<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Deng, Zhengbin</style></author><author><style face="normal" font="default" size="100%">Schiller, Martin</style></author><author><style face="normal" font="default" size="100%">Jackson, Matthew G.</style></author><author><style face="normal" font="default" size="100%">Millet, Marc-Alban</style></author><author><style face="normal" font="default" size="100%">Pan, Lu</style></author><author><style face="normal" font="default" size="100%">Nikolajsen, Katrine</style></author><author><style face="normal" font="default" size="100%">Saji, Nikitha S.</style></author><author><style face="normal" font="default" size="100%">Huang, Dongyang</style></author><author><style face="normal" font="default" size="100%">Bizzarro, Martin</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Earth's evolving geodynamic regime recorded by titanium isotopes</style></title><secondary-title><style face="normal" font="default" size="100%">Nature</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2023</style></year><pub-dates><date><style  face="normal" font="default" size="100%">sep</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">https://www.nature.com/articles/s41586-023-06304-0</style></url></web-urls></urls><number><style face="normal" font="default" size="100%">7977</style></number><publisher><style face="normal" font="default" size="100%">Springer US</style></publisher><volume><style face="normal" font="default" size="100%">621</style></volume><pages><style face="normal" font="default" size="100%">100–104</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Earth&amp;#039;s mantle has a two-layered structure, with the upper and lower mantle domains separated by a seismic discontinuity at about 660 km (refs. 1,2 ). The extent of mass transfer between these mantle domains throughout Earth&amp;#039;s history is, however, poorly understood. Continental crust extraction results in Ti-stable isotopic fractionation, producing isotopically light melting residues 3–7 . Mantle recycling of these components can impart Ti isotope variability that is trackable in deep time. We report ultrahigh-precision 49 Ti/ 47 Ti ratios for chondrites, ancient terrestrial mantle-derived lavas ranging from 3.8 to 2.0 billion years ago (Ga) and modern ocean island basalts (OIBs). Our new Ti bulk silicate Earth (BSE) estimate based on chondrites is 0.052 ± 0.006‰ heavier than the modern upper mantle sampled by normal mid-ocean ridge basalts (N-MORBs). The 49 Ti/ 47 Ti ratio of Earth&amp;#039;s upper mantle was chondritic before 3.5 Ga and evolved to a N-MORB-like composition between approximately 3.5 and 2.7 Ga, establishing that more continental crust was extracted during this epoch. The +0.052 ± 0.006‰ offset between BSE and N-MORBs requires that &amp;lt;30% of Earth&amp;#039;s mantle equilibrated with recycled crustal material, implying limited mass exchange between the upper and lower mantle and, therefore, preservation of a primordial lower-mantle reservoir for most of Earth&amp;#039;s geologic history. Modern OIBs record variable 49 Ti/ 47 Ti ratios ranging from chondritic to N-MORBs compositions, indicating continuing disruption of Earth&amp;#039;s primordial mantle. Thus, modern-style plate tectonics with high mass transfer between the upper and lower mantle only represents a recent feature of Earth&amp;#039;s history.</style></abstract></record></records></xml>