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The Norbeck Intrusive Suite is an Ordovician granitic pluton in Montgomery County, Maryland. It was originally mapped as the Norbeck Quartz Diorite by Hopson,〔 and is shown as such on the Geologic Map of Maryland of 1968. A. A. Drake later revised the name after more detailed mapping.〔Drake, A.A., Jr., 1998, Geologic map of the Kensington quadrangle, Montgomery County, Maryland: U.S. Geological Survey Geologic Quadrangle Map, GQ-1774, scale 1:24,000〕 It intrudes through the Wissahickon Formation. ==Description== Three lithologies were mapped in the Kensington quadrangle by Drake:〔 * medium- to coarse-grained, fairly massive to foliated biotite-hornblende tonalite that contains xenoliths and/or autoliths of more mafic rock * medium-grained, quartz-augite-hornblende metagabbro that forms small bodies within the tonalite * dark-green, well-foliated ultramafic rocks of serpentine and lesser soapstone 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Norbeck Intrusive Suite」の詳細全文を読む スポンサード リンク
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