Age and significance of felsic dikes from the UHP western gneiss region
Age and significance of felsic dikes from the UHP western gneiss region
复制标题
超高压西部片麻岩地区长英质岩脉的年龄和意义
DOI：
--
复制
发表时间：
2014
期刊：
影响因子：
--
通讯作者：
B. Hacker
中科院分区：
文献类型：
--
作者：
A. Kylander‐Clark;B. Hacker
对21个含斜长石岩脉进行了分析，以更严格地限制西部片麻岩区（WGR）的（超）高压（UHP）变质作用的结束。利用激光烧蚀分流岩石年代学分析了19个岩脉，将U-Pb数据与锆石稀土元素（REE）化学成分联系起来，并通过化学磨蚀热电离质谱法分析了一些关键样品，以提供高精度的约束。所有分析的岩脉都产生了与低压结晶相一致的稀土化学锆石。大约有一半的堤防产量前寒武纪的日期，这个年龄的nondeformed堤防支持以前的解释，大部分的WGR在加里东俯冲和折返进行了有限的变形。最古老的加里东岩脉的年龄与该地区约420-400 Ma榴辉岩的年龄重叠;这种差异表明：（1）隐藏结构将早期的折返材料与后来的折返材料分开，（2）一些岩脉的年龄不是低压结晶年龄，或者（3）榴辉岩的406 Ma后的年龄是后白垩纪相的退变质年龄。
Twenty‐one plagioclase‐bearing dikes were analyzed to place firmer limits on the end of (ultra)high‐pressure (UHP) metamorphism across the Western Gneiss Region (WGR). Nineteen dikes were analyzed with laser ablation split‐stream petrochronology to tie the U‐Pb dates to zircon rare earth element (REE) chemistry, and a few key samples were analyzed by chemical abrasion thermal ionization mass spectrometry to provide high‐precision constraints. All analyzed dikes yielded zircons with REE chemistry consistent with low‐pressure crystallization. Approximately half of the dikes yield Precambrian dates; nondeformed dikes of this age support previous interpretations that much of the WGR underwent limited deformation during Caledonian subduction and exhumation. The oldest Caledonian dikes have dates that overlap with the circa 420–400 Ma eclogite dates from the region; this discrepancy indicates that either (1) cryptic structures separate early exhumed material from later exhumed material, (2) some of the dike dates are not low‐pressure crystallization ages, or (3) post‐406 Ma dates from eclogites are posteclogite‐facies retrogression ages.