anorthosite

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anorthosite

[ə′nȯr·thə‚sīt]
(petrology)
A visibly crystalline plutonic rock composed almost entirely of plagioclase feldspar (andesine to anorthite) with minor amounts of pyroxene and olivine.
References in periodicals archive ?
"The silicic features we've found on the Moon are fundamentally different from the more typical basaltic mare and anorthositic highlands," said Timothy Glotch of Stony Brook University, N.Y., lead author of the second Diviner paper.
Mineral variation in anorthositic, troctolitic, and adamellitic rocks of the Barth Island Layered Structure in the Nain Anorthosite Complex, Labrador.
Samples from the Apollo missions revealed that the maria are basaltic lava flows that include an abundance of the dark minerals rich in iron and titanium, whereas the highlands are rich in bright, aluminum-rich anorthositic rocks.
Coughlan (1986) recognized five units in the Staples Mountain Gabbro, designated I to V from inferred bottom to top: I--gabbro, anorthositic gabbro, and olivine gabbro; II--subophitic augite gabbro; III--interlayered norite and anortbosite; IV--unlayered augite gabbro and minor olivine gabbro; V --unlayered gabbronorite, with increased orthopyroxene and no olivine, in contrast to unit IV.
The drilling has intersected stacked packages of both cumulate and intrusive style magnetiteilmenite mineralisation intercalated with gabbroic and anorthositic country rock.
Multispectral data showed that the Inner Rook Mountains are composed of the same anorthositic rocks thought to make up much of the upper crust of the Moon.
A new U-Pb age of 539.6 [+ or -] 1.2 Ma from one of the gabbroic plutons shows that the gabbroic plutons arc co-genetic with the dioritic to granitic plutons, although they show varied ultramafic to anorthositic and dioritic compositions as a result of crystal accumulation.
Much of the core shows extensive alteration but microprobe analyses of fresh samples revealed that the plagioclase in both anorthositic and gabbroic rocks has a fairly uniform andesine composition.
Thus, Vitello is not volcanic but rather was impact-excavated out of the anorthositic crust that formed in the early Moon's magma ocean.
A petrological study of the Lower Coverdale ferrogabbro complex has not been published, but it appears to contain a large component of anorthositic rocks (Boyle and Stirling 1994; Woods 1995; Ascough 1997) that are not present in the Caledonia Mountain Pluton, at least not at the present level of exposure.