Mineral Transformations in Low-Grade Rocks

9418108 Peacor建议通过低变质作用，在成岩作用范围内继续研究细粒泥质岩及其他以粘土矿物为主的岩石的转化过程。矿物组合的结构、化学和结构特征正在研究中，重点是利用透射电镜和分析电子显微镜，但利用包括SEM和XRD在内的各种技术，并与岩石变形、变质岩石学、稳定和放射性同位素分析以及低温地球化学方面的专家合作。样品是从连续序列中选择的，以代表关键特征，并已被广泛的现场和实验室研究充分表征。通过比较各种递进序列内部和之间的观测结果，可以确定矿物转化、变形和晶体生长的过程，特别是在固体记录晶体/流体相互作用的证据方面。具体主题包括：(1)蒙脱石、I/S和伊利石的性质：叠加关系；(2)蒙脱石从伊利石转化的机理。(3)反应机制随岩石类型的变化。(4)埋藏成岩和低变质机制下的晶体生长机制(5)伊利石和绿泥石结晶度变化的成因与结构的定量关系。(6)蒙脱石层间阳离子组成的成因。这些和其他主题将使用来自以下地区的前进泥质层序的样品序列进行研究：德克萨斯州墨西哥湾沿岸、苏格兰南部高地、威尔士沉积盆地、新西兰南岛、南开海沟、加利福尼亚方济各组、西班牙伊比利亚地块和摩洛哥裂谷链的凯塔马单元。所有序列都来自特征良好的序列，这些序列允许对一系列类型的泥岩以及整个成岩作用和低变质作用的过程进行表征，从而导致趋势和过程的记录。特别关注流体和应力的作用，因为集体数据似乎表明，所有过程都与奥斯特瓦尔德阶梯式转变相一致，从亚稳态到稳定平衡，由流体介导，并越来越多地由构造应力引起的变形引起，随着等级的增加，随后的含义是使用粘土矿物作为反应过程的指标，而不是精确的地温计。？?

9418108 Peacor Propose to continue to study processes of transformation in fine-grained pelitic rocks and other rocks dominated by clay minerals over the range of diagenesis through low-grade metamorphism. The textural, chemical, and structural characteristics of mineral assemblages are being investigated with emphasis on transmission and analytical electron microscopy but utilizing a full range of techniques including SEM and XRD, and in a context involving collaboration with specialists in rock deformation, metamorphic petrology, stable and radiogenic isotope analysis and low-temperature geochemistry. Samples are selected from continuous sequences chosen to represent critical features and which have been well-characterized by a wide range of field and laboratory studies. Comparison of observations within and between a variety of prograde sequences permits processes of mineral transformations, deformation, and crystal growth to be defined, especially insofar as solids record evidence of crystal/fluid interactions. Specific topics include: (1) Nature of smectite, I/S, and illite: Stacking relations (2) Mechanisms for the transformation of smectite of illite. (3) Variations in reaction mechanisms as a function of rock type. (4) Mechanisms of crystal growth in both burial diagenetic and low-grade metamorphic regimes (5) Quantitative relation between structure and texture as related to cause of changes in illite and chlorite crystallinity. (6) Origins of interlayer cation composition of smectite. These and other topics will be studied using sequences of samples from prograde pelitic sequences in the following localities: Texas Gulf Coast, Southern Uplands of Scotland, Welsh sedimentary basin, South Island of New Zealand, Nankai Trench, Franciscan Formation of California, Iberian Massif of Spain, and the Ketama Unit of the Rift Chain of Morocco. All sequences are from well-characterized sequences that permit characterization of processes over a range of types of pelites and over the full range of diagenesis and low-grade metamorphism, leading to documentation of trends and processes. Focusing especially on the roles of fluids and stress, as the collective data appear to show that all processes are consistent with Ostwald step-like transitions from metastable states toward stable equilibrium, as mediated by fluids, and increasingly by deformation induced by tectonic stress with increasing grade, with subsequent implications for the use of clay minerals as indicators of reaction progress rather than as accurate geothermometers. ??