Abstract
The Gardar Province of south Greenland is defined by the products of alkaline igneous magmatism during the Mesoproterozoic. The most laterally extensive Gardar intrusions are a series of giant dyke complexes best exposed on the Tuttutooq archipelago. We present new field observations and a geological map of north-east Tuttutooq island that provide fresh insights into the temporal evolution of the Younger giant dyke complex and two associated ultramafic lamprophyres. Our data demonstrate that distinctive crystallisation regimes occurred in different sectors of the dyke complex, leading to the formation of marginal gabbros and ovoid pod-like domains displaying lamination, modal layering and/or more evolved differentiates. We infer that at least two pulses of magma contributed to the formation of the Younger giant dyke complex. In addition, the relative ages of two ultramafic lamprophyre diatremes are constrained and attributed to two distinct phases of rifting in the Gardar Province.
Highlights
Determining how magmas intrude and crystallise in the crust using structural data and textural features provides fundamental insights into the processes inherent in the construction of igneous intrusions
This study presents a detailed field analysis of eastern Tuttutooq island, focusing on the sections of the Younger giant dyke complex (YGDC) exposed on the island and two ultramafic lamprophyre intrusions
We provide a summary of field relationships within the YGDC and two ultramafic lamprophyre diatremes in the study area
Summary
Determining how magmas intrude and crystallise in the crust using structural data and textural features provides fundamental insights into the processes inherent in the construction of igneous intrusions. The YGDC contains regions in which igneous layering, foliation and/or differentiated compositions are observed (Upton 1962). This study presents a detailed field analysis of eastern Tuttutooq island, focusing on the sections of the YGDC exposed on the island and two ultramafic lamprophyre intrusions. We use these data to elucidate the structural and crystallisation history of the YGDC magma and associated lamprophyres, and thereby gain insights into the processes that controlled the formation of these spectacular intrusions
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