Desert Crusts and Rock Coatings

2011 ◽  
pp. 131-180 ◽  
Author(s):  
David J. Nash
Keyword(s):  
Rock Coatings

Making silica rock coatings in the lab: synthetic desert varnish

2005 ◽  
Author(s):  
Randall S. Perry ◽  
Vera M. Kolb ◽  
Ajish I. Philip ◽  
Bridget Y. Lynne ◽  
Nicola McLoughlin ◽  
...  
Keyword(s):  
Desert Varnish ◽  
Rock Coatings

Siliceous-sulphate rock coatings at Zhenzhu Spring, Tengchong, China: the integrated product of acid-fog deposition, spring water capillary action, and dissolution

2019 ◽  
Vol 157 (2) ◽  
pp. 201-212
Author(s):  
Huaguo Wen ◽  
Wenli Xu ◽  
Yi Li ◽  
Yaxian You ◽  
Xiaotong Luo
Keyword(s):  
Amorphous Silica ◽  
Hot Spring ◽  
Capillary Rise ◽  
Volcanic Field ◽  
Spring Water ◽  
Wet Season ◽  
Acid Fog ◽  
Capillary Action ◽  
Fog Deposition ◽  
Rock Coatings

AbstractSiliceous-sulphate rock coatings were observed at Zhenzhu Spring, an acid sulphate hot spring in the Tengchong volcanic field, China. These rock coatings are mainly formed of gypsum and amorphous silica. Some alum-(K), voltaite, α-quartz and muscovite were also found. Four different laminae are developed in the rock coatings: gypsum layer, tight siliceous layer, tabular siliceous layer and siliceous debris layer. The gypsum layer is located at the top of the rock coatings, while other siliceous layers appear below the gypsum layer. Geochemical modelling of the fluids was performed to identify the mechanisms responsible for the formation of gypsum and amorphous silica. The results indicated that the occurrence of gypsum is related to the acid-fog deposition and amorphous silica mainly originates from spring water. Fog deposition provided the rock coatings with abundant SO42− and Ca, and the subsequent complete evaporation of the condensed fluids produced gypsum. Seasonal climate change (especially variation in rainfall) determines the fluctuations of capillary action and dissolution. Rainfall events in the wet season led to periods of non-precipitating gypsum and promoted the capillary rise of the spring water. Slightly diluted capillary water (a small amount of rainwater) covered the rock coatings, formed a tight siliceous layer on the rock-coating surface and/or filled the pores among the gypsum crystals forming many tabular siliceous aggregates. Heavy rainfall (high dilution), however, resulted in non-precipitating amorphous silica and accelerated the gypsum dissolution, leaving tabular pores around tabular siliceous aggregates and forming a tabular siliceous layer.

scholarly journals The black rock coatings in Rouyn-Noranda, Québec: fingerprints of historical smelter emissions and the local ore

2015 ◽  
Vol 52 (11) ◽  
pp. 952-965 ◽  
Author(s):  
Jaime N. Caplette ◽  
Michael Schindler ◽  
T. Kurtis Kyser
Keyword(s):  
Compatibility Effect ◽  
Chemical Weathering ◽  
Metal Sulfide ◽  
Silica Matrix ◽  
Metal Sulfate ◽  
Mixing Processes ◽  
Fe Oxides ◽  
Shadow Effect ◽  
Rock Coatings ◽  
Smelter Emissions

Smelting of base metal sulfide rich ore in Rouyn-Noranda, Québec, has led to the formation of black rock coatings on exposed rocks to a maximum distance of 6 km from the smelter centre. This study has shown that these coatings are excellent mineralogical and chemical fingerprints of smelter emissions, ore types, and elemental partitioning into mineral phases. The black coatings are composed of a silica-rich matrix that formed due to the intense chemical weathering of exposed silicate rocks interacting with acidic meteoric waters. They contain metal sulfate rich layers along the atmosphere-coating interface (ACI) and rock-coating interface (RCI) formed by the in situ dissolution and precipitation of metal(loid)-bearing phases. Entombed within the silica matrix are spherical particulates and particles composed of Cu- and Zn-bearing Fe oxides (e.g., spinels), Fe oxides (e.g., hematite), Pb silicates (e.g., alamosite), sulfates (anglesite (PbSO4) and minerals of the jarosite group), amphiboles, pyroxenes, micas, Na feldspar, and clinochlore. Concentrations of elements are low in proximity to the smelter but drastically increase ∼2 km from the stack, most likely the result of a shadow effect of the smelter. This shadow effect is more pronounced if an element is highly compatible with minerals of the jarosite and spinel groups; it is called the smelter-compatibility effect. Elements displaying a high smelter-compatibility effect are Ag, Cu, Se, and As, whereas elements such as Hg, which is incompatible with the jarosite and spinel groups, show a low smelter-compatibility effect. High δ34S (5.5‰) values in proximity to the smelter and their decrease with distance is the result of mixing processes between primary and secondary sulfates in the atmosphere. The relative enrichments of metal(loid)s in coatings at Rouyn-Noranda and Sudbury, Ontario, when normalised to the MUd standard from Queensland, Australia, (MUQ) reflect the composition of the smelter emissions, ore, and lithologies. Black rock coatings of the Rouyn-Noranda and Sudbury study areas are enriched, for example, in Pb and Fe, respectively, reflecting higher abundances of galena and Fe-bearing minerals in the respective ore, emissions, and rocks in the region.

Using the Rock Art Stability Index to facilitate management of rock art in Wadi Rum, Jordan

1969 ◽  
Author(s):  
Zainab Gharib
Keyword(s):  
Cultural Heritage ◽  
Rock Art ◽  
Stability Index ◽  
Decay Rates ◽  
World Heritage Site ◽  
Unesco World Heritage ◽  
Heritage Site ◽  
Natural Rock ◽  
Unesco World Heritage Site ◽  
Rock Coatings

The Wadi Rum Protected Area (WRPA) in Jordan, inscribed as a UNESCO World Heritage Site, is an iconic desert landscape and significant for both its natural and cultural heritage. The most notable form of cultural heritage in the Wadi are the thousands of petroglyphs on the local Umm Ishrin sandstone. Tourist activity, however, poses a threat and potentially accelerates the decay of this resource beyond natural rock decay rates. Therefore, in an effort to better manage this cultural resource, a large sample of these rock-art panels have been examined by an international team funded under the USAID/SCHEP program, and scored based on the degree of decay they have undergone using the Rock Art Stability Index (RASI). RASI has five general categories that rate geological stability, rock decay processes - past, present and impending - and rock-coatings; the variables within each category are scored on a scale of zero to three, corresponding to “Not Present”, “Present”, “Obvious,” and “Dominant”. This method of scoring is suitable for use by experts and non-experts alike, and data collection can be conveniently accomplished using ESRI’s Survey123, a form-centric and field-friendly mobile application. Through the use of a Geographic Information System (GIS) such as ArcGIS Online, these data can then easily be organized, analyzed, represented, and shared. In an effort to better direct attention to those panels that need the most immediate care, and to validate the RASI methodology, my research focuses on using statistical analyses of correlation to highlight any relationships between processes of decay.

scholarly journals Strategies for 14C Dating the Oxtotitlán Cave Paintings, Guerrero, Mexico

2017 ◽  
Vol 5 (2) ◽  
pp. 170-183 ◽  
Author(s):  
Jon Russ ◽  
Mary D. Pohl ◽  
Christopher L. von Nagy ◽  
Karen L. Steelman ◽  
Heather Hurst ◽  
...  
Keyword(s):  
Time Frame ◽  
Low Temperature Plasma ◽  
14C Dating ◽  
Temperature Plasma ◽  
Cave Paintings ◽  
Late Formative ◽  
Absolute Dating ◽  
Rock Coatings ◽  
Oxidation System ◽  
Early Formative

ABSTRACTOxtotitlán Cave paintings have been considered among the earliest in Mesoamerica on stylistic grounds, but confirmation of this hypothesis through absolute dating has not been attempted until now. We describe the application of advanced radiocarbon strategies developed for situations such as caves with high carbon backgrounds. Using a low-temperature plasma oxidation system, we dated both the ancient paint and the biogenic rock coatings that cover the paint layers at Oxtotitlán. Our research has significantly expanded the time frame for the production of polychrome rock paintings encompassing the Early Formative and Late Formative/Early Classic periods, statistically spanning a long era from before ca. 1500 cal B.C. to cal A.D. 600.

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