CAJ | 학술논문

着重论述了蛇绿岩地幔橄榄岩中豆荚状铬铁矿的成因,并对现今盛行的岩石/熔体反应成矿说提出了质疑.世界含铬铁矿的地幔橄榄岩均显示上部偏基性、下部偏酸性的垂直熔融分带,与蛇绿岩堆晶岩中上部偏酸性、下部偏基性的岩浆分异垂直层序恰恰相反.豆荚状铬铁矿与熔融剖面上部的纯橄岩或纯橄岩-方辉辉橄岩杂岩带紧密伴生.豆荚状铬铁矿是原始地幔岩高度熔融再造的产物,高铬型铬铁矿与PPG型蛇绿岩伴生,形成于岛弧或弧前盆地环境;高铝型铬铁矿与PTG型蛇绿岩伴生,形成于扩张脊(MOR)或弧后盆地环境.玻安岩(boninite)与高铬型豆荚状铬铁矿无成因关系,铬铁矿(或富铬矿浆)的形成反而为boninite提供了其形成所需的残余地幔;高铝型铬铁矿不是地幔橄榄岩/拉斑玄武质熔体反应形成的,而是富铬矿浆与基性熔体发生再平衡的产物.豆荚状铬铁矿中超高压矿物包体的出现为其地幔深部成因提供了佐证,而boninite形成于浅部较低压的条件;豆荚状铬铁矿中富集强相容元素IPGE(Os、Ir、Ru)合金,boninite富集不相容元素PPGE(Pt、Pd)硫(砷)化物,而亏损IPGE,显示其形成较晚.因此,boninite与铬铁矿无生因关系,两者均受岛弧(或弧前盆地)环境的制约而在空间上相伴产出.
착중논술료사록암지만감람암중두협상락철광적성인,병대현금성행적암석/용체반응성광설제출료질의.세계함락철광적지만감람암균현시상부편기성、하부편산성적수직용융분대,여사록암퇴정암중상부편산성、하부편기성적암장분이수직층서흡흡상반.두협상락철광여용융부면상부적순감암혹순감암-방휘휘감암잡암대긴밀반생.두협상락철광시원시지만암고도용융재조적산물,고락형락철광여PPG형사록암반생,형성우도호혹호전분지배경;고려형락철광여PTG형사록암반생,형성우확장척(MOR)혹호후분지배경.파안암(boninite)여고락형두협상락철광무성인관계,락철광(혹부락광장)적형성반이위boninite제공료기형성소수적잔여지만;고려형락철광불시지만감람암/랍반현무질용체반응형성적,이시부락광장여기성용체발생재평형적산물.두협상락철광중초고압광물포체적출현위기지만심부성인제공료좌증,이boninite형성우천부교저압적조건;두협상락철광중부집강상용원소IPGE(Os、Ir、Ru)합금,boninite부집불상용원소PPGE(Pt、Pd)류(신)화물,이우손IPGE,현시기형성교만.인차,boninite여락철광무생인관계,량자균수도호(혹호전분지)배경적제약이재공간상상반산출.
The author has emphatically discussed the genesis of the podiform chromite deposits in the ophiolites and thus questions the widespread rock/melt interaction metallogeny. The mantle peridotites-bearing chromite deposits in the world also exhibit a vertical zoning of melting, with more basic material in the upper part and more acid material in the lower part, being opposite to vertical zoning of magmatic differentiation with more acid material in the upper part and more basic material in the lower part. The podiform chromite deposits are closely associated with the dunite or dunite-harzburgite complex belts in the upper part of melting profile. The podiform chromite deposits are products formed by highly partial melting and reconstitution of primary peridotites. The Cr -rich chromite deposits belong to PPG ophiolite series and form in island arc (or fore-arc basin) and Al-rich one are associated with PTG ophiolite series and form in MOR or (back-arc basin). A residue depleted mande was left after the formation of Cr-rich podiform chromite deposit, which is needed to form the boninite. So, there is no genetic relationship between the chromte and boninite. The Al-rich podiform chromite deposits are products formed by re-equilibrium between the Cr-rich ore magma and basic melt and are not formed by interaction between the tholeiitic melt and peridotite. The occurrence of the UHP mineral inclusions in the chromite ores suggests a deeper mantle genesis for the podiform chromite deposits, but the boninite is segregated in the lower pressure (<10km). The podiform chromite deposits are rich in strong compatible elements IPGE (Os, Ir, Ru) alloys during partial melting, in contrast theboninites are rich in incompatible elements PPGE (Pt, Pd) surfide (arsenite) representing a later magmatic segregation. Obviously, there is no any genetic relationship between the boninite and Cr-rich podiform chromite deposit, and they are also controlled by island arc (or fore-arc) tectonic environment and thus only occur together spatially.