02516nas a2200181   4500008004100000245014700041210006900188300001400257490000800271520180300279100002502082700001602107700002202123700002102145700001502166700001802181856013502199       2017                        eng d00aLyon Mountain ferroan leucogranite suite: Magmatic response to extensional thinning of overthickened crust in the core of the Grenville orogen0 aLyon Mountain ferroan leucogranite suite Magmatic response to ex  a1472-14880 v1293 a<section class="abstract">
<p>Evidence is presented for the crystallization age (ca. 1066−1033 Ma) and origin of the Lyon Mountain Granite (formerly Lyon Mountain Gneiss), a widespread magnetite-bearing leucogranitic igneous suite in the Adirondack Highlands. Recent reinterpretations of U-Pb zircon results have led some to propose that the Lyon Mountain Granite was intruded synchronously with the Shawinigan anorthosite-mangerite-charnockite-granite (AMCG) suite at ca. 1165−1145 Ma. However, this interpretation conflicts with the recognized chronology of the region based on field and analytical studies, which have established a late to postkinematic Ottawan crystallization age (ca. 1050 Ma). Herein, we show that the older ages reported are a consequence of zircon inheritance; we summarize existing and provide new U-Pb zircon data expanding the recognized extent of the Lyon Mountain Granite; and we review long-recognized field relationships and temporal associations among structures within the region and southern Grenville Province. Field relations include a spatial, and likely temporal, link with iron oxide−apatite deposits, gabbroic and amphibolite bodies, and association with late extensional faults and hydrothermal alteration. The variable fabric of the Lyon Mountain Granite is a consequence of magmatic/intrusive processes, proximity to synintrusive structures, and timing of intrusion relative to deformation during an ∼30 m.y. period. The Lyon Mountain Granite formed during late Ottawan anatexis related to gravitational collapse of overthickened crust. Its anhydrous ferroan nature, zircon xenocryst population, and association with magnetite-apatite deposits can be explained by partial melting of Shawinigan-aged, AMCG-dominated lower crust.</p>
</section>
1 aChiarenzelli, J., R.1 aSelleck, B.1 aLupulescu, M., V.1 aBickford, M., E.1 aValley, P.1 aMcLelland, L.  uhttps://pubs.geoscienceworld.org/gsabulletin/article/doi/10.1130/B31697.1/208117/lyon-mountain-ferroan-leucogranite-suite-magmatic