• Alteration: Commonly alter to uralite (a light coloured amphibole), or may alter to serpentine, chlorite, biotite, carbonates and /or other silicates. • Relief: High positive. • Distinguishing Features: Inclined extinction, higher birefringence, 2nd order interference colours, low 2V, optically positive in comparison with opx.

The results suggest that the geothermal alteration of primary pyroxene in olivine tholeiite is dominated by dissolution-precipitation reactions. They also show that there is a significant difference in the composition of actinolite replacing pyroxene depending on the origin of the primary mineral within a lava flow or an intrusive rock.

2023年9月1日 · In the TVF, most basalts have interacted with diffuse low-temperature hydrothermal fluids, leading to variable degrees of saponite alteration. As the distance from the vents decreases, basaltic glass, olivine, and pyroxene are progressively replaced by saponite; Zn, Cu, Co, and U are enriched; and Ca and Mn are depleted.

2021年7月1日 · In 20% of samples, all with alteration scores >2.5, tremolite + talc occurs as rims around pyroxene, while chlorite occurs as haloes around spinel. A gabbro-veined lherzolite also contains pargasite replacing pyroxene, with later overprinting by tremolite-talc intergrowths.

2021年7月15日 · The downhole imaging spectroscopy trends show differences in pyroxene occurrence and alteration mineral distribution throughout the oceanic crust, with alteration of the sheeted dikes and dike-gabbro transition dominated by greenschist facies assemblages of chlorite, amphibole, and prehnite but little lower temperature zeolite.

2021年10月14日 · Considering the abundance of pyroxenes on the Earth crust, knowledge of their weathering kinetics and mechanisms may help to optimize carbonate yield in GCS. Here we report experimental results from the reaction of the clinopyroxenes augite and diopside in …

Thin section study shows alteration of mafic minerals such pyroxene and groundmass to chlorite ( fig. 5a,b) and replacement of plagioclase by calcite (fig 5c).

2017年11月1日 · As demonstrated by experiments in this study, pyroxene minerals obtained some iron from olivine during peridotite serpentinization, and serpentine formed from orthopyroxene and clinopyroxene was more enriched in FeO than its hosts, which may lead to a decrease in the production of iron oxide.

ALTERATION PRODUCTS OF OLIVINE AND PYROXENE 57 curve of Deer and Wager (1939). There is a considerable variation on the extent of alteration from one flow to another and in the more extreme cases it is difficult to characterize the basalt as belonging to …

Pyroxene in olivine-bearing gabbros is variably altered to felty green amphibole and minor talc. Locally, oxidative alteration leads to partial alteration of olivine relics to clay, Fe oxyhydroxide, and carbonate (Fig. F45D). Alteration of Troctolitic Rocks