Geochronology and geochemistry of Neoproterozoic Hamamid metavolcanics hosting largest volcanogenic massive sulfide deposits in Eastern Desert of Egypt: Implications for petrogenesis and tectonic evolution

doi:10.1016/j.precamres.2020.105751

Precambrian Research

Volume 344, 15 July 2020, 105751

https://doi.org/10.1016/j.precamres.2020.105751 Get rights and content

Highlights

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Felsic volcanic rocks from the Younger Hamamid group were emplaced at ~695 Ma.
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Partial melting of a contaminated mantle source aided pre-Neoproterozoic zircon recycling.
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Younger Hamamid lavas typically developed in a back-arc basin environment under low pressure and low oxygen fugacity conditions.

Abstract

The Gebel Abu Hamamid area forms the middle part of Shadli Metavolcanics Belt of the South Eastern Desert, which hosts the largest volcanogenic massive sulfide deposits in Egypt. The host-rock succession belongs to the Younger Hamamid Metavolcanics (YHM) group, consisting of mafic and felsic lavas with variable volcaniclastics. Although several studies have attempted to clarify the crustal evolution of the Neoproterozoic basement rocks of the South Eastern Desert, researchers have yet to develop a deep understanding of the petrogenesis, tectonic setting, and ages of these host rocks. In the current study, we newly report whole-rock geochemistry, mineral chemistry, and in-situ U–Pb zircon dating from basaltic to rhyolitic rocks of the YHM group to describe their magmatic evolution. Results indicate that the mafic rocks are characterized by tholeiitic affinity and arc-like geochemical signatures with significantly enriched large-ion lithophile elements and depleted high field strength elements. The parental magma was likely generated by partial melting (~10–15%) of a spinel-lherzolite source mantle that was metasomatized by fluids from a former subduction event, followed by magma ascent under low pressure and low oxygen fugacity conditions. The felsic lavas (~695 Ma) are characterized by subduction-related geochemical characteristics with significant enrichments in Zr, Hf, and Sm. They formed from lithosphere-derived magma enriched by melts from the ancient subducted slab, and later experienced an assimilation-fractional crystallization (AFC) process. The YHM group was formed under extensional geodynamic conditions (back-arc basin setting). The zircon grains display hydrothermal overgrowth at the rims, most likely due to regional metamorphic and hydrothermal changes. This characteristic is likely the effect of hydrothermal fluids associated with the Jurassic-Cretaceous tectonothermal event in the South Eastern Desert.

Introduction

The Arabian-Nubian Shield (ANS) covers an area of about 3 × 10⁶ km² over most of NE Africa and the Arabian Peninsula (Fig. 1). Hundreds of metals (e.g., Au, Ag, Cu, Pb, Zn) occur within it, and there is substantial evidence of a 5500-year history of gold mining (Johnson et al., 2017, Klemm et al., 2001). The upper crust of the ANS represents a collage of well-identified continental and intra-oceanic arcs with immature sediments embedded at the end of the Neoproterozoic era (Hargrove et al., 2006b, Stern, 1994). The Eastern Desert in Egypt forms the northwestern end of the ANS. The Neoproterozoic volcanic-sedimentary successions in the Eastern Desert can be classified into a late Tonian-Cryogenian island arc association and an Ediacaran post-collision Dokhan Volcanics-Hammamat sediments (El Gaby, 1990). Late Proterozoic island arcs form a significant group within the basement complex of Egypt (Stern, 1981), associated with both volcanogenic massive sulfide and banded iron formation. Stern and Hedge (1985) subdivided the Eastern Desert into three basement provinces (i.e., northern, central, and southern) based on their distinctive lithologies (Fig. 1). The South Eastern Desert is characterized by the occurrence of several polymetallic sulfide mineralizations (e.g., Um Samiuki, Hilgit, Maaqal, Egat, El Atshan, Derhib, and Abu Gurdi; Fig. 2) which identified during mining and prospecting (Hussein, 1990).

The study area (the Gebel Abu Hamamid area) is located in the southern part of the Eastern Desert (Fig. 2) and is predominantly covered by island arcs belonging to the Shadli Metavolcanics Belt (SMB). The SMB extends for ~ 80 km with an average width of 25 km and a thickness of >10 km (Shukri and Mansour, 1980, Stern et al., 1991). It is a massive pile of cyclic, submarine, and calc-alkaline to tholeiitic volcanic flows and volcaniclastics (Shadli metavolcanics) associated with immature sediments (Shadli metasediments) (Hafez and Shalaby, 1983, Searle et al., 1978). The Shadli metavolcanics are stratigraphically divided into five major volcanic units: the Marasan Metavolcanics (~1.6 km thick); Huluz Metavolcanics (~3.5 km thick); Burrad Metavolcanics (~2.8 km thick); Older Um Samiuki-Metavolcanics (avg. thickness ~ 1 km); and Younger Hamamid Metavolcanics (avg. thickness ~ 1.6–2 km) (Shukri and Mansour, 1980). The study area covers by the Older Um Samiuki Metavolcanics group and the Younger Hamamid Metavolcanics (YHM) group, which overlays the former. This study focused on the YHM group (cycle I; Fig. 2b and 3), which hosts the largest volcanogenic massive sulfide deposits in Egypt (i.e., the Um Samiuki prospect).

Despite recent progress in understanding the evolution of the Eastern Desert, the tectonic setting and petrogenesis of the SMB remain poorly understood. Many authors described the area as an island arc based on major element geochemistry and the presence of certain Zn–Cu–Ag sulfide ores (e.g., Hafez and Shalaby, 1983, Khudeir et al., 1988, Shukri and Mansour, 1980). Alternatively, Stern et al. (1991) described the area as a high volcanicity continental rift based on their geological and geochemical findings. Accordingly, they mentioned that this rift was analogous with the modern Rio Grande Rift (North American Craton) or the Afar Triangle (part of the East African Rift). The lack of geochronological studies on the South Eastern Desert, particularly the SMB, has led significant conjecture concerning the timing of the SMB formation. This study reports, for the first time, zircon U-Pb age dating results, new whole-rock geochemical and mineral chemistry data for the cycle I lavas of YHM group to constrain the tectonic setting, and area petrogenesis to better understand the geodynamic development of the SMB. The results fill a significant gap in knowledge regarding the Precambrian geochronology of the South Eastern Desert and promote a complete understanding of the magmatic evolution of the study area.

Section snippets

Regional geology

The Neoproterozoic era encompasses a protracted orogenic cycle called the “Pan-African orogeny” (~950–450 Ma; Kröner, 1984), the larger collisional belt on this cycle is known as the East African Orogen (6000 km length; Kusky et al., 2003, Stern, 1994). The Proterozoic supercontinent “Rodinia” was formed between ~1.3 and 0.9 Ga (Li et al., 2008) and began to break-up at either ~900–850 Ma (Stern, 1994) or ~870–800 Ma (Bogdanova et al., 2009, Stern and Johnson, 2010). The break-up was initiated

Field campaign and samples collection

We collected >100 representative samples distributed over the Gebel Abu Hamamid area. The sample locations were highly dependent on the availability of outcrops. Twenty-two polished thin sections were prepared for carrying out a systematic petrographic description. Based on the detailed microscopic investigation, twelve fresh samples were selected for whole rock chemical analysis, among which four samples were selected for zircon age dating.

LA-ICP-MS zircon U-Pb isotopes

Zircons were separated from four samples (EG-1, EG-5,

Zircon U-Pb geochronology

Zircon U–Pb isotope data of analyzed zircons for four samples are listed in Supplementary Data Table (SDT) I. The CL images and zircon U–Pb concordia diagrams are shown in Fig. 6, Fig. 7. Appropriate geological ages were obtained on the basis of acceptable results from a probability density plot, tight filter of concordant ages and mean age calculation (i.e., a probability of fit close to 1) for each sample. The morphology of zircon grains is summarized in SDT II. Also, the zircon

Age of the Younger Hamamid Metavolcanics group

Geochronological and isotopic studies on South Eastern Desert are limited and few reliable constraints have been determined for the SMB. From our LA-ICP-MS zircon U–Pb isotope data, mafic lavas yielded a concordia age of 751 ± 12 Ma for basalt and 739 ± 6.5 Ma for andesite, while felsic lavas displayed a concordia age of 695 ± 9.1 Ma for dacite and 695 ± 6.1 Ma for rhyolite. These ages likely reflect the timing of two volcanic pulses that occurred at ~ 750 and 695 Ma. Conversely, the lack of

Conclusions

Based on analyses and discussion, we conclude that a back-arc basin environment seems to be the most likely extensional tectonic regime for the eruption of YHM magmatic suites. The mafic volcanics represent the earliest magmatic episode and are related to the opening of back-arc basin. The felsic lavas (~695 Ma) indicate a later volcanic event that may be associated with base-metal sulfide mineralization. The compositions of host magma produced from the mantle source change at various times,

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This study is financially supported by the National Key R&D Program of China (No. 2016YFC0600404) and National Natural Science Foundation of China (41673040). We are indebted to Mr. Mohamed Gamal (Suez Canal University, Egypt) for field assistance and photomicrographs. We are also grateful to the Geology Department (Suez Canal University, Egypt) for providing logistical support during the fieldwork. The authors wish to thank Mr. Hu Xiaowen, Mr. Qi Hou and Miss. Yixin Liu (USTC, China) for their

References (152)

M. Abdeen et al.
Thrusting and multiple folding in the Neoproterozoic Pan-African basement of Wadi Hodein area, south Eastern Desert, Egypt
J. Afr. Earth Sci.
(2008)
M.G. Abdelsalam et al.
Sutures and shear zones in the Arabian-Nubian Shield
J. Afr. Earth Sc.
(1996)
M.M. Abu El-Enen et al.
P-T path and timing of crustal thickening during amalgamation of East and West Gondwana: A case study from the Hafafit Metamorphic Complex, Eastern Desert of Egypt
Lithos
(2016)
E. Aldanmaz et al.
Petrogenetic evolution of late Cenozoic, post-collision volcanism in western Anatolia, Turkey
J. Volcanol. Geoth. Res.
(2000)
K.A. Ali et al.
Age constraints on the formation and emplacement of Neoproterozoic ophiolites along the Allaqi-Heiani Suture, South Eastern Desert of Egypt
Gondwana Res.
(2010)
K.A. Ali et al.
U-Pb zircon geochronology and Hf–Nd isotopic systematics of Wadi Beitan granitoid gneisses, South Eastern Desert
Egypt. Gondwana Research
(2015)
K.A. Ali et al.
Geochemistry, Nd isotopes and U-Pb SHRIMP zircon dating of Neoproterozoic volcanic rocks from the Central Eastern Desert of Egypt: New insights into the ~750Ma crust-forming event
Precambr. Res.
(2009)
K.A. Ali et al.
Geochemical, U-Pb zircon, and Nd isotope investigations of the Neoproterozoic Ghawjah Metavolcanic rocks, Northwestern Saudi Arabia
Lithos
(2010)
S. Ali et al.
Alkali basalts from Burgenland, Austria: petrological constraints on the origin of the westernmost magmatism in the Carpathian-Pannonian Region
Lithos
(2011)
C.J. Allegre et al.
Quantitative models of trace element behavior in magmatic processes
Earth Planet. Sci. Lett.
(1978)

T. Andersen

Correction of common lead in U-Pb analyses that do not report ²⁰⁴Pb

Chem. Geol.

(2002)

K.I. Aoki et al.

Pyroxenes from lherzolite inclusions of Itinome-gata, Japan

Lithos

(1973)

E.H. Bailey et al.

Uranium and Thorium Solubilities in Subduction Zone Fluids

Earth Planet. Sci. Lett.

(1994)

L. Beccaluva et al.

Clinopyroxene Composition of Ophiolite Basalts as Petrogenetic Indicator

Chem. Geol.

(1989)

B. Bonin

Do coeval mafic and felsic magmas in post-collisional to within-plate regimes necessarily imply two contrasting, mantle and crustal, sources? A review

Lithos

(2004)

W.V. Boynton

Cosmochemistry of the rare earth elements: meteorite studies. Developments in geochemistry

Elsevier

(1984)

T.L. Carley et al.

Iceland is not a magmatic analog for the Hadean: Evidence from the zircon record

Earth Planet. Sci. Lett.

(2014)

A.J. Cavosie et al.

Correlated microanalysis of zircon: Trace element, δ¹⁸O, and U-Th–Pb isotopic constraints on the igneous origin of complex> 3900 Ma detrital grains

Geochim. Cosmochim. Acta

(2006)

K.C. Condie

Mafic crustal xenoliths and the origin of the lower continental crust

Lithos

(1999)

G.M. Cox et al.

Late Neoproterozoic adakitic magmatism of the eastern Arabian Nubian Shield

Geosci. Front.

(2019)

C. Deniel

Geochemical and isotopic (Sr, Nd, Pb) evidence for plume–lithosphere interactions in the genesis of Grande Comore magmas (Indian Ocean)

Chem. Geol.

(1998)

M.Z. El-Bialy et al.

Zircon trace element geochemical constraints on the evolution of the Ediacaran (600–614Ma) post-collisional Dokhan Volcanics and Younger Granites of SE Sinai, NE Arabian-Nubian Shield

Chem. Geol.

(2013)

M.K. El-Shafei et al.

Structural and tectonic evolution of the Neoproterozoic Feiran-Solaf metamorphic belt, Sinai Peninsula: implications for the closure of the Mozambique Ocean

Precambr. Res.

(2003)

E.S.A. El Gammal et al.

Applications of geomorphology, tectonics, geology and geophysical interpretation of, East Kom Ombo depression, Egypt, using Landsat images

Egypt. J. Rem. Sens. Space Sci.

(2013)

W.M. Fan et al.

Late Mesozoic volcanism in the northern Huaiyang tectono-magmatic belt, central China: partial melts from a lithospheric mantle with subducted continental crust relicts beneath the Dabie orogen?

Chem. Geol.

(2004)

P. Floyd et al.

Geochemistry and tectonic environment of basaltic rocks from the Misis ophiolitic mélange, south Turkey

Chem. Geol.

(1991)

H. Fritz et al.

Orogen styles in the East African Orogen: A review of the Neoproterozoic to Cambrian tectonic evolution

J. Afr. Earth Sc.

(2013)

B. Fu et al.

Distinguishing magmatic zircon from hydrothermal zircon: a case study from the Gidginbung high-sulphidation Au–Ag–(Cu) deposit, SE Australia

Chem. Geol.

(2009)

T. Geisler et al.

Improved U-Th–total Pb dating of zircons by electron microprobe using a simple new background modeling procedure and Ca as a chemical criterion of fluid-induced U-Th-Pb discordance in zircon

Chem. Geol.

(2000)

U.S. Hargrove et al.

How juvenile is the Arabian-Nubian Shield? Evidence from Nd isotopes and pre-Neoproterozoic inherited zircon in the Bi'r Umq suture zone, Saudi Arabia

Earth Planet. Sci. Lett.

(2006)

C. Hawkesworth et al.

Elemental U and Th variations in island arc rocks: implications for U-series isotopes

Chem. Geol.

(1997)

H.M. Helmy et al.

Sm–Nd and Rb–Sr isotope geochemistry and petrology of Abu Hamamid intrusion, Eastern Desert, Egypt: an Alaskan-type complex in a backarc setting

Precambr. Res.

(2015)

P.W. Hoskin

Trace-element composition of hydrothermal zircon and the alteration of Hadean zircon from the Jack Hills, Australia

Geochim. Cosmochim. Acta

(2005)

P. Kepezhinskas et al.

Trace element and Sr-Nd-Pb isotopic constraints on a three-component model of Kamchatka Arc petrogenesis

Geochim. Cosmochim. Acta

(1997)

D. Klemm et al.

Gold of the Pharaohs – 6000 years of gold mining in Egypt and Nubia

J. Afr. Earth Sc.

(2001)

A. Kröner et al.

AFRICA | Pan-African Orogeny

A. Kröner et al.

Dating of late Proterozoic ophiolites in Egypt and the Sudan using the single grain zircon evaporation technique

Precambr. Res.

(1992)

T.M. Kusky et al.

Evolution of the East African and related orogens, and the assembly of Gondwana

Precambr. Res.

(2003)

J. Leterrier et al.

Clinopyroxene composition as a method of identification of the magmatic affinities of paleo-volcanic series

Earth Planet. Sci. Lett.

(1982)

Z.-X. Li et al.

Assembly, configuration, and break-up history of Rodinia: a synthesis

Precambr. Res.

(2008)

J.-P. Liégeois et al.

Sr–Nd isotopes and geochemistry of granite-gneiss complexes from the Meatiq and Hafafit domes, Eastern Desert, Egypt: No evidence for pre-Neoproterozoic crust

J. Afr. Earth Sc.

(2010)

A.M. Lundmark et al.

Repeated magmatic pulses in the East African Orogen in the Eastern Desert, Egypt: An old idea supported by new evidence

Gondwana Res.

(2012)

H. Martin

Adakitic magmas: modern analogues of Archaean granitoids

Lithos

(1999)

M. Meschede

A method of discriminating between different types of mid-ocean ridge basalts and continental tholeiites with the Nb-Zr-Y diagram

Chem. Geol.

(1986)

N. Morag et al.

Crustal evolution and recycling in the northern Arabian-Nubian Shield: New perspectives from zircon Lu–Hf and U-Pb systematics

Precambr. Res.

(2011)

Ş. Özdamar

Geochemistry and geochronology of late Mesozoic volcanic rocks in the northern part of the Eastern Pontide Orogenic Belt (NE Turkey): Implications for the closure of the Neo-Tethys Ocean

Lithos

(2016)

J.A. Pearce

Geochemical fingerprinting of oceanic basalts with applications to ophiolite classification and the search for Archean oceanic crust

Lithos

(2008)

A.G. Abd-Allah

Two genetic types of volcanic-hosted massive sulfide mineralizations from the Eastern Desert of Egypt

Arabian J. Geosci.

(2012)

M.A. Abu El-Rus et al.

Bimodal zircon ages from Natash volcanics (southeast Egypt) and the link between eruption mechanisms and Late Cretaceous tectonics

Arabian J. Geosci.

(2019)

R.D. Aines et al.

Relationships between Radiation-Damage and Trace Water in Zircon, Quartz, and Topaz

Am. Mineral.

(1986)

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Citation Excerpt :
Ali et al. (2009) reported SHRIMP zircon U-Pb ages ranging from 769 ± 29 Ma to 730 ± 22 Ma for arc-related volcanic rocks from W. Kareim in the CED. In the SED, U-Pb zircon ages for the volcanic rocks include the W. Shilman (733 ± 7 Ma; Ali et al., 2010b) and the El-Shadli volcanic province (695 ± 6 Ma; Faisal et al., 2020 and ∼ 700 Ma; Gamaleldien et al., 2021b). Sr and Nd isotopic data for the Egyptian Nubian Shield magmatic episodes are compiled in Supplementary Tables.
The tectonic evolution of the Neoproterozoic Arabian-Nubian Shield (ANS) is widely held as an example of crustal growth processes. The ANS consists of continental crust formed prior to and during the collision between East and West Gondwana. In this contribution, we compile, review, and synthesize published whole-rock Nd-Sr isotopic and zircon U-Pb-Hf-O-trace element data for granitoids and volcanic rocks from the ANS, with a focus on the Egyptian Nubian Shield which constitutes the north-western part of the ANS. These data indicate that the tectonic evolution of the Egyptian Nubian Shield was dominated by episodes of both crustal formation and reworking during the ∼800–650 Ma time interval. Magmatism within that interval is characterized by high ɛNd_(t) (+6.5 to +8.5), low initial ⁸⁷Sr/⁸⁶Sr (∼0.702), high zircon εHf_(t) (+9 to +13), and mantle-like zircon δ¹⁸O values (∼ + 5‰), implying magma extraction from a depleted mantle source and/or reworking of juvenile crust. By contrast, Nd-Sr-Hf-O isotopic data for ∼650–550 Ma igneous rocks indicate this region experienced crustal recycling/reworking during continental collision related to the formation of Gondwana. The Egyptian Nubian Shield crust evolved through three major episodes of magmatism with peaks at ∼730 Ma, ∼700 Ma, and ∼ 600 Ma and underwent a fundamental transition in tectonic and magmatic styles around ∼650 Ma, from pre-continental collision (∼800–650 Ma, involving arc magmatism, accretion of oceanic lithosphere and oceanic arcs, and reworking of juvenile crust) to syn- and post-collision (∼650–550 Ma). The central and western terranes of the Arabian Shield share a similar south to north magmatic age progression, whereas the eastern and southern Arabian Shield has Neoproterozoic magmatism dominated by post ca. 650 Ma events associated with the final assembly of Gondwana. Collectively, the geochronological and isotopic data suggest that magmatism was protracted and occurred in discrete episodes of crustal reworking, that transformed previously accreted juvenile crust into the continental crust of the Egyptian Nubian Shield and the ANS in general.
Petrogenesis and tectonic implications of Tonian island arc volcanic rocks from the Gabgaba Terrane in the Arabian-Nubian Shield (NE Sudan)
2022, Journal of Asian Earth Sciences
Citation Excerpt :
The composition of arc magmas varies in space and time with the maturity of arc system; therefore, it is necessary to know the different progressive development stages of the intra-oceanic island arcs (e.g., Wilson, 1989; Safonova et al., 2017). The early stage (immature and short, 5–10 Ma) of an intra-oceanic arc is characterized by the formations of tholeiitic basalt and basaltic andesite in thin arc crust, while the later stage (mature) is distinguished by forming of calc-alkaline to shoshonitic andesitic and felsic lavas in a relatively thick arc crust (Faisal et al., 2020). The origin and evolution of the island arc volcanic rocks in the NE Sudan are a matter of debate.
An integrated study of zircon U-Pb geochronology and geochemistry together with Lu-Hf isotopes, has been carried out on basaltic andesite and andesite from the Haweit area (Gabgaba Terrane, NE Sudan) to indicate their magmatic evolution. In-situ U-Pb zircon dating yielded a weighted mean age of 752 ± 11 Ma for andesite and 773 ± 17 Ma for basaltic andesite, suggesting they were generated during Tonian. The Haweit volcanic rocks are generally sub-alkaline and tholeiitic lavas. They are characterized by low Mg# (29–44), low TiO₂ (0.70–1.41 wt%), and relatively high Al₂O₃ (14.60–18.30 wt%) indicating that they are not a primitive melt. The nearly flat REEs pattern of the basaltic andesites indicate that they were formed in an immature island arc setting. While andesites are slightly enriched in LREE and LILEs, suggesting more mature island arc setting. The calculated Hf-T_DM^C (0.87–1.6 Ga) ages of zircons preclude the possibility of interaction of the parental magma with a pre-Neoproterozoic crustal source. The low (La/Yb)_N (0.73–9.56) and high Zr/Nb (33–62) ratios, along with positive εHf(t) values (+1.33 to +12.5) indicate that the Haweit volcanic rocks were originated from depleted mantle with little crustal contamination. The geochemical data suggest that the parent magma of the Haweit volcanic rocks could be formed by low degree partial melting of spinel‐bearing Iherzolite depleted mantle metasomatized by slab‐derived fluids. The Haweit andesitic melts were later subjected to crustal assimilation before the final eruption of lavas during two stages of arc evolution.

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Geochronology and geochemistry of Neoproterozoic Hamamid metavolcanics hosting largest volcanogenic massive sulfide deposits in Eastern Desert of Egypt: Implications for petrogenesis and tectonic evolution

Highlights

Abstract

Introduction

Section snippets

Regional geology

Field campaign and samples collection

LA-ICP-MS zircon U-Pb isotopes

Zircon U-Pb geochronology

Age of the Younger Hamamid Metavolcanics group

Conclusions

Declaration of Competing Interest

Acknowledgments

J. Afr. Earth Sci.

J. Afr. Earth Sc.

Lithos

J. Volcanol. Geoth. Res.

Gondwana Res.

Egypt. Gondwana Research

Precambr. Res.

Lithos

Lithos

Earth Planet. Sci. Lett.

Chem. Geol.

Lithos

Earth Planet. Sci. Lett.

Chem. Geol.

Lithos

Elsevier

Earth Planet. Sci. Lett.

Geochim. Cosmochim. Acta

Lithos

Geosci. Front.

Chem. Geol.

Chem. Geol.

Precambr. Res.

Egypt. J. Rem. Sens. Space Sci.

Chem. Geol.

Chem. Geol.

J. Afr. Earth Sc.

Chem. Geol.

Chem. Geol.

Earth Planet. Sci. Lett.

Chem. Geol.

Precambr. Res.

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

J. Afr. Earth Sc.

Precambr. Res.

Precambr. Res.

Earth Planet. Sci. Lett.

Precambr. Res.

J. Afr. Earth Sc.

Gondwana Res.

Lithos

Chem. Geol.

Precambr. Res.

Lithos

Lithos

Two genetic types of volcanic-hosted massive sulfide mineralizations from the Eastern Desert of Egypt

Arabian J. Geosci.

Bimodal zircon ages from Natash volcanics (southeast Egypt) and the link between eruption mechanisms and Late Cretaceous tectonics

Arabian J. Geosci.

Relationships between Radiation-Damage and Trace Water in Zircon, Quartz, and Topaz

Am. Mineral.