海洋核杂岩形成机制及其热液硫化物成矿意义

FORMATION MECHANISM OF OCEANIC CORE COMPLEX AND ITS SIGNIFICANCE TO THE MINERALIZATION OF HYDROTHERMAL SULFIDE

海洋核杂岩是近年来新提出的洋底构造样式,其主要产出于慢速-超慢速扩张洋中脊轴两侧,目前在中大西洋脊、西南印度洋脊、中印度洋脊以及东南印度洋脊均发现海洋核杂岩。海洋核杂岩以其表面梳状构造为主要的探测特征,其构造要素还包括平行于洋脊轴的拆离断层、上盘后期正断层等;其岩石组合以出露于洋底的地幔岩石为主。海洋核杂岩的发育与慢速-超慢速洋脊的扩张速率、岩浆补给和拆离断层的发育有关:慢速-超慢速扩张洋脊的岩浆补给不足以平衡洋脊扩张所带来的空间应变量,从而以在薄弱带发育拆离断层来弥补,并继而使拆离断层下盘的地幔岩石出露洋底表面,形成海洋核杂岩。海洋核杂岩的发育经历了发育初期、发展期、成熟期和衰亡期等周期。海洋核杂岩为洋底热液硫化物矿床的发育提供了物质来源、热液通道等有利条件,或将是热液硫化物矿床发育的有利构造条件,是一种新的远离洋脊轴的热液系统。

The oceanic core complex（OCC）is a new style of sea floor structure discovered in recent years. OCCs are mainly found on both sides of the slow and ultra-slow spreading ridges. Recent study of OCCs is mainly carried out on the Mid-Atlantic Ridge, Southwest Indian Ridge, Central Indian Ridge and Southeast Indian Ridge. Surface corrugations and lineations are the main features for identification of OCCs, and de- tachment fault parallel to ridge axis, rift valleys and normal faults on the hanging wall are all the important structures of OCC systems. Serpentinite gabbro, olivinite and the thin oceanic sediments compose OCC. The development of OCCs has much link with ocean ridge spreading velocity, manga supply and detach- ment fault： the manga supply at slow and ultra-slow spreading ridges is not enough to balance the ridge spreading-caused strain vacancies. There needs detachment fault on the weak zone to bring the rocks from mantle to the sea floor for balance. The development of OCCs experiences four stages including embryonic stage, development stage, maturity stage and decline stage. OCCs maybe the favorable structural setting for hydrothermal sulfide and a new off-axis hydrothermal system to provide substance, heat resource and favorable passages for the hydrothermal system and mineralization.