MAGMATIC ROCKS OF THE TEKTURMASS ACCRETIONARY COMPLEX, CENTRAL KAZAKHSTAN: GEOLOGICAL POSITION AND GEODYNAMIC SETTINGS OF FORMATION

Abstract

The paper provides an overview of the geological structure and presents new data on petrography and geochemistry of igneous rocks of the Tekturmas accretionary complex (TAC). Consideration is being given to the age, petrogenesis and probable tectonic settings of formation of igneous rocks. It is shown that the TAC and adjacent ophiolite belt are parts of the Late Cambrian – Ordovician Pacific-type orogenic belt formed at an active margin of the Paleo-Asian Ocean. The TAC is dominated mainly by tholeiitic mafic igneous rocks (basalt, dolerite, gabbro). There are recognized three groups of rocks: high-Ti, medium-Ti and low-Ti. Geological and geochemical features of TAC igneous rocks suggest their formation in three tectonic settings: mid-ocean ridge (medium-Ti), oceanic island/seamount (high-Ti) and over subduction zones (low-Ti).

Keywords

• paleo-asian ocean
• central asian orogenic belt
• late cambrian
• ordovician
• ophiolites
• petrography
• geochemistry