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Petrology and tectonic significance of Mesozoic mafic dikes of the coastal New England igneous province, Massachusetts

By
Martin E. Ross
Martin E. Ross
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Published:
January 01, 1992

The northeast-trending composite swarm of Mesozoic mafic dikes in eastern Massachusetts consists of tholeiitic olivine dolerites, transitional-alkalic dolerites, alkaline dolerites, and alkaline lamprophyres. Chemical subtypes thus far identified among the dolerites include dikes relatively high (>9.00 wt%) or low in MgO as well as dikes having relatively low TiO2(<3.00 wt%) and low P2O5 (<1.00 wt%) contents. The low-MgO dolerites also include high-TiO2 and high-P2O5 varieties.

The major and trace element compositions indicate that the Eastern Massachusetts dolerites differ markedly from Eastern North America (ENA) dikes and are a part of the Coastal New England (CNE) igneous province.

Plotting on a variety of chemical-tectonic discriminant diagrams suggests that the dike compositions are compatable with continental rifting. The more alkaline affinity of the composite swarm relative to ENA dolerites and CNE dolerites to the west and south may be a function of the swarm’s more central location on the horst adjacent to the Connecticut rift basin.

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Contents

GSA Special Papers

Eastern North American Mesozoic Magmatism

John H. Puffer
John H. Puffer
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Paul C. Ragland
Paul C. Ragland
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Geological Society of America
Volume
268
ISBN print:
9780813722689
Publication date:
January 01, 1992

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