# Göttingen University team finds warm shallow subduction in 4.4-Myr eclogite from Papua New Guinea

- Published: 2026-11-08 01:44 UTC
- Section: Planet › Earth sciences
- Tags: ultrahigh-pressure metamorphism, coesite inclusion, Göttingen University, subduction zone thermal structure, eclogite Goodenough Island, shear heating
- URL: https://realtech.media/news/rt-fbd5d71bb72bedc39dba1cbd_g_ttingen_university/

**Analysis of mineral inclusions in garnet showed an initial gradient of 470 °C/GPa down to 45 km, challenging classical thermal models of subduction zones.**

![Göttingen University team finds warm shallow subduction in 4.4-Myr eclogite from Papua New Guinea](https://realtech.media/media/2026/11/9f87e6e67f8f6691.png)
*nature.com*

An international research team led by the University of Göttingen investigated a young ultrahigh-pressure eclogite from Goodenough Island in eastern Papua New Guinea, as reported by nature.com [1]. Geochronological analysis of zircon inclusions revealed a U–Pb age of approximately 4.4 million years, corresponding to the subduction of a rifted continental fragment of Australian provenance [1].

## Mineral inclusions and pressure regimes

The eclogite sample contains (sub)micrometre-sized inclusions of coesite within the intermediate growth zones of garnet crystals [1]. Coesite forms strictly under ultrahigh-pressure conditions, confirming that crustal rocks descended to depths greater than 90 km into its stability field before exhumation [1]. The mineral assemblage consists of approximately 38 vol% garnet, 22 vol% quartz, and omphacitic clinopyroxene [1].

## Two-stage thermal path and shear heating

Thermobarometric methods, single-grain thermometry of rutile, and thermodynamic modeling revealed that the prograde subduction path was initially warm, with an average gradient of approximately 470 °C GPa⁻¹ down to a depth of about 45 km [1]. At this depth, the rock reached around 700 °C, before switching to a colder regime with peak conditions indicating less than 330 °C GPa⁻¹ at roughly 800 °C and ultrafast vertical subduction rates exceeding 60 mm yr⁻¹ [1].

The authors state that this change in geothermal gradients can be explained by shear heating during mechanical displacement, rock formation during the non-steady-state phase of a young subduction system, or a combination of both mechanisms [1]. They propose that elevated geothermal gradients at shallow levels of deep subduction zones may be common, which challenges the standard practice of using peak metamorphic conditions alone to infer thermal structures [1].

## Sources

1. [nature.com](https://www.nature.com/articles/s41561-026-02110-1)
2. [SciTechDaily](https://scitechdaily.com/scientists-discover-something-unexpected-90-kilometers-beneath-earth)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-fbd5d71bb72bedc39dba1cbd_g_ttingen_university/