Is the Ordos Block Archean or Paleoproterozoic in age? Implications for the Precambrian evolution of the North China Craton

The Ordos Block is a large but poorly exposed crustal segment in the western part of the North China Craton. Little is known about its Precambrian basement rocks and their evolution because of an extensive cover by younger sedimentary rocks. We report SHRIMP zircon ages and Hf-in-zircon isotopic compositions for five samples recovered from drill holes that penetrated into the Ordos basement. Based on these data, two age groups of rocks can be...