Abstract
One of the key-principles of the iron-sulphur world theory is to bring organic molecules close enough to interact with each other, using the surface of pyrite as a substrate in a hydrothermal setting. The present paper explores the relationship of pyrite and organic matter in a hydrothermal setting from the geological record; in hydrothermal calcite veins from Carboniferous limestones in central Ireland. Here, the organic matter is accumulated as coatings around, and through, pyrite grains. Most of the pyrite grains are euhedral-subhedral crystals, ranging in size from ca 0.1-0.5 mm in diameter, and they are scattered throughout the matrix of the vein calcite. The organic matter was deposited from a hydrothermal fluid at a temperature of at least 200°C, and gives a Raman signature of disordered carbon. This study points to an example from a hydrothermal setting in the geological record, demonstrating that pyrite can have a high potential for the concentration and accumulation of organic materials.
Highlights
An important requirement for the origin of life is the concentration of organic compounds to allow interaction with each other and with other chemical species
We study the relationship between pyrite and migrated organic matter in the geological record, via hydrothermal deposits of the Irish Carboniferous, to assess the potential of pyrite acting as a substrate for organic matter
The veins are primarily composed of ca 5 mm in diameter sized euhedral calcite (CaCO3) crystals, but they contain pyrite (FeS2) and abundant solid migrated organic matter
Summary
An important requirement for the origin of life is the concentration of organic compounds to allow interaction with each other and with other chemical species. Pyrite and organic matter in the Irish Carboniferous The Carboniferous rocks of Ireland contain numerous sulphide ore deposits, which at some localities include visible accumulations of organic matter [14], and in some cases concentrations of up to 8.6% organic carbon [15]. The sulphide deposits formed during late Devonian to early Carboniferous, about 340 Ma ago, when Ireland suffered from rifting and extension during the break-up of an old red sandstone continent This event was accompanied by widespread volcanism and the production of hydrothermal ore deposits, including the sulphides [16]. The sample locality for this study is the Mullaghwornia quarry at Ballymahon, central Ireland (Figure 1) This is an abandoned quarry exposing Dinantian (Lower Carboniferous) limestone, with a zone of hydrothermal calcite veining, containing pyrite and organic matter, cross-cutting a limestone-host.
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