Fig. 6

Characteristics of polyhalite in polished core samples. a Polyhalite fragments in black halite of the Well ZK001. The polyhalite is grayish-black to reddish in color and is translucent, with a waxy luster. The crystal is fine-grained and exhibits conchoidal fractures. At 3083 m depth. b A polyhalite fragment in red halite of the Well HC3, 1–10-mm-thick light and dark sedimentary/primary laminae are developed in the polyhalite, which were disrupted by plastic deformation and exhibit no directionality, that is, they are not consistent with the orientation of the strata, at 3445 m depth. H = Halite; Pol = Polyhalite