Genesis of Carbonate Breccia Containing Invisible Gold in Taebaeksan Basin, South Korea

Abstract

The Yemi breccia developed and is distributed within the Paleozoic carbonate rock (Maggol Formation) in the central part of the Taebaeksan Basin, South Korea. Explanation for the genesis of the Yemi breccia has been controversial. We investigated the petrological and mineralogical properties of the breccia and the matrix materials at 60 outcrops. The Yemi breccia is divided into crackle, mosaic, and chaotic breccias based on morphology. In addition, these are divided into blackish, reddish, grayish, and white to pinkish matrix breccias according to the materials of the matrix. Quartz, calcite, pyrite, hematite (after pyrite), and minor epidote, chlorite, and opaque materials mainly comprise the matrix materials. The pyrite grains from the Yemi breccia can be divided into two types based on the mineral texture: diagenetic and hydrothermal. We analyzed the chemistry of pyrite and hematite (after pyrite) from the Yemi breccia with an electron probe X-ray microanalyzer (EPMA). Invisible gold was detected within the pyrite grains by EPMA and disseminated micron-sized isolated gold particles were discovered by backscattered electron (BSE) images. The texture of Au-bearing pyrite and gold particles in the Yemi breccia is especially well matched with pyrite and gold from the Shuiyindong Carlin-type hydrothermal gold deposits, China. Therefore, we suggest an important role of hydrothermal fluid in karstification within the Paleozoic carbonate rock.

Contribution to the Understanding of the Colour Change in Bluish-Grey Limestones

“…The presence of iron, can provide a great diversity of colours to minerals and geomaterials, as known (e.g., [37,38]): goethite, α-FeO(OH), and siderite, FeCO3, form yellow-brown ochre; hematite, α-Fe2O3, depicts a characteristic grey colour when well crystallised and a red tonality in soils (regoliths); vivianite, Fe3(PO4)2•8H2O, displays either a blue or a purple colour [39]; and green tonalities are common for olivine, (Mg,Fe)2SiO4. Moreover, in what concerns sulphides, disseminated pyrite, FeS2, gives a grey colour to a carbonate matrix [40]. The Atlantic Blue ornamental variety, also known as Azul Cadoiço [41], is very similar to Azul Valverde.…”

“…The presence of iron in the form of ferric iron, Fe 3+ and ferrous iron, Fe 2+ influences strongly the hue and durability of the stone being limestone's colour related to the FeO/Fe 2 O 3 ratio [57]. Studies regarding the genesis of carbonate breccia in South Korea [40] revealed that the greyish matrix breccia consists mainly of calcite and dolomite, and minor quartz and pyrite and the yellowish part consists of pyrite that was oxidised to goethite or iron oxi-hydroxides.…”

Implications of brecciation in Pennsylvanian Atoka Bank complex carbonates, Eddy County, New Mexico

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The term "breccia" refers to a rock, composed of angular fragments larger than two millimetres, held together by a cement or matrix (Bates and Jackson, 1984). Brecciation results from igneous, sedimentary and tectonic processes or a combination of these (Blount and Moore, 1969;Shukla and Sharma, 2018;No et al, 2020). A breccia often is observed in carbonate rocks and mostly is attributed to dissolution-collapse mechanisms (

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