Hornblende diorite

The Miocene stratigraphy in the Baguio District has been intruded by a series of Pliocene rocks. The homblende-phyric Mafic Dike Complex intruded the central part of the Baguio District at 4.5 - 4 Ma (Waters et al. submitted). The complex is characterized by dense clusters of coarsely hornblende phenocrystic dikes with evidence for multiple injections. Several Pliocene to Pleistocene dioritic intrusive complexes are associated with porphyry copper-gold mineralization in the Baguio district. The Black Mountain Intrusive Complex includes the Black Mountain quartz diorite and the Mexico Diorite, as well as andesite dykes that have yielded ages of between 3.14 and 2.78 Ma (Waters et al. submitted Sweet etal. 2008). Other Pliocene intrusive rocks... 

The original serpentinite was altered to antigorite- dolomite, talc, and tremolite, and the hornblende diorite (H,D ) was altered to chlorite with some tremolite. The numbers refer to samples taken along the alteration zone (the distance between samples 1 and 5 was about 2 ft), and the concentration of the Cr (M), Eu (i, or Sm ( ) in each sample is shown normalized to the levels found in unmetamorphosed serpentinite. The theoretical concentration profile for Sm is shown by the dashed line and was calculated assuming similar partition coefficients (mineral/solution) for all of the minerals formed from the serpentinite. 

Figure 2. Rare earth elements concentrations (normalized to chondrites) for the original rocks (serpentinite and hornblende diorite) and their alteration products...

The Shackleton Limestone of the Churchill Mountains south of the Byrd Glacier is tightly folded and was intruded by ... small plutons of hornblende granite, pyroxene-hornblende diorite or gabbro, and dikes of quartz porphyry, all probably related to the Hope Granite (Grindley and Laird 1969). Faure and Felder (1984) described and sampled a complex pegmatite that intruded the Shackleton Limestone on one of two... 

Diorite has been defined as an intermediate plutonic, granular rock composed of plagioclase and hornblende, although at times the latter may be partially or completely replaced by biotite and/or pyroxene. Plagioclase, In the form of ollgoclase and andesine, is the dominant feldspar. If orthoclase Is present. It acts only as an accessory mineral. 

This group includes diorites, syenites, andesites, and trachytes, which usually contain some heavy ferromagnesian minerals such as hornblende, augite, and biotite as essential constituents, while their accessory minerals include apatite, zircon, sphene, and iron oxides. 

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