Paleozoic Intrusive Magmatic Activity and Basement Properties of the Dananhu-Tousuquan Island Arc in the Eastern Tianshan Mountains

Zircon U-Pb dating results show that the emplacement ages of intermediate-acid intrusive rocks in the Dananhu-Tousuquan island arc of the eastern Tianshan Mountains is between 465-265 Ma in the Paleozoic era. It can be divided into 4 periods:Middle Ordovician to Late Silurian (465-413 Ma), Middle Devonian (391-377 Ma), Carboniferous (327-308 Ma), and Early-Middle Permian (284-269 Ma). Zircon Hf isotope analysis shows that εHf (t) values range from 6.81 to 15.73 with the two-stage Hf model ages 839 Ma-355 Ma, mainly at 598 Ma-429 Ma. The intrusive rocks aged 465-413 Ma are distributed in Kalatage and Dananhu, with the εHf (t) values ranging from 11.34 to 15.20, and the two-stage Hf model ages ranging from 633 Ma to 467 Ma. The 391-377 Ma intrusive rocks occurred in the Karatag, with the εHf (t) value ranging from 6.81 to 13.32, and two-stage Hf model ages ranging from 839 Ma to 497 Ma. The intrusive rocks dated 327-308 Ma are exposed in the west of Huangshan and south of Qincheng, with the εHf (t) value ranging from 11.36 to 15.73, and the two-stage Hf model ages ranging from 575 Ma to 429 Ma. The intrusive rocks with ages of 284-269 Ma are distributed in the west of Tuwu and Tuikemantashi, with the εHf (t) value ranging from 8.94 to 14.51, and the two-stage Hf model ages ranging from 671 Ma to 355 Ma.Combined with previous studies, this paper guesses that the old crustal basements beneath the Dananhu-Tou Suquan island arc contribute a lot to the paleozoic magmatic activities. In Palaeozoic era there were significant crustal accretion events near the Early Ordovician 465 Ma and the Middle Carboniferous 330 Ma in the arc, whereas in Late Ordovician-Late Silurian, Middle-Late Devonian and Early-Middle Permian crustal-reworking events occurred.