Minerals,
Journal Year:
2024,
Volume and Issue:
14(2), P. 151 - 151
Published: Jan. 30, 2024
The
Kolijan
bauxite
deposit
(southeast
Mahabad,
northwestern
Iran)
mainly
contains
aluminum-bearing
iron
ores
and
was
deposited
in
karstic
depressions
sinkholes
of
the
middle
Permian
carbonate
rocks
Ruteh
Formation.
Based
on
microscopic
observations,
were
allogenic
origin.
According
to
XRD
SEM-EDS
analyses,
hematite
goethite
are
their
main
constituents,
accompanied
by
lesser
amounts
kaolinite,
illite,
amesite,
boehmite,
rutile,
anatase,
calcite,
pyrolusite,
crandallite,
parisite-(Ce).
Chondrite-normalized
REE
patterns
indicative
fractionation
enrichment
LREE
(La–Eu)
compared
HREE
(Gd–Lu),
along
with
positive
Eu
Ce
anomalies
(Eu/Eu*
=
2.29–5.65;
Ce/Ce*
3.63–5.22).
Positive
can
be
attributed
role
bedrock
as
a
geochemical
barrier
precipitation
A
strong
correlation
between
Eu/Eu*
(r
0.84)
indicates
that
anomalies,
similar
closely
dependent
an
alkaline
pH.
distribution
elements
controlled
number
factors,
including
pH
environment
which
they
formed,
wet
climatic
conditions,
adsorption,
isomorphic
substitution,
scavenging,
co-precipitation,
fluctuations
groundwater
table
level,
barrier.
This
research
probably
generated
from
weathering
basaltic
protolith.
Ore Geology Reviews,
Journal Year:
2024,
Volume and Issue:
170, P. 106125 - 106125
Published: June 19, 2024
More
than
five
billion
tons
of
karstic
bauxites
were
formed
in
the
North
China
Craton
(NCC)
during
Late
Carboniferous
period.
Compared
to
bauxite
ore,
genesis
entire
aluminous-bearing
strata
has
received
less
attention.
In
this
study,
we
conducted
geological,
mineralogical,
and
geochemical
analyses
on
core
samples
from
located
Xingxian
area,
situated
within
northern
NCC,
aiming
elucidate
genetic
process
these
formations.
The
consist
a
layer
(diaspore–anatase–kaolinite–florencite)
sandwiched
between
upper
sandy
claystone
horizon
(kaolinite–illite–quartz)
lower
berthierine-bearing
(berthierine–diaspore–hematite–goethite).
Based
continental
crust-normalized
patterns
rare
earth
elements
yttrium
(REY),
immobile
trace
element
ratios,
mineral
inheritance
diagrams,
previous
findings,
it
is
suggested
that
was
weathered
impure
limestone
at
bottom,
whereas
mainly
originated
intermediate-felsic
igneous
rocks
margin
granite
Qinling
Orogenic
Belt,
aluminosilicate
surrounding
paleo-uplifts.
During
early
diagenetic
stage,
berthierine
transformed
under
alkaline
reducing
conditions
iron-rich
clays
(composed
clay
minerals,
ferric
etc.)
acidic
oxidizing
underlying
limestone.
coexistence
with
low-temperature
stability
diaspore
observed
claystone,
which
precludes
high-temperature
origin
strata.
Moreover,
characterized
by
small
crystal
size
usually
poorly
crystallized,
suggesting
supergene
precipitation-diagenesis
origin.
paragenetic
minerals
assemblages
(e.g.,
diaspore,
berthierine,
goethite,
hematite,
suggest
primarily
transition
zone
nearer
phreatic
environment.
Large-scale
volcanism
warm,
humid
climatic
accelerated
decomposition
allochthonous
weathering
materials,
resulting
downward
migration
metal
ions.
These
ions
then
precipitated
weakly
environment,
giving
rise
form
ore
dominated
anatase,
REY
minerals.
Ore Geology Reviews,
Journal Year:
2023,
Volume and Issue:
153, P. 105296 - 105296
Published: Jan. 9, 2023
The
metallogenic
process
of
karstic
bauxite
in
Central
Yunnan
Basin
(CYB)
remain
obscure.
Mineralogical,
geochemical,
and
isotopic
analyses
two
profiles
(profile
A
B)
the
Yuxi
deposit
within
CYB
were
conducted
to
explore
formation
environment
Early
Permian
bauxite.
Profile
uplifted
area
comprises
clayey
bauxite,
claystone,
oolitic
from
bottom
top,
while
profile
B
depression
contains
claystone.
mainly
diaspore
chamosite,
a
small
amount
kaolinite
anatase,
primarily
includes
boehmite
kaolinite,
goethite
anatase.
claystone
is
dominated
by
illite.
δ15N
value
top
close
zero
(−0.8
‰),
indicating
reducing
deposition
environment.
δ13Corg
negatively
shifted
between
that
not
significantly
changed
lower
upper
This
indicates
REDOX
changes
are
obvious,
evident.
Mineral
assemblages
results
suggest
mineralization
conditions
experienced
transition
oxidizing
weakly
alkaline
alkaline,
always
alkaline.
presence
large-scale
microorganisms,
negative
δ34S
values
(−42.2
−10.1
framboidal
cuboidal
provide
evidence
for
microbial
involvement
entire
process.
above
confirm
metallogenetic
events
deposit.
In
early
event,
water
table
was
low
most
terrains
exposed
except
some
depressions.
Abundant
thus
formed
areas
forming
chamosite
depressions
late
with
rise
table,
all
submerged,
widely
deposited,
