Collaborative Research: Petrotectonic Study of Ultrahigh-Pressure Rocks From the Kokchetav Massif, Northern Kazakhstan, and the Maksyutov Complex...

9725347 Liou本次提议的美国-日本-俄罗斯-哈萨克斯坦合作项目将继续对Kokchetav地块和Maksyutov杂岩中的克拉通内超高压和高压变质岩进行野外、岩石学、稳定、同位素、地质年代学和构造调查，在这些地方描述了柯石英（微金刚石）。主要目标是：（1）确定Kokchetav地块和Maksyutov杂岩中含金刚石的片麻岩和大理石、含柯石英的榴辉岩和片麻岩以及其他超高压岩石和高压岩石之间的区域分布和结构关系;（2）识别和表征榴辉岩、片麻岩、大理石和片岩中石榴石和锆石中的矿物包裹体，以确定超高压变质作用的条件和这种高压的影响;（3）确定榴辉岩、白片岩、石榴橄榄岩、蓝片岩、片麻岩和大理岩的矿物共生体和P-T-t轨迹，（4）测定硅酸盐的~（18）O/~（16）O比值和金刚石、菱镁矿和其它碳酸盐的碳同位素，以评价地幔深部流体的作用，（5）测定原岩的结构和地球化学特征，以推断其板块构造环境;（6）通过U-Pb和~（40）Ar/~（39）Ar定年，确定蓝片岩、榴辉岩和退变质作用的年龄;（7）将中亚和中国东部的研究结果进行对比，以阐明已知的变质、岩浆和构造特征之间的成因关系。

9725347 Liou This proposed U.S.-Japan-Russia-Kazakhstan cooperative project will continue field, petrologic, stable, isotopic, geochronologic, and tectonic investigations of intracratonal ultrahigh-pressure and high-pressure metamorphic rocks in the Kokchetav Massif and the Maksyutov Complex, where coesite ( microdiamonds have been described. Primary objectives are to: (1) determine the regional distribution and structural relationships among diamond-bearing gneiss and marble, coesite-bearing eclogite and gneiss, and other UHP and HP rocks in the Kokchetav Massif and the Maksyutov Complex; (2) identify and characterize the mineral inclusions in garnet and zircon from eclogite, gneiss, marble, and schist to establish conditions of UHP metamorphism and the effect of such elevated pressures; (3) delineate mineral parageneses and P-T-t paths for eclogite, whiteschist, garnet peridotite, blueschist, gneiss and marble; (4) characterize 18O/16O ratios of silicates and carbon isotopes of diamond, magnesite, and other carbonates in order to evaluate the role of fluids at mantle depths; (5) determine the structural and geochemical characteristics of protoliths in order to infer their plate tectonic settings; (6) establish the ages of blueschist, eclogite, and retrograde metamorphism through U-Pb and 40Ar/39Ar dating; and (7) compare findings from central Asia with those from eastern China in order to elucidate the genetic relationships among recognized metamorphic, igneous, and tectonic features.