Variations in magma source regions during large-scale continental extension

A tubular connector sleeve has a radially outwardly projecting inwardly open groove formed at one end which is defined by a radially outwardly projecting wall and a radially inwardly projecting flange at the end of the sleeve. A portion of the flange is cut away to provide access to the groove. A connector tube has a radially outwardly projecting flange at one end and the outside diameter of this flange is generally equal to the inside diameter of the connector sleeve so that the flange on the connector tube can extend inside the connector sleeve. A spiral lock ring is wound through the opening in the sleeve flange until the entire spiral lock ring is in the groove. The wall length of the spiral lock ring is greater than the depth of the groove so a portion of the ring wall extends radially inside the sleeve far enough beyond the internal surface of the sleeve so the radially outwardly projecting flange at the end of the connector tube abuts the portion of the spiral lock ring wall to prevent separation between the connector sleeve and the connector tube.