7

ing degree, some are fissile, but near Grouse creek the rocks are in general
massive and only slightly sheared. Where the Lowhee and the Rainbow
members adjoin they cannot be separated from each other as the rocks
of both are much alike. The member contains many quartz veins, but it
has not been explored underground, and very little is known about the
persistence and value of the veins. In general it seems that the veins are
leaner than those in the Rainbow member.

Under the Lowhee member is a thick series of black argillites called
the Basal member. Northwest of the Lowhee ditch the Basal and B.C.
members adjoin, and make up a band of argillite 2,500 feet wide. West
of the Lowhee Creek-Stouts Gulch divide the member is 800 to 1,000 feet
wide. It is wide along Williams creek between McCallum gulch and Rich-
field and then narrows rapidly to the southeast and reaches Grouse creek
at the mouth of Downie creek as a band only 100 feet wide. The rocks of
the member are black argillite only slightly sheared. The member con-
tains quartz veins of good size but which appear to be very lean. Under
the Basal member are quartzites, argillites, and other similar clastic sedi-
ments containing large, apparently barren or very lean quartz veins.

The Baker member caps the gold belt on the northeast and the Basal
member forms the base on the southwest. Gold seems in general to be
concentrated toward the northeast side of the belt.

STRUCTURE OF THE GOLD BELT

The gold belt rocks are on the northeastern limb of a large north-
westerly trending anticline. The rocks strike northwest and dip northeast.
In the main the folding within the belt seems simple, but in some places
minor folds were seen where the dip changed from 45 degrees to horizontal
and back to 45 degrees in a breadth of outcrop of 5 to 50 feet. Fissility
induced by shearing stresses obscures the bedding in many places, how-
ever, and minor folds may be fairly common. In view of this, and although
the structure is believed to be simple because the rocks probably all dip
northeast, an alternative interpretation of the structure is given for part
of the belt. This interpretation is based not on observed strikes and dips
but on the mapping of rock types traceable for some distance along the
belt.

The Lowhee member ends abruptly northwestward at the Lowhee
ditch and widens rapidly southeastward to Lowhee creek. If this member
lay in the trough of a southeasterly pitching minor syncline the areal dis-
tribution of the rocks would be explained very well. Northwest of the
Lowhee ditch the member would be absent because it was eroded, and to
the southeast the breadth of the Lowhee member would become greater
because of the synclinal pitch in that direction. The B.C. argillite member
would then be at the crest of a sharp anticline, and would be the same
argillite band as that called the Basal member. The Lowhee member
would overlie it and would be a correlative of the Rainbow member. This
interpretation of the structure would account for the similarity displayed by
the Basal and B.C. members, and by the Lowhee and Rainbow members,
and would also explain the areal distribution of the Lowhee member.