02814nas a2200289   4500008004100000245007400041210006900115300000800184490000600192520195700198653002502155653002902180653003102209653001502240653002302255653002002278653002002298653001102318653003202329653001502361100002602376700002202402700002102424700001802445700001802463856004302481       2019                        eng d00aAge and Origin of Silicocarbonate Pegmatites of the Adirondack Region0 aAge and Origin of Silicocarbonate Pegmatites of the Adirondack R  a5080 v93 a<div class="art-abstract in-tab hypothesis_container">Silicocarbonate pegmatites from the southern Grenville Province have provided exceptionally large crystal specimens for more than a century. Their mineral parageneses include euhedral calc–silicate minerals such as amphibole, clinopyroxene, and scapolite within a calcite matrix. Crystals can reach a meter or more in long dimension. Minor and locally abundant phases reflect local bedrock compositions and include albite, apatite, perthitic microcline, phlogopite, zircon, tourmaline, titanite, danburite, uraninite, sulfides, and many other minerals. Across the Adirondack Region, individual exposures are of limited aerial extent (&lt;10,000 m<sup>2</sup>), crosscut metasedimentary rocks, especially calc–silicate gneisses and marbles, are undeformed and are spatially and temporally associated with granitic pegmatites. Zircon U–Pb results include both Shawinigan (circa 1165 Ma) and Ottawan (circa 1050 Ma) intrusion ages, separated by the Carthage-Colton shear zone. Those of Shawinigan age (Lowlands) correspond with the timing of voluminous A-type granitic magmatism, whereas Ottawan ages (Highlands) are temporally related to orogenic collapse, voluminous leucogranite and granitic pegmatite intrusion, iron and garnet ore development, and pervasive localized hydrothermal alteration. Inherited zircon, where present, reflects the broad range of igneous and detrital ages of surrounding rocks. Carbon and oxygen isotopic ratios from calcite plot within a restricted field away from igneous carbonatite values to those of typical sedimentary carbonates and local marbles. Collectively, these exposures represent a continuum between vein-dyke and skarn occurrences involving the anatexis of metasedimentary country rocks. Those of Ottawan age can be tied to movement and fluid flow along structures accommodating orogenic collapse, particularly the Carthage-Colton shear zone.</div>
10aAdirondack Mountains10acalc–silicate minerals10aCarthage-Colton shear zone10aexhumation10aGrenville Province10aOttawan Orogeny10asilicocarbonate10askarns10aU–Pb zircon geochronology10avein-dykes1 aChiarenzelli, Jeffrey1 aLupulescu, M., V.1 aRobinson, George1 aBailey, David1 aSinger, Jared  uhttps://www.mdpi.com/2075-163X/9/9/50802367nas a2200241   4500008004100000245011500041210006900156260001200225300000800237490000600245520158200251653002501833653001701858653002301875653004701898653002601945653003001971100002602001700002202027700001602049700001802065856004202083       2018                        eng d00aAge and Origin of the Mesoproterozoic Iron Oxide-Apatite Mineralization, Cheever Mine, Eastern Adirondacks, NY0 aAge and Origin of the Mesoproterozoic Iron OxideApatite Minerali  c09/2018  a3450 v83 a<p>At the Cheever Mine, located in the eastern Adirondack Mountains of the Mesoproterozoic Grenville Province, iron oxide-apatite ore forms a narrow (&lt;3 m) sheet cross-cutting metasomatically altered, magnetite-bearing, albite-rich leucogranitic host rocks of the Lyon Mountain Granite suite. Zircon from the ore and five samples of country rock were dated by Laser Ablation-Multi-Collector-Inductively Coupled Plasma-Mass Spectrometry. The ore yielded a Concordia age of 1033.6 ± 2.9 Ma while three samples of host rock yielded ages of 1036.3 ± 2.9, 1040 ± 11, and 1043.9 ± 4.1 Ma. Two additional samples of host rock yielded older ages of 1059.6 ± 3.4 and 1066.0 ± 6.3 Ma and contain zircon xenocrystic cores with <sup>207</sup>Pb/<sup>206</sup>Pb ages up to 1242 Ma. The zircons analyzed, including those separated from the ore, have characteristics typically associated with an igneous origin including size, shape, inclusions, oscillatory zoning, typical chondrite-normalized REE patterns, U contents, and U/Th ratios. This data establishes the age of the ore and alteration and a temporal, and likely genetic, connection between the ore and members of the Lyon Mountain Granite suite. A model invoking melting of Shawinigan country rocks, magmatic differentiation, and long-lived magmatic and metasomatic input along extensional fault conduits is proposed for the ore’s genesis. At the Cheever Mine, magmatic hydrothermal fluids and/or post-intrusion alteration appears not to have had a major impact on zircon, which preserves original U-Pb systematics.</p>
10aAdirondack Mountains10aCheever Mine10aGrenville Province10airon oxide-apatite deposits (IOA deposits)10aLyon Mountain Granite10aU-Pb zircon geochronology1 aChiarenzelli, Jeffrey1 aLupulescu, M., V.1 aRegan, Sean1 aSinger, Jared  uhttp://www.mdpi.com/2076-3263/8/9/345