摘要：

Seafloor hydrothermal activity in Mid-Ocean Ridge has become one of hotspots in geosciences because of its valuable scientific researching significance.Hydrothermal systems at seafloor spreading centers are characterized by a complex interplay among magmatic,tectonic and biogeochemical processes linked by fluid circulation and heat transfer in the oceanic crust.It could be divided into three phases on the evolution of magma-controlled hydrothermal system,an initial phase,a living phase and a dying phase.The three phases simply reflects the evolution mechanism of hydrothermal system.On the basis of previous data collecting and studies,the authors consider that there are three corresponding hydrothermal activity phases at fast spreading centers,and they evolved with shorter phases,no more than ten years or decades.Although magmatic budget is not so robust at slow spreading centers,the characteristics of each phases are not obvious,and hydrothermal system with universal heat and special structure could continue more than ten thousand years or evolve with tens of thousand years episodically.So the authors affirm that hydrothermal processes are controlled by heat supply and tectonic conditions,such as Rainbow and TAG hydrothermal field in Mid Atlantic Ridge,or even Middle Valley hydrothermal field in Juan de Fuca Ridge,they all have experienced a long-term evolution caused by their sufficient heat supply and favorable superior tectonic conditions.Uncovered ultramafic rock and deeper extension brittle failure are common existent at ultra-slow spreading centers.It has been detected higher incidence of hydrothermal venting than calculated by Magmatic Budget Hypothesis in recent decades,such as Gakkel Ridge in the Arctic Ocean and Southwest Indian Ridge,certain segments areas with extra irregular heat supply and more favorable superior tectonic conditions may cause huge hydrothermal sulfide deposit by long-term cumulating.China have made great progress in prospecting seafloor hydrothermal activity at Southwest Indian Spreading Center,but we must make great efforts to uncover hydrothermal circulation processes and ore-forming mechanism by multidisciplinary exploration methods,such us mineralogical and geophysical exploration,numerical simulation and mathematical modeling,deep sea long-term in situ observations,or even intelligent robot's detecting and sampling.

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