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Carbon is constantly released from subducting slabs back to the atmosphere in the form of gases such as CO2 and CH4. This constitutes a source of greenhouse gases that can regulate atmospheric chemistry over geological timescales. However, the carbon carried by hydrothermal fluids released from slabs may be locked along their ascending paths for variably long periods of time. The processes involved in this chromatographic pathway remain unclear. Here we report the co‐occurrence of graphite and phlogopite in highly metasomatized rocks derived from the mantle wedge of a Late Neoproterozoic subduction zone in the Achankovil Suture Zone in southern India. Petrographic, isotopic, and fluid inclusion evidence suggests these rocks formed in an environment soaked in C‐bearing fluids derived from the subducting slabs. We propose that desiccation of slab‐derived fluids in contact with a dry mantle wedge is the main driver for this phenomenon, while redox change only plays a marginal role. Our work provides a perspective on the diversity of non‐traditional carbon graphitization pathways in the lithosphere. It shows that refractory forms of elemental carbon of abiotic origin may be ubiquitous in the cold mantle wedge. [ABSTRACT FROM AUTHOR]

Conventional beta counting technique based radiocarbon dating facility at Birbal Sahni Institute of Palaeosciences- Lucknow was established in 1974 (Rajagopalan,1978). In 2017-18, BSIP received an upgrade with installation of an Automated Graphitization Equipment (AGE) coupled with an Elemental Analyser, a Carbonate Handling System (CHS) along with an in-line stable isotope mass-spectrometer (IRMS). Using this combo, stable Carbon (C), Nitrogen (N) and Sulfur (S) isotopic measurements could be carried out in both organic and inorganic type samples followed by graphite preparation (~1 mg) for 14 C measurement by Accelerator Mass Spectrometry (AMS). This communication addresses details of pre-processing, processing, and quality checks adopted for achieving acceptable and demonstrable accuracy and precision of measured Δ 14 C, δ 13 C, δ 15 N, and δ 34 S measurements. Information regarding chemical preparation of samples for aforesaid stable and radio isotopic analysis is provided in succinct manner. Overall, average coefficient of variation determining precision of our graphite powders for 14 C measurements is ~2.4%. The mean age of blank (anthracite) processed using established EA-IRMS-AGE unit comes as 42,100 ± 300 years., Competing Interests: Declaration of competing interest The authors declare that they have no competing interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)