2023年5月9日 · Hydrothermal alteration is a geological process that occurs when hot, mineral-rich fluids interact with rocks and minerals, changing their physical and chemical properties.

Hydrothermal alteration is defined as any alteration of rocks or minerals by the reaction of hydrothermal fluid with preexisting solid phases. Hydrothermal alteration can be isochemical, like meta-morphism, and dominated by mineralogical changes, or it can be metasomatic and result in significant addition or removal of elements.

All igneous rocks recovered during Leg 183 have undergone secondary alteration or weathering in subaerial, shallow subaqueous, or deep marine environments. Many features of low-temperature hydrothermal alteration (both submarine and subaerial) and subaerial weathering appear similar and are difficult to distinguish in the drilled core.

1973年1月1日 · Many alteration processes reduce the average grain-size of rocks. An outstanding example is weathering alteration that converts feldspar crystals to clay aggregates of micron size. Alterations do not always reduce the competency of a rock or the average grain-size.

Hydrothermal alteration involves water–rock interaction at temperatures above 50 °C in association with plutonism or volcanic activity. The alteration is usually restricted to small regions characteristic of contact metamorphism where new minerals, clay minerals, zeolites, and (hydr)oxides form in the presence of water at the elevated ...

2020年11月23日 · The Atlas of Alteration is a practical reference, which aids in the recognition and understanding of major alteration minerals. Atlas of Alteration consists of 49 mineral entries, which are the result of numerous contributions by international authors.

Rock alteration usually involves chemical weathering in which the mineral composition of the rock is changed, reorganized, or redistributed. The rock minerals are exposed to solution, carbonation, hydration, and oxidation by circulating waters.

Hydrothermal alteration, also referred to as wallrock alteration, is a general term that encompasses many processes by which rock-forming minerals are altered due to reactions accompanying the flow of heated aqueous fluids along fractures and grain boundaries (Meyer and Hemley, 1967; Rose and Burt, 1979; Lentz, 1994; Reed, 1997). Alteration may ...

2014年11月1日 · We provide detailed descriptions of hydrothermal alteration in volcanic rocks. The type of alteration impacts the porosity and density of the altered rocks. Hydrothermal alteration and secondary minerals impact ultrasonic wave propagation. Lower UCS in shallow, low temperature regions of the field (27.7 ± 10.3 MPa).

2016年12月19日 · Alteration is any mineralogic change to a preexisting rock through chemical reaction caused by hot circulating hydrothermal fluids. Hydrothermal fluids , owing to temperature and pressure gradient, travel within a rock’s primary or secondary porosity. They react with country rock, alter original mineralogy, and produce new minerals.