Outer Rind Research Articles

Petrologic and stable isotope study of the gold-bearing breccia pipe at the Golden Sunlight Deposit, Montana

The Golden Sunlight, a gold-silver deposit in the Whitehall mining district, Jefferson County, Montana, is centered on a silica-cemented breccia pipe with fragments of both Belt Supergroup sedimentary rocks and a latite porphyry. Native gold and gold tellurides occur finely disseminated within gangue minerals that have filled open spaces in the breccia pipe.Alteration in and around ( approximately 0.8 km radius) the pipe is principally quartz-sericite. Within the pipe, breccia fragments are also characterized by a highly silicified outer rind. Openspace filling is divided into four periods as follows according to the presence of the following minerals: (I) quartz and pyrite, with minor hematite, chalcopyrite, bornitc, and gold minerals; (II) chalcopyrite, with lesser amounts of galena, sphalerite, and martasite; (III) additional gold-silver tellurides and tennantite; and (IV) barite, quartz, and sericite with minor carbonates and pyrite. Isotopic study shows delta 34 S values of sulfides between -12.2 and +3.1 per mil, whereas barite values range from 1.2 to 5.9 per mil. Oxygen isotope values of whole-rock breccia samples range from 6.5 to 13.8 per mil, quartz from 10.5 to 14.3 per mil, sericite from 9.7 to 15.5 per mil, and unaltered country rock from 12.3 to 16.6 per mil. Fluid inclusion homogenization studies indicate a temperature of deposition for period I mineralization of approximately 200 degrees C. The coexistence of sylvanitc and petzite in period III suggests a temperature less than 170 degrees C. Values of delta 18 O (sub H 2 O) computed from quartz and temperature data and sericite delta 18 O values range from -2.4 to +4.0 per mil. Hydrogen isotope values of fluid inclusions in period I quartz and water in equilibrium with late sericite fall betweem -56 and -33 per mil. Fluid inclusion freezing study of one sample of period I quartz suggests a fluid salinity of <1 equiv. wt percent NaCl.Isotopic and geologic evidence is consistent with tbrmation of a breccia pipe caused by exsolution of a vapor from a crystallizing magma. Oxygen and hydrogen isotope data suggest that extensive isotopic exchange between a magmatic fluid and igneous rocks occurred prior to open-space filling. Initial brecciation was accompanied by an isoenthalpic temperature decrease, which coupled with conductive cooling led to the precipitation of large amounts of silica. Textural features indicate that brecciation and fracturing, followed by fluid infiltration, occurred episodically. Sulfur isotope data is also consistent with derivation of sulfur from a magmatic source characterized by a delta 34 S (sub Sigma s) value between 0 and 5 per mil. Evidence from mineral assemblages and sulfur isotopes suggests that gold was most likely transported as a chloride complex and was deposited due to a pH increase accompanied by decreases in f (sub O 2 ) and possibly temperature.

Metamorphic History of a High-Grade Blueschist Exotic Block from the Franciscan Complex, California

A high-grade blueschist tectonic block from the Franciscan Complex of the northeast Diablo Range shows evidence of three episodes of retrograde blueschist facies metamorphism ± deformation developed under progressively declining P-T conditions. The first retrograde metamorphism involved formation of an outer rind of actinolite + chlorite + rutile ± phengite, and the growth of coarse-grained chlorite + pumpellyite within the block. During the second event the rind and outer edge of the blueschist were folded, sheared and fractured, and primary glaucophane within the blueschist was replaced by albite, medium-grained chlorite, and glaucophane-crossite. The third retrograde metamorphism was marked by the pseudomorphic replacement of rind actinolite by aragonite and quartz. Aragonite also crystallized extensively within th block, accompanied by lawsonite, chlorite, jadeitic pyroxene, and crossite; this last mineral assemblage is identical to that of the surrounding Franciscan metasedimentary rocks. Features characteristic of the first and second retrograde metamorphic events are readily observed in other high-grade tectonic blocks of the Franciscan Complex and the correlative Otter Point Formation of Oregon. In contrast, evidence of a third retrograde metamorphism, matching that of presently associated Franciscan and Otter Point rocks, has been found in some but not all blocks examined so far. The high P/T conditions of prograde metamorphism and the available metamorphic age determinations suggest that the tectonic blocks originally formed in a pre-Franciscan subduction zone setting. Fragments of blueschist and eclogite from this metamorphic terrain were tectonically incorporated in a serpentinite diapir, and they developed alteration rinds through interaction with the enclosing ultramafic rock. The available data suggest that the examined exotic block and at least some others were transferred to the Franciscan as detritus from a body of serpentinite that reached the earth's surface. Such blocks were then resubducted and metamorphosed along with their presently associated sedimentary sequences.

The age and mode of formation of Gaussberg, Antarctica

Abstract Circumstantial evidence indicates that Gaussberg, an isolated, 370 m high volcanic cone on the Antarctic coast at 57°S, 89°E, is the product of subglacial eruption. The vesicular, highly potassic leucitite, of which Gaussberg is composed, has been dated by K‐Ar and fission‐track methods, the former being applied to leucite concentrates, the latter to glassy leucitite from the ropy‐textured, outer rind of a pillow‐like structure. The K‐Ar geochronology yields an average date of 56 000 ± 5000 years, jwhich is interpreted as defining the time of Gaussberg's formation. The fission‐track work yields a less precise date, which supports the K‐Ar age estimate. These new age determinations indicate that previously published K‐Ar age determinations of 20 Ma and 9 Ma for Gaussberg should be rejected.

Uranium in Tertiary Sediments in Alaska: ABSTRACT

The early search for uranium in the continental Tertiary sediments in Alaska raised the question of whether the necessary processes to produce epigenetic uranium deposits ever occurred under the paleoenvironmental conditions that existed this far north. Recent discoveries, however, have demonstrated that epigenetic uranium enrichment occurred in these Tertiary sediments. At present, the most intensely explored and best known uranium occurrences in Tertiary sediments are found in the Healy Creek basin. The richest occurrence found in this area is in discontinuous beds of sideritic nodules near the base of the Oligocene and Miocene Healy Creek Formation where it overlies the Mississippian(?) Totatlanika Schist. The Healy Creek Formation consists of a clay-rich, gray to light-reddish-brown conglomeratic sandstone containing carbonized plant debris. The nodules are 2-5 cm in diameter. They have a reddish-brown, outer goethitic rind, a yellowish-brown, inner sideritic core, and scattered gray areas containing uraninite and manganite. A composite sample of the sideritic nodules contained 717 ppm uranium and 2,000 ppm manganese. A low-grade roll-front deposi has also been reported from this area. The roll front is in the Miocene Suntrana Formation, which consists of coal-bearing pebbly quartz sandstone. Slight uranium enrichment (12 ppm) had been reported from a thin carbonaceous sideritic bed in a conglomeratic part of the Tertiary Kenai Formation near Camp Creek in the Susitna Lowlands. Additional collections yielded a sample containing 72 ppm. A uranium occurrence has been reported from the Tertiary Kootznahoo Formation on Kuiu Island in southeastern Alaska. The Kootznahoo consists of arkosic dolomitic sandstone containing carbonized wood fragments. As much as 0.23% gamma eU (0.13% beta eU) was found in the carbonized wood fragments. Some of the samples also contained apatite and siderite. Siderite and carbonized plant material are common to all the known uranium deposits in Tertiary sediment in Alaska. The siderite suggests alkaline conditions and the carbonaceous material indicates reducing conditions. Tertiary ash beds and other volcanic sediments were the apparent sources of uranium for the Healy Creek and the Kuiu Island deposits. Cretaceous and Tertiary granite and quartz monzonite were the apparent sources of uranium in the Susitna Lowlands occurrence. End_of_Article - Last_Page 698------------

Alteration and mineralization associated with a vesicular dike near Yeoval in New South Wales, Australia

The Yeoval copper prospect in central New South Wales lies adjacent to the Molong rise, a belt of volcanic rocks considered to represent a fossil island arc of Siluro-Devonian age. The principal rocks of the prospect are equigranular granodiorite which has been intruded by porphyritic microgranodiorite. Porphyritic dacite dikes, up to 15 m wide, intrude both of these older intrusive rocks. Similarity in chemistry and mineralogy suggests that all three rock types are comagmatic.The widest dacite dike has a zoned mineral assemblage associated with the development of a 7 to 8 m-wide central zone of vesicles. The vesicles contain quartz, chlorite, sphene, calcite, and copper sulfides and vary in size from 1 mm in the outer parts of the zone to 4 mm in the center of the zone.It is proposed that vesiculation of the dike occurred after it intruded the granodiorite and after an abrupt fall in the confining pressure which may be related to pressure release in the parent stock. Retrograde boiling following this pressure release probably resulted in the formation of gas bubbles and in rapid cooling of the residual liquid. This boiling process accounts both for the occurrence and distribution of vesicles and for the texture observed within the dike.The zone of vesicle development was more permeable than the massive outer rind of the dike and allowed passage of solutions migrating upward from the parent stock. These solutions caused changes in mineralogy and produced chemical zonation. High copper values are associated with the depletion of K, Ca, Rb, and Sr and enrichment of Na, Si, Zn, and Mn. The assemblage quartz-chlorite-sphene-albite-epidote was produced in the most intense zone of alteration. This assemblage suggests a temperature range of 350 degrees to 400 degrees C. The pressures at the time of alteration may have been 1 kb or less since the dike is likely to have intruded to depths of approximately 2 km.

The Oldest Marine Carbonate Ooids Reinterpreted as Volcanic Accretionary Lapilli, Onverwacht Group, South Africa

ABSTRACT Sand-sized spheroids in the 3.4 billion-year old Onverwacht Group, South Africa, previously interpreted as silicified marine carbonate ooids, were constructed of loose volcanic dust and ash and closely resemble accretionary lapilli found in younger volcanic sequences. They commonly show concentric internal structuring, including a nucleus, a relatively coarse-grained detritus layer made up of recrystallized vitric and crystal grains, and an outer rind of recrystallized fine-grained ash. The outer rind was rigid when the grains were deposited whereas the detritus layer was soft and plastic. Graded lap Jill beds lacking current structures represent air-fall lapilli and ash which accumulated rapidly under shallow water to subaerial conditions. The tops of many units were reworked by curr nts to form flat- and cross-laminated layers. Accretionary lapilli are known from many younger volcanic sequences, but seldom represent more than trace accumulations and are rare as water-deposited grains. Their apparent abundance in Archean terranes in both South Africa and Australia may suggest that the geologic and hydrologic setting of certain Archean volcanic complexes favored the formation and preservation of accretionary lapilli. It may reflect, however, an abnormally wet early atmosphere or the relatively higher rate of outgassing of volatiles through early Precambrian volcanoes.

STRUCTURE OF AERIAL AND SUBMERGED SCLEROTIA OF COPRINUS LAGOPUS

SUMMARYSclerotia were formed in both aerial and submerged parts of the mycelium. In addition a layer of cells with pigmented thick walls (called brown matting) which differentiated at the air/agar interface was interpreted as an aspect of sclerotial behaviour since it was regularly formed by strains which produced submerged sclerotia and was composed of cells of similar structure to those of the outermost layer of the submerged sclerotium. Apart from producing sclerotia and oidiospores the cells of the aerial mycelium remained undifferentiated. In contrast, cells of the submerged mycelium, though initially indistinguishable from those of aerial hyphae, became individually differentiated within about 5 days of growth producing two further novel cell types; inflated cells containing glycogen, and hyaline thick‐walled cells. Submerged sclerotia were pale brown in colour, irregularly shaped and about 0.5–1.0 mm in diameter. The only structure which differentiated the submerged sclerotium from the submerged mycelium was the outer rind, a layer of cells with thick, pigmented walls. The central (medulla) region contained the same cell types in the same frequencies as the general submerged mycelium. In sharp contrast the aerial sclerotia were highly organized structures composed of distinct and compact tissues. Mature aerial sclerotia were dark brown to black spheroidal structures up to 0.5 mm in diameter. An outer layer of dead and moribund hyphae surrounded the main body of the sclerotium which was bilayered with an outer rind and inner medulla. The rind was multilayered and consisted of small cells with thick pigmented walls; intercellular spaces were cuticularized. The medulla was a closely packed tissue composed predominantly of hyaline thick‐walled cells of the same type as were encountered in the submerged mycelium.

A scanning electron microscope study of developing sclerotia of Sclerotinia sclerotiorum

The exterior features of the rind and the cut surface of sections of developing sclerotia of Sclerotinia sclerotiorum were examined with the scanning electron microscope. Before pigmentation, a developing sclerotium appears as a white mass of interwoven mycelial strands covered with numerous droplets of liquid, each of which is surrounded by membranous material. Subsurface mycelial cells swell, become pigmented, and result in the formation of the dark bulbous rind cells which darken with age. Membranous material which envelops the liquid exuded from developing sclerotia was always evident and appressed to the surface of the rind in old sclerotia. The interior of sclerotia consists of a mass of mycelia embedded in an amorphous matrix, which in young sclerotia is liquid but in older sclerotia appears solid. Openings in the outer rind cells, from sclerotia of old cultures and those removed from diseased sunflowers, indicate possible means by which other microorganisms could enter and degrade sclerotia. Multiple sclerotia were examined and the region where fusion occurs was evident.

Characterization and classification of mycorrhizae of Douglas fir. II. Pseudotsuga menziesii + Rhizopogon vinicolor

A common tuberculate ectomycorrhiza of Douglas fir in the Pacific Northwest, described earlier by Trappe, is further examined and defined. Tubercles consist of an outer rind of aseptate, amber, thick-walled hyphae encasing tightly packed inner elements mantled with septate, hyaline, thin-walled hyphae. Reported as a Phycomycete and a Basidiomycete, respectively, the two hyphal forms actually belong to a single fungus, Rhizopogon vinicolor A. H. Smith; cultural characteristics of this fungus are described. Pure culture mycorrhiza syntheses with both mycorrhizal and sporocarpic isolates and Douglas-fir seedlings are reported. Antagonism tests revealed the following inhibition of root pathogens by R. vinicolor: strong—Phytophthora cinnamomi Rands, Pythium debaryanum Heese, and Pythium sylvaticum Campbell &amp; Hendrix; moderate—Fomes annosus (Fr.) Cke. and Poria weirii Murr.; and weak or none— Fusarium oxysporum f. pini (Hartig) Snyd. &amp; Hans., Pythium ultimum Trow, Rhizoctonia solani Kuehn, and Macrophomina phaseoli (Maubl.) Ashby.

Leaf Spiral and Yield in Coconuts

THIS communication refers to the recent article by Satyabalan, Ninan and Krishna Marar1, who perhaps unconsciously give more publicity to my findings relating to foliar asymmetry in the coconut palm2–4. The very first line of their statement, referring to the work of Petch5, is misleading. Petch did not deal with leaf-spirals of coconut in his paper and, in fact, there is no mention of leaf or foliar-spiral, or the arrangement of leaves along five spirals in a clockwise or anti-clockwise direction as reported. Presumably Petch's article was not available to the above authors. Petch explained the structure of the fibres in the coconut stem. Neglecting the outer rind, he found in a stem the vascular bundles sloping to the left in the outer 3.5 cm, followed by an abrupt reversal of direction for the next 3.5 cm. This was again followed by another reversal to the original left in the remaining inner core of the stem. In another stem, the condition was reversed; the same three regions were present, but in the outer the bundles sloped up to the right, in the intermediate to the left, and in the inner to the right again. These two types of palms were regarded by Petch as right- and left-handed coconut trees.

A "Tuckahoe" Found in Kansas

On March 27, 1951, Mr. Charles Freund of Andale, Sedgwick County, Kansas, brought to the Experiment Station a 4 X 4 inch piece of timber 4 feet long, which had a fungus overgrowth about 7 X 12 inches in size at one end. This overgrowth (Fig. 1) was brown in color with a ridged, hard outer rind which looked like bark. The timber had been located about 4 feet deep in sandy soil near the stockyards in Andale, Kansas, and was excavated in building opera-

Naras seed protein.

THE naras (Acanihosicyos horrida, Hook) is a cucurbitaceous plant, which occurs particularly near Walvis Bay in South-West Africa. The fruit is a small melon consisting of an outer rind and six segments which contain numerous seeds. The fruits and the seeds derived from them were extensively used as foods by the desert dwellers of the area in earlier days, and are still used to some extent in this way. More recently, the seeds have been collected and exported to South Africa, where they have found use in the confectionery industry. Versfeld and Britten1 found that the seed kernels consist mainly of protein (35 per cent) and fat (53 per cent).