关键词: 重矿物, 物源分析, 成岩作用, 岩浆弧, 大陆地块, 西藏, 特提斯喜马拉雅, 日喀则弧前盆地

Abstract: Provenance analysis is the key of paleogeographic reconstruction and basin analysis, whose typical end-members include “magmatic arc provenance”, “continental block probvenance”, and “recycled orogen provenance”. Kinds of heavy minerals contain a wealth of parent rock information, which are widely used for provenance analysis. Modern sand researches have shown there is a link between detrital heavy mineral assemblages and their geodynamic backgrounds. Unfortunately, this law cannot be directly applied to ancient sandstone because of the diagenesis. We know little about the heavy mineral assemblages of sandstones sourced from magmatic arc and continental block. The Jurassic-Paleogene Xigaze forearc basin and Tethys Himalayan sandstones in Tibet are either from Gangdese arc of the Asian continent or from Indian continental block, which is an excellent lab to study the heavy mineral assemblages of ancient sandstones derived from magmatic arc and continental block. The quantitative analyses result of 16 sandstones shows that: 1) heavy minerals are seriously modified by diagenesis, unstable minerals (e.g. amphibole, pyroxene) are disappeared while authigenic growth of new minerals such as epidote is common; 2) sandstones derived from magmatic arc are mainly composed of epidote or apatite, with ZTR<40; while sandstones derived from continental block are mainly composed of zircon, tourmaline and rutile, with ZTR>75. The sandstones sourced from magmatic arc and continental block yield distinctive heavy mineral assemblages, which make sense for provenance interpretation.

Key words: heavy mineral, provenance analysis, diagenesis, magmatic arc, continental block, Tibet, Tethys Himalaya, Xigaze forearc basin