Early Metamorphic History of the Oceanic Lower Crust

大洋辉长岩的早期高温变质和变形记录了大洋中脊附近下地壳的演化。破译这一记录被证明是困难的，原因有两个：(1)变质作用的温度估计不准确，(2)矿物组合平衡状态的不确定性。本研究采用实验、分析和统计相结合的方法来解决这些问题。实验研究集中在利用形成于东太平洋隆起的自然变质辉长岩的次生矿物组成随温度和时间的变化。该项目的岩石学和统计成分将确定来自蛇绿岩和大洋中脊的一套辉长岩的变质矿物组成。这项研究将更好地理解大洋中脊附近下层地壳过程的时间尺度和扩展速率相关性。

Early high-temperature metamorphism and deformation of oceanic gabbros record the evolution of the lower crust near mid-ocean ridges. Deciphering this record has proven difficult for two reasons: (1) imprecise temperature estimates for metamorphism, and (2) uncertainties about the equilibrium state of mineral assemblages. This study employs a combination of experimental, analytical, and statistical methods to address these issues. Experimental studies focus on the temperature and time dependence of secondary mineral compositions using natural metamorphosed gabbros formed at the East Pacific Rise. The petrologic and statistical component of this project will determine metamorphic mineral compositions from a suite of gabbros from ophiolites and mid ocean ridges. This study will yield a better understanding of the time scales and spreading-rate dependence of lower crustal processes near mid-ocean ridges.