PANAMINT RANGE, IGNEOUS R0< 207 
contact the limestone is considerably disturbed and dips sharply 
usually away from the monzonite mass. The small limestone area 
inclosed by monzonite on the southern border of the area appears to 
have been buoyed up on the surface of the molten rock. Smaller 
inclusions are common. An aureole of limestone from one-fourth 
to 1 mile wide is metamorphosed to a rather coarse-grain mar- 
ble. In this marble are bands, lenses, and irregular bodies of white 
marble. Large brown garnets, epidote, serpentine, and tremolite are 
present in the metamorphosed limestone. The two latter minerals 
occur in veins as well as in sporadic masses through the limestone. 
The quartz monzonite intrudes Pogonip limestone and is cut by 
pre-Tertiary diorite porphyry. It is presumably contemporaneous 
with the post- Jurassic granite, since intermediate facies between it 
and the granite, described on page 208, appear to exist. It is rather 
similar in mineralogic composition to the post-Jurassic granodiorites 
of the Sierra Nevada. 
Soda syenite. — About 11J miles southeast of Tin Mountain there is 
a very irregular mass of soda syenite and soda-syenite porphyry. 300 
feet long and 200 feet wide. It intrudes the Pennsylvanian limestone 
and sends into it many straight-walled dikes and ramifying veins of 
varying width. Prior to recent erosion the limestone appears to 
have covered the syenite. Bowlders of similar rock occur in the 
gulch due west of this area, but the masses from which these were 
derived were not located. Similar rock appears from a distance to 
form a small area 1 miles west of Lost Wagons. The soda syenite is 
characterized by abrupt and great changes in granularity and in the 
relative abundance of the constituent minerals. The predominant 
form is a coarse- to medium-grained rock of gray color, composed of 
predominant gray with some pink feldspar, subordinate greenish- 
black amphibole or pyroxene, and black mica. Many of the feldspars 
have good crystal outlines and in the more porphyritic facies the 
abundant feldspar laths have a length of 1J inches and are aligned in 
flow orientation. The rock next to the limestone is very fine grained. 
Epidote has developed at the expense of the hornblende and biotite in 
all facies. Under the miscroscope this rock proves to be a soda 
syenite or nordmarkite of hypidiomorphic and uneven granular tex- 
ture. The predominant constituents are alkali feldspars, including 
the species orthoclase, microperthite, and anorthoclase. With these 
is a little oligoclase. The alkali feldspars form rude tabular crystals, 
many of which are twinned according to the Carlsbad law. Between 
these tabular forms are anhedra of augite, quartz, biotite, and yellow- 
ish-brown garnet. The augite verges toward segirite-augite. The 
accessory minerals are titanite, magnetite, apatite, and fluorite. The 
fluorite flecks the alkali feldspar and may be original or introduced 
by magmatic gases. 
