School of Earth and Space Exploration, Arizona State University, 781 East Terrace Road, Tempe, AZ, 85287-6004, USA.
Naturwissenschaften. 2022 Sep 3;109(5):48. doi: 10.1007/s00114-022-01818-5.
Ikaite is the calcium carbonate hexahydrate (CaCO·6HO), which precipitates below ~ 7 °C, first identified from Ikka Fjord in southwest Greenland and subsequently more widely reported. Here is described the serendipitous discovery of ikaite on a tree (Populus fremontii) wound from the hot Sonoran Desert, which precipitates during short cold periods in the winter, whereas monohydrocalcite forms through most of the year. The tree wound consists of infected wood, called wetwood that exudes a nutrient-rich water on which a jelly-like slime flux forms. Ikaite, along with alpha sulfur, precipitates in and on the bacterial slime flux jelly. Each tree wound occurs as an island of mineralization: all the elements for the mineral formation are supplied through the xylem sap expressed from the wetwood infection. The P. fremontii wetwood is capped and surrounded by a hard mineralized zone dominated by ikaite/monohydrocalcite, alpha sulfur, and a range of carbonates and sulfates, on which the slime flux jelly occurs. Water oozing from the wetwood is modestly alkaline (pH = 8.34), with elevated concentrations of K (5554.7 ppm) and S as SO (1662.9 ppm), with Ca (151.9 ppm) and Mg (270.3 ppm). This water chemistry favors the precipitation of ikaite/monohydrocalcite, both within and below the jelly. The ikaite is temperature sensitive, though the laboratory results show that it can persist for several days at room temperature in the sulfur-rich jelly. The ikaite, and associated mineralization within and around the slime flux jelly, illustrates a new, and likely, global form of bio-mediated mineralization.
冰长石是六水合碳酸钙 (CaCO·6HO)，在 ~7°C 以下沉淀，最初在格陵兰西南的伊卡峡湾被发现，随后被更广泛地报道。本文描述了在一棵来自炎热的索诺兰沙漠的受伤树上偶然发现冰长石的情况，冰长石在冬季的短暂寒冷期内沉淀，而一水碳酸钙则在一年中的大部分时间形成。树木的伤口由感染的木材组成，称为湿木，它会渗出富含营养的水，在这种水中会形成果冻状的粘性物质流。冰长石与α硫一起在细菌粘液流果冻中沉淀。每个树木伤口都是一个矿化岛：矿物质形成所需的所有元素都是通过从湿木感染中表达的木质部汁液提供的。彭罗斯冷杉的湿木被坚硬的矿化区覆盖和包围，矿化区主要由冰长石/一水碳酸钙、α硫以及一系列碳酸盐和硫酸盐组成，粘液流果冻就存在于其中。从湿木渗出的水呈弱碱性（pH=8.34），K（5554.7 ppm）和 S 作为 SO（1662.9 ppm）浓度升高，Ca（151.9 ppm）和 Mg（270.3 ppm）。这种水化学有利于冰长石/一水碳酸钙的沉淀，无论是在果冻内部还是外部。冰长石对温度敏感，但实验室结果表明，在富含硫的果冻中，它可以在室温下持续数天。冰长石以及粘液流果冻内和周围的相关矿化作用说明了一种新的、可能是全球性的生物介导矿化形式。
