Arizona republican., 1903-11-11
GENESIS OF ORE DEPOSITS
Some Practical Suggestions as to the
Origin Of Mineral Veins.

can Institute % Mining Engineers. /
Mr.. Max Boehner. OF Denver, read an /
interesting paper on the Genesis of !
ore Deposits" from which We quote:
rh. first and most lasting impression
made upon the mind OF him who eN-
amlnes mine or mining district
consists in the observation that in each
and every clse there h an Intimate
association % the ores with the erup-
i've rocks ln the district. The mines !
In IA. Mississippi valley seem 10 be
fh. g,Iy exception 10 this rule. II may
h. uozFlbir that further development
az closer examination viii still dis
cover these. as was the case In Butte.
Mont In that district the pOrphyry
dff.s had not been exactly noted, and
,,..ra MOI generally known 10 exist until
al.it Ten years ago. when the frequent
lav- suits nelessitetsd q closer inspec-
tion ~ the ground. This Intimate as
ISOLATION &C the eruptive rocks with
the ores. true the world over con-
yinc@s the practical mind that there
must De- d greater relation between the
fy.1 Upon "a further examination OF
the district. 10 ls frequently found that
the ore-b14riug veins are confined 10
certain areas. although the eruptive
r.cks continue for miles beyond. This,
again. proves that other factors are
local In their origin and effect because
they are limited 10 certain portions
u any given district. This fact. II
would seem precludes any attempt 10
explain the origin OF ores which does
rot specifically account for the local.
zatlou u the deposit.
The most obvious conclusion 10 be
drawn from this intimate association
a. metnlLlferous veins and eruptive
rocks b.. that the source which furnish
ID the material Tor the rocks Is like
wise the source OF the waters which
deposited the ores IN the assures. /
take h AZ conolusively established that
by FAR the larger number Of ore-de-
rlsifs are the work Of underground
water. whether Il Is possible and
probable that the source indicated Is
the true one must be demonstrated in
a discussion % the circulation OF IN
derErouud waters.
All authorities agree that. as the
earth cools. cycle after cycle. an in
,reaslng amount OF water il absorbed
and added % the sea OF underground
water The water has worked its way
downward ever since the cooling crust
q the earth permitted its accumula-
lion az the surface. And this process
viii continue until the earth cOols TO
the center and finally absorbs all the
winters 90 the globe. The lower bound
nry or bottom OF this sea " water i
limited and determined by the heat
conditions u the interior. How far
this limit reaches. IL may be impossi-
Doe o. determine. but u Is certain that
Do reaches the region Of metamorph-
ism because this process Of change Of
the sedimenfary rocks cannot be car
rleI on without the presence OF water.
Ser o. this water "a local occurrence
brought about by the opening Of some
deep-renchlng assures or By the sub
rfd~nce u blocks OF sedimentary rocks
Including masses % water. This super
heated belt u water. near the bottom
% the underground sea. must be uni
vsrsal in is scope. because the under
lying granite f. universal The granite
represents the ultimate stage Of meta
morphism. and cannot crystalline ex-
c-pt cut Of magma In hydro-thermal
fusion.
10 this o. correct. We have passed the
zone 81 rOck-iiOwage. which. accord
INK 10 Prof. Van Hise. Is the down
ward limit Of underground water Per
hays the bottom OF the zone OF rock
uuwage is Identical with the belt oil
hydro thermal fusion
10 b "a weli-knOwn fact. and has beer
repeatedly demonstrated by expert
Turnt. that rocks which require tenn
perature d 30g0 degrees F for Ordi-
nary. dry fusion. can be made to as
sumo q pasty liquid form az a TEN
perature Of 500 degrees. in the pres
.ncr OF sufficient water under pres
sure.
These conditions must exist at sOm'
depth "a all points. II the existence o
an underground sea Cf water. eve
working it, way downward. is admitted
a. universal. The extent IN depth o
chs belt Of hydro thermal fusion it d
probable impossible 10 estimate. Blu
lts waters 10 not In active circulation
are ever moving and hard at work
teaching. extracting and keeping II
solution the most soluble element
present. This region must be the sea
- continual activity. The hydratiOi
and dehydratlon OF minerals. the crys
talking and dissolvlng and recrystal
liking must be ever going on. until y
have "a steady. never-failing reservio
90 superneated waters under grea
pressure and charged 20 saturatio
with the metals and the minerals pres
emf.
Nor can this reservoir be tapped froT
above and its burden OF metals in sOlu
lion D. brought toward the surfac
without "a catastrophe. The rending c
"a creyice or assure I'm the crust abov
sufficiently deep 10 reach this belt, an
sufficiently open 20 permit operation {
gravltative stress upward. alone. ca
start the circulation Of these water
and bring them toward the surface.
II d. correct. no doubt theoretically
that the waters Of a river running int
lake AT one end. and out at the 9th
o. affect and move the entire body {
water. however deep. So IL is true tina
the surface-waters. daily pouring dow
90 Join the underground sea. affect tn
entire sea 10 some extent.
But IN the deeper region. where tn
rocks are tight and the water work
SIS way slowly and gradually down
ward. friction most certainly has oh
liberated all effects. or nearly all, c
hydrostratic head and stress by differ
ence OF temperature. The sea in II
lower portions. therefore, must be re
gnrded as stagnant. And a stagnar
mass Of water. although saturating tn