Nick Roberts

British Geological Survey, NERC Isotope Geosciences Laboratory, Faculty Member

University of Leicester, Geology, Graduate Student

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Research Interests:

U-Pb geochronology.

In-situ analysis of accessory phases using LA-ICP-MS.

Crustal evolution and the supercontinent cycle.

Precambrian tectonics, particularly the evolution of Fennoscandia and Laurentia.

Igneous petrology, particularly in arc settings.

Subduction zone geodynamics and the development of accretionary orogens.

The Caledonian orogeny, and its comparison to the Himalayan orogeny.
Phone: (+44) 1159363037
Address: NERC Isotope Geosciences Laboratory
Kingsley Dunham Centre
Keyworth
Nottingham
NG12 5GG, UK

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Daniel P Le Heron

University of Vienna

Nima Nezafati

Deutsches Bergbau-Museum, Bochum

Ernst Pernicka

Universität Heidelberg

Patrice F Rey

The University of Sydney

Nicolas Flament

University of Wollongong

Nicolas Coltice

École Normale Supérieure

Asha Vijayan

Amrita Vishwa Vidyapeetham

Ioannis Iliopoulos

University of Patras

Hemin Koyi

Uppsala University

Paul E. Olsen

Columbia University

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Papers by Nick Roberts

Crustal-lithospheric structure, geological evolution and continental extrusion of Tibet

Petrogenesis of Sveconorwegian magmatism in southwest Norway; constraints from zircon U-Pb-Hf-O and whole-rock geochemistry

ABSTRACT The Sveconorwegian orogen is traditionally interpreted as a Himalayan-scale continental ... more ABSTRACT The Sveconorwegian orogen is traditionally interpreted as a Himalayan-scale continental collision, and the eastward continuation of the Grenville Province of Laurentia; however, it has recently been proposed that it represents an accretionary orogen without full-scale continental collision (Slagstad et al., in press). We suggest that magmatism is one of the key constraints to differentiate between different types of orogens; thus, detailed investigation of the timing and petrogenesis of the magmatic record is a requirement for better understanding of the Sveconorwegian orogen as a whole. Here, we present new U-Pb geochronology, zircon Hf-O isotope, and whole-rock geochemical data to constrain the petrogenesis of the early -Sveconorwegian Sirdal Magmatic Belt (SMB). The SMB is a batholithic-scale complex of intrusions that intrudes into most of the Rogaland-Hardangervidda Block in southwest Norway. Current age constraints put emplacement between ~1050 to 1020 Ma. New ages from the Suldal region indicate that the onset of SMB magmatism can be put back to 1070 Ma, which is some 30-50 Myrs prior to high-grade metamorphism. Average initial ɛHf signatures range from ~0 to 4; these overlap with later post-Sveconorwegian granites and with early-/pre-Sveconorwegian ferroan (A-type) granites. Average δ18O signatures range from ~5.7 to 8.7, except for one anomalous granite at ~11.6. The Hf-O signatures are compatible with a mixed mantle-crustal source. Crustal sources may include ~1500 Ma Telemarkian or ~1200 Ma juvenile crust. Hf-O bulk-mixing modelling using a 1500 Ma crustal source indicates &gt;50 % mantle input. Although much further mapping and geochronological work is required, granitic magmatism appears to have persisted throughout much of the ~1100 to 900 Ma period that spans the Sveconorwegian orogen. This magmatism is consistently ferroan (i.e. dry); however, the SMB marks a clear transition to magnesian (i.e. wet) magmatism, with a return to ferroan magmatism at &gt;990 Ma. We propose that this transition corresponds to subduction-driven dehydration-melting of the mantle, producing the SMB in a traditional continental volcanic arc environment. A large lower-crustal input is typical of continental arc batholiths (DeCelles et al., 2009). The interpretation of the SMB as a continental arc is key, but not exclusive, to an accretionary model for the Sveconorwegian orogen. The exact timing and setting of syn-/late-Sveconorwegian 990 to 940 Ma ferroan magmatism thus remains a critical link in the understanding of this orogen. Slagstad et al. (in press) A Non-Collisional, Accretionary Sveconorwegian Orogen. Terra Nova, DOI:10.1111/ter.120012 DeCelles et al. (2009) Cyclicity in Cordilleran orogenic systems. Nature Geoscience 2, 251-257.

Mesoproterozoic crustal evolution of southwest Norway

ABSTRACT

Proterozoic crustal growth in SW Fennoscandia

Geochmica et Cosmochimica Acta

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