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中国大陆科学钻探主孔中的超镁铁岩主要产在603.20～683.53m深度之间。超镁铁岩的上部直接围岩为高Ti-Fe型榴辉岩;内部夹有薄层状含柯石英高镁榴辉岩和厚层状多硅白云母榴辉岩;下部直接围岩为石英榴辉岩和普通榴辉岩。超镁铁岩的主体岩性为石榴石单辉橄榄岩,主要由橄榄石(60%～70%),石榴石(10%～25%),单斜辉石(5%～15%),斜方辉石(1%～5%)和少量金云母和钛铁矿或钛斜硅镁石组成。橄榄石Fo 79～89,其中一些以包裹体形式出现的高MgO橄榄石可能形成较早,主体橄榄石属变质重结晶阶段形成;石榴石以低CaO、高MgO和Cr_2O_3含量高(达3%)为特征,保留较好的进变质成分环带;单斜辉石Na_2O含量达到4%～5%,分为绿辉石和普通辉石类,属变质成因,结合矿物对的温压估算,岩石已经经历超高压变质作用。岩石成分研究表明,石榴石单辉橄榄岩与其顶、底板榴辉岩及其中的榴辉岩夹层有一较大的成分间断,其中MgO含量约相差10%左右,认为超镁铁岩与榴辉岩的原岩不属同一岩浆演化产物。锆石SHRIMP定年表明石榴石单辉橄榄岩原岩时代为古生代346～461Ma,超高压变质作用时代为早中生代220～240Ma。认为CCSD主孔石榴石橄榄岩为古生代的超镁铁质侵入体,在印支期的中国南北板块俯冲折返过程中经历了超高压变质作用。
The main ultramafic rocks in the main hole of the Chinese mainland scientific drilling are between 603.20 and 683.53 m in depth. The upper immediate surrounding rock of the ultramafic rocks is a high-Ti-Fe eclogite with a thin layer of coesite-rich gneissic eclogite and a thick layered pleistobolite eclogite in the interior. The lower direct surrounding rock is quartz garnet Hui Yan and ordinary eclogites. The main lithology of the ultramafic rocks is garnet hectorite, which is mainly composed of olivine (60% -70%), garnet (10% -25%), clinopyroxen (5% -15% Pyroxene (1% to 5%) and a small amount of phlogopite and ilmenite or titanosite composition. Olivine Fo 79-89, some of which may form early inclusions of high MgO olivine may form the main olivine metamorphic recrystallization stage; garnet to low CaO, high MgO and Cr 2 O 3 content (up to 3% ), And retaining the good zoning of metamorphic components. The Na_2O content of clinopyroxene reaches 4% ~ 5%, which is divided into omphacite and pyroxene, which are metamorphic origin. Combined with the temperature and pressure estimation of mineral pairs, the rock Has experienced ultra-high pressure metamorphism. The study of rock composition shows that there is a large component discontinuity between the garnet hTERT and its top and bottom eclogites and the eclogite intercalation, in which the MgO content is about 10% different. It is considered that the ultramafic rocks and eclogites Rocks do not belong to the same magmatic evolution. The zircon SHRIMP dating indicates that the age of the protolith from garnet hyaluronite was 346 ~ 461Ma in the Paleozoic era, and the age of the UHP metamorphism was 220 ~ 240Ma in the early Mesozoic. It is believed that the main CCSP garnet peridotite is Paleozoic ultramafic intrusive and underwent UHP metamorphism during the Indosinian process of the north-south plate subduction and reentry.