Irving Friedman

Geochemistry and origin of formation waters in the western Canada sedimentary basin—I. Stable isotopes of hydrogen and oxygen☆

Abstract Stable isotopes of hydrogen and oxygen, together with chemical analyses, were determined for 20 surface waters, 8 shallow potable formation waters, and 79 formation waters from oil fields and gas fields. The observed isotope ratios can be explained by mixing of surface water and diagenetically modified sea water, accompanied by a process which enriches the heavy oxygen isotope. Mass balances for deuterium and total dissolved solids in the western Canada sedimentary basin demonstrate that the present distribution of deuterium in formation waters of the basin can be derived through mixing of the diagenetically modified sea water with not more than 2.9 times as much fresh water at the same latitude, and that the movement of fresh water through the basin has redistributed the dissolved solids of the modified sea water into the observed salinity variations. Statistical analysis of the isotope data indicates that although exchange of deuterium between water and hydrogen sulphide takes place within the basin, the effect is minimized because of an insignificant mass of hydrogen sulphide compared to the mass of formation water. Conversely, exchange of oxygen isotopes between water and carbonate minerals causes a major oxygen-18 enrichment of formation waters, depending on the relative masses of water and carbonate. Qualitative evidence confirms the isotopic fractionation of deuterium on passage of water through micropores in shales.

Hydration Rate of Obsidian

The hydration rates of 12 obsidian samples of different chemical compositions were measured at temperatures from 95� to 245�C. An expression relating hydration rate to temperature was derived for each sample. The SiO2 content and refractive index are related to the hydration rate, as are the CaO, MgO, and original water contents. With this information it is possible to calculate the hydration rate of a sample from its silica content, refractive index, or chemical index and a knowledge of the effective temperature at which the hydration occurred. The effective hydration temperature can be either measured or approximated from weather records. Rates have been calculated by both methods, and the results show that weather records can give a good approximation to the true EHT, particularly in tropical and subtropical climates. If one determines the EHT by any of the methods suggested, and also measures or knows the rate of hydration of the particular obsidian used, it should be possible to carry out absolute dating to � 10 percent of the true age over periods as short as several years and as long as millions of years.

Part I, The Development of the Method

A freshly exposed surface of obsidian will take up water from the atmosphere to form a hydrated surface layer. This layer has a different density and refractive index than does the remainder of the obsidian. Using special techniques, a thin section of the obsidian cut at right angles to the surface can be prepared. When examined under the microscope the hydrated layer is visible and its thickness can be measured. Photomicrographs of such thin sections are shown. Factors that determine the rate of hydration were considered. Using artifacts from archaeological sites of known age, the influence of temperature, relative humidity, chemical composition of the obsidian, burning and erosion of the obsidian on the rates of hydration was determined. Temperature and chemical composition are the main factors controlling the rate of hydration. Obsidian hydrates more rapidly at a higher temperature, and thus progresses at a faster rate in tropical than in arctic climates. Rhyolitic obsidian hydrates more slowly than does trachytic obsidian. Using archaeological data from various parts of the world, several tentative hydration rates were determined for tropical, temperate, and arctic climates. The method in its present state of development is especially suited to determine relative chronologies in layered sequences of artifacts from a single site, or region. It is also useful for detecting fake artifacts. Future work to refine the method is suggested.

Stable isotope composition of waters in southeastern California 1. Modern precipitation

Over a 7-year period from April 1982 to April 1989, integrated samples of rain and snow were collected at 32 sites by oil-sealed storage gage stations in (and adjoining) the southeast California desert; station elevations ranged from −65 m to 2280 m, and the collection network covered an area measuring about 400 km in each dimension. Deuterium (δD) analysis of 406 samples shows that the average δD of summer precipitation was −56 per mil (‰) whereas winter values averaged −78‰, averaged annual values were close to −69‰ because most of the area is in a winter-dominated precipitation regime. We found no correlation between wetness or dryness of a season and the δD of its precipitation. The δ18O versus δD plots show that rain samples define a line of slope 6.5, less than the 8 of the Meteoric Water Line, whereas snow samples define a line of slope 9.2. These differences in slope are the result of isotopic fractionation which occurred during evaporation of raindrops but not during sublimation of snow. Trajectory plots of 68 of the major storm events show that all of the winter storms originated in the Pacific, and passed over high mountains before reaching our collection stations. However, 21 of the 30 summer storms had trajectories that originated either over the Gulf of Mexico or the subtropical Pacific and traveled either west or north to reach our stations, without traversing high mountains. The difference in δD between winter and summer precipitation is due to different air flow patterns during those seasons.

Some investigations of the deposition of travertine from Hot Springs—I. The isotopic chemistry of a travertine-depositing spring☆

Abstract The isotopic compositions of the travertine and of the hot spring solutions were studied at Main Springs and New Highland Terrace in the Mammoth Hot Springs area of Yellowstone Park. The springs issue at 74°C and a pH of 6.65 and the carbon isotopic composition of the travertine depositing at the orifice is +2%.δC13 (PDB). As the water travels out from the orifice, it cools and loses CO2. The travertine depositing at lower temperature is enriched in C13, reaching values of +4.8%. and the solution has a pH of 8.2 at 27°C. The δC13 of the carbon species in solution is about −2.3%. at 74° and about +4.3 at 27°C. Therefore, the difference in δC13 between the solid and solution is approximately 4%. at 74° and decreases to zero at about 20°C. These differences are shown to be due to kinetic (non-equilibrium) factors. The δO18 contents of the travertine and water show that in most samples the carbonate oxygen is in equilibrium with the water O18 at the temperatures of deposition. This is especially true for travertine depositing slowly and at temperatures above about 50°C. Calculations based on pH and alkalinity titrations of the hot spring waters in situ show that at the spring orifice the water is very high in free CO2, which is quickly lost in transit. The springs are supersaturated with respect to both aragonite and calcite during most of their travel in the open air. The carbon isotopic composition of the travertine is similar to that in the marine carbonates that are adjacent to the springs and that are the probable source of the calcium carbonate. The travertine from inactive prehistoric springs near Mammoth has similar δC13 and O18 to that from the active springs. Soda Butte, an inactive center 25 miles east of Mammoth, contains heavier carbon and oxygen than the springs near Mammoth.

HYDRATION OF NATURAL GLASS AND FORMATION OF PERLITE

The hydration rate of rhyolitic glass has been determined at temperatures ranging from 5° C to 100° C. The relationship between the depth of hydration, x, and time, t is x 2 = kt; k varies from 0.4 μ 2 /10 3 years at 5° C to 10 4 μ 2 /10 3 years at 100° C; k is independent of the water pressure from a few hundredths of a centimeter to 1 atm. water pressure. The activation energy of hydration is about 20 kcal/mole. The determined hydration rates are consistent with the observation that perlite commonly forms by the hydration of shattered rhyolitic glass, either during the late cooling of a deposit or after the deposit has cooled to a surficial temperature.

The deuterium content of water in some volcanic glasses

Abstract The deuterium-hydrogen composition (relative to Lake Michigan water = 0.0) of water extractsd from coexisting perlite and obsidian from eleven different localities was determined. The water content of the obsidians is generally from 0.09 to 0.29 per cent by weight, though two samples from near Olancha, California, contain about 0.92 per cent. The relative deuterium concentration is from −4.6 to −12.3 per cent. The coexisting perlite contains from 2.0 to 3.8 per cent of water with a relative deuterium concentration of −3.1 to −16.6 per cent. The deuterium concentration in the perlites is not related to that in the enclosed obsidian. The deuterium concentration in the perlite water is related to the deuterium concentration of the modern meteoric water and the perlite water contains approximately 4 per cent less deuterium than does the groundwater of the area in which the perlites occur. The above relations hold true for perlites from northern New Mexico, east slope of the Sierra Nevada. California Coast Range, Yellowstone Park, Wyoming, and New Zealand. As the water in the obsidian is unrelated to meteoric water, but the enclosing perlite water is related, we believe that this is evidence for the secondary hydration of obsidian to form high water content perlitic glass.

Obsidian hydration dating and correlation of Bull Lake and Pinedale Glaciations near West Yellowstone, Montana

The ages of the last two glaciations near West Yellowstone, Montana, can be calculated by obsidian hydration techniques that are calibrated by K-Ar dating of obsidian-bearing lava flows. The average age of glacial abrasion of obsidian in the Pinedale terminal moraines is about 30,000 yr, with most age measurements between 20,000 and 35,000 yr. For the Bull Lake moraines, it is about 140,000 yr, with most measurements between 130,000 and 155,000 yr. This age for the Bull Lake moraines is also supported by geologic relations that show that the moraines are older than a rhyolite flow dated by K-Ar as 114,500 ± 7,300 yr old (lσ). These obsidian hydration ages of the Pinedale and Bull Lake Glaciations correlate well with the last two cold intervals of the marine record. The age determined for the Bull Lake Glaciation near West Yellowstone antedates the last interglaciation of the marine record, which is commonly correlated with the Sangamon Interglaciation. Our results suggest correlation of the Pinedale Glaciation near West Yellowstone with much or all of the Wisconsin Glaciation and of the Bull Lake with the late Illinoian. This differs with the commonly accepted correlation of the Pinedale with the late (“classical”) Wisconsin and of the Bull Lake with the early Wisconsin. The correlation of Bull Lake with late Illinoian appears equally or more compatible with traditional criteria for correlation, namely comparative soil development and degree of preservation of morainal morphology.

The 1.7- to 1.8-b.y.-old trondhjemites of southwestern Colorado and northern New Mexico: Geochemistry and depths of genesis

Four trondhjemitic bodies — three of intrusive and one of extrusive origin — 1.7 to 1.8 b.y. in age occur in the Precambrian rocks of northern New Mexico and southwestern Colorado. These are the metamorphosed plutonic or hypabyssal trondhjemite of Rio Brazos, New Mexico, the interlayered quartzofeldspathic and metabasaltic metavolcanic Twilight Gneiss of the West Needle Mountains, Colorado, the syntectonic Pitts Meadow Granodiorite of the Black Canyon of the Gunnison River, Colorado, and the late syntectonic to posttectonic Kroenke Granodiorite of the Central Sawatch Range, Colorado. From south to north, over a distance of 235 km, the four rock units show systematic increases in average Al2O3 from 13.7 to 16.1 percent, in K2O from 1.5 to 2.6 percent, in Rb from 28 to 76 ppm, and in Sr from 101 to 547 ppm. Initial Sr87/Sr86 ratios are low — 0.7015 to 0.7027 — and suggest a mafic or ultramafic source. All four trondhjemite bodies have similar light rare-earth element (REE) contents. The trondhjemites of Rio Brazos and the Twilight Gneiss have relatively flat patterns (Ce/Yb 10) with low heavy rare earth content and small or no Eu anomalies. Whole-rock δO18 values for siliceous rocks of three of the bodies range from 5.8 to 8.0 per mil, although the Pitts Meadow Granodiorite gives values of 8.5 to 9.4 per mil. The parent magmas for these bodies were probably generated from a parental basaltic source, either by partial melting or fractional crystallization. Fractional crystallization mechanisms would operate at crustal levels where crystallization of plagioclase and clinopyroxene or hornblende would produce the Rio Brazos and Twilight magmas, and crystallization of hornblende, plagioclase, and biotite would produce the Kroenke and Pitts Meadows magmas. The preferred partial melting mechanism would produce the Rio Brazos and Twilight magmas at shallow depth (< 50 km), leaving a residue of plagioclase and clinopyroxene or amphibole; the Pitts Meadow magma at 50 to 60 km, where hornblende, garnet, clinopyroxene, and plagioclase would be residual; and the Kroenke magma at greater than 60 km leaving a residue of garnet and clinopyroxene. The magmas probably formed in a ridge-and-basin complex that lay between the early Precambrian craton to the north and the contemporaneous quartzite-rhyolite-tholeiite terrane to the south. A northward-dipping subduction zone can be postulated from the variation in compositions and inferred depths of melting, but complete modern analogues of similar setting are not known. A better tectonic analogue might be the Archean regimes, in which vertical motion is dominant and trondhjemitic magmas may have formed by melting at the base of foundering thick volcanic piles.

Meteoric Water in Magmas

Oxygen isotope analyses of sanidine phenocrysts from rhyolitic sequences in Nevada, Colorado, and the Yellowstone Plateau volcanic field show that δ18O decreased in these magmas as a function of time. This decrease in δ18O may have been caused by isotopic exchange between the magma and groundwater low in 18O. For the Yellowstone Plateau rhyolites, 7000 cubic kilometers of magma could decrease in δ18O by 2 per mil in 600,000 years by reacting with water equivalent to 3 millimeters of precipitation per year, which is only 0.3 percent of the present annual precipitation in this region. The possibility of reaction between large magmatic bodies and meteoric water at liquidus temperatures has major implications in the possible differentiation history of the magma and in the generation of ore deposits.