Keller L P, Thomas K L, Clayton R N, Mayeda T K, DeHart J M, McKay D S
MVA, Inc., Norcross, GA 30093, USA.
Geochim Cosmochim Acta. 1994 Dec;58(24):5589-98. doi: 10.1016/0016-7037(94)90252-6.
A petrographic, geochemical, and oxygen isotopic study of the Bali CV3 carbonaceous chondrite revealed that the meteorite has undergone extensive deformation and aqueous alteration on its parent body. Deformation textures are common and include flattened chondrules, a well-developed foliation, and the presence of distinctive (100) planar defects in olivine. The occurrence of alteration products associated with the planar defects indicates that the deformation features formed prior to the episode of aqueous alteration. The secondary minerals produced during the alteration event include well-crystallized Mg-rich saponite, framboidal magnetite, and Ca-phosphates. The alteration products are not homogeneously distributed throughout the meteorite, but occur in regions adjacent to relatively unaltered material, such as veins of altered material following the foliation. The alteration assemblage formed under oxidizing conditions at relatively low temperatures (<100 degrees C). Altered regions in Bali have higher Na, Ca, and P contents than unaltered regions which suggests that the fluid phase carried significant dissolved solids. Oxygen isotopic compositions for unaltered regions in Bali fall within the field for other CV3 whole-rocks, however, the oxygen isotopic compositions of the heavily altered material lie in the region for the CM and CR chondrites. The heavy-isotope enrichment of the altered regions in Bali suggest alteration conditions similar to those for the petrographic type-2 carbonaceous chondrites.
对巴厘岛CV3碳质球粒陨石进行的岩相学、地球化学和氧同位素研究表明，该陨石在其母体上经历了广泛的变形和水蚀作用。变形纹理很常见，包括扁平的球粒、发育良好的叶理以及橄榄石中独特的（100）平面缺陷。与平面缺陷相关的蚀变产物的出现表明，变形特征在水蚀作用阶段之前就已形成。蚀变事件期间产生的次生矿物包括结晶良好的富镁皂石、莓球状磁铁矿和钙磷酸盐。蚀变产物在整个陨石中分布不均匀，而是出现在与相对未蚀变物质相邻的区域，例如沿叶理分布的蚀变物质脉。蚀变组合是在相对低温（<100摄氏度）的氧化条件下形成的。巴厘岛蚀变区域的钠、钙和磷含量高于未蚀变区域，这表明流体相中携带了大量溶解固体。巴厘岛未蚀变区域的氧同位素组成落在其他CV3全岩的范围内，然而，高度蚀变物质的氧同位素组成位于CM和CR球粒陨石的区域。巴厘岛蚀变区域的重同位素富集表明蚀变条件与岩相学2型碳质球粒陨石相似。
