Accumelting: Toward a Testable Framework for Continental Crust Maturation and Preservation

ABSTRACT

How juvenile crust matures into felsic, compositionally stratified continental crust, and how that crust is preserved over geological time, remain central problems in Earth science. Prevailing explanations, developed largely from subduction zones, invoke mass transfer across the Moho by delamination or relamination. The accumelting concept offers a fundamentally different, intracrustal pathway to crustal maturation and preservation, which involves hornblende‐dominated fractionation of hydrous basaltic magmas forming cumulate roots with variable K contents during oceanic subduction, and subsequent heat‐driven remelting of these fertile roots producing low‐ to high‐K felsic magmas, with high‐K endmembers prominent in collision zones, leaving dense residues, in some cases imaged as a double‐Moho structure. Unlike delamination, which removes the dense arc root, and relamination, which imports exotic felsic material, accumelting reframes the cumulate root not as a foundering relic but as the primary melt source for the felsic upper crust, achieving intracrustal maturation. This review explains why accumelting was proposed, what distinguishes it from delamination and relamination, where its new evidence comes from, how the two‐stage process operates, and which future directions can move the concept from hypothesis toward a testable framework. Emerging applications extend accumelting to porphyry Cu‐Mo‐Au mineralization and giant pegmatite Li deposits through metal pre‐enrichment in arc roots and resulting felsic rocks, and to H ₂ O–CO ₂ release linking crustal maturation with volatile cycling and Earth's long‐term habitability. Whether residues are retained or delaminated, what accumelting contributes to metallogeny, whether the arc lower crust is a major volatile reservoir, and whether a methodology can be developed to identify accumelting beyond the Gangdese case define the tests that will decide whether accumelting becomes a general framework for continental maturation in both collision and subduction zones or remains a regional special case.