An anomalous sample in a rock suite can result from localized alteration or contamination.
the verdict
CONTESTED
contested - the weight sits with the supporting side
refutedsupported
the weight of evidence
2 sources for · 0 against
The listed peer-reviewed source discusses an altered feldspathic cumulate rock sample found in Gale crater, though it does not fully establish the broader claim about general contamination and alteration in rock suites.
Askival is a light-toned, coarsely crystalline float rock, which was identified near the base of Vera Rubin Ridge in Gale crater. We have studied Askival, principally with the ChemCam instrument but also using APXS compositional data and MAHLI images. Askival and an earlier identified sample, Bindi, represent two rare examples of feldspathic cumulate float rocks in Gale crater with >65% relict plagioclase. Bindi appears unaltered whereas Askival shows textural and compositional signatures of silicification, along with alkali remobilization and hydration. Askival likely experienced multiple stages of alteration, occurring first through acidic hydrolysis of metal cations, followed by deposition of silica and possible phyllosilicates at low T and neutral-alkaline pH. Through laser-induced breakdown spectroscopy compositional analyses and normative calculations, we suggest that an assemblage of Fe-Mg silicates including amphibole and pyroxene, Fe phases, and possibly Mg-rich phyllosilicate are present. Thermodynamic modeling of the more pristine Bindi composition predicts that amphibole and feldspar are stable within an upper crustal setting. This is consistent with the presence of amphibole in the parent igneous rocks of Askival and suggests that the paucity of amphiboles in other known Martian samples reflects the lack of representative samples of the Martian crust rather than their absence on Mars.
Abstract Nine oils and 16 core samples were analyzed as part of the Alaskan North Slope Oil-Rock Correlation Study organized by the U.S. Geological Survey (USGS). Carbon isotopic measurements and gas chromatographic analyses were performed on whole oils, oil fractions, and rock extracts. Preliminary screening and more detailed analyses were made on the kerogens to determine their quality as sources of petroleum, maturity, and isotopic composition. Oil analyses suggest that there are three different genetic oil types. The Barrow-Prudhoe oils were defined by Magoon and Claypool (1981). They are characterized by their relatively high sulfur content, low API gravity and pristane/phytane ratio, and light carbon isotopic composition. The Simpson-Umiat oil type is identified by its low sulfur content, higher API gravity and pristane/phytane ratio, heavier carbon isotopic composition, and anomalously high concentrations of cyclic and aromatic light hydrocarbons. The third type is not an oil but represents compounds that oils, primarily Simpson-Umiat type, have extracted from immature sediments during migration. This third component was called Torok-Nanushuk and is noted by an anomalous light hydrocarbon distribution and relatively heavy carbon isotopic composition. It is possible to describe each of the oil samples in terms of mixing these three oil types in varying proportions. The Put River D-3 oil is typical of the petroleum found at the Prudhoe Bay field and contains mainly Barro
Everything we examined (2)
This check searched the claim as stated. It did not run a separate search for evidence against it.