Figure 2. Representative thin section microphotographs and scanning electron microscopic images of samples from the Isua supracrustal belt. a: Sample AW17724-2C preserves primary olivine grains (i and ii). Two generations of serpentine minerals are identified: early-stage serpentine minerals (serp1) occur as inclusions in the olivine grains (ii andiv), and late-stage serpentine minerals (serp2) occur as lepidoblastic assemblages in the matrix cutting olivine, magnesite, and Ti-humite (i–iv). Both magnesite and Ti-humite are found in the matrix (i and ii) and inside the olivine grains (iii–iv). Due to the observed alteration including talc-alteration and serpentinization, primary igneous textures of this sample cannot be identified (i and v). b:Local preservation of polygonal textures by olivine grains in sample AW17725-4. c–d: Loss of most primary ultramafic silicates and rock textures of some Isua samples due to strong alteration (e.g., serpentinization, talc alteration, and/or amphibolite facies metamorphism). Mineral abbreviations: mag: magnesite; mgt: magnetite; ol: olivine; serp: serpentine; tlc: talc; Ti-cl: Titano-clinohumite; Ti-ch: Titano-chondrodite; tr: tremolite.