Electrical Conductivity of Clinopyroxene‐NaCl‐H 2 O System at High Temperatures and Pressures: Implications for High‐Conductivity Anomalies in the Deep Crust and Subduction Zone

• Published in: Journal of geophysical research. Solid earth 2020-04, Vol.125 (4)
• Main Authors: Sun, Wenqing, Dai, Lidong, Li, Heping, Hu, Haiying, Jiang, Jianjun, Wang, Mengqi
• Format: Article
• Language: English
• ISSN: 2169-9313; 2169-9356
• DOI: 10.1029/2019JB019093

Electrical conductivities of the clinopyroxene (Cpx)‐NaCl‐H 2 O system with various salinities (5, 10, 15, 20, 25 wt%) and fluid fractions (5, 10, 15, 20, 25 vol%) were measured at 1 GPa and 673–973 K. For comparison with electrical properties of the Cpx‐NaCl‐H 2 O system, the conductivities of dry Cpx, hydrous Cpx, and a Cpx‐H 2 O system were researched at the same temperature and pressure. The experimental results included (1) the electrical conductivities of all samples that were associated with Cpx and the temperatures conform to the Arrhenius relationship that is used to fit the activation enthalpy, which decreased with increasing salinity (mass fraction of NaCl in saline fluids) and fluid fraction (volume fraction of saline fluids in the Cpx‐NaCl‐H 2 O system); (2) at a fixed fluid fraction of 10 vol%, the conductivities of the Cpx‐NaCl‐H 2 O system increased slightly with an increase in salinity, and the gap between the conductivities of the systems with 5 and 25 wt% saline fluids was approximately 1 order of magnitude; (3) at a fixed salinity of 5 wt%, the conductivity of the Cpx‐NaCl‐H 2 O system with 25 vol% saline fluids was approximately 1.5 orders of magnitude higher than that of the system with 5 vol% saline fluids. Furthermore, it was proposed that the unusually high conductivities of southern Tibetan Plateau, Dabie Orogen, Grenville province and central New Zealand can be caused by clinopyroxene with interconnected saline fluids with corresponding salinities and fluid fractions. Electrical properties of clinopyroxene‐NaCl‐H 2 O system with various salinities and fluid fractions were for the first time researched Salinity and fluid fraction significantly influence the conductivities of clinopyroxene‐NaCl‐H 2 O system, but the temperature effect is weak Some high‐conductivity anomalies in the deep crust and subduction zone can be caused by the clinopyroxene‐NaCl‐H 2 O system