Relamination is described, a mechanism that has been shaping continents for billions of years

[C C]

Relamination is described, a mechanism that has been shaping continents for billions of years
https://www.eurekalert.org/news-releases/1126474

INTRO: An international team led by researchers from the National Museum of Natural Sciences (MNCN-CSIC) has identified a key mechanism that has shaped Earth’s continents over billions of years. This mechanism is the deep re-lamination of subducted continental crust, a process that explains the origin of certain magmas and offers a new perspective on continental evolution from the Archean (between 3.8 and 2.5 billion years ago) to recent times.

The study, published today in the journal Nature Geoscience, combines numerical geodynamic modeling and high-pressure experiments to unravel how fragments of continental crust can give rise to hybrid magmas that fuel major magmatic events following continental collisions, generating new crust.

During continental collisions, one plate sinks beneath another—a process known as subduction. This study demonstrates that the less dense crust breaks away from the subducted plate and rises again, becoming integrated into the lithospheric mantle of the overlying plate in a process called relamination.

The relaminated material mixes mechanically with the mantle, creating a hybrid reservoir from which characteristic magmas emerge—known as post-collisional magmas—that form large granitic batholiths such as the Sierra de Gredos and Guadarrama in Central Spain. These processes, in which two continental masses collide, are what produce mountain ranges or orogens.

“What we have learned from this research is why these magmas are found in both modern orogens and in formations dating back to the Archean,” explains Daniel Gómez Frutos, a researcher at the MNCN who is currently working at the University of Portsmouth. “Our models show that relamination is a recurring process in continental collisions. Fragments of subducted crust do not disappear; they are reincorporated into the continent and leave a very clear chemical signature in the magmas produced millions of years later.new crust”... (MORE - no ads)
_

 

[TheVat]

The relaminated material mixes mechanically with the mantle, creating a hybrid reservoir from which characteristic magmas emerge—known as post-collisional magmas—that form large granitic batholiths such as the Sierra de Gredos and Guadarrama in Central Spain. These processes, in which two continental masses collide, are what produce mountain ranges or orogens.

I live on the Harney Peak batholith, which was formed from such an orogeny, known as the Trans-Hudson orogeny, a massive collision between the Archean Wyoming and Superior cratons - it helped build the North American continent. Mount Rushmore is a protruding bit of the granitic batholith. Old rock, 1.7 GY.

 

[exchemist]

Relamination is described, a mechanism that has been shaping continents for billions of years
https://www.eurekalert.org/news-releases/1126474

INTRO: An international team led by researchers from the National Museum of Natural Sciences (MNCN-CSIC) has identified a key mechanism that has shaped Earth’s continents over billions of years. This mechanism is the deep re-lamination of subducted continental crust, a process that explains the origin of certain magmas and offers a new perspective on continental evolution from the Archean (between 3.8 and 2.5 billion years ago) to recent times.

The study, published today in the journal Nature Geoscience, combines numerical geodynamic modeling and high-pressure experiments to unravel how fragments of continental crust can give rise to hybrid magmas that fuel major magmatic events following continental collisions, generating new crust.

During continental collisions, one plate sinks beneath another—a process known as subduction. This study demonstrates that the less dense crust breaks away from the subducted plate and rises again, becoming integrated into the lithospheric mantle of the overlying plate in a process called relamination.

The relaminated material mixes mechanically with the mantle, creating a hybrid reservoir from which characteristic magmas emerge—known as post-collisional magmas—that form large granitic batholiths such as the Sierra de Gredos and Guadarrama in Central Spain. These processes, in which two continental masses collide, are what produce mountain ranges or orogens.

“What we have learned from this research is why these magmas are found in both modern orogens and in formations dating back to the Archean,” explains Daniel Gómez Frutos, a researcher at the MNCN who is currently working at the University of Portsmouth. “Our models show that relamination is a recurring process in continental collisions. Fragments of subducted crust do not disappear; they are reincorporated into the continent and leave a very clear chemical signature in the magmas produced millions of years later.new crust”... (MORE - no ads)
_

I found this interesting. I was aware that subduction of oceanic crust behind ocean trenches gave rise to hydrated minerals with lower melting points, which form melts that rise as diapirs to create the characteristic volcanism of, for example, the Pacific Ring of Fire. But this is about what happens when continental crust is subducted, as an ocean closes, forming mountain ranges.

I found the term "relamination" a little confusing, as that suggested to me a layer is reattached to the bottom of the overlying plate. What they seem to suggest is something rather different, viz. a detachment of the felsic, lighter portion of the crust that has been subducted and then the mixing of this into the lithospheric mantle of the overriding plate. This, they say, generates hybrid minerals which partially melt to form batholiths of granite etc. So not diapirs rising to create volcanism, but deep-seated pools of partially melted material with a hybrid crust/mantle composition.

All this makes me wish I had my time again to study Earth Science. A case of "The Road Not Taken".