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《格罗玛·挑战者》号在大东海岭及其南侧深海平原进行了钻探,对所获第三纪沉积物(始新世—中新世)粗粒组分的岩芯做了重矿物分析。透明重矿物中以普通角闪石、普通辉石含量最高,淡绿—蓝绿色角闪石、绿帘石含量次之。自形晶磷灰石、黑云母、形状不规则的铬铁矿普遍存在,而含钛辉石、透辉石、霓辉石仅见于部分样品中。由于重矿物组成和透明重矿物含量的急剧变化而在海底约760米深的始新统中形成一个界面。本海域重矿物的母岩为玄武质火山岩(碱性岩)、结晶片岩、超基性岩。与九州西北部、冲绳岛、西表岛的始新统、渐新统或中新统相比,在岩石固结度、透明重矿物含量、磁铁矿含量、重矿物组成方面迥然不同。本海域是一个和日本西南部完全不同的地质区域。
The Grotma Challenger was drilled in the Dadong Ridge and its deep-sea plains on the south side of the core to make cores of the coarse-grained components of the Tertiary sediments (Eocene-Miocene) Mineral Analysis. Transparent heavy minerals to amphibole, the highest pyroxene content, light green - blue green amphibole, epidote followed. Self-shaped apatite, biotite, irregularly shaped chromite are ubiquitous, while the titanium-bearing pyroxene, diopside, niobium only found in some samples. An interface forms in the Eocene about 760 meters deep at sea due to drastic changes in heavy mineral composition and clear heavy mineral content. The parent rocks of heavy minerals in this area are basaltic volcanic rocks (alkaline rocks), crystalline schist and ultrabasic rocks. Compared with the Eocene, Oligocene or Miocene of Northwestern Kyushu, Okinawa and Iriomote Island, it is quite different in terms of rock solidity, clear heavy mineral content, magnetite content and heavy mineral composition. The sea area is a completely different geological area from the southwestern part of Japan.