An Examination of the Nature and Timing of Pluton Emplace- ment, Northern Sierra Nevada, Calfornia

已确定的深成岩体与构造变形的关系已被广泛地用来约束区域形变的时间。这一过程的有效性取决于从叠加构造中确定深成岩体中与侵位有关的构造的能力。现有的标准不是诊断性的，因此区分构造前、同生和后构造深成岩的标准是有争议的。该项目将对加利福尼亚州内华达山脉北部的Merrimac岩体进行详细检查，以估计花岗岩体内和周围的应变场。此外，还将进行计算机模拟，模拟同轴和非同轴变形下的构造前、同轴和构造后的岩体侵位。通过计算机生成应变场的平面剖面与应变场的对比，可望得到更严格的识别前、同、后构造深成岩体的标准，从而为确定造山带构造的年龄提供更可靠的约束条件。

Relationships between dated plutons and tectonic deforma- tion have been widely used to constrain timing of regional deformation. The validity of this procedure relies on the ability to determine emplacement-related structures in the plutons from super-imposed tectonic structures. Existing guide- lines are not diagnostic and therefore criteria for distinguish- ing pre-, syn-, and post- tectonic plutons are controversial. This project will carry out a detailed examination of the Merrimac pluton in the Northern Sierra Nevada, California to estimate the strain fields in and around the granitoid. Additionally, computer modeling that simulates pre-, syn-, and post- tectonic pluton emplacement under coaxial and non-coaxial deformation will be performed. By comparing planar sections through the computer generated strain fields with the strain fields obtained from the field data, it is expected that more rigorous criteria will result for recognizing pre-, syn-, and post- tectonic plutons, and therefore, provide more reliable constraints for determining the age of structures in orogenic belts.