Notes, Caveats, and References
1) Terrestrial - Meteorwrong. All of the "meteorwrongs"
in the plots (large white circles) are for rocks that people have
had analyzed by Actlabs or some other lab and for which people sent
me the data. If you obtain a chemical analysis of your rock, please
send me the numbers!
2) Terrestrial - Geostandard. Many countries
have agencies that pulverize large quantities of rock
for use as interlaboratory standards. Several hundred geostandards
are available that represent all of the common, and many uncommon,
rock types of the earth. For most of these, there are many analytical
data available. I have selected from the compilation
of Govindaraju (1994) and Korotev (1996) data for 156 such rocks.
I have avoided data for soils and unconsolidated sediments, monominerallic
rocks (except chert, sandstone, limestone, hornblendite, magnesite),
ores (except for some iron ores, because these are sometimes mistaken
for meteorites), and geostandards that don't have data for the elements
I plot here. In total there are data for 7 andesites, 5 anorthosites,
17 basalts, 2 carbonatites, 1 chert, 6 diabases, 2 diorite or diorite
gneiss, 2 dolomites, 4 dunites, 15 gabbros, 21 granites and related
rocks, 5 granodiorites, 1 hornblendite, 6 iron ore or iron formation
rocks, 2 kimberlites, 1 quartz latite, 10 limestones, 2 lujavrites,
1 magnesite, 1 monzonite, 1 norite, 3 peridotites, 1 pyroxenite,
5 rhyolites including 1 obsidian, 1 sandstone, 5 schists, 3 serpentinites,
12 shales, 2 slates, 6 syenites, 2 tonalites, 3 trachytes, and 2
"ultrabasic rocks." Data for some trace elements are missing
for some of the GRS's.
3) Terrestrial - Tektite. I have plotted data of Koeberl
(1986) for various types of tektites. Note that tektites have
compositions
like terrestrial rocks (because they are!), not like meteorites.
4) All of the white points are for terrestrial rocks. All
of the black points and colored points are for meteorites.
5) All the meteorites plotted in the plots (all square
symbols) are stony meteorites, not stony-irons or irons.
6) Most (~70%) stony meteorites are chondrites, and most
chondrites are ordinary chondrites. If you have actually found a
meteorite, it's probably some kind of chondrite. That's why I made
the points for chondrites black and the ordinary chondrites BIG
and black. Chondrites are most dissimilar to Earth rocks. Each black
point represents the average composition of one of the chondrite
groups: H, L, LL, EH, EL, CI, CM, CV, CO, CR, CO, R, Ac, & K.
Data from Wasson & Kallemeyn (1988).
7) The lunar meteorite data are from my own database. Each
point represents a different meteorite.
8) For the martian meteorites, eucrites, howardites, diogenites,
and "other rare achondrites," each point represents a
meteorite or analysis. Data mostly from Jarosewich (1990), Lodders
& Fegley (1998), and Mittlefehldt et al. (1998).
9) The plots presented here reasonably represent >99%
of all meteorites.
10) If you have a meteorite, its composition must be consistent
with ALL of the chemical-composition parameters shown here, not
just some of them!
11) I should show some plots here for chalcophile (sulfur-loving)
elements - Cu, Zn, As, In, Sn, and Sb. The problem is that the concentrations
of these elements are so low in achondrites (= meteorites that are
not chondrites) that there are few data to plot. Chondrites have
higher concentrations of chalcophile elements than achondrites:
| chalcophile-element
concentrations in chondrites
(range of group means of Wasson & Kallemeyn, 1988)
values in ppm |
|
Cu |
Zn |
As |
In |
Sn |
Sb |
|
80-185 |
17-312 |
1-4 |
2-80 |
0.7-1.8 |
0.06-0.2 |
So, for example, if you have a rock with >5 ppm
As (arsenic), then the rock is not a meteorite. Many terrestrial
sedimentary rocks, as well as metamorphic rocks that formed
from sedimentary rocks, have concentrations of chalcophile
elements much higher
than
those in the table above.
References
Govindaraju K. (1994) 1994 compilation of working values and sample
description for 383 geostandards. Geostandards Newsletter
18, 1–158.
Jarosewich E. (1990) Chemical analysis of meteorites: A compilation
of stony and iron meteorite analyses. Meteoritics 25,
323-327.
Koeberl C (2006) Geochemistry of tektites and impact glasses. Annual
Review of Earth and Planetary Sciences 1986 14,
323-350.
Korotev R. L. (1996) A self-consistent compilation of elemental
concentration data for 93 geochemical reference samples. Geostandards
Newsletter 20, 217–245.
Lodders K. and Fegley B. Jr. (1998) The
Planetary Scientist’s Companion, Oxford University
Press, New York, 371 pp.
Mittlefehldt D. W., McCoy T. J., Goodrich C. A., and Kracher A.
(1998) Chapter 4. Non-chondritic meteorites from asteroidal bodies.
In Reviews
in Mineralogy,
Vol. 36, Planetary Materials (ed. J. J. Papike), pp. 4-1–4-195,
Mineralogical Society of America, Washington.
Wasson J. T. and Kallemeyn G. W. (1988) Compositions of chondrites.
Philosophical Transactions of the Royal Society of London,
Series A 325, 535-544.
|
