Hello everyone,
In the PM-normalized diagram, my data for some basaltic rocks show slightly positive Nb-Ta anomalies. They all show positive Pb anomaly but no correlation of MgO versus 87Sr/86Sr and 143Nd/144Nd?
I am looking forward to your help. Thanks in advance.
Source of basaltic magma was metasomatic mantle. Modification of mantle was by melts/fluids from subducted crust.
Dear Valentin,
Thank you very much for your answer.
As your suggestion, subduction-related fluid mainly causes the elevated Pb in our OIB-like basalts? Should I need to check other mobile elements which also can be elevated due to subduction-related fluid? Besides the elevation of these mobile elements, are there other certain evidence to confirm the presence of subduction-related fluid (which causes metasomatism?) in the mantle source
The subduction-related fluid are riched by LIL elements (Sr, Pb, Rb, K). If the basalts are high-potassium, then the magma protholite contains phlogopite. A positive correlation of K/La to K in basalts is an indicator of the presence of phlogopite and water in the mantle. Restitic association with melting hydrated mantle comprises a titanium-containing phase (e.g., rutile) - Ta-Nb minimum in melts.
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