Francis (Joe) Boyd

Joe Boyd joined the Geophysical Laboratory staff in 1955 to conduct high-pressure experiments. One of his many contributions since then includes the development of a high-pressure apparatus called the Boyd-England device. This instrument has allowed scientists worldwide to determine critical pyroxene-garnet phase relations -- essential data for estimating the depth at which mantle rocks originate. More recently, with fellow Staff Member Yingwei Fei, Boyd created the cubic-anvil apparatus. With a pressure range from 5 to 25 GPa, this equipment allows scientists to conduct phase studies with large-volume samples.

Although Boyd officially retired in 1996, he continues to be an active researcher at the lab. He is well known for his other petrologic work on the nature and structural history of the crust and mantle. He is one of the world's leading experts on the mantle root of the Kaapvaal craton in southern Africa.

Cratons are the kernels on which continents grow. They are much older and deeper than the neighboring crust and mantle. The Kaapvaal craton is some 3.5 billion years old. At 200 kilometers deep, it is well below the crust-mantle boundary. To study it, Boyd gathers and analyzes fragments of mantle wall rocks contained in diamond-bearing volcanic breccias called kimberlite that erupted onto the southern African surface millions of years ago. (The "pipes" through which the kimberlite erupted are now actively mined for diamonds.) Each fragment of mantle rock contains a chemical signature that tells its depth, age, and chemical history. By piecing together the fragments from different locations, Boyd and his colleagues are learning about the Kaapvaal craton's early formation. This information can be applied to cratons in other parts of the world. Boyd is collaborating with Russian scientists, for example, to determine the similarities and differences between the crust and mantle forming the Kaapvaal craton with that forming the Siberian Platform. One of the long-term goals of these studies is to learn how the Earth's first early crust formed -- a crust that presumably preceded even that of the Kaapvaal and other ancient cratons around the world.

Fig. 4. This map of southern Africa shows the Kaapvaal craton with important kimberlites and kimberlite clusters.