Chabaoma Formation volcanic rocks are located at the eastern Hoh Xil, northern Tibetan plateau, belong super-K C-type adakite, and formed in Miocene, Neogene period. Their SHRIMP U-Pb ages of zircon are from 13.2 0.6 to 18.3 1.1Ma. Volcanic rocks are characterized by high SiO2 (59.48% to 64.63%), enriched in Na2O + K2O (7.52% to 8.30%), high in K2O (4.21% to 4.62%), high in MgO (0.74% to 2.48%) and Mg# values (0.26 to 0.51), and belong to shoshonite series. The ∑REE contents are very high (482.26 × 10-6 to 592. 11 × 10-6) especially enriched in LREE (466.47 × 10-6 to 571.69 × 10-6 ), but reversely depleted in HREE (14.00 × 10-6 to 20.43 × 10-6). The contents of Y and Yb are generally lower, which is from 13.29 10-6 to 19.87 10-6 (average 16.27 10-6) and 1.11 10-6 to 1.66 10-6 (average 1.37 10-6), respectively. REE patterns are strongly oblique to the HREE side with intensive enriched in LREE, and (La/Yb)N values are from 61.02 to 91.67. Eu anomaly is invisible, which Eu/Eu * values from 0.74 to 0.86. The contents of Sr and Sr/Y value are also higher, Which from 949 10-6 to 1497 10-6 and 54 to 108, respectively. In the primitive mantel-normalized spidergrams of trace elements, obvious negative anomalies showed in Nb, Ta, P, Ti and Y. Chabaoma Formation super-K adakite are generated by partial melting of eclogitic phase lower crust section because the continental crust had been thickened (75-80km) and an eclogitic lower had been formed during Miocene, Neogene period in northern Tibetan plateau area.
|Number of pages||10|
|Journal||Acta Petrologica Sinica|
|Publication status||Published - 2007|
- Chabaoma Formation
- Northern Tibetan plateau
- SHIRMP U-Pb dating of zircon
- Super-K adakite