OBSIDIAN BUTTE
IMPERIAL COUNTY,
SOUTHEASTERN CALIFORNIA
This prehistorically popular, somewhat vitrophyric obsidian source has been covered in fine detail by Richard Hughes. I refer you to his paper. We have a good source standard data library for this source at Berkeley, and routinely analyze archaeological collections from San Diego, Imperial, and Riverside Counties:
Hughes, Richard E. (1986). Trace element composition of Obsidian Butte, Imperial County, California. Southern California Academy of Science Bulletin 85:35-45.
In December 2009 the samples originally collected in the 1980s were re-analyzed on the ThermoScientific Quant'X for both oxides and trace elements as seen below. This mildly peralkaline obsidian exhibits a unique elemental composition in the region.
Raw elemental concentrations for Obsidian Butte source standards, and RGM-1 USGS obsidian standard. All measurements in parts per million (ppm).
|
Sample |
Ti |
Mn |
Fe |
Zn |
Rb |
Sr |
Y |
Zr |
Nb |
Ba |
Pb |
Th |
|
OB-1 |
1183 |
403 |
17247 |
78 |
134 |
26 |
116 |
331 |
31 |
641 |
18 |
23 |
|
OB-2 |
1664 |
438 |
21732 |
76 |
125 |
53 |
98 |
422 |
30 |
727 |
24 |
18 |
|
OB-3 |
1640 |
449 |
21495 |
76 |
132 |
52 |
100 |
435 |
27 |
767 |
19 |
18 |
|
OB-4 |
1435 |
410 |
19807 |
78 |
137 |
28 |
125 |
369 |
35 |
594 |
19 |
20 |
|
OB-5 |
1366 |
406 |
18883 |
73 |
126 |
45 |
105 |
377 |
26 |
702 |
20 |
17 |
|
OB-6 |
964 |
365 |
14559 |
72 |
131 |
20 |
119 |
303 |
33 |
552 |
20 |
26 |
|
OB-7 |
1464 |
424 |
19694 |
71 |
122 |
46 |
94 |
419 |
22 |
730 |
18 |
20 |
|
OB-8 |
969 |
381 |
16358 |
80 |
148 |
20 |
133 |
313 |
35 |
625 |
21 |
20 |
|
OB-9 |
1598 |
422 |
19922 |
75 |
121 |
47 |
98 |
415 |
24 |
684 |
19 |
15 |
|
OB-10 |
1467 |
401 |
19067 |
68 |
121 |
48 |
94 |
405 |
21 |
701 |
19 |
23 |
|
OB-11 |
1358 |
387 |
17890 |
75 |
133 |
41 |
113 |
355 |
29 |
685 |
19 |
24 |
|
OB-12 |
1758 |
462 |
22674 |
81 |
129 |
51 |
100 |
437 |
27 |
804 |
17 |
24 |
|
RGM1-S4 |
1482 |
290 |
12850 |
39 |
151 |
107 |
21 |
223 |
12 |
893 |
27 |
19 |
Mean and central tendency for the Obsidian Butte data shown in the table above.
Selected major oxides for sample Obsidian Butte-9 (OB-9)
|
Sample |
SiO2 |
Al2O3 |
CaO |
Fe2O3 |
K2O |
MgO |
MnO |
Na2O |
TiO2 |
|
Obsidian Butte, CA |
|
|
|
|
|
|
|
|
|
|
OB-9 |
73.846 |
12.485 |
1.163 |
2.951 |
4.358 |
<.001 |
0.067 |
4.402 |
0.239 |
|
RGM1-S4 |
75.680 |
12.477 |
1.3024 |
1.806 |
4.550 |
<.001 |
0.0379 |
3.77 |
0.196 |
This page maintained by Steve Shackley (shackley@berkeley.edu).
Copyright © 2009 M. Steven Shackley. All rights reserved.
Revised: 18 December 2009
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