Geochronology of Mexican mineral deposits. VII: the Pena Colorada magmatic-hydrothermal iron oxide deposits (IOCG ``clan''), Colima
Por:
Camprubi, Antoni, Centeno-Garcia, Elena, Tolson, Gustavo, Iriondo, Alexander, Ortega, Berlaine, Bolanos, Daniel, Abdullin, Fanis, Portugal-Reyna, Jose L., Ramos-Arias, Mario A.
Publicada:
1 ene 2018
Categoría:
Earth and planetary sciences (miscellaneous)
Resumen:
The Pena Colorada mineralized area contains several iron oxide-apatite
(IOA) deposits around the arguably richest known iron resource in
Mexico. The Lower Cretaceous volcano-sedimentary host rock sequence has
been subjected to several episodes of hydrothermal alteration, each
accompanied by a distinct episode of faulting and intrusion
(calc-alkaline to tholeiitic). Faulting is partly associated with the
reactivation of cryptic structural corridors in basement rocks.
High-resolution Ar-40/Ar-39 and apatite fission track (AFT) dating of
this deposit and the adjacent Arrayanes prospect reveal the following
sequence of events that range from the latest Cretaceous to the earliest
Eocene: (1) intrusion of a 67.6 +/- 3.5 Ma magnetite-bearing diorite
with associated skarn/skarnoid metamorphism that was coeval or predated
N-S to NNW-SSE faulting; (2) approximately 63.26 Ma syenite-like
potassic alteration with disseminated magnetite, predated by N-S to
NNW-SSE faulting and postdated by WNW-ESE faulting; (3) intrusion of
62.0 +/- 2.5 Ma diorite and 59.39 +/- 0.21 Ma andesite dikes that
predate the main mineralization event at 55.72 to 54.84 Ma of large
semi-stratabound massive and disseminated bodies; (4) intrusion of a
53.3 +/- 3.0 Ma magnetite-bearing gabbro and 53 +/- 2 Ma pegmatoid
magnetite + fluorapatite veins at the Arrayanes prospect, which overlap
the WNW-ESE faulting; (5) 50.70 to 48.18 Ma polymictic magnetite breccia
as the last stage of mineralization in the area, predated by E-W
faulting; and (6) reactivation of WNW-ESE faults and later NE-SW faults.
Therefore, the total age span of the Pena Colorada deposit ranges
between approximately 19 and 23 million years. The closeness in age
between intrusions and mineralization in the Arrayanes prospect, their
confinement between the WNW-ESE and E-W structural domains, and mingling
or mixing structures between gabbro and diorite with an associated
magmatic magnetite enrichment support the idea of a close genetic link
between such intrusives and IOA hydrothermal mineralization. All
mineralization events at Pena Colorada are associated with pervasive
potassic to propylitic alteration, whereas at Arrayanes they are
associated with dominant sodic alteration instead. Alteration features
are suggestive of relatively shallow and deep formation of these
deposits, respectively. Event 3 thermally reset fluorapatite in
fragments of pegmatoid magnetite + fluorapatite + diopside associations
(dated at 59 +/- 2 Ma, AFT) within the polymictic breccia, which were
sampled from a deep orebody (still to be found) and that would be likely
associated with event 1 or 2. Consequently, exploration endeavors at
depth at Pena Colorada may be considered promising.
In this study, we use numerous geological and geochemical proxies to
constrain the likeliest genetic model for the Pena Colorada and
neighboring deposits: (a) the nearness in time and space between
hydrothermal mineralization and magnetite-rich, tholeiitic, relatively
oxidized intrusive rocks; (b) the occurrence of key mineral associations
(i.e. magnetite + fluorapatite +/- diopside veins); (c) the exclusive
occurrence of fluorapatite in lieu of other apatites; (d) the
composition in key major cations (Ca, Fe, Na, Mn) in fluorapatite; (e)
the correlations between Ni/Cr vs. Ti values, between Ti+V vs.
Ni/(Cr+Mn) values, between Ti+V vs. Al+Mn values, and Mg contents in
magnetite; (f) pyroxene thermometry; (g) log integral(O-2) values
calculated from Mn contents in fluorapatite; and (h) normalized REE
patterns, and Sigma LREE and Sigma HREE contents in fluorapatite. These
proxies indicate that IOA deposits in the Pena Colorada area have a
hydrothermal origin with a strong magmatic influence
(magmatic-hydrothermal iron oxide, or MHIO, deposits) that formed under
high oxygen fugacities and ``moderate'' temperatures, and with a high
geochemical affinity with IOCG and Kiruna-type deposits or the general
IOCG ``clan'' (for both hydrothermal minerals and associated
hypabyssal rocks). Relatively high Ti contents in magnetite, and high Ce
and low Eu contents in fluorapatite in these deposits (with respect to
typical compositions in IOCG ``clan'' deposits) are geochemical
features still in need of further explanation. The correlation between
regional and local structural domains and the geochronologic study in
this paper constrain the possible ages of such domains as follows: (1)
the N-S to NNW-SSE domain can be bracketed between 67.6 and 63.26 Ma,
(2) the WNW-ESE domain between 63.26 and 59.39 Ma, (3) the E-W domain
between 54.84 and 50.70 Ma, (4) the WNW-ESE to NW-SE domain is younger
than 48.18 Ma, and (5) the NE-SW domain is still active. The structural
analysis also shows that the massive orebody at Pena Colorada is
partially stratabound but its emplacement was also controlled by
low-angle Laramide faults, and that hydrothermal fluids were
preferentially driven through volcano-sedimentary rocks. The latter
characteristic is not only a matter of the stratigraphic distribution of
relatively pervasive versus impervious rocks but also of the lateral
distribution of such rocks due to N-S strike-slip faults. As additional
results of this study, we determined that the conglomerates atop the
host volcano-sedimentary sequence that were initially attributed to the
Cerro de la Vieja Formation cannot be older than 67.6 Ma, and that the
IOA deposits at Pena Colorada would be formed at depths of only a few
hundred meters.
Filiaciones:
Camprubi, Antoni:
Univ Nacl Autonoma Mexico, Inst Geol, Ciudad Univ, Cdmx 04510, Mexico
Centeno-Garcia, Elena:
Univ Nacl Autonoma Mexico, Inst Geol, Ciudad Univ, Cdmx 04510, Mexico
Tolson, Gustavo:
Univ Nacl Autonoma Mexico, Inst Geol, Ciudad Univ, Cdmx 04510, Mexico
Iriondo, Alexander:
Univ Nacl Autonoma Mexico, Ctr Geociencias, Blvd Juriquilla 3001, Queretaro 76230, Qro, Mexico
Ortega, Berlaine:
Univ Nacl Autonoma Mexico, Inst Geol, Ciudad Univ, Cdmx 04510, Mexico
Bolanos, Daniel:
Inst Mexicano Petr, Eje Cent Lazaro Cardenas 152, Cdmx 07730, Mexico
Abdullin, Fanis:
Univ Nacl Autonoma Mexico, Ctr Geociencias, Blvd Juriquilla 3001, Queretaro 76230, Qro, Mexico
Portugal-Reyna, Jose L.:
Consorcio Minero Benito Juarez Pena Colora SA CV, Av Trabajo 1000, Manzanillo 28876, Col, Mexico
Ramos-Arias, Mario A.:
Univ Michigan, Earth & Environm Sci, 2534 CC Little Bldg,1100 North Univ Ave, Ann Arbor, MI 48109 USA
|