Vanadium, Uranium, Asteroid Impact, and Jet - Petrified Wood

Happy Jack Vanadium, Uranium Mine

Geology of the Happy Jack Mine White Canyon Area San Juan County, Utah
-By ALBERT F. TRITES, JR., and RANDALL T. CHEW, III

ABSTRACT
The Happy Jack mine is in the White Canyon area, San Juan County, Utah. Production is from high-grade uranium deposits in the Shinarump conglomerate of Triassic age. The Shinarump strata range from 16 to 40 feet in thickness and the lower part of these beds fills an eastward-trending channel that is more than 750 feet wide and 10 feet deep.The Shinarump conglomerate consists of beds of coarse- to fine-grained quartz- lose sandstone, conglomerate, siltstone, and claystone. Carbonized wood is abundant in these beds, and in the field it was classified as mineral charcoal and coal.

Channels within the Shinarump, cross-stratification, current lineation, and slumping and compaction structures have been recognized in the mine. Steeply dipping fractures have dominant trends in four directions, N. 65° W.t N. 60° E., N. 85° E., and due north.

Uranium occurs as bedded deposits, as replacement bodies in accumulations of "trash," and as replacements of larger fragments of wood. An "ore shoot" is formed where the three types of uranium deposits occur together; these ore shoots appear to be elongate masses with sharp boundaries.

Uranium minerals include uraninite, sooty pitchblende(?), and the sulfates betazippeite, johannite, and uranopilite. Associated with the uraninite are the sulfide minerals covellite, bornite, chalcopyrite, and pyrite. Galena and sphalerite have been found in close association with uranium minerals.

The gangue minerals include limonite and hematite (present in most of the sandstone beds throughout the deposit), jarosite that impregnates much of the sandstone in the outer parts of the mine workings, gypsum that fills many of the fractures, and barite that impregnates the sandstone in at least one part of the mine. Secondary copper minerals, mainly copper sulfates, occur throughout the mine, but are most abundant in the outermost 30 feet of the workings. The bulk of the country rock consists of quartz and feldspar, and clay minerals.

The amount of uranium minerals deposited in a sandstone bed is believed to have been determined by the position of the bed in the channel, the permeability of the sandstone in the bed, and the amount of carbonized wood and plant remains within the bed. Not all of these features can be demonstrated in the Happy Jack mine itself. The beds considered most favorable for uranium deposition contain an abundance of claystone and siltstone both as matrix filling and as fragments.

Suggested exploration guides for uranium ore bodies include interbedded siltstone lenses, claystone and siltstone cement and pebbles, concentrations of "trash," covellite and bornite, chalcopyrite, and carbonized wood.

INTRODUCTION SCOPE AND PURPOSE
The Happy Jack mine contains the largest known uranium deposit in the White Canyon area, San Juan County, Utah (fig. 38). A detailed study was started by the U. S. Geological Survey to determine the mode of occurrence of the uranium minerals, and the structural and lithologic features useful as ore guides at the Happy Jack mine and elsewhere in the White Canyon area.

This report gives preliminary results of detailed mapping done during the 1952 field season, summarizes habits of the uranium deposits, and presents guides that may be useful in exploring for additional deposits. A map of the Happy Jack mine is shown in figure 39. The large-scale map (pis. 8, 9) of part of the mine was prepared by Trites and Renzetti from June 15 to July 4. Between August 7 and October 2 Trites and Chew mapped the walls of about 750 feet of drifts in the northeast part of the mine on a scale of 1 inch = 5 feet. The fracture map (pi. 8) was prepared from the information on the wall maps by projecting all fractures to a waist-high datum plane.The work described in this report was done on behalf of the Division of Raw Materials of the U. S. Atomic Energy Commission.

LOCATION
The Happy Jack mine is on the southwest rim above White Canyon in the western part of the White Canyon area, San Juan County, Utah.
The mine is about 15 miles by road east of Hite, Utah, and 75 miles west of Blanding, Utah (fig. 38) ; it is reached either from Hite or Blanding by Utah Highway 95, a graded dirt road that connects Blanding with Hanksville, Utah.

MOENKOPI FORMATION
In the White Canyon area the Moenkopi formation of early Triassic age is 195 feet thick and consists of interlayered beds of brown silt- stone, fine-grained sandstone, and shale; locally, it has a bed of conglomerate at the base. The Moenkopi strata just beneath the Shinarump conglomerate consist of brown micaceous sandy siltstone that has been bleached to grayish green. This siltstone is laminated, the laminae averaging 3 mm thick.

The contact of the Moenkopi formation with the overlying Shinarump conglomerate is an erosional unconformity produced by the flowing water that deposited the sediments of the Shinarump conglomerate.

SHINARUMP CONGLOMERATE
In the White Canyon area the Shinarump conglomerate is discontinuous, occurring in lenticular beds that have exposures ranging from a few hundreds of feet to more than 5 miles in length. A section of the Shinarump as much as 40 feet thick may pinch out within a distance of 2,000 feet.

The Shinarump strata at the Happy Jack mine are about 16 feet thick at the outcrop and thicken to 40 feet behind the rim. The out- crop of the Shinarump strata forms a ledge that extends 1/2 mile northwest and 1 1/4 miles southeast of the mine. Beyond these points the Shinarump pinches out.
The lower beds of the Shinarump conglomerate fill a channel more than 750 feet wide and 10 feet deep cut into the upper part of the Moenkopi formation. Diamond drilling by the U. S. Atomic Energy Commission indicates that the channel trends about due west but that the channel apparently bends rather abruptly beyond the south- western limit of the underground workings and continues southwest.

Diamond drilling further indicates that the channel is not well-defined, and that the bottom is marked by numerous scours.

Channels in the Shinarump are common within the mine and range from a few inches to 10 feet in width. This channeling is indicated by the presence of pinched-out beds and of abrupt lithologic changes both laterally and vertically. Three channels have been mapped in the Shinarump rocks (pi. 8).The Shinarump conglomerate is comprised of beds of coarse- to fine-grained quartzose sandstone, conglomerate, siltstone, and clay- stone. Many of the conglomerate beds grade laterally into coarse- grained sandstone; gradation also has been noted between beds of fine-grained sandstone and siltstone.

The sandstone beds range from 1 to 100 feet in length and from a few inches to 4 feet in thickness. A large number of these beds have poorly developed internal stratification, the clarity of this stratification depending upon the type of cross bedding and the angle at which the unit has been transected by the mine working. Most of the stratified units are lenticular, although some tabular units are present. Nearly all of the units have erosional lower surfaces as described byMcKee and Weir (1953).

Structural features within the beds include cross-stratification and contortion of the strata. Cross-stratification is very common in the sandstone beds; most of the sets of cross-strata have planar surfaceso f erosion as their lower bounding surfaces. These planar sets have resulted from beveling of the underlying beds and Subsequent deposition. Nearly all of the cross-stratification sets are lenticular, that is, are bounded by converging surfaces, the lower of which are commonly curved, Most Of the Cross-Strata arch downward and may be described as concave upward, The cross-strata in the part of the mine mapped dip from less than 10° to more than 20° ; the general direction of dip is about N, 65° w, The dip of the cross-strata suggests that the flow of streams here was from the southeast. Most of the cross- strata are termed high angle because the average maximum inclination is greater than 20° (McKee and Weir, 1953). Both medium-scale and small-scale cross-stratification are present, but the medium-scale cross-strata, 1 to 10 feet in length, is more abundant.
Horizontal bedding is common only in sandstone beds and con- glomeratic sandstone beds that immediately overlie siltstone beds in the lower part of the Shinarump conglomerate. These conglomeratic sandstone beds contain abundant interstitial clay and silt.

Many beds have been contorted by slumping that has resulted from the collapse of steep channel sides shortly after consolidation. Such slump features are especially common in fine-grained sandstone and siltstone beds where units as much as 1 foot thick have been distorted. A fault with reverse movement near station R. (pi. 9) has a displacement of 2 feet and is believed to have been caused by rupture and movement at the time the sediments were deposited. Current lineation was observed in the siltstone in the-channel crossing the drift near station 0.

The sandstones are poorly sorted and consist predominantly of grains of quartz, from a trace to 5 percent microcline, and a trace of mafic accessory minerals. Mica seems to be absent in most of the sandstones although it is conspicuous in the sandstone of the Shinarump in most of the White Canyon area. The quartz grains range from angular to subangular, the degree of angularity depending largely upon the amount of authigenic quartz surrounding the original grains. The microcline grains are pale yellow to red, and are commonly subangular. The sandstone is cemented by. clay, iron oxides, and jarosite.

Larger granules and pebbles of quartz, quartzite, siltstone, and claystone comprise from 1 to more than 10 percent of many of the sandstone beds. The pebbles of quartz and quartzite are as much as 1 inch in diameter and are commonly well-rounded. The siltstone and claystone pebbles are most abundant in the lower parts of the sandstone beds and are as much as 4 inches across.

Siltstone occurs in beds ranging from 1 to 4 feet thick and from 10 to 100 feet in length; it is also in small stringers from one-eighth to one-half inch thick and from 1 to 6 feet long. The siltstones are gray, greenish-gray, yellow, pink, or combinations of these colors. Most of the siltstones are sandy, and many grade laterally into sandstones. Horizontal contacts, however, are very sharp and vertical gradations through large ranges in grain size have not been found.

The conglomerate occurs in poorly defined units that are lateral gradations of coarse-grained sandstone. The conglomerate consists largely of pebbles of siltstone and claystone with few pebbles of quartz and quartzite.

Carbonized wood is abundant in the Shinarump conglomerate. Two forms of carbonized woody material have been recognized, a soft black mineral charcoal and a vitreous coal. The wood occurs both as logs and as accumulations of smaller fragments which have been called "trash deposits." These trash accumulations tend to be near the bottom of the sandstone beds, and commonly the contact between two cross-stratified beds will be marked by a thin trash deposit from less than 1 inch to 6 inches thick. Carbonized vegetal material is abundant as partings and fragments in many of the siltstone beds. The largest logs mapped are 2 to 3 feet long and 4 to 6 inches in diameter. Many of the logs have been replaced by sulfide minerals, pitchblende, hematite, limonite, and secondary copper minerals. Many smaller pieces of carbonized wood have been replaced by pyrite.