TY - JOUR
T1 - Neoproterozoic-middle Paleozoic tectono-magmatic evolution of the Gorny Altai terrane, northwest of the Central Asian Orogenic Belt
T2 - constraints from detrital zircon U-Pb and Hf-isotope studies
AU - Chen, Ming
AU - Sun, Min
AU - Buslov, Mikhail M.
AU - Cai, Keda
AU - Zhao, Guochun
AU - Zheng, Jianping
AU - Rubanova, Elena S.
AU - Voytishek, Elena E.
PY - 2015/9/15
Y1 - 2015/9/15
N2 - The Gorny Altai terrane (GA) is a key area in understanding the crustal evolution of the Central Asian Orogenic Belt (CAOB). This paper reports U-Pb and Hf-isotope data for detrital zircons from Cambrian to early Devonian sedimentary sequences to constrain their provenance, as well as the tectono-magmatic events and crustal growth in this region. Nearly all the detrital zircons are characterized by euhedral to subhedral morphology, high Th/U ratios (ca. 0.1-1.6) and typical oscillatory zoning, indicating a magmatic origin. The three samples from the Gorny Altai Group (middle Cambrian to early Ordovician) yield detrital zircon populations that are composed predominantly of 530-464Ma grains, followed by a subordinate group of 641-549Ma old. The Silurian and Devonian samples exhibit similar major zircon populations (555-456Ma and 525-463Ma, respectively), but a significant amount of additional 2431-772Ma zircons occur in the early Devonian sample. Our results suggest that detritus from the nearby Kuznetsk-Altai intra-oceanic island arc served as a unitary source for the Cambrian-Silurian sedimentary sequences, but older detritus from other sources added to the early Devonian sequence. The low abundance of ca. 640-540Ma detrital zircons may testify that this island arc was under a primitive stage in this period, when mafic volcanic rocks probably dominated. In contrast, the dominant population of ca. 530-470Ma zircons may indicate an increased amount of granitic rocks in the source area, suggesting that the Kuznetsk-Altai island arc possibly evolved into a mature one in the Cambrian to early Ordovician. The ca. 530-470Ma detrital zircons are almost exclusively featured by positive εHf(t) values and have two-stage Hf model ages of ca. 1.40-0.45Ga, indicating that the precursor magmas were sourced predominantly from heterogeneous juvenile materials. We conclude that the late Neoproterozoic to early Paleozoic magmatism in the Kuznetsk-Altai arc made a significant contribution to the crustal growth in the CAOB.The absence of middle Ordovician to early Devonian detrital zircons possibly implies that the area changed to a passive margin in the middle Ordovician. Of special significance are the 2431-772. Ma zircons in the early Devonian sample, which are quite comparable to the Precambrian detrital zircons from the Altai-Mongolian terrane (AM) but distinct from those from the Siberian continent. This indicates that the AM is a plausible source for the 2431-772. Ma zircons. Our data therefore imply that the GA possibly amalgamated with the AM before the early Devonian rather than in the late Devonian to early Carboniferous as previously suggested.
AB - The Gorny Altai terrane (GA) is a key area in understanding the crustal evolution of the Central Asian Orogenic Belt (CAOB). This paper reports U-Pb and Hf-isotope data for detrital zircons from Cambrian to early Devonian sedimentary sequences to constrain their provenance, as well as the tectono-magmatic events and crustal growth in this region. Nearly all the detrital zircons are characterized by euhedral to subhedral morphology, high Th/U ratios (ca. 0.1-1.6) and typical oscillatory zoning, indicating a magmatic origin. The three samples from the Gorny Altai Group (middle Cambrian to early Ordovician) yield detrital zircon populations that are composed predominantly of 530-464Ma grains, followed by a subordinate group of 641-549Ma old. The Silurian and Devonian samples exhibit similar major zircon populations (555-456Ma and 525-463Ma, respectively), but a significant amount of additional 2431-772Ma zircons occur in the early Devonian sample. Our results suggest that detritus from the nearby Kuznetsk-Altai intra-oceanic island arc served as a unitary source for the Cambrian-Silurian sedimentary sequences, but older detritus from other sources added to the early Devonian sequence. The low abundance of ca. 640-540Ma detrital zircons may testify that this island arc was under a primitive stage in this period, when mafic volcanic rocks probably dominated. In contrast, the dominant population of ca. 530-470Ma zircons may indicate an increased amount of granitic rocks in the source area, suggesting that the Kuznetsk-Altai island arc possibly evolved into a mature one in the Cambrian to early Ordovician. The ca. 530-470Ma detrital zircons are almost exclusively featured by positive εHf(t) values and have two-stage Hf model ages of ca. 1.40-0.45Ga, indicating that the precursor magmas were sourced predominantly from heterogeneous juvenile materials. We conclude that the late Neoproterozoic to early Paleozoic magmatism in the Kuznetsk-Altai arc made a significant contribution to the crustal growth in the CAOB.The absence of middle Ordovician to early Devonian detrital zircons possibly implies that the area changed to a passive margin in the middle Ordovician. Of special significance are the 2431-772. Ma zircons in the early Devonian sample, which are quite comparable to the Precambrian detrital zircons from the Altai-Mongolian terrane (AM) but distinct from those from the Siberian continent. This indicates that the AM is a plausible source for the 2431-772. Ma zircons. Our data therefore imply that the GA possibly amalgamated with the AM before the early Devonian rather than in the late Devonian to early Carboniferous as previously suggested.
KW - Crustal evolution
KW - Detrital zircons
KW - Gorny Altai terrane
KW - Kuznetsk-Altai island arc
UR - http://www.scopus.com/inward/record.url?scp=84952922655&partnerID=8YFLogxK
U2 - 10.1016/j.lithos.2015.03.020
DO - 10.1016/j.lithos.2015.03.020
M3 - Article
AN - SCOPUS:84952922655
SN - 0024-4937
VL - 233
SP - 223
EP - 236
JO - Lithos
JF - Lithos
ER -