The regional strike of the sehistosi"l:;y is northwest·west with an average dip of 50° to the northeast. The Tertiary history of the region is mainly one of repeated uplift and erosion.
At Surf Point Mine in the central area of the stockpile are whe1-a flOViT low dull zones of. In the early stage of penetration of the stock:, before the shift along 'M30E scissor,.
STRUCTURAL PETROLOGY
CONTENTS
Structural Geology, 660 Level ) Folder Chino Limestone }
P etrofabric Diagrams ) Crestmore Q.uarries )
Petrofabric Diagrams, Crestm.ore and) Jensen ~uarries )
Structural features dipping east at -50° are (1) general dip of sediments (2) axial line of folds in limestone {3) flow lines and dip of flow beds in the Perris quartzite diorite and (4) dip of flow beds in other intrusive. 5) the axis of the band maximum for calcite optical axes. An unusual feature of the quartz diorite is two sets of flow layers that share a common lineament$.
INTRODUCTION
The general geology and physiography of the Perris Block was described by Dudley (1935 and 1936). Oriented samples of intrusive and limestone were taken from the 660 level of the Crestmor mine.
GENERAL GEOLOGY
The oldest rock of the series, a hype:rsthane diori at 11 ou· torops on the hills south-west of Crestmore. In the transitional zone the tonalite foliation is parallel to the b•dding planes of the shale. The included ions are xenoliths derived from hypersthene diorite and quartz biotite schist of the Jurupa Series.
It is probably the equivalent of the Cajalco quartz monzonite described by Dudley (1935) and the granite of the Val Verde district (Osborn, 193g). Granite Po~BhY,.~~· • In the western part of the Jurupa Mounta ins, granite porphyry is mined as a building stone. In the Crestmore quarries the pegmatites are more lens-like in outline and variable in composition than they are. the oasis in the adjacent hills.
Both Da ly (1935) and W oodford (1941) concluded that the contact rock is related to the intrusion of the quartz monzonite porphyry. On the limestone side of the garnet zone there is rapid gradation in places to rock consisting mainly of pale green or brown idoorase. Outside the garnet and idoc:ras e zones, the rare minerals merwinite, gehlenite and spurr:L te developed in the outer part of the contact zone.
STRUCTUHAL GEOLOGY
This suggests the development in this limestone of the same arcuate structure seen in the overlying Chino Quartzite and Sky Blue Limestone. The trough of the syncline (?) is penetrated by quartz diorite and quartz monzonite porphyry. The general trend of the formations is easterly with the average dip steeply to the south.
Apophyses and dykes of the tonalite strike about N.65°E. parallel running cross connections in the cracks. . r, tuartz. At Crestmore, the porphyry bodies east of the Commercial quarry are arcuate masses in the enclosing contact rocks. Flow structures in the various igneous rocks of the area were mapped with the technique developed by Hans Cloos and his collaborators.
Since m.ost limestone is too coarsely crystalline to accommodate this technique~. Throughout most of the mapped area (Plate 1) flow layers and seeps are visible internally. An unusual rate of flow structures {Figure 2.) is the development of 2 sets of flow layers.
Plate 10
- A s girdles normal to tectonic axis J:!•
The belt diagrams shown on samples in the central parts of the Chino Limestone are thought to result from rotation about the belt axis. The axis of the belt dips east at -40Q to 55° parallel to the fold axis in the Crestmore and Jensen quarries as determined by field mapping. This direction is nearly parallel to the dip of the schists and the striations in the quartz diorite.
However, if the axial fold line at Crestmo1·e is taken as .R a::i~ is for the area, then pos i ttons· e. This suggests an analogy for folding stiffness in easily deformed limestones. The projection of the limestone fold to the east would be the most favorable place to explore, but it is evidently deeply buried.
At the 660 level, the flattening of the flcrm,• lines in the .hanging wall may indicate that the limestone is quartz diorite. Exploration east of the Commercial quarry may show a similar thickening of ·the Chino Limestone on the e a st limb of the fold•. The igneous rocks of the are a display in the ir contacts and internal structures two ma in trends, one parallel to the N.15°W.
Few I nclvsion s
QUARRY
STRUCTURAL R1vERS,OE
GEOLOGY • EAST
SAN BERNARDINO
I NTRVSIVE.S
COUNTIES
PLATE 2
UPPE..R
CHINO
SECTION 1500.N
I NTRUS \VE.S
PLATE 3
660 LEVE.L
CHINO LIMESTONE. •
CALIFORNIA
PLATE 4
I NTRUS \VES
STRUCTURAL G~OLOGY
IV E RS\DE. COUNTY
J E.NSE.N QUARRIES
CAL\ FORNI A 1941
PLATE 5
38- 27 AXES
60-60AXES
DE.WSITY DIAGRAMS OF
CONTOUR INTERVAL
COMPOSITE 38,39,41,42,43,45
3\2AXES
IN PARTIAL FULFILLMENT OF THE
CALIFORNIA INSTITUTE OF TECHNOLOGY PASADENA, CALIFORNIA
MINERALOGY
Textural and paragenetic relationships of various Miners.ls minerals in transparent qu$.rl.~.
INTRODUCT!OM
Silver-Bearing: Mi:nerals9
Freibergite is relatively rare. . str:omeyerite prase:nt in operation is approximately equal to that of ruby silver,. The mineral is often found in isolated blocks, but ocoa. indicates distribution controlled by f'raeturing. In zoued lrUU<'U'alization of CQ 66 pyrit ocaurs only in silver ruhy zo:ne.
They are much less common and less widespread than ruby silver and are .fot.md only v. The oo-eurrenee most easily distinguished is that in which the gold occurs in a complex unit of heavy co:mmo:n sulphide- ruby silver mineralization" In this association. They are often apparently unaffected by KON. In several samples which are assayed at over:1" 2 ounces of gold per hour, these yellow spots are the only apparent source of value.
Coarse gold also occurs in greenish quartz and in transparent qaa.rtz, closely associated with the greenish quartz {CQ 54 and 202). Such gold may be accompanied by argentiteo. Fracture has controlled the distribution of the greenish gold and argentite. This gold mineralization is characteristic of the upper or northern end of the ore shoots at level 700 and of the shoot at Silver Prince 150 level, but is probably most extensively developed in the surface Cactus Hill pit.
Mercury and Arsenic Minerals
The low silvi9T value of the product indicates that argentojarosite is not common. The minerals determined in the superpanner studies of the ore correspond to those found in the polished section. Due to the relatively large amount of jarosites in the tailings, there may be some loss of silver as argenthojarosite.
In fact, the distribution of values seems to depend more on the rels:bive am.ounts 0£ the various idlers present than on the zoning within. The deposition of the various ga.ngues is divided into several periods of fracturing and breccia. Each subsequent fracture was the main control of the distribution of the following tailings.
The bony quartz is characterized by a lack of the small blobs either of minerals or of 'soft gangua' as occurs in the later. The transparent quartz is the host ge.ngue of the comm.on sulphide :minera.liza:tion, ·!:;he ruby silver, most of ·the t:U'gentite and some of the gold mineralization. The dark gray disseminated quartz is a variety of the transparent quartz so filled with very fine sulphides.
Calcite Boxwork Qua.rt£~
Dark gray disseminated quartz is a variety of transparent quartz thus filled with very fine sulphides. how to .appears dark gray. 23 - be more related to transparent quartz thRn earlier gnngues~ They, however, are much easier::ly mi:neral- i:zect. Qf ari oeeur inime eaitd.bonds filled with so.ft gangue (CQ 99) in a manner similar to oceur:renes in "che transparent quartz., Often.
It is found at the north or top of the three quartz lenses or segments at level 700, ()n level 150 of the Silver Prince, and reaches its maximum. In the Cactus Hill pit it is divided into areas of e.lunitization:n" kaolinizatian (diekite?) and silicification. The effects on the 150 level Silver Prince are between those seen in the Cactus Hill pit. Mound pit and snake at level 700 of the Cactus Queen.
On both the hanging and footwalls of the Silver Prhwe-vein there is a wide z-o:ua {l5' Z) of sil:lcification acicomp.nied by alunite and dickite. The soft gangue occurring in blebs in the transparent quartz is thought to be 0£ similar alunite.-diocite. It corrodes the early pyrite (CQ 109), appears to be responsible for some oi' the covell.ite, stromeyerite replacement of the common sulphides (CQ. 48), and contains small leaves (0.001 mm) of gold (CQ 99) .
TEXTURES AND PARA.GENESIS OF THE IiET.ALLIC MINERALS
At Stage 2, clear quartz accompanied the deposition of chert, gold, and ruby eulphides. At Cactus Hill Cave, the components of the soft ge.ngue are separated in zones of siliceous ice. In order for descending surface waters to have a significant effect on the enrichment of the original silver mineralization in the vein quartz, they would have to achieve the following:
Al:nmdrmee of' soft gene.gue at the northern end below the fault is probably due to its reopening. The Silver Prince has characteristics of the latter part of Stage 2 and earlier part of Stege 3. The high proportion of this bo:ny -,.quartz, relative ·ho the la:her: mineralized quartz, in pe,rts of.
In controlling the distribution and localization of the ore, the zoning is no less important than the brecciation and defecting of the inter-miner will be repeated. It has been noted that a large part of the gold and silver values in the entire deposit are of primary and hypogene origin. There should have been re:breccia.tion of this bone quartz in allm1 access of t:ra:nspa:rent quart.z and later o.re-holder.
