Petrology of low-temperature, ultrahigh-pressure marbles and interlayered coesite eclogites near Sanqingge, Sulu terrane, eastern China

作者：Zhu Yong feng^*; Massonne H J; Zhu Men fan

来源：Mineralogical Magazine, 2009, 73(2): 307-332.

DOI：10.1180/minmag.2009.073.2.307

• coesite
• eclogite
• marble
• magnesite
• Sulu UHP terrane

Marbles and interlayered coesite-bearing eclogites near the village of Sanqingge in the Sulu ultrahigh-pressure (UHP) terrane of eastern China were studied to estimate their P-T evolution. Using garnet omphacite and phengite as geothermobarometers, the coesite eclogites are calculated to have experienced P-T conditions of 3.4-3.7 GPa and similar to 600 degrees C (stage II), followed by decompression and a slight temperature decrease to 2.7-3.2 GPa and 520-560 degrees C respectively (stage II) and later to 2.6-2.8 GPa and similar to 500 degrees C (stage III). No water influx affected the eclogites until reaching amphibolite facies conditions of 0.5-1.3 Gpa and 595-685 degrees C (stage IV). As we interpret the occasional appearance of calcite with magnesite relics in the core as a reaction of UHP dolomite and magnesite with Ca-rich fluids at stage IV to form CaCO(3), the calculated pressure for stage I Could be the maximum pressure experienced by these rocks. Thus, the crustal material of the Sanqingge quarry, originally sedimentary carbonates (now marbles) and interstratified basic tuffs (now eclogites), has been buried to a depth of >= 120 km at similar to 600 degrees C. This burial occurred in a subduction setting along a very low geotherm of 5-6 degrees C/km. The exhumation possibly occurred in the environment of a subduction channel.

• 出版日期2009-4
• 单位北京大学