TY - JOUR

T1 - Evolution history of the Neoproterozoic eclogite-bearing complex of the Muya dome (Central Asian Orogenic Belt)

T2 - Constraints from zircon U-Pb age, Hf and whole-rock Nd isotopes

AU - Shatsky, V. S.

AU - Malkovets, V. G.

AU - Belousova, E. A.

AU - Skuzovatov, S. Yu

PY - 2015/5/1

Y1 - 2015/5/1

N2 - U-Pb dating and Hf-isotope analysis of zircons and whole-rock Nd-isotope analyses were carried out on country rocks of the eclogite-gneiss complex of the North Muya dome in the Anamakit-Muya zone of the Baikal Muya accretionary fold belt. Zircons from garnet-biotite gneisses (Qtz+Kfsp+Pl+Bt+Grt) and garnet-biotite-muscovite schist (Pl+Kfsp+Bt+Mu+Grt+Qtz) were dated using the LA-ICP-MS technique. Based on U-Pb isotope data and CL images zircon grains were divided into three groups: detrital, magmatic and metamorphic zircons. Metamorphic zircons display no zoning or the cloudy zoning. The grains morphology together with the well-developed oscillatory zoning clearly identifies the igneous origin of magmatic zircons. The metamorphic zircons (ages 576-680Ma) have Th/U ratios varying from 0.271 to 0.004, whereas the ratio in magmatic zircons ranges from 0.779 to 0.11. Magmatic zircons from granite-gneisses of the North Muya dome exhibit a relatively narrow spread in the crystallization age with the major peak at ca 764Ma. Younger ages are interpreted as due to the partial resetting of U-Pb system during the subsequent metamorphic evolution. Detrital zircons from two-mica schist sample Mu-93-10 give ages of 1.88-2.66Ga. The oldest detrital zircon from this sample plots near concordia and has a 207Pb/206Pb age of 3.2Ga. Zircons from this sample are characterized by the widest scatter of eHf(t) values (from +13.9 to -15.3) and TCDM model ages (0.82-3.86Ga). Zircons from other samples have a much narrower ranges of eHf(t) (+11.6 to -0.7) and TCDM (0.85-1.52Ga). The involvement of older crustal material is also evident from the whole-rock Nd isotopic compositions. The gneisses and schists exhibit a range of Nd isotopic compositions with eNd(t) values ranging from -3.5 to +3.6 and tNd(DM) from 1.64 to 1.09Ga. The integration of the Hf-isotope data with the age spectra provides with the first evidence for the existence of Mesoarchean crust in the Baykal-Muya sector of the Central Asian Orogenic Belt.

AB - U-Pb dating and Hf-isotope analysis of zircons and whole-rock Nd-isotope analyses were carried out on country rocks of the eclogite-gneiss complex of the North Muya dome in the Anamakit-Muya zone of the Baikal Muya accretionary fold belt. Zircons from garnet-biotite gneisses (Qtz+Kfsp+Pl+Bt+Grt) and garnet-biotite-muscovite schist (Pl+Kfsp+Bt+Mu+Grt+Qtz) were dated using the LA-ICP-MS technique. Based on U-Pb isotope data and CL images zircon grains were divided into three groups: detrital, magmatic and metamorphic zircons. Metamorphic zircons display no zoning or the cloudy zoning. The grains morphology together with the well-developed oscillatory zoning clearly identifies the igneous origin of magmatic zircons. The metamorphic zircons (ages 576-680Ma) have Th/U ratios varying from 0.271 to 0.004, whereas the ratio in magmatic zircons ranges from 0.779 to 0.11. Magmatic zircons from granite-gneisses of the North Muya dome exhibit a relatively narrow spread in the crystallization age with the major peak at ca 764Ma. Younger ages are interpreted as due to the partial resetting of U-Pb system during the subsequent metamorphic evolution. Detrital zircons from two-mica schist sample Mu-93-10 give ages of 1.88-2.66Ga. The oldest detrital zircon from this sample plots near concordia and has a 207Pb/206Pb age of 3.2Ga. Zircons from this sample are characterized by the widest scatter of eHf(t) values (from +13.9 to -15.3) and TCDM model ages (0.82-3.86Ga). Zircons from other samples have a much narrower ranges of eHf(t) (+11.6 to -0.7) and TCDM (0.85-1.52Ga). The involvement of older crustal material is also evident from the whole-rock Nd isotopic compositions. The gneisses and schists exhibit a range of Nd isotopic compositions with eNd(t) values ranging from -3.5 to +3.6 and tNd(DM) from 1.64 to 1.09Ga. The integration of the Hf-isotope data with the age spectra provides with the first evidence for the existence of Mesoarchean crust in the Baykal-Muya sector of the Central Asian Orogenic Belt.

KW - Central Asian Orogenic Belt

KW - Continental subduction

KW - Hf isotopes

KW - U-Pb dating

KW - Zircon

UR - http://www.scopus.com/inward/record.url?scp=84923092002&partnerID=8YFLogxK

U2 - 10.1016/j.precamres.2015.01.013

DO - 10.1016/j.precamres.2015.01.013

M3 - Article

AN - SCOPUS:84923092002

VL - 261

SP - 1

EP - 11

JO - Precambrian Research

JF - Precambrian Research

SN - 0301-9268

ER -