The meillers Autunian hydrothermal chalcedony : first evidence of a similar to 295 Ma auriferous epithermal sinter in the Frech Massif Central.
type: Dataset
description: The Meillers "quartzite" deposit represents a major hydrothermal siliceous sinter, some 50 m thick and covering an area of some 30 ha within Autunian sandstone of the northern Massif Central. This siliceous sinter comprises three facies of microcrystalline quartz: (i) a dark-colored facies (black chalcedony), locally rich in pyrite, at the base, (ii) a gray-brown fairly massive facies (gray-brown chalcedony) in the middle; and (iii) a white, finely banded, facies (white chalcedony) at the top. Orientation measurements of the banding have revealed the paleo-flow channels of the silica-saturated fluids. The geochemistry of the deposits shows modest metal values, in particular for gold (average of 0.58 g/t Au, giving a gold metal content of some 20 t). The hydrothermal event is stratigraphically well correlated with the basal Autunian (around 295 Ma); an age that has been confirmed through radiochronological determination (300±21 Ma; SHRIMP on hydrothermal zircon). The lead isotopic composition is not very radiogenic (206Pb/204Pb=18.20) and is similar to that of the Late Hercynian gold lodes in the Massif Central. The mineralized sinter appears to have derived from a geyser-type hot springs. This hydrothermal activity coincides with the auriferous metallogenic peak that occurred in the Hercynides around 300 Ma. This is the first known epithermal-type surface manifestation described for the Hercynian gold event.
landing page: 0169-1368
keyword: epithermal
keyword: france
keyword: hercynian
keyword: infoeu-reposemanticsarticle
keyword: journal-articles
keyword: massif-central
keyword: meillers
keyword: sdustutesciences-of-the-universe-physicsearth-sciencestectonics
keyword: shrimp
keyword: silica
keyword: sinter
issued: 2026-05-23T09:33:48.838878
modified: 2026-05-23T09:33:48.838884
language: en
contact point: Organization
  fn: CCSD

test_moissonnage_selune
type: Agent

The meillers Autunian hydrothermal chalcedony : first evidence of a similar to 295 Ma auriferous epithermal sinter in the Frech Massif Central.
type: Distribution
format: HTML
access URL: https://insu.hal.science/hal-00068297
issued: 2026-05-23T09:33:48.850851
modified: 2026-05-23T09:33:48.806130