ZHANG Ming-min1, 2, CHEN Hong-han3, ZHENG Jian-ping2, 4*, SU Yu-ping4
(1.Graduate School, China University of Geosciences, Wuhan 430074, China;
2. State Key Lab. of Geological Processes and Mineral Resources, Wuhan 430074,China;
3. Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China;
4. Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China)
Abstract: Kalagang Formation is developed widely in the Santanghu basin, northeast Xinjiang. The eruption age of volcanic rocks in this Formation was considered as either Permian or Carboniferous. LA -ICP-MS U-Pb dating was made on the basaltic zircons for three samples, which were collected from drill hole (Ma 17) at different depths. Zircons in the basalt at 1543.1 m yield weighed mean age of 343.5 +/-2. 4 Ma (n= 11, MSWD= 0.74). Thos e at 1954.3 m show two groups of weighted mean ages, 331.3 +/-5.0Ma ( n= 6, MSWD= 1. 4) and 306.6 +/-5.3 Ma ( n= 9, MSWD= 4.5) , respectively. Zircons in the sample at 2327.0 m give weighted mean age of 325.2 +/-3.0 Ma (n= 19, MSWD= 2.2) . This study considers the minimum age, 306.6 Ma, as the eruption age of the volcanic rocks in the Kalagang Formation, suggesting that this volcanic suite was formed in Carboniferous instead of formerly widely-accepted Permian. Zircons at the higher depth of the drill hole are old (early Carboniferous), Zircons at the lower depth are younger (Late Carboniferous). This may indicate that volcanic rocks in Malang depression developed within different ages, showing a characteristic of multi-stage eruption, old zircons at the higher depth of Kala-gang Formation may represent the early magma crystallization. Therefore, Kalagang Formation should be formed at the L at e Carboniferous.
Key words: Santanghu basin; Kalagang Format ion; basalt; zircon U-Pb dating; Late Carboniferous
*Corresponding Author, E-Mail: jpzheng@cug.edu.cn
Bulletin of Mineralogy, Petrology and Geochemistry Vol. 29, No.4, 2010, page 400-408
(Source from http://www.cnki.com.cn/)
