TY - JOUR

T1 - Diamond-inclusion system recording old deep lithosphere conditions at Udachnaya (Siberia)

AU - Nestola, Fabrizio

AU - Zaffiro, Gabriele

AU - Mazzucchelli, Mattia L.

AU - Nimis, Paolo

AU - Andreozzi, Giovanni B.

AU - Periotto, Benedetta

AU - Princivalle, Francesco

AU - Lenaz, Davide

AU - Secco, Luciano

AU - Pasqualetto, Leonardo

AU - Logvinova, Alla M.

AU - Sobolev, Nikolay V.

AU - Lorenzetti, Alessandra

AU - Harris, Jeffrey W.

PY - 2019/8/29

Y1 - 2019/8/29

N2 - Diamonds and their inclusions are unique fragments of deep Earth, which provide rare samples from inaccessible portions of our planet. Inclusion-free diamonds cannot provide information on depth of formation, which could be crucial to understand how the carbon cycle operated in the past. Inclusions in diamonds, which remain uncorrupted over geological times, may instead provide direct records of deep Earth’s evolution. Here, we applied elastic geothermobarometry to a diamond-magnesiochromite (mchr) host-inclusion pair from the Udachnaya kimberlite (Siberia, Russia), one of the most important sources of natural diamonds. By combining X-ray diffraction and Fourier-transform infrared spectroscopy data with a new elastic model, we obtained entrapment conditions, Ptrap = 6.5(2) GPa and Ttrap = 1125(32)–1140(33) °C, for the mchr inclusion. These conditions fall on a ca. 35 mW/m2 geotherm and are colder than the great majority of mantle xenoliths from similar depth in the same kimberlite. Our results indicate that cold cratonic conditions persisted for billions of years to at least 200 km in the local lithosphere. The composition of the mchr also indicates that at this depth the lithosphere was, at least locally, ultra-depleted at the time of diamond formation, as opposed to the melt-metasomatized, enriched composition of most xenoliths.

AB - Diamonds and their inclusions are unique fragments of deep Earth, which provide rare samples from inaccessible portions of our planet. Inclusion-free diamonds cannot provide information on depth of formation, which could be crucial to understand how the carbon cycle operated in the past. Inclusions in diamonds, which remain uncorrupted over geological times, may instead provide direct records of deep Earth’s evolution. Here, we applied elastic geothermobarometry to a diamond-magnesiochromite (mchr) host-inclusion pair from the Udachnaya kimberlite (Siberia, Russia), one of the most important sources of natural diamonds. By combining X-ray diffraction and Fourier-transform infrared spectroscopy data with a new elastic model, we obtained entrapment conditions, Ptrap = 6.5(2) GPa and Ttrap = 1125(32)–1140(33) °C, for the mchr inclusion. These conditions fall on a ca. 35 mW/m2 geotherm and are colder than the great majority of mantle xenoliths from similar depth in the same kimberlite. Our results indicate that cold cratonic conditions persisted for billions of years to at least 200 km in the local lithosphere. The composition of the mchr also indicates that at this depth the lithosphere was, at least locally, ultra-depleted at the time of diamond formation, as opposed to the melt-metasomatized, enriched composition of most xenoliths.

KW - EQUATION-OF-STATE

KW - INFRARED-ABSORPTION

KW - THERMAL-EXPANSION

KW - SOLID INCLUSIONS

KW - HIGH-PRESSURES

KW - SPINEL

KW - GARNET

KW - TEMPERATURE

KW - BEHAVIOR

KW - MAGNESIOCHROMITE

UR - http://www.scopus.com/inward/record.url?scp=85071643963&partnerID=8YFLogxK

U2 - 10.1038/s41598-019-48778-x

DO - 10.1038/s41598-019-48778-x

M3 - Article

C2 - 31467318

AN - SCOPUS:85071643963

VL - 9

SP - 12586

JO - Scientific Reports

JF - Scientific Reports

SN - 2045-2322

IS - 1

M1 - 12586

ER -