Plutonic and Volcanic Equivalents of Lamprophyres
As already shown (Section 3.1), lamprophyres are overwhelmingly hypabyssal, mediumgrained intrusions. Although LL commonly exist as volcanic rocks, and AL and CAL do so rarely, KlL and UML almost never do (Section 3.1.7). Again, although relatively coarsegrained (e.g. pegmatoidal) segregations do exist in some dykes (e.g. Macdonald et a1.1986), no example of a true lamprophyre ‘pluton’ has ever been identified. Because most writers can see no intrinsic reason for this (R.H.Mitchell 1986, p.43 found the absence of ‘plutonic kimberlite’ particularly strange), this raises the question of whether other named plutonic or volcanic rock-types might be equivalent to lamprophyres. The old suggestion that LL are simply volcanic lamprophyres (Section 1.3.1) can be dismissed — they are merely one type of lamprophyre — but other suggestions deserve more careful attention.
KeywordsGabbroic Rock Amphibole Composition Hornblende Gabbro Ultramafic Lamprophyre Shoshonitic Rock
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