.A., 1992.
Dating of late Proterozoic ophiolites in Egypt and Sudan using the
single grain zircon evaporation technique. Precambrian Res. 59, 15–32.
Kröner, A., Krüger, J., Rashwan, A.A., 1994. Age and tectonic setting of
granitoid gneisses in the Eastern Desert of Egypt and south-west Sinai.
Geol. Rundsch. 83, 502–513.
Loizenbauer, L., Wallbrecher, E., Fritz, H., Neumayr, P., Khudeir, A.A.,
Kloetzli, U., 2001. Structural Geology, single zircon ages and fluid
inclusion studies of the Meatiq metamorphic core complex: implications for Neoproterozoic tectonics in the Eastern Desert of Egypt.
Precambrian Res. 110, 357–383.
Moghazi, A.M., Hassanen, M.A., Mohamed, F.H., Ali, S., 2004. Late
Neoproterozoic strongly peraluminous leucogranites, south Eastern
Desert, Egypt—petrogenesis and geodynamic significance. Mineral.
Petrol. 81, 19–41.
Moore, J.M., 1989. A comparative study of metamorphosed supracrustal
rocks from the western Namaqualand Metamorphic Complex:
Precambrian Research Unit, University of Cape Town, Bulletin 37,
1–370.
Nabelek, P.I., Liu, M., Sirbescu, M., 2001. Thermo-rheological, shear
heating model for leucogranite generation, metamorphism, and
deformation during the Proterozoic Trans-Hudson orogeny, Black
Hills, South Dakota. Tectonophysics 342, 371–388.
O’Connor, J.T., 1965. A classification for quartz-rich igneous rocks based
on feldspar ratios. US Geol. Surv. Prof. Paper B525, 79–84.
186
H. Abd El-Naby, W. Frisch / Journal of African Earth Sciences 45 (2006) 173–186
Pearce, J.A., 1982. Trace element characteristics of lavas from destructive
plate boundaries. In: Thorpe, R.S. (Ed.), Andesites. Wiley, Chichester,
pp. 525–548.
Pearce, J.A., Cann, J.R., 1973. Tectonic setting of basic volcanic rocks
determined using trace element analysis. Earth Planet. Sci. Lett. 19,
290–300.
Pearce, J.A., Gale, G.H., 1977. Identification of ore deposition environment from trace element geochemistry. Spec. Publ. Geol. London 7,
14–24.
Pearce, J.A., Harris, N.B.W., Tindle, A.G., 1984. Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. J.
Petrol. 25, 956–983.
Peccerillo, A., Taylor, S.R., 1976. Geochemistry of Eocene calc-alkaline
volcanic rocks from the Kastamonu area, northern Turkey. Contrib.
Mineral. Petrol. 58, 63–81.
Raith, J.G., Meisel, T., 2001. Metabasites along the amphibolite-granulite
facies transition in the Okiep Copper District, South Africa. S. Afr. J.
Geol. 104, 77–100.
Rashwan, A.A., 1991. Petrography, Geochemistry and petrogenesis of the
Migif-Hafafit gneisses at Hafafit mine area, Egypt. Scientific Series of
the International Bureau, 5, Forschungszentrum Jülich, p. 359.
Reid, D.L., Welke, H.J., Erlank, A.J., Betton, P.J., 1987. Composition,
age and tectonic setting of amphibolites in the central Bushmanland
Group, western Namaqua Province, South Africa. Precambrian Res.
36, 99–126.
Rice, A.H.N., Sadek, M.F., Rashwan, A.A., 1993. Igneous and structural
relations in the Pan-African Hammamat Group, Igla Basin, Egypt. In:
Thorwcihe, U., Schan-delmeier, H. (Eds.), Geoscientific Research in
Northeast Africa, Proceedings of the International Conference on
Geoscientific Research in Northeast Africa. Balkema, Rotterdam, pp.
35–39.
Ries, A.C., Shackelton, R.M., Graham, R.H., Fitches, W.R., 1983. PanAfrican structures, ophiolites and melange in the Eastern Desert of
Egypt: a traverse at 26°N. J. Geol. Soc. London 140, 75–95.
Rollinson, H., 1993. Using Geochemical Data: Evaluation, Presentation,
Interpretation. Longman Group Ltd., England, 352 p.
Roser, B.P., Korsch, R.J., 1986. Determination of tectonic setting of
sandstone-mudstone suite using SiO2 content and K2O/Na2O ratio. J.
Geol. 94, 635–650.
Saunders, A.D., Tarney, J., 1991. Back-arc basins. In: Floyd, P.A. (Ed.),
Oceanic Basalts. Blackie, Glasgow and London, pp. 219–263.
Shervais, J.W., 1982. Ti–V plots and the petrogenesis of modern and
ophiolitic lavas. Earth and Planet. Sci. Lett. 59, 101–118.
Solar, G.S., Pressley, R.A., Brown, M., Tucker, R.D., 1998. Granite
ascent in convergent orogenic belts: testing a model. Geology 26,
711–714.
Stern, R.J., 1994. Neoproterozoic (900–550 Ma) arc assembly and
continental collision in the East African orogen: implications for the
consolidation of Gondwanaland. Annu. Rev. Earth Planet. Sci. 22,
319–351.
Stern, R.J., Hedge, C.E., 1985. Geochronologic and isotopic constraints
on Late Precambrian crustal evolution in the Eastern Desert of Egypt.
Am. J. Sci. 285, 97–127.
Sturchio, N.C., Sultan, M., Batiza, R., 1983. Geology and origin of
Meatiq dome, Egypt: a Precambrian metamorphic core complex.
Geology 11, 72–76.
Sun, S.S., Mcdonough, W.F., 1989. Chemical and isotopic systematic of
oceanic basalts: implications for mantle composition and processes. In:
Magmatism in the Ocean Basins. Geol. Soc. Sp. Pub. 42, 313–345.
Taylor, B., Martinez, F., 2003. Back-arc basin basalt systematics. Earth
Planet. Sci. Lett. 210, 481–497.
Vail, J.R., 1985. Pan-African (Late Precambrian) tectonic terrains
and the reconstruction of the Arabian–Nubian shield. Geology 13,
839–842.
Willis, K.M., Stern, R.J., Clauer, N., 1988. Age and geochemistry of late
Precambrian sediments of the Hammamat series from the Northeastern Desert of Egypt. Precambrian Res. 42, 173–187.
Winchester, J.A., Floyd, P.A., 1977. Geochemical discrimination of
different magma series and their differentiation products using immobile elements. Chem. Geol. 20, 325–343.
Wintsch, R.P., Kvale, C.M., 1994. Differential mobility of elements in
burial diagenesis of siliciclastic rocks. J. Sediment. Res. A64, 349–361.