The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1924-01-31
The Problem of Ore Deposition

@. e. Spur editor, in "Reviey
Number and Year Book" of Engineer
ing and Mining Journal ress)
The class of ore deposits especial
ly consider in my recent work, 9TH,
/ Ore Magmas.' is that of the metal,
which. relatively speaking, are no
abundant in the earth's crust, such a:
copper, lead, zinc and the still less
common ores of metals such as gold
and silver. Contrasted with these are
the commoner elements, such as iron
aluminium, sodium and potash. My
book contains nothing that is new
concerning the commercial deposits OF
these commoner metals and minerals
treat them briefly in one charter, in
which l also summarize the ore de-
posits due to mechanical concentra-
ton at the earths surface. such as
the placers.
''As l see it, there are two great
classes of ore deposits, or concen-
tratiOns of the earth's elements,
of commercial volume and purity
the one Characteristic of the
atmosphere-rock contact zone
above the solid crust. and marked
10y quantitativeiy large coneentra-
lions of the commoner elements,
chiefly through the precipitating
effect of organic life; the other
the result of the differentiation of
igneous magmas in the zone be-
low the solid rock crust, and
marked by concentrations of all
elements. whether common or
rare. Other forms of ore concen-
tration believe are relatively I'M
important"
The first group, formed at or near
the surface or in what 1 call the at
mosphere rock contact zone. includes
the carbon minerals. coal and petro-
leum, most iron ores. salt and potash
and phosphate deposits.
This outline, so far. leaves the field
clear to consider metals such as cop
per, lead, zinc, gold and silver. How
were they formed? When I first stud
led geology the current belief was
that they had been leached out of the
rocks by ordinary ground waters (of
atmospheric origin) and concentrated
into assures This was the view of
Sandberger. in Germany, and of Van
Hise and Emmons. among many 9TH
srs, in this country. Later on, in
1898, Posepny published treatise in !
which he directly opposed this belief |
md suggested that hot springs-as-
ending hot waters-were the agents |
hat had brought the metals from the |
epths and concentrated them in or
ear assures. This view was widely
ccepted. although modified later by a
eneral belief that these hot waters,
instead of being primarily of atmo-
pheric origin, were newborn waters
iven off from igneous rocks cooling
l depth; reverting. in this respect, to
he views of Ellie de Beaumont, set
)rth as early as 1S47. Thus arose
he conception of magmas and the
'rm magmatic, as applied to ore de-
referring the origin of
res to igneous magmas.
In 1898 I proposed that certain gold
lartz veins were formed not by slow {
position in assures from magmatic $
aters but by magmatic differentia- n
these veins were an ex-
enc form or variation of pegma-
.es. This view. since that time. has e
me TO be widely held. Il was orig =
ally proposed by Thomas Belt in o
81, as I discovered in 1916. In 1907, W
the zornal theory of ore Il
position, which postuiated that. in II
e extreme differentiation product or OF
iidual magma Of igneous rock mag
Is, many metals are preset, which, 81
the decrease of rock temperature Of
ing upward, is slow. are precipitat- pl
successfully. so that above the gold VI
lrtz veins come copper veins, then hi
c, then lead and then silver; or. If
decrease of rock temperature. go
upward, is more rapid. these met tw
C zones are combined, forming wi
nplex ores such as gold copper or ia
c-lead or lead-silver ores. This DO
lanation. also. has become widely iAs
epted. fie
low, in THE Ore Magmas" I bring lai