scholarly journals Widespread hydrothermal alteration minerals in the fine-grained matrices of the Tieschitz unequilibrated ordinary chondrite

2014 ◽  
Vol 49 (8) ◽  
pp. 1323-1349 ◽  
Author(s):  
E. Dobrică ◽  
A. J. Brearley
Keyword(s):  
Hydrothermal Alteration ◽  
Ordinary Chondrite ◽  
Fine Grained ◽  
Alteration Minerals

Putative fossil life in a hydrothermal system of the Dellen impact structure, Sweden

2010 ◽  
Vol 9 (3) ◽  
pp. 137-146 ◽  
Author(s):  
Paula Lindgren ◽  
Magnus Ivarsson ◽  
Anna Neubeck ◽  
Curt Broman ◽  
Herbert Henkel ◽  
...  
Keyword(s):  
Hydrothermal Alteration ◽  
Hydrothermal System ◽  
Hydrothermal Systems ◽  
Microbial Colonization ◽  
Early Earth ◽  
Impact Structure ◽  
Microbial Life ◽  
Fine Grained ◽  
Evolution Of Life ◽  
Alteration Minerals

AbstractImpact-generated hydrothermal systems are commonly proposed as good candidates for hosting primitive life on early Earth and Mars. However, evidence of fossil microbial colonization in impact-generated hydrothermal systems is rarely reported in the literature. Here we present the occurrence of putative fossil microorganisms in a hydrothermal system of the 89 Ma Dellen impact structure, Sweden. We found the putative fossilized microorganisms hosted in a fine-grained matrix of hydrothermal alteration minerals set in interlinked fractures of an impact breccia. The putative fossils appear as semi-straight to twirled filaments, with a thickness of 1–2 μm, and a length between 10 and 100 μm. They have an internal structure with segmentation, and branching of filaments occurs frequently. Their composition varies between an outer and an inner layer of a filament, where the inner layer is more iron rich. Our results indicate that hydrothermal systems in impact craters could potentially be capable of supporting microbial life. This could have played an important role for the evolution of life on early Earth and Mars.

Lithium-Bearing Hydrothermal Alteration Phyllosilicates Related to Portalet Fluorite Ore (Pyrenees, Huesca, Spain)

Clay Minerals ◽  
1993 ◽  
Vol 28 (2) ◽  
pp. 275-283 ◽  
Author(s):  
J. M. Gonzlez Lopez ◽  
I. Subias Pirez ◽  
C. Fernandez-Nieto ◽  
I. Fanlo Gonzalez
Keyword(s):  
Hydrothermal Alteration ◽  
Half Cell ◽  
Ore Bodies ◽  
Alteration Minerals ◽  
Structural Formulae

AbstractPhyllosilicate associations in hydrothermally altered fluorite ore bodies are: Li-chlorite ± pyrophyllite ± interstratified minerals ± muscovite +± kaolinite. Chlorites, the main alteration minerals, are dioctahedral, d060 = 1.489-1-490/~,, of Ia polytype. The structural formulae indicate substitution of AI for Si from 0.61-0.78 atoms. The total octahedral occupancy ranges from 4.52-4-71 atoms, with 0.49-0-69 Li atoms per half cell unit. This composition indicates that the chlorites are intermediate members of the donbassite-cookeite series proposed by Sudo (1978). The mineralogical associations and textural relations suggest that after intensive silicification which produced alkali alteration under acid conditions, pyrophyllite was produced at the expense of muscovite and then Li-bearing donbassite formed from the pyrophyllite. The Li needed for the formation of the chlorites could be genetically related to granitic batholiths which occur close to the fluorite ores.

Mineralogical and Isotopic Characteristics of Sodic-Calcic Alteration in the Highland Valley Copper District, British Columbia, Canada: Implications for Fluid Sources in Porphyry Cu Systems

2020 ◽  
Vol 115 (4) ◽  
pp. 841-870 ◽  
Author(s):  
Kevin Byrne ◽  
Robert B. Trumbull ◽  
Guillaume Lesage ◽  
Sarah A. Gleeson ◽  
John Ryan ◽  
...  
Keyword(s):  
Water Source ◽  
White Mica ◽  
Late Triassic ◽  
Supporting Evidence ◽  
Fine Grained ◽  
Porphyry Cu ◽  
Mineral Assemblages ◽  
Alteration Minerals ◽  
External Water ◽  
Host Rocks

Abstract The Highland Valley Copper porphyry Cu (±Mo) district is hosted in the Late Triassic Guichon Creek batholith in the Canadian Cordillera. Fracture-controlled sodic-calcic alteration is important because it forms a large footprint (34 km2) outside of the porphyry Cu centers. This alteration consists of epidote ± actinolite ± tourmaline veins with halos of K-feldspar–destructive albite (1–20 XAn) ± fine-grained white mica ± epidote. The distribution of sodic-calcic alteration is strongly influenced by near-orthogonal NE- and SE-trending fracture sets and by proximity to granodiorite stocks and porphyry dikes. Multiple stages of sodic-calcic alteration occurred in the district, which both pre- and postdate Cu mineralization at the porphyry centers. The mineral assemblages and chemical composition of alteration minerals suggest that the fluid that caused sodic-calcic alteration in the Guichon Creek batholith was Cl bearing, at near-neutral pH, and oxidized, and had high activities of Na, Ca, and Mg relative to propylitic and fresh-rock assemblages. The metasomatic exchange of K for Na, localized removal of Fe and Cu, and a paucity of secondary quartz suggest that the fluid was thermally prograding in response to magmatic heating. Calculated δ18Ofluid and δDfluid values of mineral pairs in isotopic equilibrium from the sodic-calcic veins and alteration range from 4 to 8‰ and −20 to −9‰, respectively, which contrasts with the whole-rock values for least altered magmatic host rocks (δ18O = 6.4–9.4‰ and δD = −99 to −75‰). The whole-rock values are suggested to reflect residual magma values after D loss by magma degassing, while the range of hydrothermal minerals requires a mixed-fluid origin with a contribution of magmatic water and an external water source. The O-H isotope results favor seawater as the source but could also reflect the ingress of Late Triassic meteoric water. The 87Sr/86Srinital values of strongly Na-Ca–altered rocks range from 0.703416 to 0.703508, which is only slightly higher than the values of fresh and potassic-altered rocks. Modeling of those data suggests the Sr is derived predominantly from a magmatic source, but the system may contain up to 3% seawater Sr. Supporting evidence for a seawater-derived fluid entrained in the porphyry Cu systems comes from boron isotope data. The calculated tourmaline δ11Bfluid values from the sodic-calcic domains reach 18.3‰, which is consistent with a seawater-derived fluid source. Lower tourmaline δ11Bfluid values from the other alteration facies (4–10‰) suggest mixing between magmatic and seawater-derived fluids in and around the porphyry centers. These results imply that seawater-derived fluids can infiltrate batholiths and porphyry systems at deep levels (4–5 km) in the crust. Sodic ± calcic alteration may be more common in rocks peripheral to porphyry Cu systems hosted in island-arc terranes and submarine rocks than currently recognized.

scholarly journals Trace and Rare Earth Elements Compositional Change on Andesite Alteration in Kaligesing, Purworejo

2020 ◽  
Vol 21 (1) ◽  
pp. 17
Author(s):  
Joko Subandrio ◽  
Ronaldo Irzon
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Hydrothermal Alteration ◽  
Inductively Coupled Plasma ◽  
Microscopic Analysis ◽  
Inductively Coupled ◽  
Fine Grained ◽  
Central Java ◽  
Eu Anomaly ◽  
Plasma Mass Spectrometry

The change of chemical composition because of hydrothermal alteration process is related to the modification on mineralogy and elements mobility. Different alteration conditions could lead to dissimilar geochemical character. This study aims to discuss the alteration effect on trace and rare earth elements composition of an andesite outcrop with hydrothermal alteration in Kaligesing, Purworejo, Central Java Province. Microscopic analysis at Central for Geological Survey was applied to determine the modal mineral composition of the selected samples whilst trace and rare earth elements abundances was measured using Inductively Coupled Plasma – Mass Spectrometry. Plagioclase is the major phenocryst embedded in the fine-grained feldspar and glass groundmass of relatively fresh andesite. On the other hand, sericite, chlorite, epidote, and iron oxide are detected in the altered rock. The more Sr and Rb compositions on unaltered sample exhibit their common existence in plagioclase. The bigger Rb/Sr and the lower Ba/Sr ratios inward to the center of alteration might indicate the more degree of K-bearing mineral formation than Ca-rich mineral alteration. The Ba/Zr escalation and Zr/Y reduction from relatively fresh rock through to the vein of the studied samples are parallel to the previous investigation about andesite alteration. Chondrite-normalized rare-earth elements (REE) pattern of unaltered, altered, and vein samples depicts similar patterns: strong enrichment of Low REE, positive Eu anomaly, and relatively flat high REE. The decrease of Eu anomaly may reflect the reduction of plagioclase modal composition because of alteration and might indicate a reductive alteration state.Keywords: Alteration, andesite, geochemistry, trace and rare earth elements.

Pumpellyite from the oceanic crust, DSDP/ODP Hole 504B

1999 ◽  
Vol 63 (6) ◽  
pp. 891-900 ◽  
Author(s):  
H. Ishizuka
Keyword(s):  
Costa Rica ◽  
Oceanic Crust ◽  
Hydrothermal Alteration ◽  
Fluid Phase ◽  
Plagioclase Phenocryst ◽  
Chemical Compositions ◽  
Oceanic Ridge ◽  
Sea Floor ◽  
Fine Grained ◽  
Compositional Variations

AbstractPumpellyite has been found in doleritic basalt of a sheeted dyke complex drilled from 2072.1 m below sea floor in DSDP/ODP Hole 504B, south of the Costa Rica Rift, eastern Pacific. It occurs as fine-grained crystal aggregates accompanied by albite, chlorite and chalcopyrite, which partially replace a plagioclase phenocryst (An85–88) that is also associated with primary magnetite. Chemical compositions of the pumpellyite vary antithetically in relation to Fe* and Al as well as Fe* and Mg, indicating the dominant substitution of Fe3+ by Al with the minor substitution of Fe2+ by Mg. Such compositional variations overlap with those of prehnite-pumpellyite facies rocks dredged from other oceanic ridges and intra-oceanic arcs, and those of similar facies rocks from ophiolites, but are aluminous compared with those of zeolite facies metabasites in ophiolites. These observations suggest that the breakdown of the plagioclase phenocryst and magnetite in the presence of a Cu- and S-bearing fluid phase led to the formation of pumpellyite + albite + chlorite + chalcopyrite during oceanic ridge hydrothermal alteration.

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