Nanodiamond Finding in the Hyblean Shallow Mantle Xenoliths

Abstract

Most of Earth’s diamonds are connected with deep-seated mantle rocks; however, in recent years, μm-sized diamonds have been found in shallower metamorphic rocks, and the process of shallow-seated diamond formation has become a hotly debated topic. Nanodiamonds occur mainly in chondrite meteorites associated with organic matter and water. They can be synthesized in the stability field of graphite from organic compounds under hydrothermal conditions. Similar physicochemical conditions occur in serpentinite-hosted hydrothermal systems. Herein, we report the first finding of nanodiamonds, primarily of 6 and 10 nm, in Hyblean asphaltene-bearing serpentinite xenoliths (Sicily, Italy). The discovery was made by electron microscopy observations coupled with Raman spectroscopy analyses. The finding reveals new aspects of carbon speciation and diamond formation in shallow crustal settings. Nanodiamonds can grow during the hydrothermal alteration of ultramafic rocks, as well as during the lithogenesis of sediments bearing organic matter.

Massive production of abiotic methane during subduction evidenced in metamorphosed ophicarbonates from the Italian Alps

“…In summary, the isotopic data indicate that high-pressure abiotic CH 4 and graphite with mantle-like δ 13 C compositions can form by in situ reduction of subducted marine ophicarbonates, without any contribution of mantle C. Similar processes may participate in the precipitation of mantle diamonds with this isotopic signature at greater depths 31 35 , or nanodiamonds in the graphite stability field 36 .…”

“…Graphite in blueschist-facies metasomatized metasediments was recently interpreted as the result of carbonate reduction by serpentinite-derived aqueous fluids 28 41 . Carbonaceous material and nanodiamonds have been reported in shallow, lizardite-bearing serpentinized mantle xenoliths 36 . Pasteris 67 reported graphite formed by postmagmatic aqueous serpentinization of olivine in kimberlites.…”

A shallow origin for diamonds in ophiolitic chromitites: COMMENT

“…Farré-de-Pablo et al quoted several publications supporting generation of diamond in low pressure-temperature (P-T) serpentinization environments. We note that nanodiamonds were reported in Hyblean asphaltenebearing serpentinite xenoliths in a Tortonian tuff-breccia pipe (Sicily, Italy) (Simakov et al, 2015), but no evidence was presented to confirm that the diamonds formed by serpentinization. Diamonds may also be produced by chemical vapor deposition (CVD) or other extreme conditions in the laboratory, but such chemical-physical environments would not exist during serpentinization in nature (Schwander and Partes, 2011).…”

Dynamic Environments as a Tool to Preserve Desired Output in a Chemical Reaction Network

“…Here, we demonstrate as imple way to enable robustb ehaviour by coupling the network to ad ynamic environment. We draw inspiration fromn ature, [26][27][28][29][30] in whichfluctuating environmentsa re the norm (e.g.,d ay/night cycles, tidal waves, seasons),a nd from theoretical and experimentalw ork on simplified model systems [31,32] and studies on inorganic oscillators, such as the Belousov-Zhabotinsky (BZ) reaction, [33][34][35][36][37][38][39][40][41][42][43] which show ar ange of phenomena can emerge when operatedi na dynamic environment, for example, synchronisation through periodic variations in feed concentration, [33] entrainment of spatiotemporalw ave generation with temperature forcing, [34] spiral and standing spatiotemporal waves through periodic spiking withl ight, [37,38] noise-induced oscillations, [39] and chaotic oscillations. [40] We use our previously designed enzymatic reaction network ( Figure 1) [5,44,45] to show how the behaviour of an etwork, in this case oscillations, varies upon ac hange in the environment.…”