Chemical composition of rocks and minerals from the ophiolite complex in the Hunter Fracture Zone

A collection of dredge samples from the Hunter Fracture Zone includes holocrystalline massive and cumulose basic and ultrabasic rocks and volcanites of the ophiolite complex: from basalts to rhyolites. The ultrabasic rocks are largely serpentinized harzburgites and lherzolites; their relict mineralogy is typical of peridotite considered to be the refractory residue of partial melting of the mantle. Cumulate textured ultramafic rocks probably are related to the cumulate gabbro and granodiorite rather than to the residual mantle material. The gabbroic rocks are dominantly cumulate textured Pl-Opx-Cpx±Ol gabbronorite and Pl-Cpx±Ol gabbros; the mineral features of these rocks are the result of their crystallization at moderate pressure (in a moderate level magma chamber). The massive Pl-Cpx±Ol gabbros are less common. Green and brown-green Ca-amphibole has partially or totally replaced the clinopyroxene in many samples. There is an overlap in mineral chemistry between the cumulate rocks and the Opx-Cpx-Pl volcanic rocks and boninites. It is interpreted as an indication that the cumulate rocks were co-genetic with Opx-Cpx-Pl volcanic rocks and that they both constitute remnants of an island arc volcanic-plutonic series. The petrologic evidence indicates that ophiolite gabbroic rocks were derived from an island-arc rather than from a mid-ocean ridge.本数据集收录采自亨特断裂带（Hunter Fracture Zone）的拖网采样样品，涵盖蛇绿岩套（ophiolite complex）中的全晶质块状、堆积构造基性与超基性岩及火山岩，岩性跨度从玄武岩至流纹岩。 其中超基性岩以蛇纹石化方辉橄榄岩与二辉橄榄岩为主；其残留矿物组合属于典型的橄榄岩类，被认为是地幔部分熔融的难熔残留体。 具堆积构造的超镁铁质岩大概率与堆积型辉长岩及花岗闪长岩存在成因关联，而非源于残留地幔物质。 辉长岩类以具堆积构造的斜长石-斜方辉石-单斜辉石±橄榄石辉长苏长岩（Pl-Opx-Cpx±Ol gabbronorite）和斜长石-单斜辉石±橄榄石辉长岩（Pl-Cpx±Ol gabbros）为主；这类岩石的矿物特征是其在中等压力下（中等深度岩浆房）结晶分异的产物。块状斜长石-单斜辉石±橄榄石辉长岩相对少见。 在多数样品中，绿色至棕绿色的钙角闪石已部分或完全交代单斜辉石。 堆积岩与斜方辉石-单斜辉石-斜长石火山岩及玻安岩（boninites）之间存在矿物化学特征的重叠。 该现象被解读为：堆积岩与斜方辉石-单斜辉石-斜长石火山岩具有同源成因，二者共同构成岛弧火山-侵入岩系的残留体。 岩石学证据显示，该蛇绿岩套中的辉长岩类形成于岛弧环境，而非洋中脊环境。