On the enigmatic mid-Proterozoic: Single-lid versus plate tectonics

The mid-Proterozoic (ca. 1850–850 Ma) is a peculiar period of Earth history in many respects: ophiolites and passive margins this age are rare, whereas anorthosite A-type granite suites abundant; metamorphic rocks typically record high thermobaric (temperature/pressure) ratios, ultrahigh pressure (UHP) rare; the abundance economic mineral deposits features rare porphyry Cu-Au abundant Ni-Cu Fe-oxide Cu-Ag (IOCG) deposit types. These collective observations have been used to propose that stagnant-lid, or single-lid, tectonic regime operated at time, between periods plate tectonics Paleoproterozoic Neoproterozoic. In our reappraisal geological record, we not only assess viability single-lid hypothesis for each line evidence, but also alternative. We find evidence equivocal all cases, supporting. therefore no reason abandon model time period. Instead, peculiarities enigmatic interval can be reconciled through combination two processes working tandem: secular mantle cooling exceptionally long tenure incomplete breakup Earth's first supercontinent, where both these phenomena had dramatic effect on lithospheric behaviour its resulting imprint record.