On the origin of the oolitic, spherulitic and rhomb-bearing cherts
These are fundamentally different from the oolitic cherts in their structure, and are grouped together as spherulitic cherts. The pebble illustrated in Fig. 20 is a beautiful example of its kind, particularly when viewed as a pebble mount ; when the orbs, obviously not ooliths, appear as translucent opalescent spheres, each with a tiny ...
Silica diagenesis: origin of inorganic and replacement cherts
1989年1月1日 · Partial and minor chertification occur mostly in Phanerozoic carbonates, carbonate-bearing sandstones, evaporites, and fossil wood. The source of the silica is predominantly biogenic. In petrified wood the silicification mechanism is a permeation or void-filling process, not a replacement.
Cherts, spiculites, and collapse breccias - ScienceDirect
2021年6月1日 · Spiculitic cherts are uncommon reservoir rocks and their porosity evolution is poorly understood compared to sandstones and carbonates. In the Gohta oil and gas discovery on the Loppa High in the south-western Barents Sea, the reservoir is in brecciated, silicified, and dolomitized Permian spiculites below the Permian/Triassic unconformity.
Hydrothermal alteration and microfossil artefacts of the 3,465 …
2009年8月2日 · Indeed, the formation of goethite post-dates the precipitation of Apex chert, as shown by spherulitic aggregates of iron oxides partially replacing syn-genetic barite (see Supplementary Fig....
Questioning the evidence for Earth's oldest fossils - Nature
2002年3月7日 · We reinterpret the purported microfossil-like structure as secondary artefacts formed from amorphous graphite within multiple generations of metalliferous hydrothermal vein chert and volcanic...
spherulitic growths, and this silicification appears to lead ultimately to the production of the spherulitic cherts found here and there throughout the Southern Uplands.
(PDF) Diverse microstructures from Archaean chert from the …
The presence of the microstructures at an early stage of chert formation is indicated by the relationship to the spherulitic chert matrix and because the structures are cross cut by later veins (Figs. 7c1, 13e).
A fresh look at the fossil evidence for early Archaean cellular life
2006年6月6日 · We find that the famous early Archaean, Apex Chert examples are associated with the recrystallization of amorphous glassy silica to spherulitic chalcedony and other hydrothermal fabrics (see below).
The spherulitic, and/or flow banded rhyolite discussed in this paper is a fine-grained intrusive igneous rock characterized by small (0.25 mm to 1 .5 cm) spherical to ellipsoidal structures known as spherules.
Carbonaceous microstructures from sedimentary laminated chert …
2016年6月1日 · The clotted cherts, in particular, possess textures generated from spherulitic silica growth, during which microfossil-like artifacts developed around the margins of crystals.
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