Discovery of potassic spilite (or poenite) in Langshan Group of Tanyaokou District, Inner Mongolia, China

It is believed that the albite-potash-feldspar-greenschists in the middle Proterozoic Langshan Group in Tanyackou District are synsedimentary potassic spilite (or poenite) based on the following facts and features: (i) they occur in beds and look blackish (or apple) green and compact; (ii) they bear blasto-glomeroporphyritic and blastocrystalloclastic crystals which consist of (altered) albite laths with hollow skeleton crystal texture in which there are slender dark strips and minor pyroxene, and blasto-amygdaloid filled with pyrite, chlorite, magnetite, etc.; (iii) the results of the petrochemical diagrams show that they are orthometamorphites; (iv) Sm-Nd isotopic age of them is 1 824 Ma (model age (t_DM) is 2 006–2 132 Ma).