Composite Ordovician lamprophyre (spessartite) intrusions around the Midlands Microcraton in central Britain
- 1 January 1993
- journal article
- research article
- Published by Cambridge University Press (CUP) in Geological Magazine
- Vol. 130 (5) , 657-663
- https://doi.org/10.1017/s0016756800020963
Abstract
Lamprophyre sills and dykes of Ordovician age were emplaced within Cambrian–Lower Ordovician sedimentary rocks around the northern margins of the Midlands Microcraton. The intrusions show internal mineralogical and chemical variations indicating emplacement as multiple intrusions of co-magmatic pulses. The chemical characteristics of the lamprophyre magmas indicate formation by small-degree volatile-rich partial melting of lithospheric mantle enriched and modified by Lower Palaeozoic subduction (Th/Ta 5.3–11.6, La/Ta 29–82.3), together with a contribution from within-plate mantle source (Zr/Yc. 6) and/or mineralogically heterogeneous lithosphere, followed by varying degrees of fractional crystallization during uprise.Keywords
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