Sequence of mineral deposits related to the theory of eastward migrating Global Tectonic Megacycles
Trurnit, T. P.
published: Jan 1, 1989
ArtNo. ESP136000302013, Price: 19.00 €
Due to the westward directed off-centre rotation of the spinning Earth around the gravitational centre of the Earth-Moon (-Sun) system, the lower mantle is displaced eastward in relation to the convecting upper mantle-crust system (principle of hypocycloid gearing). Together with gravity anomalies in the lower mantle the shape of the Pacific and the individual states of the Oceanic or Wilson Cycle describing with a sequence of progressive ageing both the opening and closing of an ocean (Rift/Red Sea state and Atlantic state with mainly passive margins; Pacific/Tethys state with mainly active margins; Himalayas/Collisional state) and the embryonic, geosynclinal evolution of an orogen, are displaced eastward in relation to the Earth's crust (once around the globe in 200 to 250 m. y.; some 20 to 16 cm/y East drift). The Earth's crust is continuously subjected to a series of Global Tectonic Megacycles which migrate eastwards with the same angular velocity as the shape of the Pacific and which are imposed on one another over and over again. The collisional mountain belt originating West of the Pacific and winding around the cratonic nucleus of Laurasia or North Pangaea in the form of a spiral leads westwards into the remote geological past of the Earth. It results as final product of the Global Tectonic Megacycles and could be reconstructed for the Phanerozoic and the Latest Proterozoic (the still incomplete North Pangaea collisional mountain belt spiral in the northern hemisphere and the completed South Pangaea collisional mountain belt spiral of the southern hemisphere breaking up since the Late Paleozoic). However, still older fragments or orogens and suture zones scattered all over the continents (partly hidden below younger overlap sequences) are indications for the former existence of even older segments of the collisional mountain belt, in the form of North and South Pangaea spirals. Characteristic types of mineral deposits are formed pre-collisionally during the Oceanic, Wilson or Eugeosynclinal Cycle (subdivided into the Cycle of Continental Margins or Miogeosynclinal Cycle and the Cycle of the Oceanic Crust and Eugeosynclinal Sediments or Ophiolitic Cycle) in settings along passive and active plate and continental margins, syncollisionally in the youngest segment of the collisional mountain belt originating West of the Pacific, and post-collisionally in older segments of the belt, that slowly become part of the cratonic crust. This process must already have been in progress since the early history of the Earth, when Global Tectonic Megacycles first began to operate. The principles of classification of mineral deposits in relation to the sequence of Global Tectonic Megacycles, which migrates eastward in relation to the Earth's crust, are demonstrated with a few selected examples.