Epidote in aplite from Fukaemura, Itoshimagun, Fukuoka Prefecture
The Journal of the Japanese Association of Mineralogists Petrologists and Economic Geologists (1951)
0
Citation
0
Reference
10
Related Paper
Cite
Citations (6)
Orthorhombic crystal system
Monoclinic crystal system
Cite
Citations (18)
Summary Epidote and clinozoisite are widely distributed in the andesitic lavas and tuffs of the Borrowdale Volcanic Series. Four main types of occurrence may be distinguished, namely quartz-epidote vein fillings; ‘Shap type’ veins, bordered by pink reaction zones rich in SiO 2 , Na 2 O, and K 2 O; autometasomatized lavas and tuffs; and tuffs subjected to alkali metasomatism. Epidote alone formed in the quartz-epidote veins; clinozoisite is found with epidote in the other types of occurrence. Epidote and clinozoisite formed in vesicles at pressures of 10–280 kg/cm 2 , at temperatures of 300–550° C; epidote associated with pre-Bala mineral veins formed in the range 130–550° C at 1000 kg/cm 2 ; epidote around the Caledonian granites probably formed up to 600° C at about 2000 kg/cm 2 . Clinozoisite crystallized together with epidote in the vesicles, demonstrating a gap in the clinozoisite-epidote solid solution series. Early formed epidote in vesicles is more strongly coloured than late epidote, although the compositions of the earliest and latest fractions are identical.
Cite
Citations (25)
The widespread occurrence of epidote minerals in metamorphic and igneous rocks as well as in many ore deposit types makes it a promising candidate for fluid inclusion studies. Apart from high- to very high-temperature and low- to intermediate-pressure conditions, epidote minerals are stable over a wide range of pressure and temperature in the continental and oceanic crust (e.g., Poli and Schmidt 1998). Yet fluid inclusion studies on epidote minerals are surprisingly scarce, even in fluid-saturated environments like certain vein-type deposits or hydrothermal-volcanic vugs and druses. For example, epidote minerals are not mentioned in the subject index of Roedder’s (1984) outstanding summary and review of fluid inclusion studies and occurrences, which lists more than sixty different host minerals for fluid inclusions. Nonetheless, more recent studies showed fluid inclusions in epidote minerals to be the only direct witness of the physiochemical and compositional fluid evolution during certain geodynamic processes mainly found in fossil geothermal systems, ore deposits and high-pressure to ultra-high pressure rocks.
The aim of this review is to outline and summarize some aspects and interpretations of geodynamic processes, which are based on temperature ( T ), pressure ( P ), molar volume ( V ) and composition ( X ) data from fluid inclusions in epidote minerals as well as associated host minerals from various geological environments.
The review starts with a chapter on some typical mixed volatile solid-fluid equilibria involving epidote minerals, which are relevant for the here discussed environments. This is followed by a short introduction into the basic concepts of fluid inclusion research and the role of epidote minerals. The next section covers fluid inclusion studies on epidote minerals from active and fossil geothermal systems as well as low-grade metamorphic rocks and constraints on the P - T - X properties of the fluids present in these systems. This is followed by a short introduction …
Cite
Citations (20)
Chemical compositions of epidote from active and ancient geothermal systems were summarized. Iron and aluminum contents of epidote from geothermal systems vary widely, ranging from about 4 to 19 wt % for Fe2O3 and from 18 to 30 wt % for Al2O3. It was found that the iron content of epidote has roughly a positive correlation to the Fe2O3 content of original rocks, indicating that the Fe2O3 content of original rocks affects largely the variations in iron content of epidote. This correlation is consistent with the results of theoretical calculations on the water/rock interaction under the hydrothermal conditions which show that the epidote is formed under the rock-dominated conditions. Epidote associated with hematite has high iron content, while that associated with prehnite, pyrite and pyrrhotite has low iron content. These facts indicate that CO2 and O2 fugacities are also important factors controlling the compositional variations in epidote.
Cite
Citations (23)
"Epidote, Garnet, etc., in the Kernville Area, California." Rocks & Minerals, 29(11-12), pp. 601–602
Cite
Citations (0)
The Bor metallogenic belt in Serbia is a promising region for copper-gold (Cu-Au) resources, hosting numerous porphyry copper deposits, epithermal gold deposits, and metallogenic prospects, such as the South Dulan and Vlaska exploration greenfield. Epidote alteration is integral to the propylitic and sodic-calcic alteration assemblages within this region. It is distinguished by the extensive occurrence of two primary epidote types: disseminated (Ep1) and veined (Ep2) epidote. In this study, comprehensive petrographic analysis reveals that in the propylitic zone, epidote mainly replaced hornblende (Ep1a) and plagioclase phenocrysts (Ep1b), coexisting with chlorite, apatite and titanite. In proximity to the potassic zone, epidote coexists with biotite, while epidote (Ep2), chlorite, pyrite, and chalcopyrite veinlets are observed near the ore body. Notably, Ep1 exhibits lower Fe and higher Mn contents in comparison to Ep2. Additionally, elements such as Ca, Al, and Fe in Ep1a, and Ca, Fe, Mg, Mn, and Ti in Ep1b, as well as Ca, Al, Fe, and Mn in Ep1c, are introduced into the epidote through hydrothermal fluid interactions. Variations in trace element characteristics are evident among different epidotes. Specifically, Ep1a exhibits elevated Mg content (324–6050 ppm), Ep1b is notable for its high Na (22–942 ppm) and Sr (523–3075 ppm) contents, while Ep1c contains elevated K (24–445 ppm) and Na (41–103 ppm). Which suggest that disseminated epidote (Ep1) inherits the geochemical features from its precursor minerals. In comparison to disseminated epidote, epidote in veinlet exhibits higher Fe3+, Cu, Sn, and REEs, along with lower contents of Pb, Sb, and Sc, suggesting that these elements have been integrated into epidote through isomorphism substitution and influenced by fluids compositions, physical factors (temperature, pressure, etc.) and chemical parameters (speciation, pH, fO2, etc.), as well as mineral assemblages. Therefore, the trace element contents of Pb, Sb, Sc, Cu, Sn and REEs in epidote could serve as more appropriate indicators for mineral geochemistry in porphyry deposit hydrothermal centers.
Hornblende
Cite
Citations (0)
Abstract Propylitic alteration, characterized by the occurrence of chlorite and epidote, is typically the most extensive and peripheral alteration facies developed around porphyry ore deposits. However, exploration within this alteration domain is particularly challenging, commonly owing to weak or nonexistent whole-rock geochemical gradients and the fact that similar assemblages can be developed in other geologic settings, particularly during low-grade metamorphism. We document and interpret systematic spatial trends in the chemistry of chlorite and epidote from propylitic alteration around the E48 and E26 porphyry Cu-Au deposits of the Northparkes district, New South Wales, Australia. These trends vary as a function of both distance from hydrothermal centers and alteration paragenesis. The spatial trends identified in porphyry-related chlorite and epidote at Northparkes include (1) a deposit-proximal increase in Ti, As, Sb, and V in epidote and Ti in chlorite, (2) a deposit-distal increase in Co and Li in chlorite and Ba in epidote, and (3) a pronounced halo around deposits in which Mn and Zn in chlorite, as well as Mn, Zn, Pb, and Mg in epidote, are elevated. Chlorite Al/Si ratios and epidote Al/Fe ratios may show behavior similar to that of Mn-Zn or may simply decrease outward, and V and Ni concentrations in chlorite are lowest in the peak Mn-Zn zone. In comparison to porphyry-related samples, chlorite from the regional metamorphic assemblage in the district contains far higher concentrations of Li, Ca, Ba, Pb, and Cu but much less Ti. Similarly, metamorphic epidote contains higher concentrations of Sr, Pb, As, and Sb but less Bi and Ti. These chlorite and epidote compositional trends are the net result of fluid-mineral partitioning under variable physicochemical conditions within a porphyry magmatic-hydrothermal system. They are most easily explained by the contribution of spent magmatic-derived ore fluid(s) into the propylitic domain. It is envisaged that such fluids experience progressive cooling and reduction in fs2 during outward infiltration into surrounding country rocks, with their pH controlled by the extent of rock-buffering experienced along the fluid pathway.
Paragenesis
Cite
Citations (51)
The petrography and chemistry of epidote and amphibole from the Rio Espinharas hybrid complex (REHC), northeastern Brazil are reported. The Rio Espinharas complex is composed of an intimate association of diorite to shoshonitic metaluminous quartzmonzonite to slightly peraluminous syenogranite. The epidote shows four textural relationships: three are primary and one is resulting from sub-solidus reaction. Euhedral epidote is dispersed and associated mainly with biotite and amphibole. In some cases euhedral crystals of the epidote contain allanite cores, which are subhedral to anhedral and constitute in average less than 20% of the whole grain. The contact between primary epidote and plagioclase is corroded, suggesting reaction with the host-magma. Secondary anhedral epidote is rare and results from plagioclase alteration. The preservation of magmatic epidote in granitic rocks emplaced in the upper crust is attributed to rapid magma ascent, which implies fast upward transport probably by dyking associated to shear zone. The REHC occurs between two transcurrent faults that impose an elongated shape, suggesting that magma filled fractures. The time of 14 years required for dissolution zones of 0.15 mm width of epidote on porphyritic quartz monzonite, corresponds to an average ascent rate of ≥ 700 m year-1 from 7.1 to 2.9 kbar.
Amphibole
Porphyritic
Diorite
Cite
Citations (6)