Mother Lode '92 Field Conference : August 15 to 20, 1992 : guidebook volume 1, text

190 Pages·1992·26.6 MB·English

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MOTHER LODE "92
FTELDb CONFERENCE
August 15 to 20, 1992
GUIDEBOOK VOLUME I
Text
Conducted by
BUREAU OF LAND MANAGEMENT
Gregg Wilkerson
Editor
BLM Library
Denver Federal Center
Bldg. 50, OC-521
P.O. Box 25047
Denver, CO 80225
3000 U.S. Bureau of Land
GEN MOTHER LODE /92
MoLm FIELD COONFERENCE
Aug92 AUGUST 15 TO 20,
940000671992
MOTHER LODE ke
FPILELD CONFERENCE
August 15 to 20, 1992
GUIDEBOOK VOLUME I.
Text
Conducted by
BUREAU OF LAND MANAGEMENT
Gregg Wilkerson
Editor
BLM Library
Denver Federal Center
Bldg. 50, OC-521
P.O. Box 25047
Denver, CO 80225
Denver Fe de ral te
P.O. Box 2!5 0
Ot Sizes
Denverc oll
ais
PREFACE
The Mother Lode 92 field conference is sponsored by the Bureau of
Land Management. It was conceived and conducted by personnel from
the Bakersfield District and the Folsom Resource Area Offices. This
conference seeks to bring together earth scientists, historians and
regulatory personnel to provide information to the public about the
geology, history and mine permitting procedures along the Mother
Lode Gold Belt.
The Bureau of Land Management is committed to public education and
is providing this field conference as a service to public land
users. It is part of an outreach program started in 1991 to have
monthly public earth science field trips within the Bakersfield
District.
This field conference would not be possible without the efforts of
several dozen volunteers. This project has become a community
effort and we look forward to future conferences of this type in
a3.
We appreciate particularly the volunteer efforts of:
Dana Brown
Cotati, California
David Lawler
Principle
Lawler and Associates Applied Geoscience
Berkeley, California
Far West Geoscience Foundation
David Lawler, Executive Director
Berkeley, California
Shirley Mitchell
California State Mining and Mineral Museum
Mariposa, California
Steve Hanson
West Point, California
This is the first trip BLM has conducted for which teachers may
receive college credit. Up to 5 quarter units are available through
the Extended Studies and Regional Programs Department of California
State University at Bakersfield. Course number ED-X992.546 costs
$25.00 per unit.
For more information about BLM earth science field trips contact
Dr. Gregg Wilkerson at 805-861-4210 or write BLM, 800 Truxtun Room
302, Bakersfield, CA 93301.
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Extended Studies and Regional Programs
California State University, Bakersfield
9001 Stockdale Highway /-
Bakersfield, California 93311-1099
805/664-2441
Course Title: Mother Load Gold Belt
Instructor: Dr. Gregg Wilkerson
Course Number: ED X992.546
Units: 1.0-5.0 variable quarter units
teacher in-service
Cost: $25 per unit
Checks payable to CSUB
Note: It will not be necessary to get a new course number each
time you run this course; however, teachers will only get credit for
this course number once. Also, check on the cost. It is likely that
the per unit fee will increase next year (probably on June 1).
Please return all checks attached to the completed registration form
to CSUB-Extended Studies for processing immediately. A course list
will be prepared and sent to you. It is important to return grades
promptly so that the teachers receive credit toward their pay
increases.
If you have questions or need more registration forms, call Sharon S.
Goldsmith, Program Coordinator-Extended Studies at 805-664-2444.
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The California State University
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INTRODUCTION
This field guide follows, with minor modifications, California
Division of Mines and Geology Bulletin 141 which was published in
1949. Incorporated for that portion of the trip from Mariposa to
Placerville is information provided by Landefeld and Snow in
Yosemite and the Mother Lode Gold Belt, American Association of
Petroleum Geologists Book GB68, 1991. In this guidebook sections
that are adapted from the 1949 field guide are noted by (49). Those
sections that are adapted from the 1991 guide are noted by (91).
All mine production values are from the 1941 guide and are not
adjusted for inflation or changes since then in the price of gold.
California State Highway 49, variously know as the Mother Lode
Highway or the Golden Highway, traverses over 270 miles of the
Sierra Nevada, beginning at Mariposa on the South and ending at
Sattley on the north. It passes through nine counties, each of
which represents an important part of the sierran Gold Belt (49).
This entire region has come to be known generally as the Mother
Lode country, but more technically speaking, the Mother Lode is a
belt of gold-bearing quartz veins which appears to start at
Mariposa and to terminate at Georgetown in Placer County. It forms
a more or less continuous belt of quartz veins that occupy a fault
zone approximately one mile wide and 120 airline miles long. The
10-mile segment of this belt between Jackson and Plymouth is its
richest section and was the source of one-half the gold produced in
the entire 120-mile extent, which has amounted to a quarter of a
billion dollars. It is noteworthy that this 10-mile segment lies
at the bend in the belt where its trend changes form northwest to
nearly due north. The Melones fault structure (Clark, 1964, 1970)
with which the Mother Lode quartz veins are associated may possibly
extend 50 miles farther northward to Downieville through Quincy.
Highway 49 leaves the Mother Lode at Placerville and swings 10-15
miles to the west, traversing the even more productive Grass
Valley-Nevada City district and other gold-bearing areas of the
northern Sierra Nevada (49).
The veins range from great white quartz masses 150 feet wide, down
to stringers less than the thickness of one's little finger. The
thickness of a vein is no criterion as to its potential value.
Rich pocket mines such as those of Jackass Hill were found largely
in narrow veinlets, whereas the massive silica-carbonate rock of
the Penon Blanco is practically barren of gold (49).
Mining methods and techniques developed in the California gold belt
have spread to the far corners of the earth and have become
standard practice everywhere. Many famous technicians and
financiers had their training in the Mother Lode Country before
attaining even greater distinction and achievement in other fields.
Bret Harte and Mark Twain owe much of their reputation to the gold
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