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Stagnant Lid
Early Intermediate Late

Magma Partial Melt Lithosphere
drips Rayleigh-Taylor Asthenosphere
plumes drips upwelling and
melting
Convecting
Mantle

Core
Io Venus Mars Moon, Mercury

Possible Stages Crust
in the Tectonic Lithosphere

Evolution of a Plate
Silicate Body Tectonics Asthenosphere

and Earth

Figure 1. Possible evolution of magmatotectonic styles for a large silicate body like Earth. Examples from active Solar
System bodies Io, Venus, and Mars are shown. Possible evolution of Earth is also shown. Strength of mantle convection is
indicated by arrowed curve thickness. Plate tectonics requires certain conditions of lithospheric density and strength in
order to occur and is likely to be presaged and followed by different styles of stagnant lid tectonics. See text for further
discussion. Modified after Stern et al. (2018).

perienced multiple episodes of different p. 58) admonition “… recycling of crust into tectonics. The second approach is more dif-
kinds of single-lid behavior and of plate tec- the mantle does not necessarily require sub- ficult because we are only beginning to think
tonics. Different tectonic regimes produce duction, and it may be possible for such about what kinds of rocks should be pro-
different structures, metamorphic rocks, recycling to occur in stagnant [single]-lid duced by active single-lid tectonics.
and igneous rocks that, if preserved, pro- regimes…” should be kept in mind. Consider the negative evidence first.
vide evidence about the tectonic regime that Stern (2018) identified three groups of rocks
produced them. Erosion, alteration, and EVIDENCE THAT THE and minerals that only form by plate-tectonic
burial destroy some but not all of the evi- MESOPROTEROZOIC WAS A processes. These are (1) ophiolites, indi-
dence of past tectonic regimes, at least for PROTRACTED SINGLE-LID EPISODE cators of subduction initiation and seafloor
the past 3 Ga. Erosion may remove shallow Geologic evidence—both negative and spreading; (2) blueschists, lawsonite-bear-
features such as porphyry copper deposits positive—should guide our interpretation of ing metamorphic rocks, and jadeitite,
and ophiolite nappes but cannot extirpate Mesoproterozoic tectonics. Negative evi- indicators of subduction; and (3) ultra-high
intrusive and metamorphic rocks, which dence shows an absence of key plate-tectonic pressure (UHP) metamorphic rocks along
extend to depth. Microscopic, geochemical, indicators (Figs. 2B–2D). Positive evidence with ruby and sapphire, indicators of conti-
and isotopic evidence is useful for identify- specifies geologic features expected for sin- nent-continent collision (Figs. 2B–2D). All
ing when a change occurred in Earth’s con- gle-lid behavior (Figs. 2E–2H). The first of these are abundant in Phanerozoic and
vective style but cannot reliably constrain approach is straightforward because we Neoproterozoic time and all are missing
when plate tectonics began. Condie’s (2018, know the kinds of rocks produced by plate from the Mesoproterozoic. Brown and
www.geosociety.org/gsatoday 5