Midinfrared spectral features of rocks and their powders

Abstract

1] We examined the thermal IR spectra of 35 rock samples and their fine-powder equivalents to better understand the relationship between spectral features, particle size, and composition. The Christiansen features of solid crystalline rocks differ from those of their powdered samples, and the magnitude of this difference changes systematically with rock type. Both the Christiansen feature (CF) and the transparency feature (TF) in spectra of particulate igneous rocks are useful in rock type determination. They correlate better with the SCFM chemical index of rock type than with other numerical rock type indices that we considered. Major rock type divisions (acidic, intermediate, basic, and ultrabasic) could be distinguished using both CF and TF, but some overlap occurred if one or the other spectral feature was used alone. Spectral contrast decreases as rocks become more basic, probably because of increasing opaque mineral content. Likewise, metallic iron, formed as a result of space weathering in an airless environment, appears to be the most likely cause of reduced spectral contrast in mature lunar soils. Thus reststrahlen features should be difficult to detect in remote-sensing measurements of such bodies as the Moon and Mercury. Moreover, the vacuum environment of an airless planetary surface appears to enhance the CF, but it may eliminate the TF, depending critically on particle size. The Martian pressure and radiative environment, on the other hand, appears to enhance the TF, which should be sought in spectra of finely particulate surface areas on Mars. Additional environmental simulation spectral experiments are needed to more accurately define the roles of pressure, particle size, opacity, and insolation angle on apparent emissivity.

Synchrotron-based infrared microspectroscopy as a useful tool to study hydration states of meteorite constituents

“…Christiansen features in reflectance spectra are very useful for characterization of mineral composition, since the wavelength positions of these features do not vary as a function of grain size, crystal orientation, or crystallinity (Conel et al 1969;Salisbury et al 1991;Cooper et al 2002). Figure 4 shows the Reststrahlen bands and Christiansen features in the spectrum of a calcite inclusion from CM2 chondrite Cold Bokkeveld.…”

Sentinel-2 for Mapping Iron Absorption Feature Parameters

“…Geologic remote sensing is based on spectral analysis of minerals and rocks, initially conducted by Hunt and Salisbury [17][18][19]. Goetz and Rowan [20] used Landsat Multispectral Scanner (MSS) to derive iron oxide maps for the first time.…”

Infrared Emissivity of Major Minerals Measured by FT-IR

“…(8) Salisbury and Walter, 1989;Cooper et al, 2002;Donaldson Hanna et al, 2012). RB는 방출도 스펙트 럼에서 다른 파장에 비해 값이 작게 나타나는 구간으 로 광물 구성 분자들의 진동에 의해 에너지가 흡수되 는 파장 영역이다.…”

“…석영의 경우 Si-O의 늘임 진동에 의한 흡수대가 8.2~9.2 μm에서 나타난다고 보고된 바 있다 (Salisbury and Walter, 1989). Conel (1969)에 의 해 처음 사용된 CF는 방출도가 최대가 되는 구간으 로 시료의 실수부 굴절율이 시료를 둘러싼 매질의 굴 절율에 근접한 파장에 나타나는 것으로 광물을 구분 하는 지표로 활용된다 (Cooper et al, 2002;Johnson et al, 2002;Bras and Erard, 2003). …”