The occurrence of gold rich carbonaceous rock series and the extensive development of altered rock bodies in the region made the mobilization and concentration of gold possible.

区域上赋金层炭质岩系的存在和蚀变体的广泛发育，使金元素活化、富集成为可能。

youdao

That is a necessary but not a sufficient condition, as the type of rock involved, called carbonaceous chondrite, is found in other asteroids, too.

他有两方面的证据：第一，现存的灾难性撞击的残骸与Baptistina和她的后代有相同的成分，这是必要条件，但并非充分条件，因为含碳的球粒状陨石在其它小行星上也有；

youdao

Coal is a sedimentary rock composed principally of organic carbonaceous macerals and inorganic minerals.

煤是一种有机沉淀岩，主要包括有机碳化合物和无机矿物。

youdao

That is a necessary but not a sufficient condition, as the type of rock involved, called carbonaceous chondrite, is found in other asteroids, too.

ECONOMIST: Asteroid impacts

Assuming that the figure was similar during the Cretaceous, it would be a long shot that the first fossil meteorite to turn up from 65m years ago was made of such a rock unless a huge extra supply of carbonaceous chondrite had suddenly arrived on the planet.

ECONOMIST: Paleoforensic science