Authigenic Green Mica in Interflow Horizons within Late Cretaceous Deccan Volcanic Province, India and Its Genetic Implications

Green authigenic mica, i.e., celadonite, is commonly associated with submarine alteration of basic igneous rock. However, very few studies have reported the formation of celadonite under nonmarine conditions. An integrated study involving field investigation, petrography, mineralogy, and mineral chemistry highlighted the origin of celadonite in two clay-rich horizons (green boles) of the Late Cretaceous Deccan volcanic province. Within the Salher green bole, the celadonite occurred as the dissolution and alteration of plagioclase, volcanic glass, and pore-filling cement. In the case of the Pune green bole, the celadonite was formed by the alteration of plagioclase, pyroxene, and precipitation as film within intergranular pores, along with zeolite. The celadonite in the Salher green bole exhibited slightly lower K2O and Fe2O3 and higher Al2O3 than in the Pune. The mineral chemistry of the former showed a composition closer to ferro-aluminoceladonite. Although the mineral chemistry of celadonite overlaps with glauconite, the distinct 10 Å and 15 Å reflections in XRD, euhedral lath and honeycomb morphology under SEM, and characteristic absorption bands in VNIR spectroscopy (0.4–2.5 µm) and FTIR spectroscopy (400–4000 cm−1) identified celadonite and Fe-smectite within green boles. The green boles were formed either by the alteration of a volcaniclastic deposit in local pools of water or by the in situ alteration of the fragmentary flow top. The present study is significant due to the occurrence of celadonite in a nonmarine environment, as it otherwise forms under submarine conditions.

Alteration of high alkaline and alkaline basaltic rocks: parent rocks in the Lava Durian orchard, Sisaket Province, NE Thailand

Lava Durian Sisaket is the first geographically identified (GI) fruit related to the volcano in Thailand and distributed in three districts of Sisaket Province, the southernmost edge of the Khorat Plateau. The parent rocks of orchards are important for the description of soil and rock relation with respect to mineralogical and geochemical characteristics. This work aims to study lithology, mineralogy, and geochemistry of basaltic rocks, parent rocks of in situ soil in these orchards, and delineate the existing basaltic soil models. The several orchards are covered by reddish-brown to brown in situ soils, weathered from mafic volcanic rocks: porphyritic olivine basalt, vesicular olivine basalt, and nephelinite. The microscopic image analysis, XRD, and MiniSEM-EDS are used to classify mineralogy, while XRF and analysis of large and rare elements in ICP-MS/ICP-OES were used to determine parental rocks geochemistry and alteration. The olivine basalts comprise forsterite microphenocrysts associated with bytownite, diopside, augite, pigeonite, and ilmenite groundmass, while nephelinite is composed of nepheline groundmass and bytownite-labradorite, diopside, augite, pigeonite, and ilmenite crystals. In addition, these basalts display high alteration rates, especially olivine highly altered to iddingsite. According to the geochemical data, Sisaket's basalts were identified as alkali basalt and nepheline basanite with high LILEs and LREEs (La, Nd, Pr, Gd, Eu). The kaolinite, smectite, and illite are altered from felsic minerals, while the chlorite and iddingsite are from mafic minerals. The mineralogical analyses classified secondary phyllosilicates related to low-moderate temperature hydrothermal fluid, very high cation exchange capacity (H⁺, K⁺, Ca²⁺, Mg²⁺), and tropical weathering. The alkaline and high alkaline basalts, presenting as parent rocks, are one of the parameters that produced good nitisal soil of Sisaket's agricultural areas.

Plasma Spectroscopy of Various Types of Gypsum: An Ideal Terrestrial Analogue

The first detection of gypsum (CaSO4·2H2O) by the Mars Science Laboratory (MSL) rover Curiosity in the Gale Crater, Mars created a profound impact on planetary science and exploration. The unique capability of plasma spectroscopy, which involves in situ elemental analysis in extraterrestrial environments, suggests the presence of water in the red planet based on phase characterization and provides a clue to Martian paleoclimate. The key to gypsum as an ideal paleoclimate proxy lies in its textural variants and terrestrial gypsum samples from varied locations and textural types have been analyzed with laser-induced breakdown spectroscopy (LIBS) in this study. Petrographic, sub-microscopic, and powder X-ray diffraction characterizations confirm the presence of gypsum (hydrated calcium sulphate; CaSO4·2H2O), bassanite (semi-hydrated calcium sulphate; CaSO4·½H2O), and anhydrite (anhydrous calcium sulphate; CaSO4), along with accessory phases (quartz and jarosite). The principal component analysis of LIBS spectra from texturally varied gypsums can be differentiated from one another due to the chemical variability in their elemental concentrations. The concentration of gypsum is determined from the partial least-square regressions model. The rapid characterization of gypsum samples with LIBS is expected to work well in extraterrestrial environments.

Volcanogenic fluvial-lacustrine environments in iceland and their utility for identifying past habitability on Mars

The search for once-habitable locations on Mars is increasingly focused on environments dominated by fluvial and lacustrine processes, such as those investigated by the Mars Science Laboratory Curiosity rover. The availability of liquid water coupled with the potential longevity of such systems renders these localities prime targets for the future exploration of Martian biosignatures. Fluvial-lacustrine environments associated with basaltic volcanism are highly relevant to Mars, but their terrestrial counterparts have been largely overlooked as a field analogue. Such environments are common in Iceland, where basaltic volcanism interacts with glacial ice and surface snow to produce large volumes of meltwater within an otherwise cold and dry environment. This meltwater can be stored to create subglacial, englacial, and proglacial lakes, or be released as catastrophic floods and proglacial fluvial systems. Sedimentary deposits produced by the resulting fluvial-lacustrine activity are extensive, with lithologies dominated by basaltic minerals, low-temperature alteration assemblages (e.g., smectite clays, calcite), and amorphous, poorly crystalline phases (basaltic glass, palagonite, nanophase iron oxides). This paper reviews examples of these environments, including their sedimentary deposits and microbiology, within the context of utilising these localities for future Mars analogue studies and instrument testing.