CONTINENTAL ORIGIN AND GROWTH FROM ACCUMULATION OF SUBDUCTED DEEP SEA SEDIMENTS

We argue continental origin and growth from accumulation of subducted deep sea sediments based on the following facts:

1. Sedimentation process never stopped throughout geological history;

2. Sedimentation process is an efficient way to fractionate elements with sediments enriched in silica, especially chert precipitation exist almost whole geological time;

3. Continental crusts consist mainly of granitoids, has similar chemical composition with deep sea sediments, their age distributions indicate gradual growth throughout geological history;

4. Traditional idea of continental growth from partial melting from the mantle, but it is hard to explain generally heavier oxygen isotope signatures of continental crusts. Deep sea sediments, represented by chert, have a heavier oxygen signature, diffusion of oxygen isotope in silicate melt in subduction factory can not flatten the signature on km scale, but on cm to m scale, so they still keep heavier oxygen.

5. Plate tectonic mechanism exists since Archean, probably throughout whole geological history. This is supported by the discovery of Archean ophiolite and geochemical signatures of subduction related tectonic setting;

6. Age distribution of continental crusts show continental grew through accretion of near linear patches of granite batholiths to continental nuclei. Large scale granite batholiths usually appear along orogenic zone, which can be explained by accumulation of subducted deep sea sediments in subcrust, lighter densities of these materials play a role in uplift of these orogenies;

7. Granite crystallization ages are generally older than their crustal residence age because they experienced sedimentation cycle and/or involving with older crustal material recycling;

8. From typical deep sea sediments accumulation rate, it is enough to accumulate the total continental crust material throughout geological time, the lighter density of these materials keep them in crust, rather than subducted;

9. Granites contain water, indicating surface origin, “no water, no granite-no ocean, no continents”. In addition, carbon isotope of granite indicates surface or organic origin.

If this hypothesis is correct, the felsic rocks in the intraoceanic subduction zones is continental embryos.