Table of Contents
What is hydrothermal alteration of rocks?
Hydrothermal alteration is defined as any alteration of rocks or minerals by the reaction of hydrothermal fluid with preexisting solid phases.
What causes hydrothermal alteration?
Permeability of the rocks controls the access of thermal fluids, which cause hydrothermal alteration of the rocks and precipitation of secondary minerals in open spaces. Rocks which have very restricted permeability or are completely impervious to fluid will be only slightly altered.
How does olivine react with water?
First, olivine dissolves: When the concentrations of dissolved species become sufficiently high, serpentine and brucite nucleate and precipitate according to: Reactions (4) and (5) consume water and generate hydrogen ions (H+) that in turn promote forsterite dissolution (reaction 3).
What is the importance of hydrothermal alteration for mineral exploration?
Hydrothermal fluids chemically attack the mineral constituents of the wall rocks , which tend to re- equilibrate by forming new mineral assemblages that are in equilibrium with the new conditions.
Is olivine soluble in water?
It was found that the nominally anhydrous mineral olivine can incorporate surprisingly large quantities of water. In the alpha-stability phase up to 20,000 ppm H/Si (corresponding to 1200 wt. ppm H2O) can be dissolved into the solid.
What minerals are produced during chemical weathering of olivine?
For example, pyroxene can be converted to the clay minerals chlorite or smectite, and olivine can be converted to the clay mineral serpentine.
What does hydrothermal metamorphism do to rocks?
Hydrothermal metamorphism takes place when hot, volatile solutions percolate into and react with the protolith, or the original rock. The heat of the intrusive igneous body and the hot volatile fluids serves to catalyze metamorphic reactions in the host rock.
Why is the mineral olivine weathered more readily than quartz?
Mafic silicates like olivine and pyroxene tend to weather much faster than felsic minerals like quartz and feldspar. Different minerals show different degrees of solubility in water in that some minerals dissolve much more readily than others.
What happens to rocks in hydrothermal metamorphism?
What is hydrothermal alteration in geology?
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.
What minerals are formed from hydrothermal alteration during metamorphism?
These hydrothermal alteration minerals may be transformed during metamorphism into andalusite, corundum, topaz, sil- limanite, kyanite, cordierite, garnet, phlogopite, and various orthopyroxenes and orthoamphiboles (Bonnet and Corriveau, 2007).
How to induce serpentinization in San Carlos olivine?
A single-pass flow-through experiment was conducted to induce serpentinization, and to relate serpentine mineralogy to reaction progress during open-system alteration of San Carlos olivine by air-saturated water. The fluid flowed at 300 °C and 300 bars for 1368 hours through crushed olivine contained in a tubular titanium reaction cell.
What is alteration intensity in geology?
ALTERATION INTENSITY •A measure of how completely the rock has reacted to produce new minerals (i.e. hydrothermal). •A measure of the percentage of the rock that has been altered. •Critical to mapping and understanding alteration patterns.