A. K. Baird

Inorganic analyses of Martian surface samples at the Viking landing sites

Elemental analyses of fines in the Martian regolith at two widely separated landing sites, Chryse Planitia and Utopia Planitia, produced remarkably similar results. At both sites, the uppermost regolith contains abundant Si and Fe, with significant concentrations of Mg, Al, S, Ca, and Ti. The S concentration is one to two orders of magnitude higher, and K(<0.25 percent by weight) is at least 5 times lower than the average for the earths crust. The trace elements Sr, Y, and possibly Zr, have been detected at concentrations near or below 100 parts per million. Pebblesized fragments sampled at Chryse contain more S than the bulk fines, and are thought to be pieces of a sulfate-cemented duricrust.

Mineralogic and Petrologic Implications of Viking Geochemical Results From Mars: Interim Report

Chemical results from four samples of martian fines delivered to Viking landers 1 and 2 are remarkably similar in that they all have high iron; moderate magnesium, calcium, and sulfur; low aluminum; and apparently very low alkalies and trace elements. This composition is best interpreted as representing the weathering products of mafic igneous rocks. A mineralogic model, derived from computer mixing studies and laboratory analog preparations, suggests that Mars fines could be an intimate mixture of about 80 percent iron-rich clay, about 10 percent magnesium sulfate (kieserite?), about 5 percent carbonate (calcite), and about 5 percent iron oxides (hematite, magnetite, maghemite, goethite?). The mafic nature of the present fines (distributed globally) and their probable source rocks seems to preclude large-scale planetary differentiation of a terrestrial nature.

On the original igneous source of Martian fines

The composition of the silicate portion of Martian regolith fines indicates derivation of the fines from mafic to ultramafic rocks, probably rich in pyroxene. Rock types similar in chemical and mineralogical composition include terrestrial Archean basalts and certain achondrite meteorites. If these igneous rocks weathered nearly isochemically, the nontronitic clays proposed earlier as an analog to Martian fines could be formed. Flood basalts of pyroxenitic lavas may be widespread and characteristic of early volcanism on Mars, analogous to maria flood basalts on the moon and early Precambrian basaltic komatiites on earth. Compositional differences between lunar, terrestrial, and Martian flood basalts may be related to differences in planetary sizes and mantle compositions of the respective planetary objects.

Preliminary results from the viking x-ray fluorescence experiment: The first sample from chryse planitia, Mars

Iron, calcium, aluminum, silicon, and sulfur are major elements in the first surface sample of Mars that has been analyzed by the Viking x-ray fluorescence spectrometer. Titanium is present in minor quantities. This is consistent with the sample being a mixture of fine silicate and oxide mineral grains, with a significant proportion of sulfates, possibly hydrated. Ferric oxide is regarded as the red pigmenting agent on the martian surface, but if it coats silicate grains, the coatings must be very thin (≤ 2 micrometers) or discontinuous. A high abundance of Fe, relatively low abundances of Al, Rb, Sr, and Zr, and a high Ca/K ratio are distinctive features of the spectra. Preliminary determinations indicate the following abundances (as percentages by weight): Fe, 14 � 2; Ti < 1; S, 2 to 5; the Ca/K ratio by weight is greater than 5.

Heterogeneous phase reactions of Martian volatiles with putative regolith minerals

SummaryThe chemical reactivity of several minerals thought to be present in Martian fines is tested with respect to gases known in the Martian atmosphere. In these experiments, liquid water is excluded from the system, environmental temperatures are maintained below 0°, and the solar illumination spectrum is stimulated in the visible and UV using a Xenon arc lamp. Reactions are detected by mass spectrometric analysis of the gas phase over solid samples. No reacions were detected for Mars nominal gas over sulfates, nitrates, chloride, nontronite clay, or magnetite. Oxidation was not observed for basaltic glass, nontronite, and magnetite. However, experiments incorporating SO2 gas - an expected product of volcanism and intrusive volatile release - gave positive results. Displacement of CO2 by SO2 occurred in all four carbonates tested. These reactions are catalyzed by irradiation with the solar simulator. A calcium nitrate hydrate released NO2 in the presence of SO2. These results have implications for cycling of atmospheric CO2, H2O, and N2 through the regolith.

Inorganic chemical investigation by X-ray fluorescence analysis - The Viking Mars Lander

Abstract The inorganic chemical investigation added in August 1972 to the Viking Lander scientific package will utilize an energy-dispersive X-ray fluorescence spectrometer in which four sealed, gas-filled proportional counters will detect X-rays emitted from samples of the Martian surface materials irradiated by X-rays from radioisotope sources ( 55 Fe and 109 Cd). The output of the proportional counters will be subjected to pulse-height analysis by an on-board step-scanning single-channel analyzer with adjustable counting periods. The data will be returned to Earth, via the Viking Orbiter relay system, and the spectra constructed, calibrated, and interpreted here. The instrument is inside the Lander body, and samples are to be delivered to it by the Viking Lander Surface Sampler. Calibration standards are an integral part of the instrument. The results of the investigation will characterize the surface materials of Mars as to elemental composition with accuracies ranging from a few tens of parts per million (at the trace-element level) to a few percent (for major elements) depending on the element in question. Elements of atomic number 11 or less are determined only as a group, though useful estimates of their individual abundances maybe achieved by indirect means. The expected radiation environment will not seriously hamper the measurements. Based on the results, inferences can be drawn regarding (1) the surface mineralogy and lithology; (2) the nature of weathering processes, past and present, and the question of equilibrium between the atmosphere and the surface; and (3) the extent and type of differentiation that the planet has undergone. The Inorganic Chemical Investigation supports and is supported by most other Viking Science investigations.

Geochemical and Structural Studies in Batholithic Rocks of Southern California: Part II, Sampling of the Rattlesnake Mountain Pluton for Chemical Composition, Variability, and Trend Analysis

New techniques of X-ray fluorescence spectrography have extended the lower atomic-number limit of determination to 0.01 weight per cent Na in silicates. As a result, chemical analyses of coarse-grained rocks can now be obtained more easily than modal analyses. This paper is a discussion of results obtained from nearly 1000 new rock analyses of samples from the Rattlesnake Mountain pluton, San Bernardino Mountains, California. The new method of obtaining chemical data from granitic rocks has necessitated reexamination of sampling methods and designs. Samples must be large enough to be rocks, not merely fragments of constituent minerals. A portable diamond drill is a practical means of decreasing bias and extending the population sampled. Trend-surface analysis of individual elements is a useful computational technique for establishing general patterns of distribution. Factor (vector) analysis makes it possible to study simultaneously the variation of many elements. A more conventional way of achieving this result is to recast chemical analyses as norms; nearly 800 such norms have been computed for this paper. High-speed computers and automatic plotting devices have proved essential for the processing and reduction of our chemical data. Hierarchical sampling enables one to analyze the variance and to measure its components on different scales, information which is essential to the justification of supposed chemical differences between rocks. Chemical mapping requires knowledge of the variance within localities, and more than one sample must be collected at each locality if this variance is to be measured. It is concluded that the analytical precision is more than adequate for this geochemical purpose; local variability in the rocks themselves is usually the limiting factor.

Transverse Ranges Province: A Unique Structural-Petrochemical Belt across the San Andreas Fault System

The San Gabriel and San Bernardino mountain ranges of southwestern California, and associated mountains and basins westward to the Pacific Ocean, make up a unique east-trending geomorphic, stratigraphic, petrologic, and structural belt 400 km long that is offset only a few tens of kilometers right laterally by northwest-striking faults of the San Andreas type. Spot correlations across these faults, suggesting displacements of hundreds of kilometers, perhaps have other explanations. Within the transverse ranges and basins, the east trend is shown by the general petrology, the crystalline rock patterns, pre- and post-batholithic structural features, and batholithic chemical patterns. The east-west unity is especially striking west of the San Andreas fault, but it is also evident in the central and southern San Bernardino Mountains, east of that fault. The Salton Trough and the southern boundary of the Transverse Ranges Province appear to be the most important provincial boundaries in southwestern California. West of the San Jacinto fault, which is just southwest of the San Andreas fault and nearly parallel to it, the Transverse Ranges Province is bounded on the south by the Malibu Coast–Cucamonga fault zone. At and just east of the San Jacinto fault, the southern boundary fault zone is displaced by faulting 30 to 40 km to the southeast, and is continued as the Banning fault. East of the eastern (Mission Creek) branch of the San Andreas fault, east-trending faults are present, but the San Bernardino Mountains rocks and structures merge into the southeast-trending Little San Bernardino Mountains.

Chemical Trends across Cretaceous Batholithic Rocks of Southern California

Nine major and minor chemical elements and specific gravity have been determined for composite samples from 542 localities in Cretaceous batholithic rocks of southern California. The rocks range from gabbro to quartz monzonite. Chemical variations reflect the strong petrographic zonation of the region from abundant low-silica rocks near the continental margin to abundant high-silica rocks inland 100 to 150 km. The rocks are mostly quartz plutonites, and within each quartz plutonite group, most chemical variations are opposite those of the batholith as a whole; potassium, however, increases consistently inland. The variation of K cannot be correlated with the variation of any other major or minor element of the batholithic rocks in any of the rock types except gabbro. Though field relations and radiometric ages prove that the gabbroic rocks belong to the batholith, their magmatic origins appear to be separate from those of the intermediate- and high-silica rocks.

The Lakeview Mountains Pluton, Southern California Batholith Part II: Chemical Composition and Variation

Major elemental analyses and specific gravity determinations were made on bulked rock samples from 162 localities over the Lakeview Mountains pluton. Mineral separates from 126 localities were also analyzed. Results show that the pluton is highly homogeneous on the large scale with high heterogeneity on the small scale. Despite the high homogeneity, all analytical results define consistent zonational patterns approximately parallel to the walls of the body and to the concordant schlieren. This zonation shows that the Lakeview Mountains pluton has a relatively basic and dense core compared to its margin and implies that the last rock to crystallize was more basic than rock formed earlier.