Revaluation of “equilibrium” P-T paths from zoned garnet in light of quartz inclusion in garnet (QuiG) barometry
Revaluation of “equilibrium” P-T paths from zoned garnet in light of quartz inclusion in garnet (QuiG) barometry
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DOI：
10.1016/j.lithos.2020.105650
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发表时间：
2020-11
期刊：
影响因子：
3.5
通讯作者：
F. Spear;Oliver M. Wolfe
中科院分区：
文献类型：
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作者：
F. Spear;Oliver M. Wolfe
变质P-T路径为碰撞造山带的构造提供了有价值的约束，许多这样的路径已经从石榴石的化学分带分析中推导出来。包裹体气压测定（如石榴石中的石英或QuiG）提供了关于石榴石分带的解释和由此得出的P-T路径的补充，有时甚至是矛盾的信息。例如，对来自新罕布什尔州Fall Mountain的几代特征良好的石榴石样品进行QuiG气压测定，与从其他方法推断的P-T路径一致。然而，QuiG气压测量与从奥福德维尔带（佛蒙特州）、汤森大坝（佛蒙特州）、康涅狄格谷槽（佛蒙特州）和锡弗诺斯（希腊）的石榴石分区推断的P-T路径不一致。来自新罕布什尔州东南部佩里山地层的新数据表明，QuiG可能保存了多变质事件的记录。具体地说，小球粒样品中的QuiG气压测量被解释为记录了以前未被识别的早期中压（约0.9 GPa）变质作用和后来的低压（约0.3 GPa）变质作用。
Metamorphic P–T paths provide valuable constraints on the tectonics of collisional orogens and many such paths have been deduced from analysis of chemical zoning in garnet. Inclusion barometry (e.g. quartz-in-garnet or QuiG) provides complementary and sometimes contradictory information regarding the interpretation of garnet zoning and the P–T paths derived therefrom. For example, QuiG barometry on several generations of garnet from well-characterized samples from Fall Mountain, New Hampshire, is consistent with the P–T path inferred from other methods. However, QuiG barometry is inconsistent with P–T paths inferred from garnet zoning from the Orfordville Belt (Vermont), Townshend Dam (Vermont), the Connecticut Valley Trough (Vermont), and Sifnos (Greece). New data from the Perry Mountain Formation, southeastern New Hampshire, suggests that QuiG may preserve a record of polymetamorphic events. Specifically, QuiG barometry in coticule samples is interpreted to record a previously unrecognized early medium pressure (ca. 0.9 GPa) metamorphism and a later low pressure (ca. 0.3 GPa) metamorphism.