Pyroxenes and coexisting minerals in the Cheviot granite

Haslam, H. W.

doi:10.1180/minmag.1986.050.358.13

Cited by 4 publications

(1 citation statement)

References 17 publications

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“…However, the phase diagrams also show that early formed pyroxenes will not generally survive into the subsolidus. As temperature falls and a H 2 O increases in the residual melts, these pyroxenes are predicted to react with the melts, to produce hydrous mafic minerals such as biotite and hornblende (e.g., Haslam 1986 ; Clemens and Wall 1988 ).…”

Section: Phase Petrology: Predictions and Physical Proofsmentioning

confidence: 99%

How deceptive are microstructures in granitic rocks? Answers from integrated physical theory, phase equilibrium, and direct observations

Holness

Clemens

Vernon

2018

Contrib Mineral Petrol

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In this contribution, we address the vexed question of the extent to which microstructures in granitic rocks reflect their igneous histories or have been masked by later events. The previous works have tended to address the problem either using theoretical or modelling considerations, or by interpretation of observed microstructures. Here, we use an approach that integrates the theory of microstructural development and the results of experimental phase-equilibrium studies with direct observation of natural examples on a variety of scales. We show that the predictions of the theoretical and experimental approaches agree perfectly with the mesoscopic and microscopic evidence from granitic rocks themselves. Our conclusion is that although, in many cases, granitic rock microstructures have been modified by near-solidus reactions and crystallisation, in the absence of tectonic deformation the fundamental elements of their igneous heritage remain intact. This means that it is perfectly in order to infer aspects of crystallisation sequences, magmatic reactions, and magma flow through careful microstructural observations. Thus, our answer to the question of how deceptive granitic textures are is, in most instances, ‘not very’. However, some undeformed plutons have undergone fluid-driven alteration, and others have been affected by contact metamorphism. Thus, each case should be examined on its own merits.

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Section: Phase Petrology: Predictions and Physical Proofsmentioning

confidence: 99%

How deceptive are microstructures in granitic rocks? Answers from integrated physical theory, phase equilibrium, and direct observations

Holness

Clemens

Vernon

2018

Contrib Mineral Petrol

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Tectonic controls on post-subduction granite genesis and emplacement: The late Caledonian suite of Britain and Ireland

2016

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Rates of magma emplacement commonly vary as a function of tectonic setting. The late Caledonian granites of Britain and Ireland are associated with closure of the Iapetus Ocean and were emplaced into a varying regime of transpression and transtension throughout the Silurian and into the early Devonian. Here we evaluate a new approach for examining how magma volumes vary as a function of tectonic setting. Available radiometric ages from the late Caledonian granites are used to calculate probability density functions (age spectra), with each pluton weighted by outcrop area as a proxy for its volume. These spectra confirm an absence of magmatic activity during Iapetus subduction between c. 455 Ma and 425 Ma and a dominance of post-subduction magmas between c. 425 Ma and 380 Ma. We review possible reasons why, despite the widespread outcrop of the late Caledonian granites, magmatism appears absent during Iapetus subduction. These include shallow angle subduction or extensive erosion and tectonic removal of the arc.In contrast to previous work we find no strong difference in the age or major element chemistry of post-subduction granites across all terranes. We propose a common causal transpression reduced and eventually suppressed magma emplacement.

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The Nature of the Orthopyroxene Isograd in Precambrian High-Grade Terrains

Newton¹

1990

Precambrian Continental Crust and Its Economic Resources

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Pyroxenes and coexisting minerals in the Cheviot granite

Cited by 4 publications

References 17 publications

How deceptive are microstructures in granitic rocks? Answers from integrated physical theory, phase equilibrium, and direct observations

How deceptive are microstructures in granitic rocks? Answers from integrated physical theory, phase equilibrium, and direct observations

Tectonic controls on post-subduction granite genesis and emplacement: The late Caledonian suite of Britain and Ireland

The Nature of the Orthopyroxene Isograd in Precambrian High-Grade Terrains

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