Fluid control on low-temperature mineral formation in volcanic rocks of Kahrizak, Iran

The article presents new petrogeochemical data on the Middle Miocene-Pliocene volcanic rocks from central part of Iturup Island (Great Kurile Chain). It is shown that volcanism of the Middle Miocene-Early Pliocene age in the central part of the Iturup Island took place in a suprasubduction setting. The distribution of high field strength elements (HFSE) and their ratio in the basaltoids indicate their formation upon partial melting of the depleted upper mantle, while the enrichment of rocks with large ionic lithophilic elements (LILE) indicates both a fluid mantle additive introduced into the melts during the evolution of primary magma and the participation of a low-temperature suprasubduction fluid. The established differences in the composition of the basaltoids of the frontal and rear zones due to the limited number of analyzed samples are considered preliminary. Thus, basaltoids in the rear zone are distinguished by higher concentrations of Th, Pb, HFSE (Nb, Zr, Y, Hf), relative enrichment in LREE, pronounced negative Zr and Hf anomalies, and positive Eu.

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High-Ti magnetite in some fine-grained carbonatites and the magmatic implications

Mineralogical Magazine ◽

10.1180/0026461026630035 ◽

2002 ◽

Vol 66 (3) ◽

pp. 379-384 ◽

Cited By ~ 11

Author(s):

D. K. Bailey ◽

S. Kearns

Keyword(s):

High Temperature ◽

Low Temperature ◽

Composition Range ◽

Volcanic Rocks ◽

Coarse Grained ◽

Slow Cooling ◽

Fine Grained ◽

Narrow Composition Range ◽

Fast Quenching ◽

Temperature Crystallization

AbstractMagnetite is present in most carbonatites, and in the most abundant and best-known form of carbonatite, coarse-grained intrusions, it typically falls in a narrow composition range close to Fe3O4. A fine-grained carbonatite from Zambia contains magnetites with an extraordinary array of compositions (from 18–1% TiO2, 10–2% Al2O3, and 16–4% MgO) outranging previously-reported examples. Zoning trends are from high TiO2 to high Al2O3 and MgO. No signs of exsolution are seen. Checks on similar rocks from Germany, Uganda and Tanzania reveal magnetites with comparable compositions, ranges, and zoning. Magnetites from alkaline and alkaline ultramafic silicate volcanic rocks cover only parts of this array. Magnetite analyses from some other fine-grained carbonatites, reported in the literature, fall in the same composition field, suggesting that this form of carbonatite may be distinctive. The chemistry and zoning would be consonant with rapid high-temperature crystallization in the carbonatite melts, with the lack of exsolution pointing to fast quenching: this contrasts with coarse-grained intrusive carbonatites, in which the magnetite compositions are attributed to slow cooling, with final equilibration at low temperature. In some complexes, both forms of carbonatite, with their different magnetite compositions, are represented.

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The petrogenesis and origin of the analcime in the volcanic rocks of the Crowsnest Formation, Alberta

Canadian Journal of Earth Sciences ◽

10.1139/e78-006 ◽

1978 ◽

Vol 15 (1) ◽

pp. 69-77 ◽

Cited By ~ 14

Author(s):

L. J. Ferguson ◽

A. D. Edgar

Keyword(s):

Experimental Data ◽

Low Temperature ◽

Volcanic Rocks ◽

Crustal Material ◽

Igneous Origin ◽

Partial Fusion ◽

Extensive Exchange ◽

Inclusion Trails ◽

Convincing Data ◽

Differentiation Trend

The Crowsnest Formation consists of trachytes, analcime phonolites and blairmorites, metamorphosed to zeolite facies. The latter rocks contain large analcime phenocrysts variously suggested as being of primary igneous origin or due to transformation from original leucite by reaction of Na-rich fluids. Although neither field relationships or petrography provide convincing data favouring either hypothesis, the presence of primary undisrupted inclusion trails in the analcime tend to support the former hypothesis. Compositions of the analcimes differ from that of an analcime formed by transformation from leucite. The chemistry of the rocks and their constituent pyroxenes are consistent with a sodic rather than a potassic differentiation trend; feldspar and garnet analyses support this conclusion. Oxygen isotope values for the pyroxenes indicate no extensive exchange with a low temperature fluid. Thus it seems unlikely that leucite was ever a constituent of the Crowsnest suite as necessitated by the hypothesis of transformation from leucite. Geochemistry and known experimental data indicate that the analcime phonolites and blairmorites differentiated from a trachytic magma under restricted conditions at depths greater than 25 km by early sanidine and later analcime fractionation. The parental trachyte may be produced by partial fusion of crustal material at depths greater than 35 km.

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Timing of low-temperature mineral formation during exhumation and cooling in the Central Alps, Switzerland

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2012.01.007 ◽

2012 ◽

Vol 327-328 ◽

pp. 1-8 ◽

Cited By ~ 10

Author(s):

Tobias B. Weisenberger ◽

Meinert Rahn ◽

Roelant van der Lelij ◽

Richard A. Spikings ◽

Kurt Bucher

Keyword(s):

Low Temperature ◽

Central Alps ◽

Mineral Formation

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Geology and characteristics of Pb-Zn-Cu-Ag skarn deposit at Ruwai, Lamandau Regency, Central Kalimantan

Journal of Applied Geology ◽

10.22146/jag.7181 ◽

2015 ◽

Vol 3 (1) ◽

Author(s):

Arifudin Idrus ◽

Lucas Donny Setijadji ◽

Fenny Tamba ◽

Ferian Anggara

Keyword(s):

Low Temperature ◽

Hydrothermal Fluid ◽

Meteoric Water ◽

Volcanic Rocks ◽

Thrust Fault ◽

Strike Slip ◽

Skarn Deposit ◽

Central Kalimantan ◽

Low Salinity ◽

Ore Mineralization

This study is dealing with geology and characteristics of mineralogy, geochemistry and physicochemical conditions of hydrothermal fluid responsible for the formation of skarn Pb-Zn-Cu-Ag deposit at Ruwai, Lamandau Regency, Central Kalimantan. The formation of Ruwai skarn is genetically associated with calcareous rocks consisting of limestone and siltstone (derived from marl?) and controlled by NNE-SSW-trending strike slip faults and localized along N 70° E-trending thrust fault, which also acts as contact zone between sedimentary and volcanic rocks in the area. Ruwai skarn is mineralogically characterized by prograde alteration (garnet and clino-pyroxene) and retrograde alteration (epidote, chlorite, calcite and sericite). Ore mineralization is characterized by sphalerite, galena, chalcopyrite and Ag-sulphides (particularly acanthite and argentite), which formed at early retrograde stage. Geochemically, SiO2 is enriched and CaO is depleted in limestone, consistent with silicic alteration (quartz and calc-silicate) and decarbonatization of the wallrock. The measured reserves of the deposit are 2,297,185 tonnes at average grades of 14.98 % Zn, 6.44 % Pb, 2.49 % Cu and 370.87 g/t Ag. Ruwai skarn orebody originated at moderate temperature of 250-266 °C and low salinity of 0.3-0.5 wt.% NaCl eq. The late retrograde stage formed at low temperature of 190-220 °C and low salinity of ~0.35 wt.% NaCl eq., which was influenced by meteoric water incursion at the late stage of the Ruwai Pb-Zn-Cu-Ag skarn formation. Keywords: Geology, skarn, mineralogy, geochemistry, Ruwai, Central Kalimantan

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Characteristics of the Ahmadabad hematite/barite deposit, Iran – studies of mineralogy, geochemistry and fluid inclusions

Geologos ◽

10.2478/logos-2018-0004 ◽

2018 ◽

Vol 24 (1) ◽

pp. 55-68 ◽

Cited By ~ 1

Author(s):

Amir Haji Babaei ◽

Alireza Ganji

Keyword(s):

Low Temperature ◽

Fluid Inclusions ◽

Open Space ◽

Volcanic Rocks ◽

Major And Trace Elements ◽

Hydrothermal Conditions ◽

Hydrothermal Origin ◽

Fe Oxyhydroxides ◽

Host Rocks ◽

Ree Patterns

Abstract The Ahmadabad hematite/barite deposit is located to the northeast of the city of Semnan, Iran. Geostructurally, this deposit lies between the Alborz and the Central Iran zones in the Semnan Subzone. Hematite-barite mineralisation occurs in the form of a vein along a local fault within Eocene volcanic host rocks. The Ahmadabad deposit has a simple mineralogy, of which hematite and barite are the main constituents, followed by pyrite and Fe-oxyhydroxides such as limonite and goethite. Based on textural relationships between the above-mentioned principal minerals, it could be deduced that there are three hydrothermal mineralisation stages in which pyrite, hematite and barite with primary open space filling textures formed under different hydrothermal conditions. Subsequently, in the supergene stage, goethite and limonite minerals with secondary replacement textures formed under oxidation surficial conditions. Microthermometric studies on barite samples show that homogenisation temperatures (TH) for primary fluid inclusions range from 142 to 256°C with a temperature peak between 200 and 220°C. Salinities vary from 3.62 to 16.70 NaCl wt% with two different peaks, including one of 6 to 8 NaCl wt% and another of 12 to 14 NaCl wt%. This indicates that two different hydrothermal waters, including basinal and sea waters, could have been involved in barite mineralisation. The geochemistry of the major and trace elements in the samples studied indicate a hydrothermal origin for hematite and barite mineralisation. Moreover, the Fe/Mn ratio (>10) and plots of hematite samples of Ahmadabad ores on Al-Fe-Mn, Fe-Mn-(Ni+Co+ Cu)×10, Fe-Mn-SiX2 and MnO/TiO2 – Fe2O3/TiO2 diagrams indicate that hematite mineralisation in the Ahmadabad deposit occurred under hydrothermal conditions. Furthermore, Ba and Sr enrichment, along with Pb, Zn, Hg, Cu and Sb depletion, in the barite samples of Ahmadabad ores are indicative of a low temperature hydrothermal origin for the deposit. A comparison of the ratios of LaN/YbN, CeN/YbN, TbN/LaN, SmN/NdN and parameters of Ce/Ce* and La/La* anomalies of the hematite, barite, host volcanic rocks and quartz latite samples to each other elucidate two important points: 1) the barite could have originated from volcanic host rocks, 2) the hematite could have originated from a quartz latite lithological unit. The chondrite normalised REE patterns of samples of hematite barite, volcanic host rocks and quartz latite imply that two different hydrothermal fluids could be proposed for hematite and barite mineralisation. The comparison between chondrite normalised REE patterns of Ahmadabad barite with oceanic origin barite and low temperature hydrothermal barite shows close similarities to the low temperature hydrothermal barite deposits.

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Mineralogical Evidence of Pre-caldera Magma Petrogenesis in the Jemez Mountains Volcanic Field, New Mexico, USA

Journal of Petrology ◽

10.1093/petrology/egaa064 ◽

2020 ◽

Vol 61 (7) ◽

Cited By ~ 1

Author(s):

Jie Wu ◽

Michael C Rowe ◽

Shane J Cronin ◽

John A Wolff

Keyword(s):

Low Temperature ◽

Magma Mixing ◽

Volcanic Rocks ◽

Mineral Chemistry ◽

Volcanic Field ◽

Magmatic System ◽

Upward Migration ◽

Jemez Mountains ◽

Almost All ◽

Shallow Crust

Abstract The Jemez Mountains volcanic field (JMVF) is the site of the two voluminous, caldera-forming members of the Bandelier Tuff, erupted at 1·60 and 1·25 Ma, following a long and continuous pre-caldera volcanic history (∼10 Myr) in this region. Previous investigations utilizing whole-rock geochemistry identified complex magmatic processes in the two major pulses of pre-caldera magmatism including assimilation–fractional crystallization (AFC) and magma mixing. Here we extend the petrological investigation of the pre-caldera volcanic rocks into the micro-realm and use mineral chemistry and textural information to refine magma evolution models. The results show an increasing diversity of mineral populations as the volcanic field evolved. A range of plagioclase textures (e.g. sieved cores and rims) indicate disequilibrium conditions in almost all pre-caldera magmas ranging from andesite to rhyolite, reflecting plagioclase dissolution and regrowth. Coarsely sieved or dissolved plagioclase cores are explained by resorption via water-undersaturated decompression during upward migration from a deep melting, assimilation, storage and homogenization (MASH) zone. Plagioclase crystals with sieved rims are almost ubiquitous in dacite-dominated magmatism (La Grulla Plateau andesite and dacite erupted at ∼8–7 Ma, as well as Tschicoma Formation andesite, dacite and rhyolite at ∼5–2 Ma), reflecting heating induced by magma mixing. These plagioclase crystals often have An-poor cores that are chemically distinct from their An-rich rims. The existence of different plagioclase populations is consistent with two distinct amphibole groups that co-crystallized with plagioclase: a low-Al, low-temperature, high-fO2 group, and a high-Al, high-temperature, low-fO2 group. Calculation of melt Sr, Ba, La, and Ce concentrations from plagioclase core and rim compositions suggests that these chemical variations are largely produced by magma mixing. Multiple mafic endmembers were identified that may be connected by AFC processes in the MASH zone in the middle to lower crust. The silicic component in an early andesite-dominated magmatic system (Paliza Canyon andesite, dacite and rhyolite, 10–7 Ma) is represented by contemporaneous early rhyolite (Canovas Canyon Rhyolite). A silicic mush zone in the shallow crust is inferred as both the silicic endmember involved in the dacite-dominant magmatic systems and source of the late low-temperature rhyolite (Bearhead Rhyolite, 7–6 Ma). Recharging of the silicic mush by mafic melts can explain observed diversity in both mineral disequilibrium textures and compositions in the dacitic magmas. Overall, the pre-caldera JMVF magmatic system evolved towards cooler and more oxidized conditions with time, indicating gradual thermal maturation of local crust, building up to a transcrustal magmatic system, which culminated in ‘super-scale’ silicic volcanism. Such conditioning of crust with heat and mass by early magmatism might be common in other long-lived volcanic fields.

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A multi-system geochronology in the Ad-3 borehole, Pannonian Basin (Hungary) with implications for dating volcanic rocks by low-temperature thermochronology and for interpretation of (U-Th)/He data

Terra Nova ◽

10.1111/ter.12155 ◽

2015 ◽

Vol 27 (4) ◽

pp. 258-269 ◽

Cited By ~ 15

Author(s):

Martin Danišík ◽

László Fodor ◽

István Dunkl ◽

Axel Gerdes ◽

János Csizmeg ◽

...

Keyword(s):

Low Temperature ◽

Pannonian Basin ◽

Volcanic Rocks

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Low-temperature demagnetization of volcanic rocks containing multi-domain magnetic grains: Implications for the Thellier paleointensity determination

Geofísica Internacional ◽

10.22201/igeof.00167169p.2001.40.4.412 ◽

2001 ◽

Vol 40 (4) ◽

pp. 293-300

Author(s):

Juan Morales ◽

Avto Goguitchaichvili ◽

Luis Alva-Valdivia ◽

Ana-María Soler

Keyword(s):

Low Temperature ◽

Volcanic Rocks

Seleccionamos trece muestras de unidades volcánicas previamente estudiadas del Cáucaso, Islandia y las Filipinas para usarse en este estudio de estructura de dominio magnético y desmagnetización de baja temperatura. Se aplicó el tratamiento de baja temperatura a las magnetizaciones termoremanentes parciales para remover la parte de magnetización remanente portada por granos multi-dominio. En general, 10 a 40% de la ‘termoremanencia parcial multidominio’ fue removido con este tratamiento, lo que puede ayudar a incrementar el éxito de las mediciones de paleointensidad. Las muestras de Filipinas provienen de la erupción del volcán Pinatubo y muestran un fenómeno de auto-inversión total debido a la presencia de ilmeno-hematitas y una autoinversión parcial entre 500° y 575°C debido a las titanomagnetitas. La desmagnetización de baja temperatura aplicada por primera vez a remanencia auto-inversa muestra que el pico de alta temperatura es casi eliminado por el tratamiento.

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