SHRIMP U-Pb dating and Hf isotopic analyses of Middle Ordovician meta-cumulate gabbro in central Qiangtang, northern Tibetan Plateau

• DOI: 10.1007/s11430-010-0063-6
• Publication Date: 2010-05-17T21:20:38Z
• Authors: QingGuo Zhai; Jun Wang; Cai Li; Li Su
• Keywords: 01 natural sciences; 0105 earth and related environmental sciences

Metabasites consisting of metamorphic ultra-mafic rocks, cumulate gabbro, gabbro (diabase), basalt, and plagiogranite are exposed at the Taoxinghu area in central Qiangtang, northern Tibetan Plateau. Zircon SHRIMP U-Pb dating for the cumulate gabbro yields a weighted mean age of 467±4 Ma, which is the oldest and most reliable magmatic age in this area. Zircon 176 Hf/ 177 Hf ratios range from 0.282615 to 0.282657, with e Hf(t) values of 5.02±0.28, indicating that the cumulate gabbro was mainly derived from the depleted mantle. In addition, geochemical data of metabasites suggest that they have similar characteristics to those in the mid-ocean ridge basalts (MORB). The Taoxinghu metabasites may represent the fragment of Early Paleozoic ophiolite in the “Central Uplift” of the Qiangtang, northern Tibetan Plateau. Qiangtang, cumulate gabbro, SHRIMP dating, Hf isotope