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Peter Robert. Johnson

Peter Robert. Johnson

B.Sc (Honours Geology), D.Phil

About

60
Publications
64,114
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4,728
Citations
Citations since 2017
11 Research Items
2822 Citations
20172018201920202021202220230200400600
20172018201920202021202220230200400600
20172018201920202021202220230200400600
20172018201920202021202220230200400600
Education
October 1961 - June 1965
Indian Statistical Institute
Field of study
  • Geology
September 1958 - June 1961
University College London
Field of study
  • Geology

Publications

Publications (60)
Conference Paper
Secular variation of 87Sr/86Sr in carbonate strata has been widely used in regional and global chemostratigraphic correlations. Typically, diagenesis results in higher 87Sr/86Sr signals relative to their primary composition due to the alteration by Rb-rich fluids and radiogenic decay of 87Rb to 87Sr. Surprisingly, 87Sr/86Sr values in the Ediacaran...
Article
Secular variation of 87 Sr/ 86 Sr in carbonate strata has been widely used in regional and global chemostratigraphic correlations. Typically, diagenesis results in higher 87 Sr/ 86 Sr signals relative to their primary composition due to the alteration by Rb-rich fluids and the radiogenic decay of 87 Rb to 87 Sr. Surprisingly, the 87 Sr/ 86 Sr value...
Article
Full-text available
The Arabian-Nubian Shield (ANS) is a rapidly emerging world-class province for gold resources mainly in structurally-controlled quartz ± carbonate veins that are best classified as late Neoproterozoic orogenic gold deposits. Gold has been mined in the Eastern Desert of Egypt, in the northwestern part of the ANS, for >6000 years, that is since the t...
Chapter
Full-text available
As the Earth’s best-known example of an active, incipient ocean basin, the Red Sea provides crucial information about continental rifting and the tectonic transition from extended continental crust to seafloor spreading. Study of the Red Sea over the past decades has given many answers, but significant questions remain about how and when it opened...
Article
Full-text available
The southern Midyan terrane is a composite Tonian to Ediacaran tectonostratigraphic crustal block in the northern Arabian Shield that prior to Red Sea opening was contiguous with coeval rocks in the Eastern Desert of Egypt and Sinai. Ion microprobe (sensitive high-resolution ion microprobe [SHRIMP]) dating of 12 rock samples described here and the...
Article
Full-text available
The Wadi Bidah Mineral District of Saudi Arabia contains more than 16 small outcropping strata-bound volcanogenic Cu–Zn–(Pb) ± Au-bearing massive sulphide deposits and associated zones of hydrothermal alteration. Here, we use major and trace element analyses of massive sulphides, gossans, and hydrothermally altered and least altered metamorphosed h...
Article
Full-text available
The Nubian Shield is a large region of juvenile Neoproterozoic rocks that, together with its counterpart in the Arabian Shield, is part of a major accretionary orogen. It originated as late Tonian-Cryogenian island arcs on the site of the Mozambique Ocean formed by breakup of Rodinia. Arc collisions, subsequent magmatism, volcanism, sedimentation,...
Article
Full-text available
The Nubian Shield is a large region of juvenile Neoproterozoic rocks that, together with its counterpart in the Arabian Shield, is part of a major accretionary orogen. It originated as late Tonian-Cryogenian island arcs on the site of the Mozambique Ocean formed by breakup of Rodinia. Arc collisions, subsequent magmatism, volcanism, sedimentation,...
Article
Numerical time-temperature models derived from a 2D network of apatite and zircon (U-Th)/He ages reveal a three-stage thermotectonic history for the central Arabian rift flank (CARF) of the Red Sea Rift (RSR) system. The pre-rift Arabian-Nubian Shield existed as part of a passive Paleo-Tethyan margin until a widespread tectonic event ca. 350 Ma exh...
Article
Full-text available
The Allaqi–Heiani suture is an ~250 km-long ophiolite-associated fold-and-thrust belt in the South Eastern Desert of Egypt. It comprises imbricate thrust sheets of ophiolites (serpentinite, amphibolite, metagabbro, and metabasalt) and island-arc metavolcanic/metasedimentary rocks. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTE...
Conference Paper
The middle Ediacaran Jibalah Group fills a series of small, isolated, and minimally deformed sedimentary basins in the eastern and northern Arabian Shield. These mixed volcanic-siliciclastic-carbonate basins lay along strands of the Najd Fault System, an array of transpressional structures related to lateral escape during the late stages of the Eas...
Article
Full-text available
The Arabian-Nubian Shield (ANS) includes Middle Cryogenian-Ediacaran (790-560 Ma) sedimentary and volcanic terrestrial and shallow-marine successions unconformable on juvenile Cryogenian crust. The oldest were deposited after 780-760 Ma shearing and suturing in the central ANS. Middle Cryogenian basins are associated with ~700 Ma suturing in the no...
Conference Paper
Small, middle to late Ediacaran intermontane basins occur in the northern and eastern Arabian shield. The Jibalah basins are a subset of these basins that are minimally deformed and concentrated along the Najd strike-slip fault system, where they likely originated as pull-apart basins during the late stages of the East African orogeny. Whereas the...
Article
Full-text available
The East African Orogen, extending from southern Israel, Sinai and Jordan in the north to Mozambique and Madagascar in the south, is the world´ s largest Neoproterozoic to Cambrian orogenic complex. It comprises a collage of individual oceanic domains and continental fragments between the Archean Sahara–Congo–Kalahari Cratons in the west and Neopro...
Article
The Ediacaran Jibalah Group comprises volcano-sedimentary successions that filled small fault-bound basins along the NW–SE-trending Najd fault system in the eastern Arabian-Nubian Shield. Like several other Jibalah basins, the Antaq basin contains exquisitely preserved sedimentary structures and felsic tuffs, and hence is an excellent candidate for...
Article
Full-text available
A Technical Report prepared by the Saudi Geological Survey, Jeddah, Kingdom of Saudi Arabia The work on which this report is based was performed in support of Saudi Geological Survey Subproject Subproject-The Eastern Arabian Shield: Window into Supercontinental Assembly at the Dawn of Animal Life. It has been edited and reviewed by staff of the Sau...
Chapter
Full-text available
Arabian–Nubian Shield (ANS), including structural framework, stratigraphy, lithological descriptions and relationships with younger and older units, banded iron formation chemostratigraphy, other characteristics, geochronological constraints, and discussion. The ANS is a broad tract of juvenile continental crust, formed from accreted arc-backarc ba...
Article
Full-text available
During the late Cryogenian–Ediacaran (650–542 Ma), the Arabian–Nubian Shield (ANS) underwent final assembly and accretion to the Saharan Metacraton concurrent with the assembly of eastern and western Gondwana. At the end of the Precambrian it lay at one end of the East African Orogen, with its northern margin (present coordinates) forming a low-rel...
Article
New geochemical, Nd-isotope and U–Pb zircon data from Neoproterozoic volcanic rocks from Wadi Sawawin in northwestern Saudi Arabia provide important constraints on the evolution of the crust in this part of the Arabian–Nubian Shield (ANS). The Ghawjah volcanic rocks range from tholeiitic to calc-alkaline and are metamorphosed to greenschist facies....
Article
Full-text available
Igneous rocks of the Arabian-Nubian Shield (ANS) have lithologic associations (ophiolites, calc-alkaline igneous rocks, immature sediments) and radio-genic isotopic compositions consistent with formation as juvenile continental crust as a result of accreting intraoceanic arc systems during 880 to 630 Ma, with crustal differentiation continuing unti...
Article
Full-text available
The Arabian Plate originated ∼ 25 Ma ago by rifting of NE Africa to form the Gulf of Aden and Red Sea. It is one of the smaller and younger of the Earth's lithospheric plates. The upper part of its crust consists of crystalline Precambrian basement, Phanerozoic sedimentary cover as much as 10 km thick, and Cenozoic flood basalt (harrat). The distri...
Article
Full-text available
The Neoproterozoic Atud diamictite in Wadi Kareim and Wadi Mobarak in the Eastern Desert of Egypt and the Nuwaybah formation in NW Saudi Arabia consist of poorly sorted, polymictic breccia, with clasts up to 1m of granitoid, quartz porphyry, quartzite, basalt, greywacke, marble, arkose, and microconglomerate in fine-grained matrix. Stratigraphic re...
Conference Paper
The Red Sea rift system is a prime example of continental rifting and has contributed significantly to our understanding of the geologic processes that manage the rupture of continental lithosphere. Using a combined geo- and thermochronometric approach, we explore the modes and mechanisms of rift margin development by studying Red Sea rift-related...
Article
Full-text available
The Arabian plate has been converging with Eurasia for 20-30 Ma, currently at 2-3 cm/year. Convergence is manifested differently along strike, with collision and tectonic escape in the west (Anatolia) and subduction of Arabia beneath Eurasia in the east (Iran). The reason for these differences may reflect the greater density of the Arabian lithosph...
Article
Full-text available
We report sedimentologic, geochemical, and zircon U-Pb geochronologic data for the Dhaiqa formation, a 300 m thick carbonate succession (Dhaiqa basin, NW Arabian shield) thought to represent one of Saudi Arabia's youngest Precambrian basement exposures within the Ediacaran age Jibalah Group. The evidence supports that Dhaiqa formation deposition oc...
Article
Lithostratigraphy, which describes the spatial and temporal relationships between rock units, is fundamental to an adequate understanding of geologic history. The structural complexity, great variety of rock types, large range of volcanic, sedimentary, and intrusive environments, and multiplicity of metamorphic events, make the task of lithostratig...
Conference Paper
Improvement in our modeling of continental lithosphere rupturing and rifting dynamics requires an absolute understanding of the temporal and spatial strain distribution throughout an entire rift system. This statement holds especially true for our understanding of Red Sea rift system dynamics. However, critical geologic data used to determine the t...
Article
The Neoproterozoic Ar Rayn terrane is exposed along the eastern margin of the Arabian shield. The terrane is bounded on the west by the Ad Dawadimi terrane across the Al Amar fault zone (AAF), and is nonconformably overlain on the east by Phanerozoic sedimentary rocks. The terrane is composed of a magmatic arc complex and syn- to post-orogenic intr...
Conference Paper
Numerous models exploring the rupturing modes and mechanisms of continental lithosphere are based on geological evidence from the Red Sea/Gulf of Suez rift system. Individually, the Red Sea basin is the prototype for many models of orthogonal continental rifting. Despite being a classic example of continental extension, many temporal and spatial st...
Chapter
Full-text available
Ophiolites of mid-Neoproterozoic age are abundant in the Arabian-Nubian Shield (ANS) of NE Africa and Arabia. The ANS ophiolitic mantle was mostly harzburgitic, containing magnesian olivines and spinels that have compositions consistent with extensive melting. Cumulate ultramafics transition upwards into layered gabbro. Several crystallization sequ...
Article
This chapter describes the lithology, structure, and field relations of selected Arabian shield ophiolites, thereby providing examples of Neoproterozoic ophiolites and illustrating the outcrop characteristics and degrees of dismemberment and structural complexity that may be expected of Neoproterozoic ophiolites elsewhere. Peridotite is mainly expo...
Article
Neoproterozoic plutonic rocks of the Makkah batholith along the northern margin of the Jiddah terrane in western Saudi Arabia record >50 Ma of arc magmatism. Results of the first detailed survey using U-Pb zircon geochronology by SHRIMP-RG and trace-element geochemistry by ICP-MS provide important new constraints on subduction-related magmatism in...
Article
The Bi'r Umq-Nakasib suture zone, 5-65 km wide and over 600 km long, consists of highly deformed ophiolite nappes and metavolcanic, metasedimentary, and intrusive rocks contained in one of the longest ophiolite-decorated shear zones in the Arabian-Nubian Shield. The rocks originated in a variety of juvenile oceanic environments and include assembla...
Article
The development and structure of Neoproterozoic III volcanosedimentary basins in the northeastern part of the Arabian shield record periods of uplift, erosion, extension, subsidence, compression, and strike-slip faulting that postdated the completion of terrane amalgamation in the northern East African orogen (EAO) and predated the initiation of a...
Article
Full-text available
This study combines new field and orbital remote sensing data to determine geologic controls on sulfide mineralization in the Wadi Bidah Mineral District (WBMD) located in the Neoproterozoic (900–550 Ma) Arabian Shield of southwestern Saudi Arabia. The brittle and ductile deformation of these massive sulfide deposits and host rock reflect tectonic...
Article
The Arabian-Nubian Shield forms the suture between East and West Gondwana at the northern end of the East African Orogen (EAO). The older components of the shield include Archaean and Palaeoproterozoic continental crust, and Neoproterozoic (c.870-670 Ma) continental-marginal and juvenile intraoceanic magmatic-arc terranes that accumulated in an oce...
Article
The Hulayfah-Ad Dafinah-Ruwah fault zone is a belt of highly strained rocks that extends in a broad curve across the northeastern Arabian shield. It is a subvertical shear zone, 5–30 km wide and over 600 km long, and is interpreted as a zone of oblique sinistral transpression that forms the suture between the Afif terrane and the Asir-Jiddah-Hijaz-...
Article
Full-text available
The Al Wajh gold district contains small deposits of gold-bearing quartz veins located in sheared and altered Neoproterozoic mafic lavas and volcaniclastic sandstone and siltstone. The veins formed during multiple episodes of deformation and have structual and mineralogic features characteristic of mesothermal, low sulfide, gold-bearing quartz vein...
Article
A compilation of magnetic data acquired during the past three decades for a region in central Saudi Arabia where Precambrian basement is partly exposed on the Arabian shield and partly concealed by overlying Phanerozoic strata, shows a central sector of conspicuous N-S-trending anomalies, a heterogeneous western sector of short-wavelength, high-int...
Article
Low-intensity magnetic and negative gravity anomalies in northern Mississippi, north-western Alabama, and western Tennessee are viewed as being similar to the magnetic and gravity low associated with the Mississippi Valley graben. The anomalies are interpreted as shallow grabens, and it is proposed that the grabens, like the Mississippi Valley grab...
Article
A new compilation of magnetic data for the western conterminous United States and offshore areas provides significant information about crustal units and structures in the region. Features shown on the compilation include a magnetic quiet zone along the coast and two lineaments inland. The magnetic quiet zone correlates with the accretionary prism...
Article
Using the results of recent research, the geotectonic setting of selected mineral occurrences in the Saudi Arabian Late Proterozoic shield south of latitude 21° N is described and an initial metallogenic cycle is presented. The occurrences selected are types common in the region, or are economically significant. They include volcanic-hosted copper—...

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Projects

Projects (2)
Project
This project aims to better constrain the formation and evolution of one the largest regions of Proterozoic juvenile crust on the planet - the northern East African Orogen. This region includes the so-called Arabian-Nubian Shield - that stretches from Sudan and Ethiopia to Saudi Arabia, Egypt and parts of the Levant, but also includes the Omani basement and, arguably, the NW Indian subcontinent. The region largely formed as a series of volcanic arc terranes and were accreted to the Neoproterozoic continents that now form Africa and India. The project is a long-running endeavour including many studies of geochemistry, structural geology, sedimentology and geochronology from throughout the region. It also involves collaboration with many researchers across many countries.
Project
GOLD-BEARING VOLCANOGENIC MASSIVE SULFIDES AND OROGENIC-GOLD DEPOSITS IN THE NUBIAN SHIELD