The second one corresponds to greenschist facies (Figure 30, represented by chlorite + muscovite + epidotesr-plagioclase (albite) + quartz + actinolite
Most samples contain relict igneous minerals, variably replaced by fine-grained metamorphic minerals dominated by chlorite, epidote, actinolite
, prehnite, pumpellyite, quartz, and opaque minerals.
The sources of these noncommercial amphiboles varied and included tremolite contamination of chrysotile (cases 1 and 4, Table 3), tremolite and actinolite
contamination of vermiculite (case 5, Table 3), environmental exposure to tremolite and actinolite
(case 2, Table 3), and exposure to anthophyllite during the manufacture of cement pipes (case 3, Table 3).
In Wadi Sikait, these rocks are represented by phlogopite and actinolite
schists in the schist melange.
Within the contact breccia zones strong magnetite and actinolite
also occur within the propylitic assemblage.
Mineralization is described as a black, yellow and brown, highly magnetic and zoned magnetite-copper-zinc skarn containing disseminated to massive magnetite, with variable garnetite, actinolite
, quartz-calcite stringers, and sulphide stringers and clusters mainly pyrite, pyrrhotite, chalcopyrite and sphalerite.
Five varieties of amphiboles are known: anthophyllite, amosite, tremolite, crocidolite, and actinolite
Numerous experimental animal studies have demonstrated the carcinogenicity of fibers of the six commercially used asbestos minerals [the serpentine chrysotile and the amphiboles cumming-tonite-grunerite asbestos (amosite), tremolite asbestos, riebeckite asbestos (crocidolite), actinolite
asbestos, and anthophyliite asbestos in multiple species (rats, hamsters, mice) by exposure via inhalation, intrapleural injection, implantation, and ingestion (reviewed by Kamp 2009; Lippmann 1990).
Amphibole forms of asbestos are often divided into those with considerable commercial exploitation (amosite and crocidolite) and those that are encountered largely as intrusions into other mineral deposits (tremolite, actinolite
, anthophyllite); thus, tremolite is found in many chrysotile ore beds, and an amphibole that has been variously labeled as tremolite, richterite, or winchite is found in vermiculite ore from Libby, Montana.
Biotite and actinolite
formed in the highest-strain part of the Waite ductile shear zone.
There are two main families of asbestos: amphiboles (tremolite, actinolite
, crocidolite) and serpentines (chrysorile, antigorite, lizard-ite).
Important relationships seen at both macroscopic and microscopic scales include (1) rocks of the shear zone have undergone polymetamorphism, (2) an earlier phase of actinolitic amphibole (greenschist facies) is replaced in areas by a later phase of hornblendic amphibole (amphibolite facies), (3) zones of high strain correlate with rocks with a larger amount of hornblende, and (4) zones of lower strain correlate with rocks with a larger amount of porphyroclastic actinolite
, surrounded by significant amounts of hornblende.