Iron Ore in the Llano Region, Central Texas. Digital Download

RI0005D. Iron Ore in the Llano Region, Central Texas, by V. E. Barnes, S. S. Goldich, and F. Romberg. 50 p., 9 figs., 8 plates, 1949. ISSN: 2475-367X. doi.org/10.23867/ri0005D. Downloadable PDF.


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ABSTRACT
The magnetic iron-ore prospects of the Llano region of central Texas were investigated in a program which combined dip-needle and gravity-meter surveys by the Bureau of Economic Geology of The University of Texas and the U.S. Geological Survey with exploration by the U.S. Bureau of Mines. Magnetic observations were made on the Iron Mountain, the Bader, the Gamble, and the Olive mine prospects. Gravity observations were made over the first three areas, which subsequently were drilled. Approximately 65,000 long tons of ore is indicated for the Iron Mountain deposit. The investigations indicate the applicability of combined dip-needle and gravity-meter surveys in search of magnetic iron-ore deposits.


Keywords: iron ore, Llano area, Llano County, Central Texas, mines, magnetic data


CONTENTS

Abstract

Introduction

Location

Previous work

Field work

Methods

     Magnetic observations

     Gravimetric data

Geology

     General features
     Pre-Cambrian rocks
     Paleozoic rocks
Iron ores

     General description
     Origin

     Description of prospects

         Iron Mountain

           Bader prospect

           Gamble prospect

           Olive mine prospect
           Minor prospects

               Willow Creek area

               Keyser Creek area
               Elm Creek area

               Martin (Deep) Creek area

               Northeastern Gillespie County

           Showings
               North of Llano

               Waters Creek area

               South of Valley Spring

               Waddell property

           Residual deposits

               Garrett property

               Riley Mountain area

Summary and conclusions

References cited

Appendix

     Logs of diamond-drill holes, Llano and Mason counties, Texas
         Table 1. Iron Mountain
         Table 2. Bader prospect
         Table 3. Gamble prospect

     Analyses of samples from diamond-drill holes, Llano County, Texa
         Table 4. Iron Mountain
         Table 5. Bader prospect

Index

FIGURES

1. Index map showing location of iron-ore prospects in central Texas
2. Geologic map of Iron Mountain and vicinity, Llano County, Texas
3. Sketch showing geology of the 50-foot level, Iron Mountain, Llano County, Texas
4. Cross sections of the Iron Mountain deposit from drilling and mine workings data
5. Index map of the Bader prospect, Llano County, Texas
6. Sketch of U. S. Bureau of Mines trench showing location of samples, Bader prospect,Llano County, Texas
7. Dip-needle observations, Gamble iron-ore prospect, Mason County, Texas
8. Gravitational force, Gamble iron-ore prospect, Mason County, Texas
9. Dip-needle observations, Olive mine prospect, Llano County, Texas

PLATES

I. Graphic logs of U.S. Bureau of Mines diamond-drill holes, Iron Mountain, Llano County, Texas
II. Map of Iron Mountain magnetite deposit with gravitational force contours
III. Longitudinal section of force over Iron Mountain ore body and longitudinal section of ore body
IV. Diagram of Iron Mountain ore body from drilling data; mass from gravity data for comparison
V. Dip-needle observations, Bader iron-ore prospect, Llano County, Texas
VI. Gravitational force, Bader iron-ore prospect, Llano County, Texas
VII. Gravitational force with regional gradient subtracted, Bader iron-ore prospect, Llano County, Texa
VIII. Graphic logs of U. S. Bureau of Mines diamond-diamond-drill holes, Bader and Gamble iron-ore prospects, Llano and Mason counties, Texas


Citation
Barnes, V. E., Goldich, S. S., and Romberg, F., 1949, Iron Ore in the Llano Region, Central Texas: The University of Texas at Austin, Bureau of Economic Geology, Report of Investigations No. 5, 50 p. doi.org/10.23867/ri0005D.