The Paleoproterozoic Bakhuis Granulite Belt (BGB) in Surinam, South America, shows ultrahigh-temperature metamorphism (UHTM) at temperatures of around 1000 °C which, unusually, produced peak-to-near-peak cordierite with sillimanite and, in some cases, Al-rich orthopyroxene on a regional scale. Mg-rich cordierite (Mg/(Mg + Fe) = 0.88) in a sillimanite-bearing metapelitic granulite has a maximum birefringence of second-order blue (ca. 0.020) indicative of a considerable amount of CO₂ (> 2 wt%) within its structural channels. SIMS microanalysis confirms the presence of 2.57 ± 0.19 wt% CO₂, the highest CO₂ concentration found in natural cordierite. This high CO₂ content has enabled the stability of cordierite to extend into UHT conditions at high pressures and very low to negligible H₂O activity. Based on a modified calibration of the H₂O–CO₂ incorporation model of Harley et al. (J Metamorph Geol 20:71–86, 2002), this cordierite occupies a stability field that extends from 8.8 ± 0.6 kbar at 750 °C to 11.3 ± 0.65 kbar at 1050 °C. Volatile-saturated cordierite with 2.57 wt% CO₂ and negligible H₂O (0.04 wt%) indicates fluid-present carbonic conditions with a CO₂ activity near 1.0 at peak or near-peak pressures of 10.5–11.3 kbar under UHT temperatures of 950–1050 °C. The measured H₂O content of the cordierite in the metapelite is far too low to be consistent with partial melting at 1000–1050 °C, implying either that nearly all of any H₂O originally in this cordierite under UHT conditions was lost during post-peak cooling or that the cordierite was formed after migmatization. The high level of CO₂ required to ensure fluid saturation of the c. 11 kbar UHT cordierite is proposed to have been derived from an external, possibly mantle, source.

南美洲苏里南的古元古代 Bakhuis 麻粒岩带 (BGB) 在大约 1000 °C 的温度下显示出超高温变质作用 (UHTM)，异常地产生峰到近峰堇青石和硅线石，在某些情况下，区域范围内富铝斜方辉石。含硅线石的变泥质麻粒岩中的富镁堇青石 (Mg/(Mg + Fe) = 0.88) 具有二级蓝色的最大双折射率 (ca. 0.020)，表明含有大量 CO 2 (> 2 wt _% )在其结构通道内。SIMS 微量分析证实存在 2.57 ± 0.19 wt% CO ₂ ，​​这是天然堇青石中发现的最高 CO _2浓度。这种高 CO ₂含量使堇青石的稳定性扩展到高压和非常低至可忽略的 H ₂ O 活性的 UHT 条件。基于Harley 等人的H ₂ O–CO ₂结合模型的修正校准。(J Metamorph Geol 20:71–86, 2002)，这种堇青石占据的稳定场从 750 °C 时的 8.8 ± 0.6 kbar 延伸到 1050 °C 时的 11.3 ± 0.65 kbar。含有 2.57 wt% CO ₂和可忽略不计的 H ₂ O (0.04 wt%) 的挥发性饱和堇青石表明在950 的 UHT 温度下，在 10.5–11.3 kbar 的峰值或近峰值压力下， CO ₂活度接近 1.0 的流体存在的碳条件–1050°C。测得的H ₂变泥质岩中堇青石的 O 含量太低，无法与 1000–1050 °C 的部分熔化相一致，这意味着在 UHT 条件下最初在这种堇青石中的几乎所有 H ₂ O 在峰值后冷却过程中都消失了，或者堇青石是在混合化后形成的。确保 c 的流体饱和所需的高水平 CO _{2 。}11 kbar UHT 堇青石被认为来自外部来源，可能是地幔来源。