 |
| Titel |
Geochronology and thermochronology of Cretaceous plutons and metamorphic country rocks, Anyui-Chukotka fold belt, North East Arctic Russia |
| VerfasserIn |
E. L. Miller, S. M. Katkov, A. Strickland, J. Toro, V. V. Akinin, T. A. Dumitru |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1868-4556
|
| Digitales Dokument |
URL |
| Erschienen |
In: Geology, geophysics and tectonics of Northeastern Russia: a tribute to Leonid Parfenov ; Nr. 4 (2009-09-17), S.157-175 |
| Datensatznummer |
250001446
|
| Publikation (Nr.) |
 copernicus.org/smsps-4-157-2009.pdf |
|
|
|
|
|
| Zusammenfassung |
| U-Pb isotopic dating of seven granitoid plutons and associated intrusions
from the Bilibino region (Arctic Chukotka, Russia) was carried out using the
SHRIMP-RG. The crystallization ages of these granitoids, which range from
approximately 116.9±2.5 to 108.5±2.7 Ma, bracket two regionally
significant deformational events. The plutons cut folds, steep foliations and
thrust-related structures related to sub-horizontal shortening at lower
greenschist facies conditions (D1), believed to be the result of the
collision of the Arctic Alaska-Chukotka microplate with Eurasia along the
South Anyui Zone (SAZ). Deformation began in the Late Jurassic, based on
fossil ages of syn-orogenic clastic strata, and involves strata as young as
early Cretaceous (Valanginian) north of Bilibino and as young as
Hauterivian-Barremian, in the SAZ. The second phase of deformation (D2) is
developed across a broad region around and to the east of the Lupveem
batholith of the Alarmaut massif and is interpreted to be coeval with
magmatism. D2 formed gently-dipping, high-strain foliations (S2).
Growth of biotite, muscovite and actinolite define S2 adjacent to the
batholith, while chlorite and white mica define S2 away from the
batholith. Sillimanite (± andalusite) at the southeastern edge the
Lupveem batholith represent the highest grade metamorphic minerals associated
with D2. D2 is interpreted to have developed during regional extension
and crustal thinning. Extension directions as measured by stretching
lineations, quartz veins, boudinaged quartz veins is NE-SW to NW-SE. Mapped
dikes associated with the plutons trend mostly NW-SE and indicate NE-SW
directed extension. 40Ar/39Ar ages from S2 micas range from
109.3±1.2 to 103.0±1.8 Ma and are interpreted as
post-crystallization cooling ages following a protracted period of magmatism
and high heat flow. Regional uplift and erosion of many kilometers of cover
produced a subdued erosional surface prior to the eruption of volcanic rocks
of the Okhotsk-Chukotka volcanic belt (OCVB) whose basal units
(~87 Ma) overlie this profound regional unconformity. A single
fission track age on apatite from granite in the Alarmaut massif yielded an
age of 90±11 Ma, in good agreement with this inference. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|